Hydrological evaluation of satellite precipitation products in La Plata basin
1Fengge Su, 2Yang Hong, 3William L. Crosson,
and 4Dennis P. Lettenmaier
1,3USRA at NSSTC/NASA/MSFC, Huntsville, AL 2University of Oklahoma, Norman, OK 4University of Washington, Seattle, WA
1. Objective
• To evaluate the satellite-based precipitation estimates, and their
utility in hydrologic predictions.
• To provide insights into the potential utility of Global Precipitation
Measurement mission (GPM) products for hydrologic applications.
• To make a first step toward a hydrologically based global
assessment framework for satellite-based precipitation products
(particularly those using minimal in situ data).
Satellite-based precipitation:
(1) The TRMM Multi-satellite Precipitation Analysis (TMPA) research product
3B42 V.6 and real-time version 3B42-RT (Huffman et al 2007) .
(2) The Precipitation Estimation from Remotely Sensed Information Using
Artificial Neural Networks (PERSIANN) (Sorooshian et al 2000).
(3) The Climate Prediction Center morphing method (CMORPH) (Joyce et al
2004).
Data resolution: 3-hour time step and 0.25° degree spatial resolution.
Study period: January 1, 2003 ~ August 31, 2006
Study area: La Plata basin (-38 ° S ~ -14 ° S, -56 ° W ~ -41 ° W, 3.1×106 km2)
All three products are satellite only (no gauge-based post-processing, as in
TMPA RP)
2. Data sets and methodology
South American gridded
daily precipitation (0.25 °)
constructed from daily
meteorological station data
(Liebmann and Allured,
2005).
Four sub-basins
(highlighted) have
relatively dense
station coverage.
Gauge-based precipitation in La Plata basin
Methodology
• Spatially-distributed and basin-wide precipitation estimates from
satellite precipitation products are compared with gauge-derived
precipitation at time scales from annual to daily for the period 2003
through 2005.
• The Variable Infiltration Capacity (VIC) land surface hydrology model
is forced by the daily satellite-based and gridded gauge precipitation
estimates over La Plata basin. Simulated runoff fields and
streamflow driven by satellite precipitation are compared with those
driven by gauge precipitation inputs.
Annual mean
precipitation over La
Plata basin from gridded
gauge, TMPA V.6 (gauge
adjusted), TMPA-RT,
CMORPH, and PERSIANN
estimates for the years
2003-2005.
Difference of annual
precipitation between
satellite and gauge
estimates.
mm/yr
mm/yr
3. Precipitation evaluation- spatial fieldsGauge TMPA V.6
Gauged (mm/dy) Gauged(mm/dy) Gauged (mm/dy) Gauged (mm/dy)
Basin 6682 Basin 6301 Basin 6598 Basin 3802
PE
RS
IAN
N
C
MO
RP
H
T
MP
A-R
T
TM
PA
V.6 Scattergrams of daily basin-
averaged precipitation from
gauge and satellite estimates
for four sub-basins in La Plata
for the period 2003 to 2005.
Bias = 0.17
Bias = 0.36
Bias = 0.44
Bias = 0.63
Bias = 0.10
Bias = 0.42
Bias = 0.49
Bias = 0.31
Bias = 0.11
Bias = 0.08
Bias = 0.16
Bias = -0.03
Bias = 0.09
Bias = 0.24
Bias = 0.31
Bias = 0.19
Basin-averaged precipitation
Bias relative to gauge estimates for each year ( 2003, 2004, and 2005).
The bias significantly decreased in 2005 over basins 3802 and 6598 for the three real-time satellite precipitation products.
4. Hydrological Modelling4. Hydrological Modelling
The VIC (Liang et al, 1994;1996) model is a grid-based land surface scheme designed both for inclusion in GCMs, and for use as a stand-alone macro-
scale hydrological model.
Model features:
• multiple vegetation classes in each cell;
• energy and water budget closure at each time step;
• subgrid infiltration and runoff variability;
• and non-linear baseflow generation.
Annual mean simulated
runoff forced by the
gauge, TMPA V.6, TMPA-
RT, CMORPH, and
PERSIANN estimates for
the years 2003-2005.
Difference of annual
simulated runoff between
satellite-driven and gauge-
observation-driven
simulations.
mm/yr
mm/yr
Gauge TMPA V.6
Spatial fields of annual mean simulated runoff (2003-2005)
Daily simulated streamflow for basin 3802, Uruguay at Paso de los Libres (Area: 189, 300km2, Jan 2003~Aug 2006)
Simulated with satellite Precip
Simulated with gauge Precip Bias TMPA (%)
RT (%)
CMORPH (%)
PERSIANN (%)
2003 20 110 110 105
2004 32 120 142 73
2005 22 39 55 17
Daily simulated streamflow for basin 6598, Iguazu at Estreito (Area: 63,236 km2, Jan 2003~Aug 2006)
Simulated with satellite Precip.
Simulated with gauge Precip.
Bias TMPA (%)
RT (%)
CMORPH (%)
PERSIANN (%)
2003 27 95 104 101
2004 28 56 80 35
2005 9 18 26 -3
Daily simulated streamflow for basin 6301, Parana at Jupia (Area: 478,000km2, Jan 2003 - Aug 30 2006)
Simulated with satellite Precip.
Simulated with gauged Precip.
Bias TMPA (%)
RT (%)
CMORPH (%)
PERSIANN (%)
2003 22 45 34 -3
2004 25 8 66 -7
2005 35 34 36 7
Summary
• All satellite precipitation products captured the general precipitation regime of
the La Plata basin, but with significant overestimation compared with gauge
estimates over the middle part of the basin and slight underestimation in the
northeastern part.
• The four satellite products show different performance over different sub-basins,
indicating the effects topography and possibly land cover on the precipitation
retrieval algorithms.
• Biases of the precipitation estimates significantly decreased in 2005 over the
central sub-basins, likely due to algorithm changes and increased coverage from
microwave sensors.
• The plausible performance of the satellite products in streamflow simulations in
recent years suggests that even without the monthly gauge correction, there is
considerable potential for hydrologic prediction using satellite precipitation
estimates in data sparse areas.
• Further evaluation is needed with more complete daily gauge data over other
global river basins.
Thank You!