Evaluation of GPM Precipitation Estimates
for Land Data Assimilation Applications
Mississippi State University
Geosystems Research Institute
RPC Review (03/02/09)
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GPM Evaluation Team & Collaborators
• MSU Team
–
–
–
–
–
–
Robert Moorhead
Valentine Anantharaj
Georgy Mostovoy
Yangrong Ling
QiQi Lu
Graduate students (2)
• External Collaborators
– Paul Houser (GMU CREW)
– Joe Turk (Naval Research Laboratories & JPL)
• Partner Agencies
– Garry Schaeffer (USDA NRCS)
– Steve Hunter (United States Bureau of Reclamation)
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GPM Evaluations: Purpose and Activities
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Purpose of RPC GPM Experiments
•
Evaluate usefulness of GPM data for decision
support in water resources management and
other cross-cutting applications.
Test, characterize, and evaluate GPM data in
conjunction with other precipitation products in the
context of land surface modeling for earth science
applications.
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Experimental Objectives of GPM Evaluation
1. Verify space-based precipitation
estimation using ground-based radar and
rain gauge data for different cases
representing different synoptic condition
and surface types
2. Validate precipitation forcing impacts
using land surface model simulations.
3. Evaluate potential impacts on water
resources applications.
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Satellite Omission Experiments
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Motivation
• Precipitation is the main forcing for hydrological and land surface
models
• Precipitation events that result in flooding often evolve over short
space and time scales, where properly instrumented surface
networks may not be available
• Satellite data often provides the only source of timely precipitation
data over many of the world’s remote watersheds
• Hydrological modeling is a key focus of the future NASA/JAXA
Global Precipitation Measurement Mission (GPM) in 2013; however
• The members of the GPM constellation will change owing to launch
schedules before and during the mission; therefore
• How can we leverage today’s existing environmental satellite
constellation to examine the impact of (existing and future) satellites
and orbits on hydrological applications?
NASA RPC Review (4/14/08)
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Current
(10-Satellite)
LEO Satellite
Constellation
Revisit Time
Color Codes:
SSMI
DMSP F-13/14/15
AMSR-E
Aqua
AMSU-B
NOAA-15/16/17
TMI
TRMM
Coriolis
Windsat
SSMIS
F-16
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Revisit Scale: White= 0 hours Black= 6+ hours (shaded boxes represent 15-minute coverage)
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Observing Times for an Ideal Precipitation-Based Low-Earth
Orbiting Satellite Observing Constellation
0
18
Pattern
progresses
from day to day
6
12
Orbits are equally spaced with a 1.5 to 3-hour revisit time
Ascending
Descending
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What We Have Today: DMSP and NOAA Satellites
0
0
F-16
NOAA-17
F-15
F-13
18
6 18
6
F-14
NOAA-15
NOAA-16
NOAA-18
12
12
NOAA Satellites as of Late 2006
Ascending Descending
DMSP Satellites as of Late 2006
Ascending Descending
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“Building Blocks” for HRPPs: NOAA/DMSP Satellites
Late Summer 2008
Midnight
TRMM 28-day
repeat at
equator
NOAA-17
F16
6 PM
F15
F13
Coriolis
F17
NOAA-15
NOAA-16 F14
6 AM
METOP-A
FY-3A (launched 29 May 2008)
NOAA-18
Aqua
Noon
F14 only direct-broadcast since 24 Aug 2008
F18 launch date: 8 November 2008
Ascending
Descending
Examining Impact of Satellite Type for the GPM Era
Satellite Omission Experiments
Case 0:
All satellites included (baseline)
Case 1:
Case 2:
Case 3:
Omit all crosstrack sounders
Omit morning crosstrack sounders
Omit afternoon crosstrack sounders
Case 4:
Case 5:
Case 6:
Case 7:
Omit TRMM TMI and PR and Aqua
Omit TRMM PR only
Omit TRMM TMI only
Omit TRMM TMI and PR
Case 8:
Case 9:
Omit all morning satellites
Omit all afternoon satellites
NASA RPC Review (4/14/08)
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Examining Impact of Satellite Type for the GPM Era
Satellite Omission Experiments: Baseline
24-hour accumulations ending 2007/06/29 12Z
12-hour accumulations ending 2007/06/29 12Z
6-hour accumulations ending 2007/06/29 12Z
3-hour accumulations ending 2007/06/29 12Z
NASA RPC Review (4/14/08)
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Seasonal Performance
East of 100W Longitude (> 1 mm/day)
Not much difference amongst
sat-omission runs for the NRLBlend “adjustment-based” HRPP
technique
Green box illustrates largest
performance impact is the
omission of the morning
overpass crosstrack
sounders (“No AM XT” and
“No AM” configurations)
ALL Satellites Case
NOAA 15/16/17/18 (crosstrack)
METOP-A (crosstrack)
DMSP F-13/14/16/17 (conical)
Aqua (conical)
Coriolis (conical, over water)
TRMM TMI (conical), PR
summer
winter
Bias
Equitable
Threat
Score
Probability
of
Detection
False
Alarm
Rate
NOGAPS
NWP model
Seasonal Performance
West of 100W Longitude (> 1 mm/day)
Generally less skill in winter
months over western US “high
altitude” region
Larger bias and spread for both
satellites and model, especially
in summer months
Higher false alarm rate for
satellite-estimated, especially in
winter months
“All Satellites” Case
NOAA 15/16/17/18 (crosstrack)
METOP-A (crosstrack)
DMSP F-13/14/16/17 (conical)
Aqua (conical)
Coriolis (conical, over water)
TRMM TMI (conical), PR
summer
winter
Bias
Equitable
Threat
Score
Probability
of
Detection
False
Alarm
Rate
NOGAPS
NWP model
Using Land Surface Models for GPM Ground Validation
Principle
Use land surface models (LSM) and
other
types
of
hydrological
observations (other than raingauge)
to examine the impact of these GPM
proxy
data
upon
streamflow,
discharge, soil moisture and other
runoff measurements
GPM Ground
Validation
Experimental Setup
• Incorporate the NASA Land Information System (LIS) with the NOAH
LSM to simulate land surface and hydrological states
• Examine performance impact of different GPM constellations (e.g,
Gottschalk et. al, 2005)
Impact of GPM Precipitation Estimates Upon Land Surface Models
The analysis domain below covers the south-central United States where there are
several well-instrumented watersheds. The impact of precipitation in a LSM is dependent
upon many physical factors, soil type, vegetation, etc. Soil moisture analysis at a given
time is likely to be the cumulative result of precipitation that has fallen for weeks or
months prior.
To accommodate this, the results are shown after 5 months of simulation time, valid at 18
UTC on 31 October 2007. Soil moisture simulations are performed with 0.1o latitude x
0.1o longitude resolution and the North American Land Data Assimilation System
(NLDAS) forcing fields (except for precipitation) are used to run the Noah LSM.
Arkansas-Red River Basins
Arkansas
Cimarron
The Arkansas River is the longest tributary in the
Mississippi-Missouri system. From its source in
Colorado, the river travels through Kansas and
northeastern Oklahoma. There it is joined by the
Canadian, Cimarron, Neosho-Grand, and Verdigris
Rivers, crosses the state of Arkansas where it
empties into the Mississippi River.
Canadian
Red
Satellite Denial Experiments: Effect on LSM
No Crosstrack Sounders
No TMI+PR+Aqua
No AM Crosstrack Sounders
No AM Satellites
No PM Crosstrack Sounders
No PM Satellites
Satellite Denial Experiments: Effect on LSM
Example: Omit All Crosstrack Sounders
Upper Layer
(0-10 cm)
Soil moisture
difference
relative to the
“all-satellites”
configuration
Deep Layer
(0.4-1 m)
Valid at 18 UTC on 31 October 2007
Conclusions and Future Efforts
Both the gauge-based verification analysis and the LSM satellite denial
experiments indicate that the greatest impact to the “all satellites” GPM
configuration appears when the crosstrack sounders and the morning crossing
(LTAN near 1800) satellites are omitted.
The removal of the morning satellites likely has less to do with the specific local
time-of-day observation than it does with the fact that the bulk of the current
(2008) satellites such as DMSP, Coriolis and several NOAA have early morning
crossing times.
While this example demonstrates only one time step, these LSM simulations are
being extended to cover multi-year DJF and JJA seasonal analyses.
Summary of Progress
• Completed Tasks
– Synthesis of GPM-proxy data (based on NRL-blend algorithm)
– Verification of precipitation products
• Manuscript in draft, to be submitted to an AMS journal
– Satellite Omission Experiments
• Book chapter accepted (Springer Verlag)
• Manuscript in final draft, to be submitted to IEEE-JSTARS
• Final Steps (in progress)
– Evaluation against USBR application metrics (soil moisture and
evaporation)
– Final evaluation (document and publish)
Note: “verification” refers specifically to the satellite precipitation verification approach as used by the International
Precipitation Working Group which is different from the systems engineering verification process defined by ASP.
NASA RPC Review (3/2/09)
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Contact Information
Valentine Anantharaj
<vga1@msstate.edu>
Tel: (662)325-5135
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