# Presentation: 200382

## <number>

***S. W. Bidwell, S. Yuter,****** (1)****** E. A. Smith, W. J. Adams, G. M. Flaming, D. F. Everett, and G. M. Skofronick-Jackson******(2)***
***NASA GSFC, Greenbelt, MD***
***  ******U. Wash., Seattle, WA***
***  ******UMBC, GESTC, Greenbelt, MD***
***IGARSS 2002, Toronto***
***June 24-28, 2002 ***

*Global Precipitation Measurement*

*Steven Bidwell / Code  556.0*
*bidwell@agnes.gsfc.nasa.gov*
*Goddard Space Flight Center*

## Ground Validation

_**Outline:**_
**Status**
**Overview**
**Subprograms**
**Fixed GV Sites:  Supersites, Regional Rain Gauge**
**	****Networks**
**Error Characterization:**
**Bias Removal (Systematic Error)**
**Error Covariance (Random Error)**
**Conclusions**

## Ground Validation Status

_**GV Planning to Date:**_
_**[http://](http://gpmscience.gsfc.nasa.gov/)**__**[gpmscience.gsfc.nasa.gov](http://gpmscience.gsfc.nasa.gov/)**__**[/](http://gpmscience.gsfc.nasa.gov/)**_
_**[http://](http://gpm.gsfc.nasa.gov/science.html)**__**[gpm.gsfc.nasa.gov/science.html](http://gpm.gsfc.nasa.gov/science.html)**_
**Nine science themes  and associated working groups within GPM.  “Ground Validation Working Group” was formed last year.  GV Working Group is led by Drs. Sandra Yuter and Bob Houze of the University of Washington.**
**First GV workshop was held on February 6-8, 2002 at the U. Wash. in Seattle.  **
**“****GV Science Implementation Plan” is nearly complete.  It will be compiled with the other eight science themes into a single plan.**
**Research opportunities available through an upcoming NASA Research Announcement (NRA): “Research Opportunities for Precipitation Measurement Missions.”**

## Ground Validation Overview

_**Goals of Ground Validation**_
**(from Draft Science Plan)**
_**Evaluate**_**:  Quantifiable estimates on the quality of satellite precipitation products in terms of systematic and random error.**
_**Diagnose**_**:  Ascertain causes of errors within satellite products.**
_**Improve:**_** Improvement of satellite algorithms and retrievals by refinement of physical assumptions and underlying models (e.g. cloud resolving models, radiative transfer equations).**

## Ground Validation Overview

_**Ground Validation Clients / Customers:**_
**(1)****	****Algorithm Developers**
**(2)****	****Data Assimilation Specialists**
**(3)****	****Climate Researchers**
**(4)****	****Ground Validation Scientists**

## Ground Validation Overview

_**External Instrument Calibration:  Parallel Effort with GV**_
**External Instrument Calibration includes...**
**Ground-based, active radar calibration for the Dual-frequency Precipitation Radar (DPR) aboard the core satellite.**
**‘****Vicarious’ radiometer calibration (i.e. spacecraft intersections).  The core satellite with its radar + radiometer will be used as a transfer standard.**
**Stable Earth surface, ocean surface, ice surface conditions**
**Others?**

## Vicarious Calibration:  
Core/DMSP-F18 Calibration Opportunities
(1-Minute Separation)
June 2002

***Core/DMSP-F18 Calibration Opportunities***
***(1-Minute Separation)***
***June 2002***

*Ground Validation Overview*

## Ground Validation Overview

_**Ground Validation Subprograms:**_
**Ground Validation is divided into two subordinate **
**programs:**
_**Routine**_** Product Program**
_**Focused**_** Measurement Program**

## Ground Validation Overview

_**Routine Program:**_
**Multi-year, continuous, observation program ****	****overlapping with the satellite operational period.**
**Routine observations will be conducted from fixed GV ****	****sites located around the globe.**
**Produces near real-time GV products on regular ****	****schedule. **
**Products delivered the Precipitation Processing System ****	****(the successor to  TSDIS, TRMM Science Data and ****	****Information System)**

## Ground Validation Overview

_**Focused Program: (‘Field Campaigns’) **_
**Addresses specific GPM algorithm and model validation needs.**
** ****Complements geography and climatology missed by fixed GV sites.**
**Experiments may involve aircraft and other observational platforms and may be co-located at a fixed GV site.**
**Findings / results are delivered directly to the GPM Science Team and not to a project functional element.**

## Ground Validation Overview

_**Routine Program :  **_
**Fixed ground sites are termed ****Supersites**** and ****Regional Rain **
**	****Gauge Networks**
**Sites selection will represent a diversity of geographic and **
**	****climatic regimes.**
**Of the two components, Supersites are the more complex and critical ****	**
**	****GV component. Some Supersites may include a Regional Rain Gauge **
**	****Network.**
**Regional Rain Gauge Networks will typically span a scale of ~ 250 km**
**	****with inter-gauge spacing of ~ 50 km. (sometimes termed “Mesonets”)**
** **

## Ground Validation Overview

_**GV Sites Measurement Objectives:**_
**Determination of minimum detectable surface precipitation rate of the satellite instrumentation.**
**	****Determination of the spatial pattern of surface precipitation intensity.**
**Generation of a quantitative estimate of surface precipitation intensity.**
**Classification of precipitation in 3 dimensions into categories such as rain, snow, mixed, and graupel/hail.**
**Classification of precipitation structure (e.g. stratiform, convective).**

## Ground Validation Overview

_**Driving Requirements on the ‘Routine’ GV Program:**_
**NASA will provide two Supersites**
**NASA is pursuing partners for up to eight additional Supersites**
**NASA will provide one Regional Rain Gauge Network**
**NASA is pursuing partners for up to five additional Regional Rain**
**	****Gauge Networks**
**Supersites operational in November 2005, i.e. two years prior to core**
**	****satellite launch**

## Ground Validation Overview

_**Supersite Regional Regimes:**_
**Tropical Open-Ocean (e.g. Kwajalein)**
**Mid-Latitude Open-Ocean **
**	****(no location identified)**
**	****addressed by Focused Program**
**Tropical Continent (e.g. Brazil)**
**Mid-Latitude Continent (e.g. Continental U.S.)**

**Extratropical Baroclinic**

## Ground Validation Overview

- Japan

- South Korea

- EC

- Brazil

- England

- NASA KSC

- NASA Land

- Canada

- Taiwan

- ARM/UOK

- Supersite

- Regional Raingauge
- Network

- Supersite & Regional
- Raingauge Network

- North Europe BALTEX

- NASA Ocean

_**Potential Supersites and Regional Raingauge Networks**_

## Ground Validation Error Characterization

- 150 km

**Triple Gauge Site**
- (3 Economy Scientific Gauges)

**Single Disdrometer/**
**Triple Gauge Site**
- (1 High Quality-Large Aperture/
- 2 Economy Scientific Gauges)

- 150 km

**Low Resolution Domain **
- 100-Gauge Site, Centered on Multi-Parameter Radar

- 5 km

**High Resolution Domain**
- 50-Gauge Site, Center-Displaced with
-    Matched Radar / Radiometer                                                                        	[ 14, 35 / 10, 19, 22, 37, 85 GHz ]
-    S-/X-band Doppler Radar Profilers
-    Cloud Radar Profiler

**DELIVERY**

**Supersite Template**

**GV Products**
- (1)  Error Biases & Bias Uncertainties
- (2)  Error Structures / Error Covariances
**GV Product Customers**
- (1)  Data Assimilation Specialists
- (2)  Climate Diagnosticians
- (3)  Algorithm Specialists

- Data Analysis Facility

**Legend**

- Multi-Parameter Radar

-  Matched Dual Freq. Radar &
-  Multi-Channel Radiometer
-  S-/X- Band Radars / Profilers
- Cloud Radar Profiler

- Meteorological Tower &
- Sounding System

- Site Scientist (3)

- Technician (3)

- {

## Ground Validation Error Characterization

_**Instrument:**_
**Scanning, research-quality, ****	****Doppler radar.**
**(2) Dense network of research-quality ****	****rain gauges and various ****	****disdrometers.**
**(3)****	****Matched-beam  radar / radiometer ****	****equivalent to the GMI and DPR. **
**Zenith-pointing Doppler ****	****precipitation and cloud profiling ****	****radar.**
**(5)****	****Meteorological tower equipped for ****	****measurement of surface properties.**

_**Rationale:**_
**Precipitation spatial/temporal structure (used for random error characterization)**
**Precipitation surface structure          (used for random error characterization)**
**Core satellite retrieval constraint     (used for bias characterization)**
**Drop size distribution estimation **
**Cloud profiles for models and Ka-band attenuation**
**Surface emission information for satellite retrieval constraint**

_**Supersite Instrument Complement:**_

**_____________________________________________________**

**_____________________________________________________**

**_____________________________________________________**

**_____________________________________________________**

## Ground Validation Error Characterization

_**Two Supersite Error Characterization ‘Deliverables’:**_
**“****Bias Reports”**
**	****Provides an estimate of systematic error**
**(2)****	****“Regional Error Covariance Expansion Rules”**
**Method of providing random error and random error space/time structure**
**	**

## Ground Validation Error Characterization

_**GV Bias Estimation Technique:**_
***Proposed Supersite Instrument:***
**Dual-frequency radar and multi-channel radiometer with**
** ****	****frequencies and ****	****channels identical to that of the GPM core**
** ****	****instrumentation.**
***Proposed Measurement:***
**Observe overpass events (w/ coincident precipitation) from both a **
**	****space and ground-based perspective.**
***Proposed Bias Retrieval:***
**Ground-Based Z and T****B**** combined with Space-Based Z and T****B**** to **
**	****provide a more accurate retrieval from which bias is found.**

## Ground Validation Error Characterization

_**Bias Reports**_**:**
**Requires that satellite rainfall retrievals be sent to the ****	****Supersites for comparison purposes.  **
**Updated weekly by each Supersite and delivered to the ****	****Precipitation Processing System.**
**Bias reports include an estimate of bias uncertainty.**
**Bias removal from satellite retrievals is a first step in ****	****error ****	****adjustment process at the Precipitation ****	****Processing ****	****System.****	**

## Ground Validation Error Characterization

_**Overpass Scenarios for Bias Estimation:**_

## Ground Validation Error Characterization

_**Development of Bias Technique (Experimental Program):**_
**NASA / JPL ****Airborne Precipitation Radar – 2 (APR-2)**** modified for **
**ground-based capability.**
**	****	****	****	****	**_**Frequency**_**	**_**Antenna BW**_
**	****	****	****APR-2:  ****	****13.4 GHz (Ku)****	****4.2°**
**	****	****	****	****	****35.6 GHz (Ka)****	****4.2°**
**Similarly, the NASA / MSFC  ****Advanced Precipitation Radiometer **
**(AMPR)**** prepared for ground-based observations.**
**	**
**	****	****	****	****	**_**Frequency**_**	**_**Antenna BW**_
**	****	****	****AMPR: ****	**** 10.7 GHz****	****1.8°**
**	****	****	****	****	****19.35 GHz****	****4.2°**
**	****	****	****	****	****37.1 GHz****	****8.0°**
**	****	****	****	****	****85.5 GHz****	****8.0°**
**These instruments, under perhaps TRMM coverage, used to **
**validate the bias technique in a “Pilot Experiment” in FY 2004.**
**	****	****	****	****	**

## Ground Validation Error Characterization

***Ground***

***Satellite***

***Radiative Transfer Calculations: Cumulus Clouds***

_**Development of Bias Technique (Theory Studies):**_

## Ground Validation Error Characterization

***Ground***

***Satellite***

***Radiative Transfer Calculations:  Light Rain***

_**Development of Bias Technique (Theory Studies):**_

## Ground Validation Error Characterization

***Ground***

***Satellite***

***Radiative Transfer Calculations:  Moderate Rain***

_**Development of Bias Technique (Theory Studies):**_

## Ground Validation Error Characterization

***Ground***

***Satellite***

***Radiative Transfer Calculations:  Rain + Snow***

_**Development of Bias Technique (Theory Studies):**_

## Ground Validation Error Characterization

_**Regional Error Covariance Expansion Rules:**_**   **
**Attaches observational error covariance to the satellite**
**	****rainfall retrievals.  **
**Important to Data Assimilation Customers.**
**Expresses the underlying spatial and temporal error ****	**
**	****structure within the satellite rainfall retrievals.**
**Developed at the processing and analysis facility ****	**
**	****of each Supersite and delivered to the Precipitation**
** ****	****Processing System.**

## Ground Validation Error Characterization

_**Regional Error Covariance Expansion Rules (cont**_**.):  **
***‘******Regional’***
**Supersite develops rules for representative region / regime**
***‘******Error Covariance’***
**A measure of random error and any correlation in space and time**
***‘******Expansion’***
**Information learned at the local Supersite is extrapolated to the **
**broader region / regime**
***‘******Rules’***
**A combined algorithm and data base provided by the Supersite to the **
**Precipitation Processing  System for the automatic generation of error **
**covariance and attachment to satellite retrievals**

## Ground Validation Error Characterization

_**Data Assimilation / Observational Error Covariance:**_

**where**

**is the analysis vector (state vector, control variable)**

**is the background vector (forecast from the previous analysis time)**

**is the forecast model error covariance**

**is the observational error covariance **GV will provide estimate****

**is the forward model error covariance**

**is the observation vector**

**is the forward operator which transforms the analysis vector into**
**the form of the observations**

## Ground Validation Error  Characterization

_**Regional Error Covariance Expansion Rules (cont.):**_
***Instrumentation:***
**Scanning Doppler radar and rain gauge network**
**	****of the Supersite are critical for developing error covariance**
***Rationale:***
**Greater resolution both in space and duration in time than **
**	****is possible with satellite**
**Allows examination of precipitation structure and error **
**	****structure in space and time**

## Ground Validation Error Characterization

- _Data_
- _Flow:_

## Ground Validation

_**Conclusions:**_
_**New:**_**  **
**Global Precipitation Measurement represents a new approach to **
**Ground Validation**
_**Service to GV Customers:**_** **
**(1) Algorithm Developers, **
**(2) Data Assimilation Specialists, **
**(3) Climate Researchers **
**(4) GV Scientists**
_**Goals:**_
***Evaluate*****:  Error Characterization on Satellite Retrievals**
***Diagnose*****:  Determine Causes of Errors**
***Improve*****:  Improve Models, Physical Assumptions, and Algorithms**_** **_