**File Specification for GEOS-5 MERRA Reanalysis Gridded Output**

*Global Modeling and Assimilation Office*

*Goddard Space Flight Center, Greenbelt, Maryland*

http://gmao.gsfc.nasa.gov

Release Date: tbd

Version 1.0

Latest Revisions: suarez27/2007 9:05 AM

Document maintained by Rob Lucchesi (GMAO, SAIC)

*Permission to quote from this document should be obtained from the
GMAO.*

![](media/image1.png){width="0.5979166666666667in"
height="0.5180555555555556in"}

**Michele Rienecker**

**Global Modeling and Assimilation Office**

**Earth Sciences Division**

**NASA Goddard Space Flight Center**

**Greenbelt, Maryland 20771**

This page intentionally left blank.

**File Specification for GEOS-5 MERRA Reanalysis Gridded Output**

**Document No. GMAO-100XvX.0**

**September 21, 2006**

Approved by:

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Michele Rienecker Date Gi-Kong Kim Date

Head CCB Chair

Global Modeling and Assimilation Office Global Modeling and Assimilation
Office

Code 610.1, NASA GSFC Code 610.2, NASA GSFC

**REVISION HISTORY**

  ------------------------------------------------------------------------
  **Version    **Revision    **Extent of Changes**           **Approval
  Number**     Date**                                        Authority**
  ------------ ------------- ------------------------------- -------------
  1.0          03/24/2006    Baseline                        

                                                             

  2.0                                                        
  ------------------------------------------------------------------------

04/19/2007First version posted for comment on MERRA web site.
2.1Xx/xx/2007TAB

**1. Introduction 3**

**2. Format and File Organization 4**

2.1 Dimensions 5

2.2 Variables 6

2.3 Global Attributes 7

**ArchivedMetadata.0 character The ECS archive metadata. 8**

**3. Instantaneous vs Time-averaged Products 8**

**4. Grid Structure 8**

4.1 Horizontal Structure 8

4.2 Vertical Structure 9

**5. File Naming Conventions 11**

5.1 File Names 11

5.2 Earth Science Data Types (ESDT) Name 14

**6. Summary of MERRA file collections 15**

**7. Metadata 17**

7.1 EOSDIS Metadata 17

7.2 CF Metadata 17

**8. Sample Software 18**

8.1 HDF-EOS Example 18

8.2 HDF (non EOS) Example 20

**Appendix A: The IAU procedure 24**

**Appendix B: Observational Inputs to MERRA 25**

**Appendix C: Collection Metadata 29**

**Appendix D: Vertical Structure 32**

**Appendix E: GEOS-5 data collections 33**

E.1 Time-independent Variables 33

const_2d_asm_Nx 33

E.2 Analysis Files 34

inst6_3d_ana_Nv 34

inst6_3d_ana_Np 35

E.3 History Files 36

inst3_3d_asm_Cp 36

tavg3_3d_cld_Cp 37

tavg3_3d_mst_Cp 38

tavg3_3d_rad_Cp 39

tavg3_3d_trb_Cp 40

tavg3_3d_tdt_Cp 41

tavg3_3d_udt_Cp 42

tavg3_3d_qdt_Cp 43

tavg3_3d_odt_Cp 44

tavg1_2d_slv_Nx 45

tavg1_2d_flx_Nx 47

tavg1_2d_rad_Nx 49

tavg1_2d_lnd_Nx 51

tavg1_2d_int_Nx 53

E.4 Chemistry Forcing Files 55

const_2d_chm_Fx 55

tavg3_3d_chm_Fv 56

tavg3_3d_chm_Fe 57

tavg3_2d_chm_Fx 58

tavg3_3d_chm_Nv 59

tavg3_3d_chm_Ne 60

inst_3d_chm_Ne 61

**Appendix F: Detailed Description of Output Variables 62**

F.1 Three-dimensional Fields 62

F.2 Two-dimensional Fields 66

**Appendix G: Surface Representation 70**

**References 72**

Web Resources 73

**65360 \\h µ72§**

§

# **1. Introduction** 

The Modern Era Retrospective-analysis for Research and Applications
(MERRA) is a NASA reanalysis for the satellite era using a major new
version of the Goddard Earth Observing System Data Assimilation System
Version 5 (GEOS-5). MERRA focuses on historical analyses of the
hydrological cycle on a broad range of weather and climate time scales
and places the NASA EOS suite of observations in a climate context. It
is one of NASA's deliverables for the Climate Change Science Program
(CCSP). MERRA covers the period 1979-2007, with plans to extend the
analysis forward in time as resources allow.

MERRA uses the GEOS-5 Data Assimilation System (GEOS-5 DAS), which
represents a radical evolution of the system, with the adoption of a
joint analysis with the National Centers for Environmental Prediction
(NCEP) and of a new set of physics packages for the atmospheric general
circulation model (AGCM). The first choice allows the Global Modeling
and Assimilation Office (GMAO) to take advantage of the developments,
especially that of radiance assimilation, at NCEP and the Joint Center
for Satellite Data Assimilation (JCSDA), and facilitates our own
contributions to the operational system. The second choice allows us to
tune the system for both weather and climate applications and to enhance
the usefulness of satellite observations.

The new GEOS-5 AGCM uses the finite-volume dynamics (Lin, 2004)
integrated with various physics packages under the Earth System Modeling
Framework (ESMF) (e.g., Collins et al., 2005) including the Catchment
Land Surface Model (CLSM) (e.g., Koster et al., 2000). The GSI analysis
is a new three-dimensional variational (3DVar) analysis applied in
grid-point space to facilitate the implementation of anisotropic,
inhomogeneous covariances (e.g., Wu et al., 2002; Derber et al., 2003).
In contrast, in the Spectral Statistical Interpolation (SSI) analysis,
used for the NCEP/NCAR Reanalyses, the background error covariances were
defined spectrally and were nearly homogeneous around a latitude band.
The GSI implementation incorporates a set of recursive filters that
produce approximately Gaussian smoothing kernels and isotropic
correlation functions. By superposition of Gaussian kernels with
different length scales it is possible to generate non-Gaussian shapes,
and generally to implement a large class of flow-dependent inhomogeneous
background error covariance models (Purser et al., 2003a, b).

The GEOS-5 DAS is a marked change from the GEOS-4 DAS which was based on
the Physical-space Statistical Analysis System (PSAS) coupled to the
GEOS-4 model. The GEOS-4 system is documented in Bloom et al. (2005).
Like GEOS-5, GEOS-4 used the finite-volume dynamical core, but
integrated in version 3 of the Community Climate Model (CCM3) and
version two of the Community Land Model (CLM2). PSAS assimilated
retrievals of satellite data, not radiances, and the analysis was a
height-wind analysis. Like GEOS-5, the background error covariance
functions were in grid-point space, but were horizontally-isotropic,
compactly-supported spline functions. The GEOS-4 system assimilated
roughly 10^5^ observations per analysis time whereas the GEOS-5 system
assimilates over an order of magnitude more -- roughly 2 × 10^6^
observations are actively assimilated each analysis, including about 7.5
× 10^5^ AIRS radiance data. The input stream is roughly twice this
volume, but because of the large volume, the data are thinned
commensurate with the analysis grid to reduce the computational burden.
Data are also rejected from the analysis through quality control
procedures designed to detect, for example, the presence of cloud.

To minimize the spurious periodic perturbations of the analysis, MERRA
uses the Incremental Analysis Update (IAU) technique developed by Bloom
et al. (1996). More details of this proceduendix_A:\_The\" Appendix A.

The version of the DAS used for MERRA is: GEOS-5.03.

Observations used for MERRA arbservational\" Appendix B. The data
streams assimilated by the GEOS-5 DAS for MERRA are shown in Table B.1;
their availability and the source of the data assimilated for MERRA are
shown in Table B.2.

The analysis is performed at a horizontal resolution of 2/3 degrees
longitude by ½ degree latitude and at 72 levels, extending to 0.01 hPa.
Some products, such as the instantaneous analysis fields, are available
on the native three-dimensional grid. Hourly two-dimensional diagnostic
fields are also available at the native horizontal resolution. Other
products are available on a coarser horizontal grid with resolution of
1.25 ×1.25 degrees or 1 × 1.25 degrees, the latter for use by the
chemistry transport community. These may be on the model's native
vertical grid or at 42 pressure surfaces extending to 0.1 hPa. Surface
data, near surface meteorology, selected upper-air levels, and
vertically integrated fluxes and budgets are produced at one-hour
intervals, which will help the development of offline land and ocean
models and data assimilation systems by resolving the diurnal cycle.
Monthly mean versions of most of these products will also be available.

This document describes the gridded output files produced by the MERRA
reanalysis. These are considerably different from the operational GEOS-5
DAS output. The MERRA data will be available online through the Goddard
Earth Sciences (GES) Data and Information Services Center DISC). The
disk cache and interface tools in this Modeling DISC (MDISC) system
leverage new DISC capabilities in serving active data archives. More
information .gsfc.nasa.gov/. Detailed documentation of the system
.nasa.gov/merra

# 2. Format and File Organization 

GEOS-5 files .gsfc.nasa.gov/) format, which is an extension of the
Hierarchical Data Format (HDF), Version 4 developed at the National
Center for Supercomputing Appl[hdfgroup.org/\"
http://w](../(NCSA))ww.hdfgroup.org/ . Each GEOS-5 file will contain a
single HDF-EOS grid, which in turn contains a number of geophysical
quantities that we will refer to as \"fields\" or \"variables.\" Some
files will contain 2-D variables on a longitude-latitude grid, and some
files will contain 3-D variables, or a mixture of 2-D and 3-D variables
on the same longitude-latitude grid, but with a vertical dimension
applicable to all the 3D variables.

The variables are created using the **GDdeffield** function from the
HDF-EOS GD (GriD) API, which stores them as HDF Scientific Data Set
(SDS) arrays, so that they can be read with standard HDF routines. In
addition to the geophysical variables, the files will have SDS arrays
that define dimension scales (or coordinate variables). There will be
two distinct scales for each dimension, which will ensure that a wide
variety of graphical display tools can interpret the data. In
particular, there are dimension scales thaLINK \\l \"CF\" CF
conventions, as well as ones that adhe \\l \"COARDS\" COARDS
conventions.

Due to the size of the MERRA archive, all data will be compressed with a
GRIB-like method that is invisible to the user. This method does degrade
the precision of the data, but every effort has been made to ensure that
differences between the product and the original, uncompressed data are
not scientifically meaningful. Once the precision has been degraded, the
files are written using the standard gzip deflation available in HDF-4.

EOS Core System (ECS) metadata and other information will be stored as
global attributes.

##  {#section .unnumbered}

## ***2.1 Dimensions*** 

GMAO HDF-EOS files will contain two sets of dimension scale (coordinate)
information. One set of dimensions is defined using the
**SDsetdimscale** function of the standard HDF SD interface. This set of
scales will have an attribute named "units," set to an appropriate
string defined by the CF and COARDS conventions that can be used by
applications to identify the dimension. The other set of dimension
scales is created using the **GDdeffield/GDwritefield** functions.

Table 2.1-1. Dimension Variables Contained in GMAO HDF-EOS Files

  ----------------- ---------------------- ---------- ------------------------
  Longitude float32 **Description**        **Type**   ***units* attribute**
  degrees_east Name                                   

  YDim:EOSGRID      Latitude               float32    degrees_north
  XDim:EOSGRID                                        

                                                      

  Height:EOSGRID\   pressure or layer      float32    hPa or layer
  (3D only)         index                             

                                                      

  TIME:EOSGRID      minutes since first    float32    minutes
                    time in file                      

                                                      

  XDim              Longitude, in degrees  float64    
                    east                   N/A YDim   
  ----------------- ---------------------- ---------- ------------------------

Latitude, in degrees northfloat64 N/A Height\
(3D only) pressure or level indices float64 N/A Time seconds since
00:00Z on 1 January 1993 float64 N/A

The 32-bit dimension variables have a \"units\" attribute that makes
them COARDS-compliant, while the 64-bit dimension variables satisfy ECS
requirements.

## ***2.2 Variables***  {#variables .unnumbered}

Variables are stored as SDS arrays, even though they are defined with
the HDF-EOS **GDdeffield** function. As a result, one can use the SD
interface of the HDF library to read any variable from the file. The
only thing one must know is the *short name* of the variable and the
dimensions. You can quickly list the variables in the file by using
common utilities such as *ncdump* or *hdp*. Both utilities are
distributed from NCSA with the re\" Section 8 we will present sample
code for reading one or more data fields from this file. The *short
names* for all variables in all GMAO data
product[dix_E:\_GEOS](http://listed/#_Appen)-5\" Appendix E. A glossary
with a brief description of each varia_F:\_Detailed\" Appendix F.

Each variable will have several useful metadata attributes. Many of
these attributes are required by the CF and COARDS conventions, while
others are specific for GMAO products. The following table lists
required attributes. Other attributes may be included for internal GMAO
use and can be ignored.

Table 2.2-1 Metadata attributes associated with each SDS.

  ---------------------------------------------------------------------------------
  **Name**          **Type**[]{#FillValue   **Description**
                    .anchor}                
  ----------------- ----------------------- ---------------------------------------
  \_FillValue       float32                 Floating-point value used to identify
                                            missing data. Will normally be set to
                                            1e15. Required by CF.

  float32, array(2) float32                 Same as \_FillValue. Required for
  This attribute                            COARDS backwards compatibility.
  defines the valid                         
  range of the                              
  variable. The                             
  first element is                          
  the smallest                              
  valid value and                           
  the second                                
  element is the                            
  largest valid                             
  value. Required                           
  by CF.                                    
  missing_value                             

  long_name         String                  Ad hoc description of the variable.
  valid_range                               Required by COARDS.

  standard_name     String                  Standard description of the variable as
                                            defined in CF conventions. (See
                                            References).

  float32If         String                  The units of the variable. Must be a
  variable is                               string that can be recognized by
  packed as 16-bit                          UNIDATA\'s Udunits package.
  integers, this is                         
  the scale_factor                          
  for expanding to                          
  floating-point.                           
  Currently we do                           
  not plan to pack                          
  data, thus value                          
  will be 1.0 units                         

  add_offset        float32                 If variable is packed as 16-bit
  scale_factor                              integers, this is the offset for
                                            expanding to floating-point. Currently,
                                            we do no plan to pack data, thus value
                                            will be 0.0.
  ---------------------------------------------------------------------------------

## ***2.3 Global Attributes***  {#global-attributes .unnumbered}

In addition to SDS arrays containing variables and dimension scales,
there is global metadata stored in GMAO HDF-EOS files. Some metadata are
required by the CF/COARDS conventions, some are present to meet ECS
requirements, and others as a convenience to users of GMAO products. A
summary of global attributes present in all MERRA files is shown in
Table 2.3-1.

Table 2.3-1 Global metadata attributes associated with each SDS.

  ------------------------------------------------------------------------
  **Name**           **Type**      **Description**
  ------------------ ------------- ---------------------------------------
  Conventions        character     Identification of the file convention
                                   used, currently "CF-1.0"

  title              character     Experiment identification: "MERRA"

  history            character     CVS tag of this release. CVS tags are
                                   used internally by the GMAO to
                                   designate versions of the system.

  institution        character     "NASA Global Modeling and Assimilation
                                   Office"

  source             character     CFIO Version (CFIO is the GMAO's IO
                                   layer)

  references         character     GMAO website address

  comment            character     As required

                                   

  HDFEOSVersion      character     Version of the HDF-EOS library used to
                                   create this file.

  StructMetadata.0   character     This is the GridStructure metadata that
                                   is created by the HDF-EOS library.

  CoreMetadata.0     character     The ECS inventory metadata.
  ------------------------------------------------------------------------

# ArchivedMetadata.0 character The ECS archive metadata.  {#archivedmetadata.0-character-the-ecs-archive-metadata. .unnumbered}

# **3. Instantaneous vs Time-averaged Products**  {#instantaneous-vs-time-averaged-products .unnumbered}

Each file collection listed in Section 6 contains either instantaneous
or time-averaged products, but not both.

All instantaneous collections contain fields at *synoptic times* (00
GMT, 06 GMT, 12 GMT, and 18 GMT). In addition, three-hourly
instantaneous collections also include snapshots at *mid-synoptic times*
(03 GMT, 09 GMT, 15 GMT, and 21 GMT). 

Time-averaged collections may contain either hourly, three-hourly,
monthly, or seasonal means, but not mixtures of these. Each collection
contains data over a continuous sequence of averaging intervals, which
are time stamped with the central time of the interval. For hourly data,
these times are 00:30 GMT, 01:30 GMT, 02:30 GMT, etc.. Only products
consisting exclusively of two-dimensional (horizontal) fields are
produced hourly. Three-hourly time-averaged files contain averages over
time intervals centered and time stamped at 01:30 GMT, 04:30 GMT, 07:30
GMT, and so on. Monthly files represent averages for the calendar
months, accounting for leap years. For monthly means, each file contains
a single month.

Hourly, three-hourly, or six-hourly collections, instantaneous or
time-averaged, are kept as templated sets of daily files. For
collections of monthly or seasonal means each month or season is in a
separate file, and file names are also include templated times.

# 

# **4. Grid Structure** 

## ***4.1 Horizontal Structure***  {#horizontal-structure .unnumbered}

Fields will be produced on three different horizontal grids: the a
native grid of the Finite-Volume dynamical core, with a resolution of
2/3 longitude by 1/2 degree latitude, a coarse version of the FV grid,
with a resolution of 1.25 longitude by 1 degree latitude, and a uniform
coarse grid, with a resolution of 1.25 by []{#Native .anchor}1.25
degrees.

GEOS-5 ***native resolution*** gridded output is on a global horizontal
grid, consisting of **IMn=540** points in the longitudinal direction and
**JMn=361** points in the latitudinal direction. The horizontal native
grid origin, associated with variables indexed (*i=*1*,j=*1) represents
a grid point located at (180W, 90S). Latitude and longitude of grid
points as a function of their indices (*i, j*) can be dBED EquatioBED
Equatο and $(Dj)_{n}$ = 1/2o. For example, (*i* = 271, *j* = 181)
corresponds to a grid point at ($\lambda = 0,j = 0$).

[]{#FVCoarse .anchor}FV ***reduced resolution*** gridded output is used
only for the specialized chemistry forcing files (see Appendix E). It is
on a global horizontal grid, consisting of **IMf=288** points in the
longitudinal direction and **JMf=181** points in the latitudinal
direction. The horizontal native grid origin, associated with variables
indexed (*i=*1*,j=*1) represents a grid point located at (180W, 90S).
Latitude and longitude of grid points as a function of their indices
(*i, j*) can be determined by:

$$\begin{array}{r}
\lambda_{i} = - \text{180} + (\Delta\lambda)_{f}(i - 1),\text{   }i = 1,\text{IMf} \\
\phi_{j} = - \text{90} + (\Delta\phi)_{f}(j - 1),\text{    }j = 1,\text{JMf}
\end{array}$$

where $(\Delta\lambda)_{f}$ = 1.25ο and $(\Delta\phi)_{f}$ = 1o.

MERRA ***reduced resolution*** gridded output is on a global horizontal
grid consisting of **IMc=288** points in the longitudinal direction and
**JMc=144** points in the latitudinal direction. The horizontal coarse
grid origin, associated with variables indexed (*i=*1*, j=*1) represents
a grid point at (179.375W, 80.375S), so that the Dateline and the South
Pole are "edges" of the first grid box. Latitude and longitude as a
function of their indices (*i, j*) for the coarse grid can be determined
by:

$$\begin{array}{r}
\lambda_{i}\text{=-}\text{180} + (D\lambda)_{c}(i - 1),\text{   }i = 1,\text{IMc} \\
j_{j}\text{=-}\text{90} + (Dj)_{c}(j - 1),\text{    }j = 1,\text{JMc}
\end{array}$$

where $(D\lambda)_{c}$= $(Dj)_{c}$=1.25o.

## ***4.2 Vertical Structure*** 

Gridded products will use four different vertical configurations:
Horizontal-only (can be vertical averages, single level, or surface
values), pressure-level, model-level, or model-edge. Horizontal-only
data for a given variable appear as 3-dimensional fields (x, y, time),
where multiple times can span multiple files, while pressure-level,
model-level, or model-edge data appear as 4-dimensional fields (x, y, z,
time). Pressure-level data will be output on the **LMp=42** pressure
levels shown in [Appendix D](#APPENDIXC) . The GEOS-5 model layers used
for MERRA output are on a terrain-following hybrid sigma-p coordinate.
Model-level data will be output on the **LM=72** layers shown in
[Appendix D](#APPENDIXC). The model-edge products contain fields with
**LMe = LM + 1** levels representing the layer edges. Model-level files
will contain the [LM](#LM)-layer 3D variable ([DELP](#DELP)**ijl**), the
pressure thickness for each layer, as well as the surface pressure
([PS](#PS)**ij**). The pressure at the model top is a fixed constant,
**PTOP=0.01 hPa**. Pressures at model edges should be computed by
summing the DELP starting at PTOP. A representative pressure for the
layer can then be obtained from these. In the GEOS-4 *eta* files, one
could compute the pressure on the edges by using the "ak" and "bk"
values and the surface pressure. In GEOS-5, the full 3-dimensional
pressure variables are explicitly provided through
([DELP](#DELP)**ijl**), PTOP, and ([PS](#PS)**ij**). For the MERRA
products documented here, all model-level fields are on a hybrid-sigma
coordinate, and their vertical location could be obtained from the
"ak-bk" relationship as well. But this may change in future GMAO
systems. We thus recommend that users rely on the reported 3D pressure
distribution, and not use ones computed from the "ak" and "bk".

Figure 1 is a schematic (not to scale) of the GEOS-5 lcv coordinate
system. Note that the indexing in the vertical is top to bottom, i.e.,
layer 1 is the top layer of the atmosphere, while layer [LM](#LM) is
adjacent to the earth's surface. The same is true for edge variables,
with level 1 being the top of the model's atmosphere (PTOP), and level
LM+1 being the surface.

# **5. File Naming Conventions** 

Each GEOS-5 product file will have a complete file name identified in
the EOSDIS metadata as \"LocalGranuleID\". EOSDIS also requires
abbreviated naming indices (8-character limit) for each Earth Science
Data Type (ESDT). In MERRA each file collection has a unique ESDT index.
The ESDT index convention is described in section 5.2.

## ***5.1 File Names*** {#file-names .unnumbered}

The standard full name for the assimilated GEOS-5 MERRA products will
consist of five dot-delimited nodes:

***runid*.*runtype.config.collection.timestamp***

The node fields, which vary from file to file, are defined as follows:

> ***runid***
>
> All MERRA runs will be identified by **MERRA***SV* , where the
> qualifiers *S* and *V* denote the production *Stream* and the
> *Version* numbers.
>
> MERRA will be run in three production *Streams*, each covering
> approximately a third of the MERRA period, plus overlaps and spin-up
> periods. If the stream number is not applicable (the case for
> ancillary products, such as forecasts), *S* is set to 0, otherwise it
> is 1, 2, or 3.
>
> *Version* is non-zero when there is more than one version of the
> dataset. It is usually zero, denoting the original processing. MERRA
> will be conducted with a frozen assimilation system, so there will be
> no updates or patches to the GEOS-5 software during a complete
> experiment. Version changes indicate either that a problem was
> encountered after product release and a reprocessing was necessary or
> a period was reprocessed with a modified version of the data system
> for scientific studies. For any such reprocessing, we will increment
> the version number appropriately and this will be documented by adding
> the cvs tag in the metadata parameter "History." Information on
> version differences will also be available at the MERRA web site
> ([http://gmao.gsfc.nasa.gov/research/merra](http://gmao.gsfc.nasa.gov/research/merra/)/).
>
> ***runtype*:**
>
> The main GEOS-5 MERRA products will be from standard production
> (**prod**) runs. Products from other runs or run segments may be made
> available for specialized analyses.
>
> **prod**   - Standard product
>
> **ovlp**  - Overlap product
>
> **spnp** - Spin-up product
>
> **swep** - Sweeper Run product
>
> **rosb**  - Reduced observing system product
>
> **cers**  - CERES observing system product
>
> ***config*:**
>
> The GEOS-5 analysis and forecast system can run in different
> configurations.
>
> **assim** -- Assimilation. Uses a combination of atmospheric data
> analysis and model forecasting to generate a time-series of global
> atmospheric quantities.
>
> **simul** -- Simulation. Uses a free-running atmospheric model with
> some prescribed external forcing, such as sea-surface temperatures.
>
> **frcst** -- Forecasts. Uses a free-running atmospheric model
> initialized from an analyzed state.
>
> The main configuration used to support MERRA will be assimilation
> (**assim**). A long, AMIP-style simulation will also be performed and
> it will be labeled **simul**.
>
> ***collection*:**
>
> All MERRA data are organized into file *collections* that contain
> fields with common characteristics. These collections are used to make
> the data more accessible for specific purposes. Fields may appear in
> more than one collection. Collection names are of the form
> *freq_dims_group_HV*, where the four attributes are:
>
> *freq:* time-independent (**cnst**), instantaneous (**inst***F***),**
> or time-average (**tavg*F***), where ***F*** indicates the frequency
> or averaging interval and can be any of the following:
>
> **1** = Hourly
>
> **3** = 3-Hourly
>
> **6** = 6-Hourly
>
> **D** = Daily
>
> **M** = Monthly (**tavg** only)
>
> **U** = Monthly-Diurnal (**tavg** only)
>
> **S** = Seasonal (**tavg** only)
>
> **A** = Annual (**tavg** only)
>
> **0 =** Not Applicable
>
> *dims:* Only 2-dimensional fields (**2d)** or a mix ofa 2- and
> 3-dimensional fields (**3d**)
>
> *group:* Any of the following:
>
> **ana** = direct analysis products
>
> **asm** = assimilated (from the corrector segment of the iau, see
> [Appendix A](#_Appendix_A:_The_IAU_procedure))
>
> **chm** = chemistry
>
> **lnd** = land variables
>
> **tdt =** temperature tendencies
>
> **qdt =** specific humidity tendencies
>
> **udt =** zonal wind tendencies
>
> **vdt =** meridional wind tendencies
>
> **mst** = moist processes
>
> **cld** = clouds
>
> **rad =** radiation
>
> **srf** = surface variables
>
> **slv** = single level
>
> *HV*: Horizontal and Vertical grid.
>
> *H* can be:
>
> **N**: Native (2/3 x ½) horizontal resolution
>
> **C**: Reduced (1.25 x 1.25) horizontal resolution
>
> **F**: Reduced FV (1.25 x 1) horizontal resolution
>
> *V* can be:
>
> **x**: horizontal-only data (surface, column-integrated, single-level)
>
> **p**: pressure-level data (see [Appendix D](#APPENDIXC) for pressure
> levels)
>
> **v**: model layer centers (see [Appendix D](#APPENDIXC) )
>
> **e**: model layer edges (see [Appendix D](#APPENDIXC) )
>
> ***timestamp:***
>
> This node defines the date and time associated with the data in the
> file. It has the form *yyyymmdd* for either instantaneous or
> time-averageaveraged daily files, *yyyymm* for monthly-mean files, or
> *yyyysss* for seasonal-mean files*.*
>
> **yyyy** - year string (e.g. , \"2002\")
>
> **mm** - month string (e.g.., \"09\" for September)
>
> **dd** - day of the month string (optional)
>
> **sss** - season (e.g., DJF) (optional)

***EXAMPLE***:

**MERRA30.prod.assim.tavg3_3d_tdt_Cp.20020915.hdf**

This is an example of a MERRA filename from the production segment of
the original version of the third (most recent) assimilation stream. The
data are time-averaged, three-dimensional, temperature tendency
products, at reduced horizontal resolution, interpolated to pressure
levels. The file contains all data for 15 September 2002.

## ***5.2 Earth Science Data Types (ESDT) Name***  {#earth-science-data-types-esdt-name .unnumbered}

To accommodate EOSDIS toolkit requirements, all MERRA files are
associated with an 8-character ESDT. The ESDT is a short (and rather
cryptic) handle for users to access sets of files. In MERRA the ESDT
will be used to identify *collections* and will consist of a compressed
version of the collection name of the form:

*CTFHVGGG\
*

where

> *C*: Configuration
>
> **A** = Assimilation
>
> **F =** Forecast
>
> **S =** Simulation
>
> *T*: Time Description:
>
> **I** = Instantaneous
>
> **T =** Time-averaged
>
> **C** = Time-independent
>
> *F*: Frequency
>
> **1** = Hourly
>
> **3** = 3-Hourly
>
> **6** = 6-Hourly
>
> **D** = Daily
>
> **M** = Monthly
>
> **S** = Seasonal
>
> **A** = Annual
>
> **0 =** Not Applicable
>
> *H*: Horizontal Resolution
>
> **N** = [Native](#Native).
>
> **F =** [Reduced resolution version of model grid](#FVCoarse)
>
> **C =** [Reduced resolution](#FVCoarse)
>
> *V*: Vertical Location
>
> **X** = Two-dimensional
>
> **P** = Pressure
>
> **V =** model layer center
>
> **E** = model layer edge
>
> *GGG*: Group
>
> **ANA** = direct analysis products
>
> **ASM** = assimilated state variables (from the corrector segment of
> the iau, see [Appendix A](#_Appendix_A:_The_IAU_procedure))
>
> **TDT =** tendencies of temperature
>
> **UDT =** tendencies of eastward and northward wind components
>
> **QDT =** tendencies of specific humidity
>
> **ODT =** tendencies of ozone
>
> **LND** = land surface variables
>
> **FLX =** surface turbulent fluxes and related quantities
>
> **OCN** = ocean surface variables
>
> **MST** = moist processes
>
> **CLD** = clouds
>
> **RAD =** radiation
>
> **TRB =** turbulence
>
> **SLV** = single level
>
> **INT** = vertical integrals

**CHM =** chemistry forcing

#  {#section-2 .unnumbered}

# **6. Summary of MERRA file collections** {#summary-of-merra-file-collections .unnumbered}

The GEOS-5 MERRA product is organized into the 25 collections listed in
Tables 6.1 and 6.2. These are described in detail in [Appendix
E](#_Appendix_E:_GEOS-5_data_collections). The 18 collection in Table
6-1 are the "standard" product intended for most diagnostic work. The
seven "chemistry" collections in table 6-2 are more specialized
products, intended for forcing off-line chemistry transport models
(CTMs). The last three of these, in particular, are for CTMs using the
GEOS-5 transport cores.

Collection names follow the conventions described in [Section
5](#_5._File_Naming_Conventions). Sizes are given in Gbytes/day and
Tbytes for the entire collection. Numbers in parentheses are estimates
for the corresponding compressed file.

Table 6-1 List of standard collections

  ---------------------------------------------------------------------------------------------------------
  **Name**                                  **Description**                          **Size Gbytes/day //
                                                                                     Tbytes**
  ----------------------------------------- ---------------------------------------- ----------------------
  [**const_2d_asm_Nx**](#Xcnst)             Constant fields                          

  **[inst6_3d_ana_Nv](#Xana)**              Analyzed fields on [model                1.347 (0.455) // 14.8
                                            layers](#Elevs)                          (5.0)

  **[inst6_3d_ana_Np](#Xanap)**             Analyzed fields at [pressure             0.792 (0.290) // 8.71
                                            levels](#Plevs)                          (3.2)

  **[inst3_3d_asm_Cp](#Xasm)**              Basic assimilated fields from            0.616 (x.xxx)
                                            [IAU](#_Appendix_A:_The_IAU_procedure)   
                                            corrector                                

  **[tavg3_3d_cld_Cp](#Xcld)**              Upper-air cloud related diagnostics      0.512 (x.xxx)

  **[tavg3_3d_mst_Cp](#Xmst)**              Upper-air diagnostics from moist         0.900 (x.xxx)
                                            processes                                

  **[tavg3_3d_trb_Cp](#Xtrb3)**             Upper-air diagnostics from turbulence    0.501 (x.xxx)

  **[tavg3_3d_rad_Cp](#Xrad)**              Upper-air diagnostics from radiation     0.228 (x.xxx)

  **[tavg3_3d_trb_Cp](#Xtrb3)**             Upper-air diagnostics from turbulence    0.501 (x.xxx)

  **[tavg3_3d_tdt_Cp](#Xtdt)**              Upper-air temperature tendencies by      0.445 (x.xxx)
                                            process                                  

  **[tavg3_3d_udt_Cp](#Xudt)**              Upper-air wind tendencies by process     0.557 (x.xxx)

  **[tavg3_3d_qdt_Cp](#Xqdt)**              Upper-air humidity tendencies by process 0.613 (x.xxx)

  **[tavg3_3d_odt_Cp](#Xodt)**              Upper-air ozone tendencies by process    0.279 (x.xxx)

  [**tavg1_2d_slv_Nx**](#Xslv)              Single-level atmospheric state variables 0.546 (0.248) // 6.0
                                                                                     (2.73)

  [**tavg1_2d_flx_Nx**](#Xtrb)              Surface turbulent fluxes and related     0.505 (x.xxx)
                                            quantities                               

  [**tavg1_2d_rad_Nx**](#Xrad2)             Surface and TOA radiative fluxes         0.561 (x.xxx)

  [**tavg1_2d_lnd_Nx**](#tavg1_2d_lnd_nx)   Land related surface quantities          x.xxx (x.xxx)

  [**tavg1_2d_int_Nx**](#tavg1_2d_int_nx)   Vertical integrals                       x.xxx (x.xxx)

  **TOTAL**                                                                          x.xxx (x.xxx)
  ---------------------------------------------------------------------------------------------------------

#  {#section-3 .unnumbered}

Table 6-2 List of chemistry collections

  --------------------------------------------------------------------------------------------------------------
  **Name**                                              **Description**                             **Size
                                                                                                    (Gbytes)**
  ----------------------------------------------------- ------------------------------------------- ------------
  **[const_2d_chm_Fx](#const_2d_chm_fx)**               2-D invariants on chemistry grid            x.xxx
                                                                                                    (x.xxx)

  [**tavg3_3d_chm_Fv**](#tavg3_3d_chm_fv)               Chemistry related 3-D at model layer        x.xxx
                                                        centers                                     (x.xxx)

  [**tavg3_3d_chm_Fe**](#tavg3_3d_chm_fe)               Chemistry related 3-D at model layer edges  x.xxx
                                                                                                    (x.xxx)

  [**tavg3_2d_chm_Fx**](#tavg3_2d_chm_fx)               Chemistry related 2-DSingle-level           x.xxx
                                                                                                    (x.xxx)

  [**inst3_3d_chm_Nv**](#_5._File_Naming_Conventions)   Instantaneous fields for off-line transport x.xxx
                                                                                                    (x.xxx)

  [**tavg3_3d_chm_Nv**](#_tavg3_3d_chm_Nv)              Accumulated transport fields                x.xxx
                                                                                                    (x.xxx)

  [**tavg3_3d_chm_Ne**](#tavg3_3d_chm_ne)               Accumulated transport fields on edges       x.xxx
                                                                                                    (x.xxx)

  **TOTAL CHEM**                                                                                    x.xxx
                                                                                                    (x.xxx)
  --------------------------------------------------------------------------------------------------------------

# **7. Metadata**  {#metadata .unnumbered}

GEOS-5 gridded output files will include or be linked to two types of
metadata. When using the HDF-EOS library and tools, the EOSDIS metadata
will be used. Other utilities such as GrADS will use the CF metadata.

## ***7.1 EOSDIS Metadata***  {#eosdis-metadata .unnumbered}

The EOSDIS toolkit will only use the EOSDIS metadata. EOSDIS identifies
two major types of metadata:, collection and granule.

Collection metadata are stored in a separate index file. This file
describes an ESDT and is like a card in a library catalog. Each GMAO
data product will have an ESDT description in the EOS Core System that
contains its unique collection attributes. [Appendix
C](#_Appendix_C:_Collection_Metadata) describes the ESDT collection
metadata.

Granule metadata is the \"table of contents\" information stored on the
data file itself. The EOSDIS granule metadata include:

-   File name (local granule ID)

-   Grid structure

-   Number of time stamps stored in the file

-   Number of vertical levels for each variable in this file

-   Names of variables in this file

-   Variable format (32-bit floating point, 16-bit integer, etc.)

-   Variable storage dimensions

time, latitude and longitude for 2-d fields

time, latitude, longitude and vertical levels 3-d fields

-   \"Missing\" value for each variable

## ***7.2 CF Metadata***  {#cf-metadata .unnumbered}

When GrADS or FERRET are used to view GEOS-5 gridded data sets, the
application will use the CF metadata imbedded in the data products.
These metadata will comply with the CF conventions and include the
following information:

-   Space-time grid information (dimension variables)

-   Variable names and descriptions

-   Variable units

-   \"Missing\" value for each variable

# **8. Sample Software**  {#sample-software .unnumbered}

The following example illustrates the use of the standard HDF library or
the ECS HDF-EOS library to read GEOS-5 products. The program shown below
will accept as command line arguments a file name and a field name. It
will open the file, read the requested field at the first time, compute
an average for this field, and print the result to standard output.
There are two versions of this program. The first version uses the
HDF-EOS library to read the file. The second version uses the standard
HDF library to read the file. Electronic copies of these programs can be
obtained from the Operations section of the GMAO [web
page](http://gmao.gsfc.nasa.gov/operations/).

## 8.1 HDF-EOS Example 

/\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/

/\* This program demonstrates how to read a field from a GMAO HDF-EOS
\*/

/\* product using the HDF-EOS library. It will take a file name and \*/

/\* field name on the command line, read the first time of the given \*/

/\* field, calculate an average of that time and print the average. \*/

/\* \*/

/\* usage: avg \<file name\> \<field name\> \*/

/\* \*/

/\* Rob Lucchesi \*/

/\* rlucchesi@GMAO.gsfc.nasa.gov \*/

/\* 2/12/1999 \*/

/\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/

#include \"hdf.h\"

#include \"mfhdf.h\"

#include \<stdio.h\>

#define XDIM 540

#define YDIM 361

#define ZDIM 42

main(int argc,char \*argv\[\]) {

int32 sd_id, sds_id, status;

int32 sds_index;

int32 start\[4\], edges\[4\], stride\[4\];

char \*fname, \*vname;

float32 data_array\[ZDIM\]\[YDIM\]\[XDIM\];

float32 avg, sum;

int32 i,j,k;

int32 file_id, gd_id;

if (argc != 3) {

printf(\"Usage: avg \<filename\> \<field\> \\n\");

exit (-1);

}

fname = argv\[1\];

vname = argv\[2\];

/\* Open the file (read-only) \*/

file_id = GDopen (fname, DFACC_RDONLY);

if (file_id \< 0) {

printf (\"Could not open %s\\n\",fname);

exit(-1);

}

/\* Attach to the EOS grid contained within the file. \*/

/\* The GMAO uses the generic name \"EOSGRID\" for the grid in all
products. \*/

gd_id = GDattach (file_id,\"EOSGRID\");

if (gd_id \< 0) {

printf (\"Could not open %s\\n\",fname);

exit(-1);

}

/\* Set positioning arrays to read the entire field at the first time.
\*/

start\[0\] = 0;

start\[1\] = 0;

start\[2\] = 0;

start\[3\] = 0;

stride\[0\] = 1;

stride\[1\] = 1;

stride\[2\] = 1;

stride\[3\] = 1;

edges\[0\] = 1;

edges\[1\] = ZDIM;

edges\[2\] = YDIM;

edges\[3\] = XDIM;

/\*In this program, we read the entire field. By manipulating the start

and edges arrays, it is possible to read a subset of the entire array.

For example, to read a 3D section defined by x=100, 224; y=50,149;

z=15,16 you would set the start and edges arrays to the following:

start\[0\] = 0; time start location

start\[1\] = 15; z-dim start location

start\[2\] = 50; y-dim start location

start\[3\] = 100; x-dim start location

edges\[0\] = 1; time length

edges\[1\] = 2; z-dim length

edges\[2\] = 100; y-dim length

edges\[3\] = 125; x-dim length

\*/

/\* Read the data into data_array \*/

status = GDreadfield (gd_id, vname, start, stride, edges, data_array);

printf (\"Read status=%d\\n\",status);

/\* Calculate and print the average \*/

sum=0.0;

for (i=0; i\<XDIM; i++)

for (j=0; j\<YDIM; j++)

for (k=0; k\<ZDIM; k++)

sum += data_array\[k\]\[j\]\[i\];

avg = sum/(XDIM\*YDIM\*ZDIM);

printf (\"Average of %s in 3 dimensions is=%f\\n\",vname,avg);

/\* Close file. \*/

status = GDdetach (gd_id);

status = GDclose (file_id);

## ***8.2 HDF (non EOS) Example***

}/\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/

/\* This program demonstrates how to read a field from a GMAO HDF-EOS
\*/

/\* product using the HDF library (HDF-EOS not required). It will take
\*/

/\* a file name and field name on the command line, read the first time
\*/

/\* of the given field, calculate an average of that time and print the
average. \*/

/\* \*/

/\* usage: avg \<file name\> \<field name\> \*/

/\* \*/

/\* Rob Lucchesi \*/

/\* rlucchesi@GMAO.gsfc.nasa.gov \*/

/\* 2/12/1999 \*/

/\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/

#include \"hdf.h\"

#include \"mfhdf.h\"

#include \<stdio.h\>

#define XDIM 540

#define YDIM 361

#define ZDIM 42

main(int argc,char \*argv\[\]) {

int32 sd_id, sds_id, status;

int32 sds_index;

int32 start\[4\], edges\[4\], stride\[4\];

char \*fname, \*vname;

float32 data_array\[ZDIM\]\[YDIM\]\[XDIM\];

float32 avg, sum;

int32 i,j,k;

if (argc != 3) {

printf(\"Usage: avg \<filename\> \<field\> \\n\");

exit (-1);

}

fname = argv\[1\];

vname = argv\[2\];

/\* Open the file (read-only) \*/

sd_id = SDstart (fname, DFACC_RDONLY);

if (sd_id \< 0) {

printf (\"Could not open %s\\n\",fname);

exit(-1);

}

/\* Find the index and ID of the SDS for the given variable name. \*/

sds_index = SDnametoindex (sd_id, vname);

if (sds_index \< 0) {

printf (\"Could not find %s\\n\",vname);

exit(-1);

}

sds_id = SDselect (sd_id,sds_index);

/\* Set positioning arrays to read the entire field at the first time.
\*/

start\[0\] = 0;

start\[1\] = 0;

start\[2\] = 0;

start\[3\] = 0;

stride\[0\] = 1;

stride\[1\] = 1;

stride\[2\] = 1;

stride\[3\] = 1;

edges\[0\] = 1;

edges\[1\] = ZDIM;

edges\[2\] = YDIM;

edges\[3\] = XDIM;

/\*

In this program, we read the entire field. By manipulating the start

and edges arrays, it is possible to read a subset of the entire array.

For example, to read a 3D section defined by x=100, 224; y=50,149;

z=15,16 you would set the start and edges arrays to the following:

start\[0\] = 0; time start location

start\[1\] = 15; z-dim start location

start\[2\] = 50; y-dim start location

start\[3\] = 100; x-dim start location

edges\[0\] = 1; time length

edges\[1\] = 2; z-dim length

edges\[2\] = 100; y-dim length

edges\[3\] = 125; x-dim length

\*/

/\* Read the data into data_array \*/

status = SDreaddata (sds_id, start, stride, edges, (VOIDP) data_array);

printf (\"read status=%d\\n\",status);

/\* Calculate and print the average \*/

sum=0.0;

for (i=0; i\<XDIM; i++)

for (j=0; j\<YDIM; j++)

for (k=0; k\<ZDIM; k++)

sum += data_array\[k\]\[j\]\[i\];

avg = sum/(XDIM\*YDIM\*ZDIM);

printf (\"Average of %s in 3 dimensions is=%f\\n\",vname,avg);

/\* Close file. \*/

status = SDendaccess (sds_id);

status = SDend (sd_id);

# **Appendix A: The IAU procedure** 

The implementation of the Incremental Analysis Update (IAU, Bloom et
al., 1996) used for MERRA is summarized in Figure A.1. Every six hours,
at the synoptic times, an analysis is performed using backgrounds at
that time, three hours earlier, and three hours later, which
incorporates observations during the six-hour period spanned by the
three backgrounds. The results of this analysis are the products
included in the two [analysis
collections](#_5._File_Naming_Conventions). The analysis increments
(i.e., the difference between the analysis and the corresponding
synoptic background) are then divided by a time scale (in MERRA we used
6 hours) to produce an "analysis tendency." The model is then
"backed-up", restarting it from its state three hours before the
analysis time, and run for six hours, adding in the time-invariant
"analysis tendency" in addition to its normal physics tendencies. At
that point a restart is created that will be used next time the model is
backed-up, and the first background for the next analysis cycle is
saved. We refer to this first 6-hour run as the "corrector" segment of
the IAU. The run is then continued without an analysis tendency for
another six hours, saving the other two backgrounds needed by the next
analysis\-\--one at the next synoptic time and another at the end of the
six hours. We refer to this 6-hour run as the "predictor" segment of the
IAU. The entire cycle is then repeated for subsequent synoptic times.
Note that during each of the four daily analysis cycles the model is run
for 12 hours\-\--a 6-hour "corrector" followed by a 6-hour "predictor."

[]{#IAU .anchor}

![](media/image2.png){width="5.7131944444444445in"
height="2.8881944444444443in"}

**Figure A.1**

Except for the analyses themselves, all products from MERRA are produced
as model histories during the corrector run segment. The sequence of
corrector segments (follow the green line in the figure) is a continuous
model run, with the extra forcing term from the analysis tendencies. The
analysis tendencies do change abruptly every six hours, but state
variables are continuous (within the model's time step) solutions of the
equations of motion, albeit with the extra forcing term.

# **Appendix B: Observational Inputs to MERRA** {#appendix-b-observational-inputs-to-merra .unnumbered}

Table 1.1 Input observation data.

+------------------------------------------+---------------------------+
| **Conventional Data**                    |                           |
+------------------------------------------+---------------------------+
| Radiosondes                              | u, v, T, q, P~s~          |
+------------------------------------------+---------------------------+
| PIBAL winds                              | u, v                      |
+------------------------------------------+---------------------------+
| Wind profiles                            | u, v                      |
+------------------------------------------+---------------------------+
| Conventional, ASDAR, and MDCARS aircraft | u, v, T                   |
| reports                                  |                           |
+------------------------------------------+---------------------------+
| NEXRAD radar winds                       | u, v                      |
+------------------------------------------+---------------------------+
| Dropsondes                               | u, v, T, P~s~             |
+------------------------------------------+---------------------------+
| PAOB                                     | P~s~                      |
+------------------------------------------+---------------------------+
| GMS, METEOSAT, cloud drift IR and        | u, v                      |
| visible winds                            |                           |
+------------------------------------------+---------------------------+
| MODIS clear sky and water vapor winds    | u, v                      |
+------------------------------------------+---------------------------+
| GOES cloud drift IR winds                | u, v                      |
+------------------------------------------+---------------------------+
| GOES water vapor cloud top winds         | u, v                      |
+------------------------------------------+---------------------------+
| Surface land observations                | P~s~                      |
+------------------------------------------+---------------------------+
| Surface ship and buoy observations       | u, v, T, q, P~s~          |
+------------------------------------------+---------------------------+
| SSM/I                                    | Rain rate, wind speed     |
+------------------------------------------+---------------------------+
| TMI                                      | Rain rate                 |
+------------------------------------------+---------------------------+
| QuikSCAT                                 | Wind speed and direction  |
+------------------------------------------+---------------------------+
|                                          |                           |
+------------------------------------------+---------------------------+
| **Satellite Data**                       |                           |
+------------------------------------------+---------------------------+
| TOVS 1b Radiances                        | AMSU-A: N15, N16, N18     |
|                                          |                           |
|                                          | AMSU-B: N15, N16, N17     |
|                                          |                           |
|                                          | MHS: N18                  |
|                                          |                           |
|                                          | HIRS2: TIROS-N, N6, N7,   |
|                                          | N8, N9, N10, N11, N12,    |
|                                          | N14                       |
|                                          |                           |
|                                          | HIRS3: N16, N17           |
|                                          |                           |
|                                          | HIRS4: N18                |
|                                          |                           |
|                                          | MSU: TIROS-N, N6, N7, N8, |
|                                          | N9, N10, N11, N12, N14    |
|                                          |                           |
|                                          | SSU: TIROS-N, N6, N7, N8, |
|                                          | N9, N10, N11, N14         |
+------------------------------------------+---------------------------+
| EOS/Aqua Level 1b Radiances              | AIRS (150 channels),      |
|                                          | AMSU-A                    |
+------------------------------------------+---------------------------+
| SSM/I radiances                          | DSMP-13, DSMP-14, DSMP-15 |
|                                          | (7 channels)              |
+------------------------------------------+---------------------------+
| GOES sounder T~B~                        | GOES-08, GOES-10, GOES-12 |
|                                          | Channels 1-18             |
+------------------------------------------+---------------------------+
| SBUV2 ozone (Version 8 retrievals)       | Nimbus 7, NOAA 9, 11, 14, |
|                                          | 16, 17                    |
+------------------------------------------+---------------------------+

Table 1.2 Observation data availability and MERRA data source.

  ------------------------ ---------------------- ------------------------
  **DATA SOURCE/TYPE**     **PERIOD**             **DATA SUPPLIER**

  **Conventional Data**                           

  Radiosondes              1970 - present         NOAA/NCEP

  PIBAL winds              1970 - present         NOAA/NCEP

  Wind profiles            1992/5/14 - present    UCAR CDAS

  Conventional, ASDAR, and 1970 - present         NOAA/NCEP
  MDCARS aircraft reports                         

  Dropsondes               1970 - present         NOAA/NCEP

  PAOB                     1978 - present         NCEP CDAS

  GMS, METEOSAT, cloud     1977 -- present        NOAA/NCEP
  drift IR and visible                            
  winds                                           

  GOES cloud drift winds   1997 -- present        NOAA/NCEP

  EOS/Terra/MODIS winds    2002/7/01 - present    NOAA/NCEP

  EOS/Aqua/MODIS winds     2003/9/01 - present    NOAA/NCEP

  Surface land             1970 - present         NOAA/NCEP
  observations                                    

  Surface ship and buoy    1977 - present         NOAA/NCEP
  observations                                    

  SSM/I rain rate          1987/7 - present       NASA/GSFC/DAAC

  SSM/I V6 wind speed      1987/7 - present       RSS

  TMI rain rate            1997/12 - present      NASA/GSFC/DAAC

  QuikSCAT surface winds   1999/7 - present       JPL

  ERS-1 surface winds      1991/8/5 -- 1996/5/21  CERSAT

  ERS-2 surface winds      1996/3/19 -- 2001/1/17 CERSAT

                                                  

  **Satellite Data**                              

  TOVS/tn (TIROS N)        1978/10/30 --          NCAR
                           1980/06/01             

  TOVS/na (NOAA 6)         1979/07/02 --          NCAR
                           1983/04/17             

  TOVS/nc (NOAA 7)         1981/07/11 -           NCAR
                           1986/06/01             

  TOVS/ne (NOAA 8)         1983/04/26 -           NCAR
                           1985/01/01             

  TOVS/nf (NOAA 9)         1985/01/01 -           NOAA/NESDIS & NCAR
                           1988/11/01             

  TOVS/ng (NOAA 10)        1986/11/25 -           NOAA/NESDIS & NCAR
                           1991/09/17             

  TOVS/nh (NOAA 11)        1988/09/02 -           NOAA/NESDIS & NCAR
                           1994/12/31             

  TOVS/nd (NOAA 12)        1991/08/18 -           NOAA/NESDIS & NCAR
                           1997/07/14             

  TOVS/nj (NOAA 14)        1995/01/19 - present   NOAA/NESDIS

  TOVS/nk (NOAA 15)        1998/07/01 - present   NOAA/NESDIS

  TOVS/nl (NOAA 16)        2001/03/02 - present   NOAA/NESDIS

  TOVS/nm (NOAA 17)        2003/03/01 - present   NOAA/NESDIS

  TOVS/nn (NOAA 18)        2005/10/05 -- present  NOAA/NESDIS

  EOS/Aqua                 2002/10 - present      NOAA/NESDIS

  SSM/I V6 (F08)           1987/7 - 1991/12       RSS

  SSM/I V6 (F10)           1990/12 -- 1997/11     RSS

  SSM/I V6 (F11)           1991/12 -- 2000/5      RSS

  SSM/I V6 (F13)           1995/5 - present       RSS

  SSM/I V6 (F14)           1997/5 - present       RSS

  SSM/I V6 (F15)           1999/12 -- 2006/8      RSS

  GOES sounder T~B~        2001/01 - present      NOAA/NCEP

  SBUV2 ozone (Version 8   1978/10 - present      NASA/GSFC/Code 613.3
  retrievals)                                     
  ------------------------ ---------------------- ------------------------

# **Appendix C: Collection Metadata** 

GEOS-5 collection metadata will contain the following. To view the ESDTs
associated with GMAO products, which include collection metadata, see
the GMAO Operations web page: <http://gmao.gsfc.nasa.gov/operations>.

*ECS Collection*

Revision Date

Suggested Usage

*Single Type Collection*

Collection State

Maintenance and Update Frequency

*Spatial*

Spatial Coverage Type

*Bounding Rectangle*

West Bounding Coordinate

North Bounding Coordinate

East Bounding Coordinate

South Bounding Coordinate

*Altitude System Definition (for 3d files only)*

Altitude Datum Name

Altitude Distance Units

Altitude Encoding Method

Altitude Resolution Class

Altitude Resolution

*Depth System Definition (land surface files only)*

Depth Datum Name

Depth Distance Units

Depth Encoding Method

Depth Resolution Class

Depth Resolution

*Geographic Coordinate System*

Latitude Resolution

Longitude Resolution

Geographic Coordinate Units

*Temporal*

Time Type

Date Type

Temporal Range Type

Precision of Seconds

Ends at Present Flag

*Range Date Time*

Range Beginning Date

Range Beginning Time

Range Ending Date

Range Ending Time

*Contact Person*

Role

Hours of Service

Contact Job Position

Contact First Name

Contact Middle Name

Contact Last Name

*Contact Person Address*

Street address

City

State/Province

Postal Code

Country

*Telephone*

Telephone Container

Telephone Number

Telephone Number Type

*Email*

Electronic Mail Address

*Contact Organization*

Role

Hours of Service

Contact Instruction

Contact Organization Name

*Contact Organization Address*

Street Address

City

State/Province

Postal Code

Country

*Organization Telephone Number*

Telephone Number

Telephone Number Type

*Organizational Email*

Electronic Mail Address

*Discipline Topic Parameters*

ECS Discipline Keyword

ECS Topic Keyword

ECS Term Keyword

ECS Variable Keyword

ECS Parameter Keyword

*Temporal Keyword Class*

Temporal Keyword

*Spatial Keyword Class*

Spatial Keyword

*Processing Level*

Processing Level Description

Processing Level ID

*Analysis Source*

Analysis Short Name

Analysis Long Name

Analysis Technique

Analysis Type

*CSDT Description*

Primary CSDT

*Additional Attributes*

Additional Attribute Data Type

Additional Attribute Description

Additional Attribute Name

*Physical Parameter Details*

Parameter Units of Measure

Parameter Range

Parameter Value Accuracy

Parameter Value Accuracy Explanation

Parameter Measurement Resolution

*Storage Medium Class*

(filled in by DAAC)

# **Appendix D: Vertical Structure** 

Pressure-level data will be output on the following 42 pressure levels:

Products on the native vertical grid will be output on the following
levels. Pressures are nominal for a 1000 hPa surface pressure and refer
to the top edge of the layer. Note that the bottom layer has a nominal
thickness of 15 hPa.

[]{#Elevs .anchor}

  --------- ------------ --------- ------------ --------- ------------ --------- ------------ --------- ------------ --------- ------------
  **Lev**   **P(hPa)**   **Lev**   **P(hPa)**   **Lev**   **P(hPa)**   **Lev**   **P(hPa)**   **Lev**   **P(hPa)**   **Lev**   **P(hPa)**

  1         0.0100       13        0.6168       25        9.2929       37        78.5123      49        450.000      61        820.000

  2         0.0200       14        0.7951       26        11.2769      38        92.3657      50        487.500      62        835.000

  3         0.0327       15        1.0194       27        13.6434      39        108.663      51        525.000      63        850.000

  4         0.0476       16        1.3005       28        16.4571      40        127.837      52        562.500      64        865.000

  5         0.0660       17        1.6508       29        19.7916      41        150.393      53        600.000      65        880.000

  6         0.0893       18        2.0850       30        23.7304      42        176.930      54        637.500      66        895.000

  7         0.1197       19        2.6202       31        28.3678      43        208.152      55        675.000      67        910.000

  8         0.1595       20        3.2764       32        33.8100      44        244.875      56        700.000      68        925.000

  9         0.2113       21        4.0766       33        40.1754      45        288.083      57        725.000      69        940.000

  10        0.2785       22        5.0468       34        47.6439      46        337.500      58        750.000      70        955.000

  11        0.3650       23        6.2168       35        56.3879      47        375.000      59        775.000      71        970.000

  12        0.4758       24        7.6198       36        66.6034      48        412.500      60        800.000      72        985.000
  --------- ------------ --------- ------------ --------- ------------ --------- ------------ --------- ------------ --------- ------------

# **Appendix E: GEOS-5 data collections**  {#appendix-e-geos-5-data-collections .unnumbered}

This section lists the variables in eachh the data collection. More
details on the variable definitions may be found in Appendix F. Most
variables tabled in this section are hyperlinked to their definitions in
Appendix F. In the tables, variable names refer to HDF names, which are
uppercase. Sizes refer to the daily files.

## ***E.1 Time-independent Variables*** 

These are prescribed 2-dimensional fields that do not vary during the
reanalysis. They are available as:
**MERRA00.prod.assim.const_2d_asm_Nx.00000000.hdf** at the full
resolution.

### const_2d_asm_Nx 

[]{#Xcnst .anchor}

ECS short name: **AC0NXCNS**

ECS long name: MERRA DAS 2d constants,

Characteristics: **Constant at [native resolution](#Native)**

Dimensions: longitude: **540**, latitude: **361**

Size/file: 5.5 MBytes

## ***E.2 Analysis Files*** 

These are the fields resulting from the GSI analyses performed at the
four synoptic times (states labeled ANALYSIS in [Figure A.1](#IAU)).
They are produced on the native horizontal grid and on both model levels
and pressure levels in the vertical. The data on model levels are the
values actually analyzed.

### inst6_3d_ana_Nv 

[]{#Xana .anchor}

ECS short name: **AI6NVANA**

ECS long name: MERRA DAS 3d analyzed state,

Characteristics: **Instantaneous, on model levels, at [native
resolution](#Native)**

Dimensions: longitude: **540**, latitude: **361**, levels: **72** (see
[Appendix D](#_Appendix_D:_Vertical_Structure))

Times: **00, 06, 12, 18 GMT**

Size/day: 1347 *(800)* MBytes

Size/30 years: 14.8 *(8.9)* TBytes

  -----------------------------------------------------------------------------
  **Variable Name**  **Dims**   **Description**                     **Units**
  ------------------ ---------- ----------------------------------- -----------
  PS                 2D         Surface pressure                    Pa

  DELP               3D         Layer pressure thickness            Pa

  T                  3D         Air temperature                     K

  U                  3D         Eastward wind component             m s^-1^

  V                  3D         Northward wind component            m s^-1^

  QV                 3D         Specific humidity                   kg kg^-1^

  O3                 3D         Ozone mixing ratio                  kg kg^-1^
  -----------------------------------------------------------------------------

### inst6_3d_ana_Np

[]{#Xanap .anchor}

ECS short name: **AI6NPANA**

ECS long name: MERRA DAS 3d analyzed state on pressure,

Characteristics: **Instantaneous, on pressure levels, at [native
resolution](#Native)**

Dimensions: longitude: **540**, latitude: **361**, pressure levels:
**42** (see [Appendix D](#_Appendix_D:_Vertical_Structure))

Times: **00, 06, 12, 18 GMT ; monthly and seasonal also available.**

Size/day: 792 *(xxx)* MBytes

Size/30 years: 8.70 *(x.xx)* TBytes

+----------------+-----+---------------------------------+------------+
| > **Variable   | >   | > **Description**               | >          |
| > Name**       |  ** |                                 |  **Units** |
|                | Dim |                                 |            |
|                | s** |                                 |            |
+================+=====+=================================+============+
| > SLP          | >   | > Sea-level pressure            | > Pa       |
|                |  2D |                                 |            |
+----------------+-----+---------------------------------+------------+
| > PS           | >   | > Surface pressure              | > Pa       |
|                |  3D |                                 |            |
+----------------+-----+---------------------------------+------------+
| > H            | >   | > Geopotential height           | > m        |
|                |  3D |                                 |            |
+----------------+-----+---------------------------------+------------+
| > T            | >   | > Air temperature               | > K        |
|                |  3D |                                 |            |
+----------------+-----+---------------------------------+------------+
| > U            | >   | > Eastward wind component       | > m s^-1^  |
|                |  3D |                                 |            |
+----------------+-----+---------------------------------+------------+
| > V            | >   | > Northward wind component      | > m s^-1^  |
|                |  3D |                                 |            |
+----------------+-----+---------------------------------+------------+
| > QV           | >   | > Specific humidity             | > kg       |
|                |  3D |                                 | > kg^-1^   |
+----------------+-----+---------------------------------+------------+
| > O3           | >   | > Ozone mixing ratio            | > kg       |
|                |  3D |                                 | > kg^-1^   |
+----------------+-----+---------------------------------+------------+

##  ***E.3 History Files*** 

These histories are produced from the GCM during the "corrector" segment
of the IAU cycle. All collections in this group are at [reduced
horizontal resolution](#FVCoarse) and 3-D fields are on [pressure
levels](#Plevs).

### inst3_3d_asm_Cp 

[]{#Xasm .anchor}

ECS short name: **AI3CPASM**

ECS long name: MERRA IAU 3d assimilated state on pressure,

Characteristics: **Instantaneous, on pressure levels, at [reduced
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **144**, pressure levels:
**42** (see [Appendix D](#_Appendix_D:_Vertical_Structure))

Times : **00, 03, 06, 09, 12, 15, 18, 21 GMT**

### tavg3_3d_cld_Cp

[]{#Xcld .anchor}

ECS short name: **AT3CPCLD**

ECS long name: MERRA IAU 3d cloud diagnostics,

Characteristics: **Time averaged, on pressure levels, at [reduced
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **144**, levels: **42** (see
[Appendix D](#_Appendix_D:_Vertical_Structure))

Times : **1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT**

### tavg3_3d_mst_Cp 

[]{#Xmst .anchor}

ECS short name: **AT3CVMST**

ECS long name: MERRA IAU 3d moist processes diagnostic,

Characteristics: **Time averaged, on pressure levels, at [reduced
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **144**, levels: **42** (see
[Appendix D](#_Appendix_D:_Vertical_Structure))

Times : **1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT**

### **tavg3_3d_rad_Cp** 

[]{#Xrad .anchor}

ECS short name: **AT3CPRAD**

ECS long name: MERRA IAU 3d radiation diagnostics,

Characteristics: **Time averaged, on pressure levels, at [reduced
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **144**, levels: **42** (see
[Appendix D](#_Appendix_D:_Vertical_Structure))

Times : **1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT**

### **tavg3_3d_trb_Cp** 

[]{#Xtrb3 .anchor}

ECS short name: **AT3CPTRB**

ECS long name: MERRA IAU 3d turbulence diagnostics,

Characteristics: **Time averaged, on pressure levels, at [reduced
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **144**, levels: **42** (see
[Appendix D](#_Appendix_D:_Vertical_Structure))

Times : **1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT**

### **tavg3_3d_tdt_Cp**

[]{#Xtdt .anchor}

ECS short name: **AT3CPTDT**

ECS long name: MERRA IAU 3d temperature tendencies,

Characteristics: **Time averaged, on pressure levels, at [reduced
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **144**, levels: **42** (see
[Appendix D](#_Appendix_D:_Vertical_Structure))

Times : 1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT

### **tavg3_3d_udt_Cp**  {#tavg3_3d_udt_cp .unnumbered}

[]{#Xudt .anchor}

ECS short name: **AT3CPUDT**

ECS long name: MERRA IAU 3d eastward wind tendencies,

Characteristics: **Time averaged, on pressure levels, at [reduced
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **144**, levels: **42** (see
[Appendix D](#_Appendix_D:_Vertical_Structure))

Times : 1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT

Size/day: 560 *(xxx)* MBytes

Size/30 years: 6.2 *(x.x)* TBytes

### **tavg3_3d_qdt_Cp** 

[]{#Xqdt .anchor}

ECS short name: **AT3CPQDT**

ECS long name: MERRA IAU 3d moisture tendencies,

Characteristics: **Time averaged, on pressure levels, at [reduced
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **144**, pressure levels:
**42** (see [Appendix D](#_Appendix_D:_Vertical_Structure))

Times : 1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT

Size/day: 613 *(xxx)* MBytes

Size/30 years: 6.7 *(x.x)* TBytes

### **tavg3_3d_odt_Cp** 

[]{#Xodt .anchor}

ECS short name: **AT3CPODT**

ECS long name: MERRA IAU 3d ozone tendencies,

Characteristics: **Time averaged, on pressure levels, at [reduced
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **144**, levels: **42** (see
[Appendix](#_Appendix_D:_Vertical_Structure) D)

Times : 1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT

Size/day: 280 *(xxx)* MBytes

Size/30 years: 3.1 *(x.x)* TBytes

  -----------------------------------------------------------------------------
  **Variable Name**     **Dims**   **Description**                  **Units**
  --------------------- ---------- -------------------------------- -----------
  DOXDTMST              3D         Ozone tendency from moist        kg kg-1 s-1
                                   physics                          

  DOXDTTRB              3D         Ozone tendency from turbulence   kg kg-1 s-1

  DOXDTCHM              3D         Ozone tendency from chemistry    kg kg-1 s-1

  DOXDTDYN              3D         Ozone tendency from dynamics     kg kg-1 s-1

  DOXDTANA              3D         Ozone tendency from analysis     kg kg-1 s-1
  -----------------------------------------------------------------------------

###  **tavg1_2d_slv_Nx** 

[]{#Xslv .anchor}

ECS short name: **AT1NXSLV**

ECS long name: MERRA IAU 2d atmospheric single-level diagnostics

Characteristics: **Time averaged, single-level, at [native
resolution](#Native)**

Dimensions: longitude: **540**, latitude: **361**

Times : 0:30, 1:30, 2:30, 3:30, 4:30, ... GMT

Size/day: 546 *(xxx)* MBytes

Size/30 years: 6.0 *(x.x)* TBytes

+-------------+----------------------------------------------+--------+
| **Variable  | **Description**                              | **U    |
| Name**      |                                              | nits** |
+=============+==============================================+========+
| >           | > Sea level pressure                         | > Pa   |
| [SLP](#SLP) |                                              |        |
+-------------+----------------------------------------------+--------+
| > [PS](#PS) | > Time averaged surface pressure             | > Pa   |
+-------------+----------------------------------------------+--------+
| > **U850**  | > Eastward wind at 850 hPa                   | > m    |
|             |                                              | > s-1  |
+-------------+----------------------------------------------+--------+
| > **U500**  | > Eastward wind at 500 hPa                   | > m    |
|             |                                              | > s-1  |
+-------------+----------------------------------------------+--------+
| > **U250**  | > Eastward wind at 250 hPa                   | > m    |
|             |                                              | > s-1  |
+-------------+----------------------------------------------+--------+
| > **V850**  | > Northward wind at 850 hPa                  | > m    |
|             |                                              | > s-1  |
+-------------+----------------------------------------------+--------+
| > **V500**  | > Northward wind at 500 hPa                  | > m    |
|             |                                              | > s-1  |
+-------------+----------------------------------------------+--------+
| > **V250**  | > Northward wind at 250 hPa                  | > m    |
|             |                                              | > s-1  |
+-------------+----------------------------------------------+--------+
| > **T850**  | > Temperature at 850 hPa                     | > K    |
+-------------+----------------------------------------------+--------+
| > **T500**  | > Temperature at 500 hPa                     | > K    |
+-------------+----------------------------------------------+--------+
| > **T250**  | > Temperature at 250 hPa                     | > K    |
+-------------+----------------------------------------------+--------+
| > **Q850**  | > Specific humidity at 850 hPa               | > kg   |
|             |                                              | > kg-1 |
+-------------+----------------------------------------------+--------+
| > **Q500**  | > Specific humidity at 500 hPa               | > kg   |
|             |                                              | > kg-1 |
+-------------+----------------------------------------------+--------+
| > **Q250**  | > Specific humidity at 250 hPa               | > kg   |
|             |                                              | > kg-1 |
+-------------+----------------------------------------------+--------+
| > **H850**  | > Height at 850 hPa                          | > m    |
+-------------+----------------------------------------------+--------+
| > **H500**  | > Height at 500 hPa                          | > m    |
+-------------+----------------------------------------------+--------+
| > **H250**  | > Height at 250 hPa                          | > m    |
+-------------+----------------------------------------------+--------+
| > *         | > Vertical pressure velocity at 500 hPa      | > Pa   |
| *OMEGA500** |                                              | > s-1  |
+-------------+----------------------------------------------+--------+
| > [U        | > Eastward wind at 10 m above displacement   | > m    |
| 10M](#U50M) | > height                                     | > s-1  |
+-------------+----------------------------------------------+--------+
| > [         | > Eastward wind at 2 m above the             | > m    |
| U2M](#U50M) | > displacement height                        | > s-1  |
+-------------+----------------------------------------------+--------+
| > [U        | > Eastward wind at 50 m above surface        | > m    |
| 50M](#U50M) |                                              | > s-1  |
+-------------+----------------------------------------------+--------+
| > [V        | > Northward wind at 10 m above the           | > m    |
| 10M](#V50M) | > displacement height                        | > s-1  |
+-------------+----------------------------------------------+--------+
| > [         | > Northward wind at 2 m above the            | > m    |
| V2M](#V50M) | > displacement height                        | > s-1  |
+-------------+----------------------------------------------+--------+
| > [V        | > Northward wind at 50 m above surface       | > m    |
| 50M](#V50M) |                                              | > s-1  |
+-------------+----------------------------------------------+--------+
| > [T        | > Temperature at 10 m above the displacement | > K    |
| 10M](#T10M) | > height                                     |        |
+-------------+----------------------------------------------+--------+
| > [         | > Temperature at 2 m above the displacement  | > K    |
| T2M](#T10M) | > height                                     |        |
+-------------+----------------------------------------------+--------+
| > [QV1      | > Specific humidity at 10 m above the        | > kg   |
| 0M](#QV10M) | > displacement height                        | > kg-1 |
+-------------+----------------------------------------------+--------+
| > [QV       | > Specific humidity at 2 m above the         | > kg   |
| 2M](#QV10M) | > displacement height                        | > kg-1 |
+-------------+----------------------------------------------+--------+
| > TS        | > Surface skin temperature                   | > K    |
+-------------+----------------------------------------------+--------+
| > [DIS      | > Displacement height                        | > m    |
| PH](#DISPH) |                                              |        |
+-------------+----------------------------------------------+--------+
| > [TRO      | > Tropopause pressure                        | > Pa   |
| PP](#TROPP) |                                              |        |
+-------------+----------------------------------------------+--------+
| > [TRO      | > Tropopause specific humidity               | > kg   |
| PQ](#TROPQ) |                                              | > kg-1 |
+-------------+----------------------------------------------+--------+
| > [TRO      | > Tropopause temperature                     | > K    |
| PT](#TROPT) |                                              |        |
+-------------+----------------------------------------------+--------+

###  **tavg1_2d_flx_Nx** 

ECS short name: **AT1NXFLX**

ECS long name: MERRA IAU 2d surface turbulent flux diagnostics

Characteristics: **Time averaged, single level, at [native
resolution](#Native)**

Dimensions: longitude: **540**, latitude: **361**

Size/day: *(509)* MBytes

Size/30 years: 5.6 *(x.x)* TBytes

+--------------+---------------------------------------+--------------+
| > **Variable | > **Description**                     | > **Units**  |
| > Name**     |                                       |              |
+==============+=======================================+==============+
| > [EF        | > Latent heat flux (positive upward)  | > W m-2      |
| LUX](#EFLUX) |                                       |              |
+--------------+---------------------------------------+--------------+
| > [          | > Surface evaporation                 | > kg m-2 s-1 |
| EVAP](#EVAP) |                                       |              |
+--------------+---------------------------------------+--------------+
| > [HF        | > Sensible heat flux (positive        | > W m-2      |
| LUX](#HFLUX) | > upward)                             |              |
+--------------+---------------------------------------+--------------+
| > [          | > Eastward surface wind stress        | > N m-2      |
| TAUX](#TAUX) |                                       |              |
+--------------+---------------------------------------+--------------+
| > [          | > Northward surface wind stress       | > N m-2      |
| TAUY](#TAUX) |                                       |              |
+--------------+---------------------------------------+--------------+
| > [TAUG      | > Eastward gravity wave surface       | > N m-2      |
| WX](#TAUGWX) | > stress                              |              |
+--------------+---------------------------------------+--------------+
| > [TAUG      | > Northward gravity wave surface      | > N m-2      |
| WY](#TAUGWX) | > stress                              |              |
+--------------+---------------------------------------+--------------+
| > [          | > Planetary boundary layer height     | > m          |
| PBLH](#PBLH) |                                       |              |
+--------------+---------------------------------------+--------------+
| > [DI        | > Displacement height                 | > m          |
| SPH](#DISPH) |                                       |              |
+--------------+---------------------------------------+--------------+
| > [BS        | > Surface buoyancy scale              | > m s-1      |
| TAR](#BSTAR) |                                       |              |
+--------------+---------------------------------------+--------------+
| > [US        | > Surface velocity scale              | > m s-1      |
| TAR](#USTAR) |                                       |              |
+--------------+---------------------------------------+--------------+
| > TSTAR      | > Surface temperature scale           | > K          |
+--------------+---------------------------------------+--------------+
| > QSTAR      | > Surface humidity scale              | > kg kg-1    |
+--------------+---------------------------------------+--------------+
| > RI         | > Surface Richardson number           | > no         |
|              |                                       | ndimensional |
+--------------+---------------------------------------+--------------+
| >            | > Roughness length, sensible heat     | > m          |
|  [Z0H](#Z0H) |                                       |              |
+--------------+---------------------------------------+--------------+
| >            | > Roughness length, momentum          | > m          |
|  [Z0M](#Z0M) |                                       |              |
+--------------+---------------------------------------+--------------+
| > HLML       | > Height of center of lowest model    | > m          |
|              | > layer                               |              |
+--------------+---------------------------------------+--------------+
| > TLML       | > Temperature of lowest model layer   | > K          |
+--------------+---------------------------------------+--------------+
| > QLML       | > Specific humidity of lowest model   | > kg kg-1    |
|              | > layer                               |              |
+--------------+---------------------------------------+--------------+
| > ULML       | > Eastward wind of lowest model layer | > m s-1      |
+--------------+---------------------------------------+--------------+
| > VLML       | > Northward wind of lowest model      | > m s-1      |
|              | > layer                               |              |
+--------------+---------------------------------------+--------------+
| > RHOA       | > Surface air density                 | > kg m-3     |
+--------------+---------------------------------------+--------------+
| > SPEED      | > Effective surface wind speed        | > m s-1      |
+--------------+---------------------------------------+--------------+
| > CDH        | > Surface exchange coefficient for    | > kg m-2 s-1 |
|              | > heat                                |              |
+--------------+---------------------------------------+--------------+
| > CDQ        | > Surface exchange coefficient for    | > kg m-2 s-1 |
|              | > moisture                            |              |
+--------------+---------------------------------------+--------------+
| > CDM        | > Surface exchange coefficient for    | > kg m-2 s-1 |
|              | > momentum                            |              |
+--------------+---------------------------------------+--------------+
| > CN         | > Surface neutral drag coefficient    | > no         |
|              |                                       | ndimensional |
+--------------+---------------------------------------+--------------+
| > TSH        | > Effective turbulence skin           | > K          |
|              | > temperature                         |              |
+--------------+---------------------------------------+--------------+
| > QSH        | > Effective turbulence skin humidity  | > kg kg-1    |
+--------------+---------------------------------------+--------------+

###  **tavg1_2d_rad_Nx** 

[]{#Xrad2 .anchor}

ECS short name: **AT1NXRAD**

ECS long name: MERRA IAU 2d surface and TOA radiation fluxes

Characteristics: **Time averaged, single level, at [native
resolution](#Native)**

Dimensions: longitude: **540**, latitude: **361**

Size/day: *561 ()* MBytes

Size/30 years: 6.2 *(x.x)* TBytes

  ---------------------------------------------------------------------------------
  **Variable Name**       **Description**                               **Units**
  ----------------------- --------------------------------------------- -----------
  [EMIS](#EMIS)           Surface emissivity                            fraction

  TS                      Surface skin temperature                      K

  [ALBEDO](#ALBEDO)       Surface albedo                                fraction

  [ALBNIRDF](#ALBVSIDF)   Diffuse beam NIR surface albedo               fraction

  [ALBNIRDR](#ALBVSIDF)   Direct beam NIR surface albedo                fraction

  [ALBVISDF](#ALBVSIDF)   Diffuse beam VIS-UV surface albedo            fraction

  [ALBVISDR](#ALBVSIDF)   Direct beam VIS-UV surface albedo             fraction

  LWGEM                   Emitted longwave at the surface               W m-2

  LWGAB                   Absorbed longwave at the surface              W m-2

  LWGABCLR                Absorbed longwave at the surface with no      W m-2
                          clouds                                        

  LWGABCLRCLN             Absorbed longwave at the surface with no      W m-2
                          clouds or aerosol                             

  LWGNT                   Net downward longwave flux at the surface     W m-2

  LWGNTCLR                Net downward longwave flux at the surface for W m-2
                          cloud-free sky                                

  LWGNTCLRCLN             Net downward longwave flux at the surface for W m-2
                          clear sky                                     

  [LWTUP](#LWTUP)         Upward longwave flux at top of atmosphere     W m-2
                          (TOA)                                         

  [LWTUPCLR](#LWTUP)      Upward longwave flux at TOA assuming clear    W m-2
                          sky                                           

  LWTUPCLRCLN             Upward longwave flux at TOA assuming clear    W m-2
                          clean sky                                     

  [SWTDN](#SWGDN)         TOA incident shortwave flux                   W m-2

  [SWGDN](#SWGDN)         Surface incident shortwave flux               W m-2

  [SWGDNCLR](#SWGDN)      Surface incident shortwave flux assuming      W m-2
                          clear sky                                     

  [SWGNT](#SWGNT)         Surface net downward shortwave flux           W m-2

  [SWGNTCLR](#SWGNT)      Surface net downward shortwave flux assuming  W m-2
                          clear sky                                     

  [SWGNTCLN](#SWGNT)      Surface net downward shortwave flux assuming  W m-2
                          clean sky                                     

  [SWGNTCLRCLN](#SWGNT)   Surface net downward shortwave flux assuming  W m-2
                          clear clean sky                               

  [SWTNT](#SWGNT)         TOA outgoing shortwave flux                   W m-2

  [SWTNTCLR](#SWGNT)      TOA outgoing shortwave flux assuming clear    W m-2
                          sky                                           

  [SWTNTCLN](#SWGNT)      TOA outgoing shortwave flux assuming clean    W m-2
                          sky                                           

  [SWTNTCLRCLN](#SWGNT)   TOA outgoing shortwave flux assuming clear    W m-2
                          clean sky                                     
  ---------------------------------------------------------------------------------

###  **tavg1_2d_lnd_Nx** 

ECS short name: **AT1NXLND**

ECS long name: MERRA IAU 2d land surface diagnostics

Characteristics: **Time averaged, single level, at [native
resolution](#Native)**

Dimensions: longitude: **540**, latitude: **361**

Size/day: *561 ()* MBytes

Size/30 years: 6.2 *(x.x)* TBytes

  --------------------------------------------------------------------------
  **Variable Name**       **Description**                        **Units**
  ----------------------- -------------------------------------- -----------
  [GRN](#GRN)             Vegetation greenness fraction          Fraction

  [LAI](#LAI)             Leaf area index                        m2 m-2

  [GWETROOT](#GWETROOT)   Root zone soil wetness                 fraction

  [GWETTOP](#GWETROOT)    Top soil layer wetness                 fraction

  TPSNOW                  Top snow layer temperature             K

  TUNST                   Surface temperature of unsaturated     K
                          zone                                   

  TSAT                    Surface temperature of saturated zone  K

  TWLT                    Surface temperature of wilted zone     K

  [PRECSNO](#PRECSNO)     Surface snowfall                       kg m-2 s-1

  [PRECTOT](#PRECTOT)     Total surface precipitation            kg m-2 s-1

  SNOMAS                  Snow mass                              kg m-2

  SNODP                   Snow depth                             m

  EVPSOIL                 Bare soil eEvaporation                 W m-2

  EVPTRNS                 Transpiration                          W m-2

  EVPINTR                 Interception loss                      W m-2

  EVPSBLN                 Sublimation                            W m-2

  RUNOFF                  Overland runoff                        kg m-2 s-1

  BASEFLOW                Baseflow                               kg m-2 s-1

  SMLAND                  Snowmelt                               kg m-2 s-1

  FRUNST                  Fractional unsaturated area            fraction

  FRSAT                   Fractional saturated area              fraction

  FRSNO                   Fractional snow-covered area           fraction

  FRWLT                   Fractional wilting area                fraction

  [PARDF](#PARDF)         Surface downward PAR diffuse flux      W m-2

  [PARDR](#PARDF)         Surface downward PAR beam flux         W m-2

  SHLAND                  Sensible heat flux from land           W m-2

  LHLAND                  Latent heat flux from land             W m-2

  EVLAND                  Evaporation from land                  kg m-2 s-1

  LWLAND                  Net downward longwave flux over land   W m-2

  SWLAND                  Net downward shortwave flux over land  W m-2

  GHLAND                  Downward heat flux at base of top soil W m-2
                          layer                                  

  TWLAND                  Total water store in land reservoirs   kg m-2

  TELAND                  Energy store in all land reservoirs    J m-2

  WCHANGE                 Total land water change per unit time  kg m-2 s-1

  ECHANGE                 Total land energy change per unit time W m-2

  SPLAND                  Spurious land energy source            W m-2
  --------------------------------------------------------------------------

### **tavg1_2d_int_Nx** 

ECS short name: **AT1NXINT**

ECS long name: MERRA IAU 2d Vertical integrals

Characteristics: **Time averaged, single level, at [native
resolution](#Native)**

Dimensions: longitude: **540**, latitude: **361**

Size/day: *561 ()* MBytes

Size/30 years: 6.2 *(x.x)* TBytes

  --------------------------------------------------------------------------
  **Variable      **Description**                                **Units**
  Name**                                                         
  --------------- ---------------------------------------------- -----------
  [TPW](#TPW)     Total precipitable water                       kg m-2

  [TQI](#TQL)     Total cloud ice water                          kg m-2

  [TQL](#TQL)     Total cloud liquid water                       kg m-2

  [TO3](#TO3)     Total column ozone                             Dobson

  [TTO3](#TTO3)   Tropospheric total column ozone Column         Dobson

  DMDTANA         Vertically integrated atmospheric mass         kg m-2 s-1
                  tendency for analysis                          

  DQVDTDYN        Vertically integrated water tendency for       kg m-2 s-1
                  dynamics                                       

  DQVDTMST        Vertically integrated water tendency for moist kg m-2 s-1

  DQVDTTRB        Vertically integrated water tendency for       kg m-2 s-1
                  turbulence                                     

  DQVDTCHM        Vertically integrated water tendency for       kg m-2 s-1
                  chemistry                                      

  DQVDTANA        Vertically integrated water tendency for       kg m-2 s-1
                  analysis                                       

  DQLDTDYN        Vertically integrated liquid water tendency    kg m-2 s-1
                  for dynamics                                   

  DQLDTMST        Vertically integrated liquid water tendency    kg m-2 s-1
                  for moist                                      

  DQIDTDYN        Vertically integrated ice water tendency for   kg m-2 s-1
                  dynamics                                       

  DQIDTMST        Vertically integrated ice water tendency for   kg m-2 s-1
                  moist                                          

  DOXDTDYN        Vertically integrated total ozone tendency for kg m-2 s-1
                  dynamics                                       

  DOXDTCHM        Vertically integrated total ozone tendency for kg m-2 s-1
                  dynamics                                       

  DOXDTANA        Vertically integrated total ozone tendency for kg m-2 s-1
                  analysis                                       

  DKEDTDYN        Vertically integrated kinetic energy tendency  W m-2
                  for dynamics                                   

  DPEDTDYN        Vertically integrated cpT tendency for         W m-2
                  dynamics                                       

  DTEDTDYN        Vertically integrated g ps tendency for        W m-2
                  dynamics                                       

  DKEDTPHY        Vertically integrated kinetic energy tendency  W m-2
                  for physics                                    

  DPEDTPHY        Vertically integrated cpT tendency for physics W m-2

  DKEDTANA        Vertically integrated kinetic energy tendency  W m-2
                  for analysis                                   

  DPEDTANA        Vertically integrated cpT tendency for         W m-2
                  analysis                                       

  DTEDTANA        Vertically integrated g ps tendency for        W m-2
                  analysis                                       

  UFLXCPT         Vertically integrated eastward flux of dry     J m-1 s-1
                  enthalpy                                       

  VFLXCPT         Vertically integrated northward flux of dry    J m-1 s-1
                  enthalpy                                       

  UFLXPHI         Vertically integrated eastward flux of         J m-1 s-1
                  geopotential                                   

  VFLXPHI         Vertically integrated northward flux of        J m-1 s-1
                  geopotential                                   

  UFLXKE          Vertically integrated eastward flux of kinetic J m-1 s-1
                  energy                                         

  VFLXKE          Vertically integrated northward flux of        J m-1 s-1
                  kinetic energy                                 

  UFLXQV          Vertically integrated eastward flux of         kg m-1 s-1
                  specific humidity                              

  VFLXQV          Vertically integrated northward flux of        kg m-1 s-1
                  specific humidity                              

  UFLXQL          Vertically integrated eastward flux of liquid  kg m-1 s-1
                  condensate                                     

  VFLXQL          Vertically integrated northward flux of liquid kg m-1 s-1
                  condensate                                     

  UFLXQI          Vertically integrated eastward flux of ice     kg m-1 s-1
                  condensate                                     

  VFLXQI          Vertically integrated northward flux of ice    kg m-1 s-1
                  condensate                                     

  CONVCPT         Vertically integrated convergence of dry       W m-2
                  enthalpy                                       

  CONVPHI         Vertically integrated convergence of           W m-2
                  geopotential                                   

  CONVKE          Vertically integrated convergence of kinetic   W m-2
                  energy                                         

  KEGEN           Vertically integrated generation of kinetic    W m-2
                  energy                                         
  --------------------------------------------------------------------------

##  ***E.4 Chemistry Forcing Files***  {#e.4-chemistry-forcing-files .unnumbered}

These histories are intended for forcing off-line chemistry/aerosol
models with the results of the reanalysis. Like other histories, they
are produced from the GCM during the "corrector" segment of the IAU
cycle. As explained in [Appendix A](#_Appendix_A:_The_IAU_procedure),
such results represent a continuous evolution of the model's state,
without the shocks of data insertion and initialization. By doing it in
this way, we can provide consistent data at intervals finer than the
six-hour analysis interval. In order to provide the most accurate
forcing for off-line calculations, these forcings are produced at
3-hourly intervals and on the native vertical grid using a reduced
horizontal resolution version of the model's horizontal grid. This
horizontal grid was chosen for backward compatibility with earlier
products. In addition, the last three streams in this section consist of
those fields needed to reproduce as closely as possible the model's
large-scale transport calculation. These are on the 3-dimansional C-grid
used by the model and can reproduce, within time truncation, the
[model's continuity equation](#MFZ). These native streams are fairly
specialized and are intended primarily for users of Goddard's Chemistry
Transport Model or its Finite-Volume advection module.

### const_2d_chm_Fx 

ECS short name: **AC0FXCNS**

ECS long name: MERRA CHM 2d constants,

Characteristics: **Constant at [native FV resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **181**

Size/file: x.x MBytes

### tavg3_3d_chm_Fv

ECS short name: **AT3FVCHM**

ECS long name: MERRA IAU 3d Chem On Layers

Characteristics: **Time averaged, 3D model levels, at [reduced FV
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **181**, levels: **72** (see
[Appendix D](#_Appendix_D:_Vertical_Structure))

Times : **1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT**

Size/day: *()* MBytes

  -----------------------------------------------------------------------------------
  **Variable Name**    **Description**                               **Units**
  -------------------- --------------------------------------------- ----------------
  [DELP](#DELP)        Layer pressure thickness                      Pa

  T                    Air temperature                               K

  QV                   Specific humidity                             kg kg-1

  [QL](#QL)            Cloud liquid water mixing ratio               kg kg-1

  [QI](#QL)            Cloud ice mixing ratio                        kg kg-1

  U                    Eastward component of wind                    m s-1

  V                    Northward component of wind                   M s-1

  [CFLS](#APPENDIXC)   Large-scale cloud fraction                    fraction

  [CFAN](#APPENDIXC)   Anvil cloud fraction                          fraction

  [CFCU](#APPENDIXC)   Convective cloud fraction                     fraction

  [DQRCON](#DQRCON)    Precipitation production rate -- convective   kg kg^-1^ s^-1^

  [DQRLSC](#DQRCON)    Precipitation production rate - large-scale   kg kg^-1^ s^-1^

  [DQRANV](#dqrccon)   Precipitation production rate - anvils        kg kg^-1^ s^-1^

  [DTRAIN](#DTRAIN)    Detrainment cloud mass flux                   kg m-2 s-1

  [TAUCLI](#TAUCLI)    Layer ice cloud optical thickness             nondimensional

  [TAUCLW](#TAUCLI)    Layer liquid cloud optical thickness          nondimensional
  -----------------------------------------------------------------------------------

### tavg3_3d_chm_Fe

ECS short name: **AT3FECHM**

ECS long name: MERRA IAU 3d Chem On Layer Edges

Characteristics: **Time averaged, 3D model levels, at [reduced FV
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **181**, levels: **73** (see
[Appendix D](#_Appendix_D:_Vertical_Structure))

Times : **1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT**

Size/day: *()* Mbytes

  ------------------------------------------------------------------------
  **Variable Name**     **Description**                        **Units**
  --------------------- -------------------------------------- -----------
  [MFZ](#MFZ)           Upward resolved mass flux              kg m-2 s-1

  [CMFMC](#CMFMC)       Upward moist convective mass flux      kg m-2 s-1

  PFLLSAN               Liquid large-scale plus anvil          kg m-2 s-1
                        precipitation                          

  PFILSAN               Ice large-scale plus anvil             kg m-2 s-1
                        precipitation                          

  PFLCU                 Liquid convective precipitation        kg m-2 s-1

  PFICU                 Ice convective precipitation           kg m-2 s-1

  [KH](#KH)             Total scalar diffusivity               m2 s-1
  ------------------------------------------------------------------------

### tavg3_2d_chm_Fx

ECS short name: **AT3FXCHM**

ECS long name: MERRA IAU 2d Chem

Characteristics: **Time averaged, single-level, at [reduced FV
resolution](#FVCoarse)**

Dimensions: longitude: **288**, latitude: **181** (see [Appendix
D](#_Appendix_D:_Vertical_Structure))

Times : **1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT**

  -------------------------------------------------------------------------
  Variable Name           Description                            Units
  ----------------------- -------------------------------------- ----------
  [PRECANV](#PRECANV)     Surface precipitation flux from anvils kg m-2 s-1

  [PRECCON](#PRECANV)     Surface precipitation flux from        kg m-2 s-1
                          convection                             

  [PRECLSC](#PRECANV)     Surface precipitation flux from        kg m-2 s-1
                          large-scale                            

  FRCLS                   Fractional area of large-scale         Fraction
                          precipitation                          

  FRCAN                   Fractional area of anvil precipitation Fraction

  FRCCN                   Fractional area of convective          Fraction
                          precipitation                          

  [PRECSNO](#PRECSNO)     Surface snowfall flux                  kg m-2 s-1

  TS                      Surface skin temperature               K

  [QV2M](#QV10M)          Specific humidity 2 m above            kg kg-1
                          displacement height                    

  [T2M](#T10M)            Temperature 2 m above displacement     K
                          height                                 

  [U10M](#U50M)           Eastward wind 10 m above displacement  mM s-1
                          height                                 

  [V10M](#V50M)           Northward wind 10 m above the          mM s-1
                          displacement height                    

  [PARDF](#PARDF)         Surface downward PAR diffuse flux      W m-2

  [PARDR](#PARDF)         Surface downward PAR beam flux         W m-2

  [NIRDF](#PARDF)         Surface downward NIR diffuse flux      W m-2

  [NIRDR](#PARDF)         Surface downward NIR beam flux         W m-2

  LWGNET                  Surfece net downward longwave flux     W m-2

  SWGNET                  Net surface downward shortwave flux    W m-2

  LWGDWN                  Surface downward longwave flux         W m-2

  SWGDWN                  Surface downward shortwave flux        W m-2

  [EVAP](#EVAP)           Surface evaporation                    kg m-2 s-1

  [HFLUX](#HFLUX)         Sensible heat flux (positive upward)   W m-2

  [GWETROOT](#GWETROOT)   Root zone soil wetness                 fraction

  [GWETTOP](#GWETROOT)    Top soil layer wetness                 fraction

  [CLDHGH](#CLDHIGH)      High-level (above 400 hPa) cloud       fration
                          fraction                               

  [CLDLOW](#CLDHIGH)      Low-level (1000-700 hPa) cloud         fraction
                          fraction                               

  [CLDMID](#CLDHIGH)      Mid-level (700-400 hPa) cloud fraction fraction

  [CLDTOT](#CLDHIGH)      Total cloud fraction                   fraction

  [PBLH](#PBLH)           Planetary boundary layer height above  m
                          surface                                

  PBLTOP                  Pressure at PBL top                    Pa

  PS                      Surface pressure                       Pa
  -------------------------------------------------------------------------

### tavg3_3d_chm_Nv 

ECS short name: **AT3NVCHM**

ECS long name: MERRA IAU 3d Chem On Layers

Characteristics: **Time averaged, 3D model levels, at [native
resolution](#FVCoarse)**

Dimensions: longitude: **540**, latitude: **361**, model levels: **72**
(see [Appendix D](#_Appendix_D:_Vertical_Structure))

Times : **1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT**

  ------------------------------------------------------------------------------
  **Variable Name**   **Description**                                **Units**
  ------------------- ---------------------------------------------- -----------
  MFXC                Eastward mass flux on C-Grid                   Pa m s-1

  MFYC                Northward mass flux on C-Grid                  Pa m s-1

  UC                  Eastward component of wind on C-Grid           m s-1

  VC                  Northward component of wind on C-Grid          m s-1

  [DTRAIN](#DTRAIN)   Detrainment cloud mass flux                    kg m-2 s-1
  ------------------------------------------------------------------------------

###  **tavg3_3d_chm_Ne** 

ECS short name: **AT3NECHM**

ECS long name: MERRA IAU 3d Chem On Layer Edges

Characteristics: **Time averaged, 3D model levels, at [native
resolution](#FVCoarse)**

Dimensions: longitude: **540**, latitude: **361**, model levels: **73**
(see [Appendix D](#_Appendix_D:_Vertical_Structure))

Times : **1:30, 4:30, 7:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT**

  ----------------------------------------------------------------------------
  **Variable Name** **Description**                                **Units**
  ----------------- ---------------------------------------------- -----------
  MFZ               Upward mass flux on C-Grid                     kg m-2 s-1

  [CMFMC](#CMFMC)   Upward moist convective mass flux              kg m-2 s-1

  [KH](#KH)         Total scalar diffusivity                       m2 s-1
  ----------------------------------------------------------------------------

### inst_3d_chm_Ne 

ECS short name: **AT3NECHM**

ECS long name: MERRA IAU 3d Chem On Layer Edges

Characteristics: **Instantaneous, 3D model levels, at [native
resolution](#FVCoarse)**

Dimensions: longitude: **540**, latitude: **361**, model levels: **73**
(see [Appendix D](#_Appendix_D:_Vertical_Structure))

Times : **0, 3, 6, 9, 12, 15, 18, 21 -GMT**

  ------------------------------------------------------------------------
  **Variable    **Description**                                **Units**
  Name**                                                       
  ------------- ---------------------------------------------- -----------
  PLE           Edge pressures                                 kg m-2 s-1

  ------------------------------------------------------------------------

# **Appendix F: Detailed Description of Output Variables**  {#appendix-f-detailed-description-of-output-variables .unnumbered}

## F.1 Three-dimensional Fields 

**CFLS,CFAN,CFCU:** The horizontal fractional cloud cover of each cloud
type for each layer. In the vertical, clouds are assumed to fill the
layer. The sum of these fractions may exceed one. See [CLOUD](#CLOUD)
for the single fraction used in the radiation calculations.

**CLOUD:** The horizontal fractional cloud cover for each layer. In the
vertical, clouds are assumed to fill the layer. This fraction is the
combination of the model's predicted large-scale and convective
fractions that is used for radiative purposes. See [CLDTOT](#CLDHIGH)
for a description of how these fractions are overlapped in the radiation
calculations.

**CMFMC:** The total vertical convective mass flux through levels
between model layers (edges), in kg m-2 s-1. This is produced by the
convection parameterization (RAS) and it includes the mass flux due to
all cloud types crossing the level. Constituent transport due to these
fluxes can be computed off-line as described in [DTRAIN](#DTRAIN)

**DELP:** Pressure thickness of model layers, in Pa. See [PLE](#PLE).
The layer mass is **DELP / 9.81** kg m-2.

**DDPDTANA**: Tendency of the layer's pressure thickness due to
analysis, in Pa s^-1^[]{#dqrccon .anchor}. The GSI analyzes the surface
pressure and this is the vertical distribution of that mass increment.

**DQRCON, DQRLSC, DQRANV:** The layer production rate of precipitating
condensate from convective, large-scale, and anvil clouds, per unit
horizontal area, in kg m-2 s-1. They include both liquid and frozen
precipitating condensate, but not the production of cloud condensates.

**DQVDTMST, DQLDTMST, DQIDTMST:** Tendency of vapor, liquid and ice
water due to moist processes, in kg kg-1 s-1. This includes the effects
of the convection parameterization (RAS) and all other effects from the
cloud microphysics and large scale and anvil precipitation schemes.

**DQVDTDYN:** Tendency of water vapor due to resolved dynamics, in kg
kg-1 s-1.

**DQVDTTRB:** Tendency of water vapor due to turbulence, including
surface evaporation,\
in kg kg-1 s-1.

**DTDTANA:** The analysis tendency introduced during the corrector
segment of the IAU cycle, in K s-1.

**DTDTDYN:** Temperature tendency due to dynamics, including the
spurrious frictional dissipation of kinetic energy by numerical
processes, in K s-1.

**DTDTFRI:** Temperature tendency due to the frictional dissipation of
kinetic energy by turbulence, including surface friction, in K s-1. It
does not include dissipation from gravity wave drag or the implicit
dissipation in the model's dynamics.

**DTDTGWD:** Temperature tendency due to the frictional dissipation of
kinetic energy by gravity wave drag, in K s-1.

**DTDTLWR, DTDTLWRCLR:** Temperature tendency due to terrestrial
(longwave) radiation for all-sky and clear-sky conditions, in K s-1.

**DTDTMST:** Temperature tendency due to moist processes, in K s-1.

**DTDTSWR, DTDTSWRCLR:** Temperature tendency due to solar (shortwave)
radiation for all-sky and clear-sky conditions, in K s-1.

**DTDTTOT:** The total diabatic temperature tendency for the model
layers, in K s-1 . It is the same as the sum
**DTDTFRI+DTDTGWD+DTDTLWR+DTDTSWR+DTDTMST+DTDTTRB,** and in the
long-term mean should balance [DTDTDYN](#DTDTDYN).

**DTDTTRB:** Temperature tendency due to turbulence, including surface
sensible heat flux, but not including the heating due to frictional
dissipation (see [DTDTFRI](#DTDTFRI)), in K s-1. Above the surface it
includes the diffusive effects due to the Louis and Lock turbulence
schemes (see [KH](#KH)).

**DTRAIN:** The total detrained convective mass flux into each model
layer, in kg m^-2^ s^-1^. This is produced by the convection
parameterization (RAS). The total entrainment mass, *E*, due to all
clouds crossing a layer can be computed from
$E = \delta_{Z}\text{CMFMC - DTRAIN}$, where
$\delta_{Z}\text{CMFMC } \equiv \text{  CMFMC}_{\text{L-1/2}} - \text{CMFMC}_{L + \text{1/2}}$.

**DUDTDYN, DVDTDYN:** Eastward (zonal) and northward (meridional) wind
tendency due to dynamics, in m s-2.

**DUDTGWD, DVDTGWD:** Eastward (zonal) and northward (meridional) wind
tendencies due to gravity wave drag, in m s-2.

**DUDTMST, DVDTMST:** Eastward (zonal) and northward (meridional) wind
tendencies due to moist processes, in m s-2. Currently this represents
the "cumulus friction" effect of mixing momentum in a conservative way,
using the convective mass fluxes from RAS.

**DUDTTRB, DVDTTRB:** Eastward (zonal) and northward (meridional) wind
tendencies due to turbulent processes, in m s-2. This includes surface
friction. Above the surface, it includes the diffusive effects due to
the Louis and Lock turbulence schemes (see [KM](#KH)).

**H**: Geopotential height, in m. It is simply the height,
$\frac{\phi}{g}$, interpolated linearly in $\text{log}(p)$from the
model's edge levels to the desired pressure level. The model's edge
heights are computed using the hydrostatic equation:
$\frac{1}{g}($PHIS +
c~P~$\sum_{l = L}^{\text{LM}}{}\theta_{v}\Delta P)$**,** where
$\Delta P$is the difference in
$\left( \frac{p}{p_{o}} \right)^{\kappa}$at the lower and upper edges of
layer $l$, and $\theta_{v}$ is the virtual potential temperature in the
layer.

[]{#KH .anchor}**KH, KM :** Turbulent diffusivity for heat and other
scalars and for momentum, in m2 s -1. This is defined at the layer
edges, beginning at the top, where it is zero. At the surface
([LM](#LM)+1) it is set .......... It includes the diffusive effects due
to the Louis and Lock turbulence schemes.

**MFX, MFY,** []{#MFZ .anchor}**MFZ:** The eastward and northward
pressure weighted velocity components, in Pa m2 s-1, and the vertical
component of the large-scale mass flux at the layer edges, in kg m-2
s-1. **MF\[X,Y\] =**
$\lbrack u_{c}\Delta y,v_{c}\Delta x\rbrack\delta_{z}p$ **,** where
$\lbrack u_{c},v_{c}\rbrack$ are the velocity components as defined by
the dynamical core on the Arakawa C grid and
$\lbrack\Delta y,\Delta x\rbrack = \lbrack a\Delta\phi,a\text{cos}(\phi)\Delta\lambda\rbrack$
are the meridional and zonal grid spacings, in meters.. These cannot be
computed from **UC** and **VC** and the pressures because the time
average of the product is done over every step taken by the core, so
that the following continuity equation is exactly satisfied.

$\frac{\partial(\text{DELP})}{\partial t}\text{ = } - \frac{1}{\text{AREA}}\lbrack\delta_{i}(\text{MFX})\text{ + }\delta_{j}(\text{MFY})\rbrack - {g\delta}_{k}\text{MFZ} + \text{DDPDTANA}$.

**OMEGA:** The kinematic vertical pressure velocity estimated by the
Finite-Volume dynamics. It is defined for the layers, not the edges. For
layer *l*, it is discretized vertically as
$w_{l} = \left( \overline{\frac{¶p}{¶t}} + \overline{\overset{\cdot}{h}\frac{¶p}{\text{¶h}}} \right)_{l} + (V\text{·Ñ}\overline{p})_{l}$,
where the pressure is defined at the layer edges and the overbar
indicates the average of the layer's upper and lower edges.

**PL:** The layer pressure defined as the average of the upper and lower
edge pressures, [PLE](#PLE)**,** in Pa (see [DELP](#DELP)).

**PLE:** The time-averaged pressure at the upper edge of a layer**.
PLE** = [PS](#PS) **+** $\sum_{l = L}^{\text{LM}}{}$[DELP](#DELP) ~l~.
This is the preferred way of obtaining edge pressures in
lcv-coordinates, rather than relying on the model's hybrid-sigma
coordinate system (i.e., the **AK**s **A**~k~s and **BK**s**B**~k~s),
which may change in future releases.

**PFLCU, PFICU, PFLLSAN, PFILSAN:** Downward flux of precipitating
liquid and ice condensate from convective and combined anvil and
large-scale clouds, in kg m-2 sec-1.

**PV**: The Ertel's potential vorticity, approximated as
$g(V + f)\frac{¶\text{ln}(q_{v})}{¶p}$, in m2 kg-1 sec-1. Here, $V$is
the vertical component of relative vorticity,, $f$is the Coriolis
parameter, and $q_{v}$ is the virtual potential temperature., Note the
definition in terms of entropy instead of potential temperature and the
neglect of the part associated with the horizontal components of
vorticity.

[]{#QL .anchor}**QL, QI:** The liquid and ice cloud condensate mixing
ratios. These are grid-averaged, not in-cloud, values. They include
condensate produced by both large-scale condensation and that detrained
from convective clouds. They *do not* include the condensate within
convective updrafts.

**QLLS, QILS, QLAN, QIAN, QCCU:** The liquid and ice cloud condensate
mixing ratios. These are grid-averaged, not in-cloud, values. These are
the separate contributions from ice and liquid, anvil and large-scale
clouds predicted by the model. **QCCU** is a diagnostic estimate of the
total condensate in convective updrafts; it does not enter any model
calculations, but may be useful in comparing with satellite data.

**REEVAP:** Total re-evaporation of all precipitating condensates, in kg
m-2 sec-1.

[]{#TAUCLI .anchor}**TAUCLI, TAUCLW:** Each layer's total cloud optical
thickness in the visible (0.40 to 0.69 micron band), for ice clouds and
liquid water clouds, respectively.

**TAUIR:** Total (liquid + ice) in-cloud optical thickness in the
infrared (540-980 cm-1 band).

## F.2 Two-dimensional Fields 

**ALBEDO:** The time-averaged surface albedo defined as the ratio of the
time-averaged incident and reflected fluxes and should satisfy **ALBEDO
=** [SWGDWN](#SWGDWN)**/(SWGDWN-**[SWGNET](#SWGNET)**).** At night
points, this is set to [\_FillValue](#FillValue).

**ALBVISDF, ALBVISDR, ALBNIRDF, ALBNIRDR:** The direct (beam) and
diffuse albedos for the "visible" (the GCM uses the same albedos for the
UV and the PAR spectral regions----0.175 to 0.69 microns) and the
"near-infrared" (0.69 to 3.85 microns). These are simply time-averaged
surface properties, but are defined only where there was daylight at the
point during the averaging interval. They do not correspond to the
ratios of time-averaged incident and reflected fluxes.

**BSTAR:** The bouyancy scale of the surface layer in m s-2. It is
defined as $\frac{g}{\rho_{a}u^{}}\frac{F_{S_{v}}}{c_{P}T_{a}}$, where
$\rho_{a}$ is the near-surface air density ([RHOA](#RHOA)) and $T_{a}$
the near-surface air temperature, $u^{}$ is the friction velocity
([USTAR](#USTAR)), and $F_{S_{v}}$ is the surface flux of virtual dry
static energy in W m-2, $F_{S_{v}}$ = ([HFLUX](#HFLUX) +
$(1 - e)$[EFLUX](#EFLUX)**).**

**CLDHGH, CLDMID, CLDLOW, CLDTOT:** High, middle, low, and total
cloudiness. The high, middle, low level values correspond to the three
superlayers used in the GEOS-5 solar and terrestrial radiation
parameterizations. Clouds within these superlayers are assumed to be
maximally overlapped. High clouds are those occuringoccurring above
roughly 400 hPa and low clouds are those occuringoccurring below 700
hPa, although the groupings are done ion the model's terrain following
coordinate and so the bounding pressures will differ significantly from
these values over high topography. The model assumes that the overlapped
between the superlayers is random, and the total cloudiness uses this
assumption. The total cloudiness is computed each time the radiation is
called, and so its time mean cannot be exactly constructed from the
time-mean cloudiness in the three super layers.

**CLDPRS, CLDTMP:** The cloud-top temperature and pressure of the first
cloud "seen" from above at 540-980 cm-1 in the infrared. Clouds are
visible if in-cloud (not layer) optical thickness in this band exceeds
0.14, independent of their fractional areal coverage.

**DISPH:** Surface displacementy height in meters. See the description
of the neutral drag coefficient.

**DTG:** Change in surface temperature during the averaging interval in
deg K. This refers to the area-mean surface temperature under each
atmospheric column, and so, it may contain contributions from land-,
water-, and ice-covered parts of the grid box.

**EFLUX:** The upward turbulent flux of latent heat flux at the surface,
in W m-2. This includes the latent heat relative to liquid of all
turbulent moisture fluxes through the surface (see [EVAP](#EVAP)**)**.

**EMIS:** The surface emissivity. This is areally averaged over all
surface tiles and is constant in time.

**EVAP:** Evaporation in kg m-2 s-1., a Actually the total turbulent
flux of water vapor at the surface, including fluxes from transpiration,
sublimation, and surface condensation. The turbulent flux of could cloud
condensate (fog) is assumed to be zero. .

**FRLAKE, FRLAND, FRLANDICE, FROCEAN:** GEOS-5 uses these four primary
surface types and these are their fractions under each atmospheric
column.

**GRN:** The "greenness" or fraction of transpiring leaves averaged over
the land areas of a grid box. If there are several vegetation tiles
within the land part of a grid box, the average is **LAI** weighted.
**GRN** is set to [\_FillValue](#FillValue) where [FRLAND](#FRLAKE) = 0.

**GWETROOT, GWETTOP:** The degree of saturation or "wetness" in the
root-zone (top meter of soil) and top soil layer (top 2 cm). These are
defined as the ratio of the volumetric soil moisture to the porosity.
These quantities are set to [\_FillValue](#FillValue) where
[FRLAND](#FRLAKE) = 0. Elsewhere they are time-mean and area-mean values
of the ratio over the land part of the grid box.

**HFLUX:** The upward turbulent sensible heat flux at the surface, in W
m-2.

**LAI:** The areal average of the leaf-area index over all land parts of
a grid box. **LAI** is set to [\_FillValue](#FillValue) where
[FRLAND](#FRLAKE) = 0.

**LWGDWN, LWGDWNCLR:** The all-sky and cloud-free fluxes of downwelling
terrestrial (longwave) radiation at the surface in W m-2.

**LWGNET:** The net downward flux of terrestrial (longwave) radiation at
the surface in W m-2. This is identical to **LWGDWN- LWGUP.**

**LWGUP:** The all-sky upwelling terrestrial (longwave) radiation at the
surface, in W m-2. This includes both the surface emmission and the
reflection..

**LWI:** A Land-Water-Ice mask provided for backward compatibility with
the GEOS-4 product. It is 1 over continental areas, 0 over open ocean,
and 2 over sea-ice covered ocean. Since in GEOS-5 a grid box can be a
combination of these, continental areas are arbitrarily defined as those
where [FRLAND+FRLANDICE](#FRLAKE)**\>=≥0.5.** The remaining grid boxes
are designated as sea-ice if the ice cover exceeds 50%; otherwise they
are open (ice-free) ocean.

**LWTUP, LWTUPCLR:** Outgoing longwave (terrestrial) radiation at the
top of the model's atmosphere (currently 0.01 hPa) for all-sky and
clear-sky conditions, in W m-2.

**PARDF, PARDR, NIRDR, NIRDF:** Incident flux of of diffuse and direct
PAR and NIR at the surface, in W m-2. PAR is defined as the solar
radiation between 0.4 and 0.69 microns. NIR is the solar near- infrared,
defined as the solar radiation between 0.69 and 3.85 microns. These are
scaled so that the total solar flux is accounted for in a band from
0.175 to 3.85 microns.

**PBLH:** Height above the surface of the planetary boundary layer in
meters. This is obtained diagnostically at every time step from the heat
diffusivity in the model layers. It is defined as the height of the
lowest layer in which the diffusivity falls below 2 m2 s-1. Where no
layer is above this value, the boundary layer height is set to the
height of the surface layer.

**PHIS:** The surface geopotential, $\text{gh}_{s}$, in m-2 s-2. Here
$h_{s}$is the height of the surface above sea level, and $g$ m s-2.

**PRECANV, PRECLSC, PRECCON:** the large-scale precipitation from
anvils, the non-anvil large-scale precipitation, and the convective
precipitation, in kg m-2 s-1. These include both rainfall and snowfall.

**PRECTOT:** The total precipitation (**PRECANV+PRECLSC+PRECCON**) in kg
m-2 s-1.

**PRECSNO:** The "snowfall" includes all frozen precipitation, in kg m-2
s-1.

**PS:** The surface pressure in Pa. The height at this pressure can be
obtained from the surface geopotential [PHIS](#PHIS)**.** The total
atmospheric mass is $\frac{1}{g}$**PS** kg m-2.

**QV10M, QV2M:** The specific humidity at 10 m and 2m above the
displacement height ([DISPH](#DISPH)) in the surface layer, in kg kg-1.

**REEVAP:** Total re-evaporation of precipitating condensate, in kg m-2
s-1. Includes evaporation and sublimation and is the total contribution
from all three cloud types.

**RH**: The relative humidity. This is approximated by q/qs where q is
the specific humidity and qs is its saturated value. The saturated value
is computed over liquid for temperatures above 273.16K and over ice for
temperatures below 253.16K. At intermediate temperatures the values over
liquid and ice are averaged with weights that vary linearly with
temperature.

**RHOA:** Surface air density in the lowest model layer, in kg m-3. This
is the density used in bulk formulasformulae.

**SGH**: The isotropic standard deviation of topography used for the
subgrid-scale gravity wave drag parameterization, in m. Currently the
effect of orographic gravity waves is independent of the angle between
the flow and the orographic ridges, so only this isotropic component is
relevant.

**SLP:** The surface pressure reduced to sea level, in Pa. Over
topography the reduction is done by assuming a lapse rate of 6.5 K km-1
from a free atmospheric temperature, which is currently taken as the
lowest model layer above 150 hPa above the surface.

**SNOMAS:** The mass of snow per unit of ice-free land area
([FRLAND](#FRLAKE)), in kg m-2. In grid boxes with no land it is set to
[\_FillValue](#FillValue)**.** Over other land areas it represents an
average over the non-glaciated part.

**SNODP:** The geometric snow depth in meters. This accounts for packing
and aging of the snow.

[]{#SWGDN .anchor}**SWGDN, SWGDNCLR, SWTDN**: Incident solar radiation
(0.175 to 3.85 microns) at the surface for all-sky and clear-sky
conditions and the top of the atmosphere, in W m-2. Since we do a single
atmospheric radiative transfer calculation in a grid box, we assume the
incident radiation is the same for all surface tiles within the box.
MERRA uses a solar constant of 1365 W m-2.

[]{#SWGNT .anchor}**SWGNT, SWGNTCLR, SWGNTCLN, SWGNTCLRCLN, SWTNT,
SWTNTCLR, SWTNTCLN, SWTNTCLRCLN:** Net downward flux of solar radiation
at the surface and the top of the model's atmosphere (0.01 hPa) averaged
over all land tiles for all-sky, clear-sky, clean-sky, and
clear-clean-sky conditions, in W m-2. The term "clean-sky" refers to
fluxes computed with the aerosol loading set to zero.

**TAUGWX, TAUGWY:** The eastward (zonal) and northward (meridional)
components of the atmospheric stress on the surface due to atmospheric
gravity wave drag, in N m-2.

**TAUHGH, TAUMID, TAULOW, TAUTOT:** Total cloud optical thickness in the
0.40 to 0.69 micron band for the high, middle, and low cloud regions
(see [CLDHGH](#CLDHIGH)**)** and for the entire column.

**TAUX, TAUY:** The eastward (zonal) and northward (meridional)
components of the atmospheric frictional stress on the surface, in N
m-2.

**TO3 :** The vertically integrated ozone, in Dobson units.

**TPW, TQV:** The vertically integrated water vapor in the column, in kg
m-2.. These are synonyms.

**TQL, TQI:** The vertically integrated liquid and ice water in the
column, in kg m-2.

**TROPP:** The tropopause pressure in Pa. The tropopause pressure is
defined as the pressure where the function
$\alpha T(p) - \text{log}_{\text{10}}p$ reaches its first minimum above
the surface. Here $\alpha = 0\text{.}\text{03}$ and $p$ is in hPa. If no
minimum is found between 550 hPa and 40 hPa, **TROPP** is set to
[\_FillValue](#FillValue)**.**

**TROPQ:** The tropopause specific humidity in kg kg-1. The tropopause
is defined as in **TROPP.**

**TROPT:** The tropopause temperature in K. The tropopause is defined as
in **TROPP.**

**TSRAD:** The area weighted skin temperature of all surface tiles in a
grid box, in K. This is the skin temperature used for radiation.

**TTO3:** The vertically integrated ozone in the troposphere, in Dobson
units. The troposphere is defined as all levels below [TROPP](#TROPP)**.
TTO3** and **TROPP** are computed at every time step and averaged
separately.

**U50M, U10M, U2M, V50M, V10M, V2M:** The eastward and northward wind
component at 50m, 10 m, and 2m in the surface layer, in m s-1. The 2m
and 10m values are defined above displacement height ([DISPH](#DISPH)),
the 50m values are above the surface.

**USTAR:** The surface friction velocity,
$u^{} = \sqrt{\frac{|t|}{\rho_{a}}}$, in m s-1. This mean quantity is
formed by doing the the areal average over the surface tiles in a grid
box instantaneously to $|t|$ , and the time averaging on $u^{}$ itself.
It is thus not exactly what would be obtained from [TAUX,
TAUY](#TAUX)**,** and [RHOA](#RHOA)**.**

**Z0H:** The surface roughness for heat, in m.

**Z0M:** The dynamic surface roughness, in m.

# 

# Appendix G: Surface Representation

In GEOS-5 the surface below each atmospheric column consists of a set of
tiles that represent various surface types. Tiles can be of four
different types: Ocean, Land, Ice, Lake, as illustrated in the figure.
In each grid box a single Ice tile represents those areas covered by
permanent ice. Similarly a single Lake tile represents continental areas
covered permanently by water. Other continental areas (non Lake or Ice)
can be further subdivided into tiles that represent parts of the grid
box in different hydrological catchments, defined according to the
Pfaffsteter (19xx) system. Each of these is, in turn, divided into
subtiles (not shown in figure) that represent the wilted, unsaturated,
saturated, and snow-covered fractions of the tile. These fractions vary
with time and are predicted by the model based on the hydrological state
of the catchment and its fine-scale topographic statistics. Details of
the land model, including the partitioning into subtiles, can be found
in Koster et al. (2001). The Ocean tile can be divided into two subtiles
that represent the ice-covered and ice-free parts of the ocean part of
the atmospheric grid box. The fractional cover of these subtiles also
varies with time. In MERRA, the fractional cover of sea ice and the
ocean surface temperature are specified from the climatology of Reynolds
and Smith (19xx).

![](media/image3.png){width="4.03125in" height="3.5416666666666665in"}

# References 

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assimilation using incremental analysis updates. *Mon. Wea. Rev.*,
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Derber, J. C., R. J. Purser, W.-S. Wu, R. Treadon, M. Pondeca, D.
Parrish, and D. Kleist, 2003: Flow-dependent Jb in a global grid-point
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deWitt, Shaun, 1996: Writing HDF-EOS Grid Products for Optimum
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Gross, C., 1997: B.0 Earth Science Data Model for the ECS Project.
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Pfaffsteter

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Reynolds and Smith or Hadley??

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# Web Resources

[]{#APPENDIXC .anchor}GMAO web site: <http://gmao.gsfc.nasa.gov/>

GMAO Operations page: <http://gmao.gsfc.nasa.gov/operations/>

CF Standard Description:
<http://www.cgd.ucar.edu/cms/eaton/cf-metadata/CF-current.html>

CF Standard Names:
<http://www.cgd.ucar.edu/cms/eaton/cf-metadata/standard_name.xml>

NCSA, 1999: The NCSA HDF Home Page. <http://hdf.ncsa.uiuc.edu/>

NASA, 1999: HDF-EOS Standards.
[http://hdfeos.gsfc.nasa.gov/](http://hdfeos.gsfc.nasa.gov/ )

[]{#_5._File_Naming_Conventions .anchor}