Evaluation of TRMM satellite precipitation product in hydrologic

simulations of La Plata Basin

Fengge Su1, Yang Hong2, and Dennis P. Lettenmaier1

1University of Washington, Seattle, WA 2 NASA Goddard Space Flight Center, Greenbelt, MD

1. Background

• The objective of this study is to evaluate the TRMM-based

precipitation estimates, and their utility in hydrologic

predictions.

• Precipitation is the primary atmospheric input to hydrology

models.

• Satellite-based precipitation estimates show potential

attractions for hydrologic predictions.

• High resolution TRMM-based products are available to

research community.

• The TRMM product evaluated in this study is the TRMM

Multi-satellite Precipitation Analysis (TMPA) research

product Version 6 3B42.

• It combines precipitation estimates from multiple

satellites, as well as gauge analyses, where available, at a

3-hour time step and 0.25° degree spatial resolution.

• The data set covers the latitude band 50°N-S for the

period 1998 to the delayed present.

2. Data sets and methodology

Huffman et al., 2006, The TRMM Multi-satellite Precipitation Analysis (TMPA): Quasi-Global, Multi-Year, Combined-Sensor Precipitation Estimates at Fine Scales (to appear in Journal of Hydrometeorology)

Rain gauge distribution in 1998 (846)

Rain Gauge distribution in 1999 (676)

La Plata Basin and Gauged data (1998-1999)

from NCAR and GDCN (Global Daily Climatology Network) station data

Uruguay

Parana

Paraguay

Methodology

1. Basin average precipitation estimates from the TRMM Satellite

precipitation product (Version 6 3B42) and gauges are

compared with each other at both daily and monthly time

scales.

2. The Variable Infiltration Capacity (VIC) land surface hydrology

model is forced by daily 3B42 and gauged precipitation over

several subbasions of La Plata. The simulated streamflow is

compared with each other and with available observed

streamflow.

3. Precipitation evaluation

Scattergrams of daily basin-averaged precipitation estimated from gauged and TRMM data.

Rrmse=60% Rrmse=13%

Rrmse=134% Rrmse=15%

Rrmse=44%

Scattergrams of monthly basin-averaged precipitation estimated from gauged and TRMM data.

Monthly Basin-averaged Precipitation

Daily time series of precipitation for basin 3861

19991998

Gauged TRMM

1 2 3

4 5 6

7 8 9

10 11 12

1 2 3

4 5 6

7 8 9

10 11 12

Month Month

mm

/dy

mm

/dy

Monthly time series of

precipitation from

gauged and TRMM 3B42

data for five subbasins

(1998-1999).

BasinRelative Error (%)

1998 1999 Average

3861 6 5 5.5

7870-3802 7 9 8

6301 1 7 4.0

6682 5 15 10.0

6598 5 0 2.5

FBI can indicate whether there is a tendency to underestimate (FBI<1) or overestimate (FBI>1) rainy events.

POD gives a proportion of observed rain events successfully estimated by the TRMM data.

FAR provides a measure of the 3B42’s tendency to estimate rain where none was observed.

Statistical evaluation over different subbasinsFrequency Bias Index

0

0.5

1

1.5

2

2.5

0.1 0.5 1 2 5 10 20

Threshold (mm)

FB

I

3861

6301

6682

Probability of Detection

0

0.2

0.4

0.6

0.8

1

0.1 0.5 1 2 5 10 20

Threshold (mm)P

OD

3861

6301

6682

False Alarms Ratio

0

0.2

0.4

0.6

0.8

1

0.1 0.5 1 2 5 10 20

Thresholds (mm)

FA

R

3861

6301

6682

Frequency Bias index

Probability of Detection

False Alarms Ratio

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.

Observed

Simulated with TRMM Prce.

Simulated with gauged Prce.

Nash-Sutcliffe efficiency (Ef)

Relative error (Er)

Daily streamflow for basin 3802

3802, Uruguay at Paso de Los Libres (Area: 189, 300 km2)

Green VS. Black: Ef = 0.85, Er = 2%

Red VS. Black: Ef = 0.48, Er = 12%

Red VS. Green: Ef = 0.54, Er = 16%

1998 1999

1998 1999

1998 1999

m3

/s m

3/s m

3/s

Daily streamflow for basin 6301, 6598, and 6682

Observed

Simulated with TRMM Prce.

Simulated with gauged Prce.

Nash-Sutcliffe efficiency (Ef)

Relative error (Er)

Red VS. Green: Ef = 0.73, Er = 4%

Red VS. Green: Ef = 0.73, Er = -1%

Red VS. Green: Ef = 0.72, Er = 18%

(a) 6301, Parana at Jupia (Area: 478,000km2)

(b) 6598, Iguazu at Estreito (Area: 63,236 km2)

(c) 6682, Paraguay at Ladario (Area: 459,990 km2)

m3

/s m

3/s m

3/s

1998 1999

1998 1999

1998 1999

Monthly streamflow for the four subbasins

Observed

Simulated with TRMM Prce.

Simulated with gauged Prce.

m3

/s m

3/s

m3

/s m3

/s

(a) 3802, Uruguay at Paso de Los Libres

(b) 6301, Parana at Jupia

(c) 6598, Iguazu at Estreito

(d) 6682, Paraguay at Ladario

1998 1999

• The Version 6 3B42 provides good performance at monthly time

scale. The daily estimates show a good performance for the low

and medium precipitation thresholds. For higher thresholds,

satellite estimates tend to overestimate the frequency of rain

events, and show low POD and high FAR.

• The 3B42-driven model results show a good ability in reproducing

the timing of floods, and in representing the low peak flows, but

tend to overestimate the high-flow peaks.

• Despite the errors in the satellite-based precipitation estimates,

this study provides encouraging results of using the TRMM 3B42

product in basin-scale hydrology predictions.

5. Conclusion