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!