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**CFS Retrospective Forecasts :**

**Time Series of Daily Data**

**in the EMC/NCEP *CFS* public server**

**Catherine Thiaw and Suranjana Saha**

Environmental Modeling Center, NCEP/NWS/NOAA

Email for all correspondence : <cfs@noaa.gov>

Revised: February 27, 2007

Daily time series of 30 commonly used atmospheric variables from the
retrospective forecasts of the NCEP Climate Forecast System (Saha et al,
2005) have been archived to the EMC CFS public server in GRIB format.
These include forecasts from all 15 members initialized in each calendar
month of the year, covering a period of 24 years from 1981-2004, and an
ensemble mean of the 15 members. The forecast lead is zero to 8 months.
For a subset of variables, the verifying observations (from Reanalysis-2
and GODAS) are available .

Daily time series of 13 oceanographic variables are also variables, out
to 45 days forecasts.

*PLEASE BE ADVISED THAT THE TWICE DAILY OUTPUT DATASETS DESCRIBED BELOW
ARE NOT CHECKED FOR TECHINCAL QUALITY. USERS MAY WANT TO PERFORM SOME
QUALITY CONTROL ON THE DATA BEFORE USE, OR ELSE USE THEM AT THEIR OWN
RISK.*

*THIS DATA IS NOT CALIBRATED (BIAS CORRECTED) IN ANYWAY. IT IS STRONGLY
RECOMMENDED THAT USERS PERFORM SOME CALIBRATION ON THE FORECAST DATA
BEFORE USING IT IN A PREDICTIVE ENVIRONMENT.*

For this purpose, we have constructed forecast and observed daily
climatologies for selected variables, for both the mean and standard
deviation. Section 4 deals with these datasets and its application.

[Where to find the time series of the daily data ?]{.underline}

The time series for each variable can be accessed by 2 methods:

-   by an **anonymous ftp login into cfs.ncep.noaa.gov, then go to the
    pub/daily/glb directory**

-   by downloading the data from a web browser :
    <http://cfs.ncep.noaa.gov/daily/glb>

***Please be advised that we will not be providing any more
retrospective forecasts beyond 2005. For maintaining a continuing
history of the CFS, please start downloading the two operational CFS
forecasts for your archives as soon as possible***.

**[References]{.underline}**

S. Saha, S. Nadiga, C. Thiaw, J. Wang, W. Wang, Q. Zhang, H. M. van den
Dool, H.-L. Pan, S. Moorthi, D. Behringer, D. Stokes, M. Pena, S. Lord,
G. White, W. Ebisuzaki, P. Peng, P. Xie , 2006 : The NCEP Climate
Forecast System. Journal of Climate, Vol. 19, No. 15, pages 3483-3517.

1.  **Twice Daily Data**

Twice daily data (0 and 12 UTC) time series of 30 variables are
available in the CFS server. The variables are stored in a regular 2.5
degrees lat/lon grid in GRIB format. They are:

  -----------------------------------------------------------------------
  144 x 73 (2.5 degrees)

  **z1000**: geopotential at 1000 hPa

  **z850**: geopotential at 850 hPa

  **z700**: geopotential at 700 hPa

  **z500**: geopotential at 500 hPa

  **z200**: geopotential at 200 hPa

  **mslp**: mean seal level pressure

  tmp2m: temperature at 2meters

  prate: total precipitation. rate

  pwat: precipitable water

  ps: surface pressure

  shtfl: sensible heat flux

  lhtfl: latent heat flux

  ulwtop: upward long wave radiation at the top of the atm

  ulwsfc: upward long wave radiation at the surface

  uswtop: upward short wave radiation at the top of the atm

  uswsfc: upward short wave radiation at the surface

  dswsfc: downward short wave radiation at the surface

  dlwsfc: downward long wave radiation at the surface

  wnd10m: zonal and meridional wind at 10meters

  wndstr: zonal and meridional wind stress at the surface

  **wnd850**: zonal and meridional winds at 850 hPa

  **wnd200**: zonal and meridional winds at 200 hPa

  **sfvp200**: strean function velocity potential at 200 hPa

  **sfvp850**: stream function velocity potential at 850 hPa
  -----------------------------------------------------------------------

For each variable, the complete dataset includes all 15 members
initialized in each calendar month of the year, covering a period of 24
years from 1981-2004. It also includes an ensemble mean of the 15
members. The verifying observations (from Reanalysis-2) are located in a
subdirectory R2 for selected variables (in **bold** in the above table).
The forecast lead is up to 7140 hours.

[How to read the twice daily data:]{.underline}

Each variable (example: z500) is a subdirectory that contains 12
subdirectories corresponding to the calendar month (jan to dec). In each
monthly directory, there are 24 subdirectories, one for every year of
the 24 years (1981-2004) of the CFS retrospective forecasts. These last
subdirectories contain the daily data laid out as follows:

variable.mxx.month.year.cfs.data

variable.ensm.month.year.cfs.data

where xx represents the member : 01 to 15 , month and year are the month
and year of the initial condition of the forecast (zero lead).

Example of members for Sep 1990:

m01-m05 : 9 - 13 Aug 1990

m06-m10 : 19 - 23 Aug 1990

m11-m12 : 30 - 31 Aug 1990 (last 2 days of the previous month)

m13-m15 : 1 - 3 Sep 1990

ensm : Ensemble mean of all 15 members

Example for geopotential time series at 500 hPa, for September 1990:

In the server: /pub/daily/glb/z500/sep/1990/

Contains 16 files:

Example for September:

1\. z500.m01.sep.1990.cfs.data : member 1

2\. z500.m02.sep.1990.cfs.data : member 2

3-14. z500.m..... : etc., etc.

15\. z500.m15.sep.1990.cfs.data : member 15

16\. z500.ensm.sep.1990.cfs.data : ensemble mean of the 15 members

Each file contains the twice daily data (0 and 12 UTC) up to 7140 hours.

So
<http://cfs.ncep.noaa.gov/daily/glb/z500/sep/1990/z500.m03.sep.1990.cfs.data>
contains the 500 hPa geopotential forecast daily ouput from initial
conditions of 11 August 1990

Yearly observation files (from Reanalysis-2) for some variables (in
**bold** in the above table) are located in a subdirectory R2 under the
variable name directory: for example for z500, we have
/pub/daily/glb/z500/R2/z500.year.obs.data, where year varies from 1981
to 2004

**2**. **Once Daily CFS Sea Surface Temperature Forecast Data**

Once daily sea surface temperature GRIB data (csstf) in a regular 1x1
degree is available in same time series format. The data is located in:
http://cfs.ncep.noaa.gov/daily/glb/csstf or **by anonymous ftp login to
cfs server, in the pub/daily/glb/csstf directory**

**3. Once Daily CFS Oceanographic Data**

Once daily oceanographic GRIB data (13 variables) in a regular 2x1
degree are available in same time series format as above. The data is
available only for the first 45 days of the integration. The data is
located in:
[http://cfs.ncep.noaa.gov/daily/ocndaily](http://cfs.ncep.noaa.gov/cfs/daily/ocndaily)
or **by anonymous ftp login to cfs server, in the pub/daily/ocndaily
directory**

  -----------------------------------------------------------------------
  180 x 139 (2x1 degree)

  dt2.5c: depth of the 2.5C isotherm in the ocean

  dt5c: depth of the 5C isotherm in the ocean

  dt10c: depth of the 10C isotherm in the ocean

  dt15c: depth of the 15C isotherm in the ocean

  dt20c: depth of the 20C isotherm in the ocean

  dt25c: depth of the 25C isotherm in the ocean

  dt28c: depth of the 28C isotherm in the ocean

  oceansild: ocean surface isothermal layer depth

  oceanmld: ocean mixed layer depth

  oceanheat: ocean heat content

  oceansst: ocean temperature at 5m depth

  oceanslh: sea level height

  oceantchp: ocean tropical cyclone heat potential
  -----------------------------------------------------------------------

**4. How to download and apply the climatology to the retrospective
forecasts:**

These datasets are available at the CFS website and can be accessed by 2
methods:

-   by an **anonymous ftp login into cfs.ncep.noaa.gov**,

> **then go to the following directory:
> pub/cfs/daily/climatology/\$var/\$type**,

where var is variable and type is meanf (forecast mean) or sd (standard
deviation)

-   by downloading the data from a web browser :
    <http://cfs.ncep.noaa.gov/dailyclim>

Please match the ***month*** (mm) and ***day*** (dd) of the initial
condition of the real time operational forecast with its counterpart in
the daily climatology.

An example:

For the retrospective forecast:

<http://cfs.ncep.noaa.gov/daily/glb/z500/sep/1990/z500.m03.sep.1990.cfs.data>

which contains the 500 hPa geopotential forecast daily ouput from
initial conditions of 11 August 1990, the corresponding forecast mean
climatology can be found in:

<http://cfs.ncep.noaa.gov/dailyclim/z500/meanf/z500.08.11.mean.clim.daily>

which needs to be subtracted from the retrospective forecast to get a
bias-corrected forecast anomaly, and the standard deviation climatology
can be found in:

<http://cfs.ncep.noaa.gov/dailyclim/z500/sdf/z500.08.11.sd.clim.daily>

This is what the bias corrected forecast (obtained in the previous step)
needs to be divided by, in order to get the standardized forecast
anomaly.

Climatologies from the observations (R2) were also computed:

<http://cfs.ncep.noaa.gov/dailyclim/z500/R2/z500.R2.mean.data>

which needs to be subtracted from the observation data to get a
bias-corrected observation anomaly, and the standard deviation
climatology can be found in:

[http://cfs.ncep.noaa.gov/dailyclim/z500/R2/z500.R2.sd.data](http://cfs.ncep.noaa.gov/dailyclim/z500/R2/z500.R2.sd.data%0D)

[This is what the bias corrected observation (obtained in the previous
step) needs to be divided by, in order to get the standardized
observation
anomaly.](http://cfs.ncep.noaa.gov/dailyclim/z500/R2/z500.R2.sd.data%0D)

For further information on the construction of these climatologies and a
list of the variables, please see:
<http://cfs.ncep.noaa.gov/cfs.daily.climatology.doc>