# Presentation: 167369

## Hydrological evaluation of satellite precipitation products in the La Plata Basin

**Hydrological evaluation of satellite precipitation products in the La Plata Basin**
**Fengge Su****1****, Yang Hong****2****, William L. Crosson****1****, and Dennis P. Lettenmaier****3**
-    1Universities Space Research Association at NSSTC/NASA/MSFC, Huntsville, AL
-    2University of Oklahoma, Norman, OK, 3University of Washington, Seattle, WA

**T****he objective of this study is to evaluate state-of-the-art satellite precipitation products,  and their utility in prediction of the discharge of large rivers.  ****This initial hydrologic effectiveness assessment of satellite precipitation products in the La Plata Basin can provide useful insights into the potential utility of the proposed Global Precipitation Measurement  mission (GPM), and is a first step in development of a global assessment framework for satellite-based precipitation products. **

**1. Objective**

**2. Datasets and Methodology**

**Gauge-based precipitation**

**Sources: ****South American gridded daily precipitation (0.25°) constructed from daily meteorological station data (Liebmann and Allured, 2005).**
**Blue triangles are streamflow stations. Colored areas highlight four sub-basins with relatively dense station coverage.**

**Satellite-based precipitation****:**
**The TRMM Multi-satellite Precipitation Analysis (TMPA) research  product ****3B42 V.6 which incorporates monthly gauge analysis ****and real-time version ****3B42-RT  ****(Huffman et al. 2007) .**
**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:      1998~2006 for 3B42 V.6,  2003 ~ 2006 for the others   **
**Study area:          La Plata basin (-38° S ~ -14° S, -56° W ~ -41° W, ****3.1×10****6**** km**

**3****. ****Precipitation Evaluation at Basin-wide scale**

** **

**Real-time products VS. gauge estimates**

**The Variable Infiltration Capacity (VIC) land surface hydrology model is forced by the daily satellite-based and gridded gauge precipitation estimates over the La Plata basin. ** **Simulated runoff fields and streamflow driven by satellite precipitation are compared with those driven by gauge precipitation inputs. **

**The VIC land surface model**

**       ****TMPA V.6  VS.  gauge estimates**

**The ****TMPA V.6 ****estimates agree well with the gridded gauge data at monthly time scales for all the sub-basins most likely because of the monthly adjustment to gauges performed in ****TMPA V.6****, while the real-time products which do not include any gauge adjustment significantly overestimate the gauge estimates over basins 6682, 6598 and 3802. **

**A. Monthly  precipitation**

**B. Daily precipitation**

**TMPA V.6 shows the best performance in term of R****2**** and bias due to the adjustment by monthly gauge estimates. **
**All the precipitation products present the best performance over basin 6301 where there is good gauge coverage and the worst over basin 6682, which is fairly flat with large areas of wetlands. **
** **

**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 Modeling**

**Nash-Sutcliffe efficiency (Ef)**
**Relative error (Er)**

**The TMPA V.6-driven model results show a good ability in capturing the daily flooding events and in representing the low peak flows, although they tend to overestimate the high-flow peaks.**

| Bias (%) | TMPA | RT | CMORPH | PERSIANN |
| --- | --- | --- | --- | --- |
| 2003 | 20 | 110 | 110 | 105 |
| 2004 | 32 | 120 | 142 | 73 |
| 2005 | 22 | 39 | 55 | 17 |

| 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 3802**

**Daily simulated streamflow for basin 6598**

**Bias relative to gauge-driven daily simulated streamflow**

**Basin 3802**

**Basin 6598**

**Daily simulated streamflow for basin 6302**

**5****. Conclusions**

**References: **

**The TMPA V.6-driven model simulations showed good ability to capture daily flood events and to represent low flows, although peak flows tended to be biased upward. The encouraging aspects of the performance of TMPA V.6 are substantially attributable to the monthly gauge correction, which requires a reasonably dense gauge network.**
**All the real-time satellite products captured the general precipitation regime of the La Plata basin, but with significant overestimation compared with gauge estimates particularly over the central part of the basin.**
**The four satellite products showed different performance over different sub-basins, indicating the effects of ****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 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.**

- Huffman et al., 2007: The TRMM Multi-satellite Precipitation Analysis (TMPA): Quasi-Global, Multi-Year, Combined-Sensor Precipitation Estimates at Fine Scales. *J. Meteor., ****8, 38-55.***
- Joyce et al., 2004: CMORPH: A method that produces global precipitation estimates from passive microwave and infrared data at high spatial and temporal resolution*. J. Hydrometeor., ****5, 487–503.***
- Sorooshian et al. 2000: Evaluation of PERSIANN System Satellite-Based Estimates of Tropical Rainfall. *Bull. **Am. Meteor. Soc., ****81(9), 2035-2046.***
- Su et al., 2007: Evaluation of TRMM Multi-satellite Precipitation Analysis (TMPA) and its utility in hydrologic prediction in La Plata Basin, *J. Hydrometeorology* (accepted).