Laboratory for Remote Sensing and Geoinformatics


Directed by  Dr. Hongjie Xie , Associate Professor


NEXRAD Rainfall Validation, Flash-flood Forecasting and Modeling


Precipitation, characterized by high spatial and temporal variation, is one of critical inputs for hydrological modeling. It is also an important factor influencing agriculture, water resources and ecosystems.  Accurate measurements of precipitation are very important for all rainfall-related applications. Traditionally, rain gauges physically measure rainfall accumulation at a point (~ 324 cm2) and generally provide good quality data for a small area. These point measurements of precipitation have been used in all kinds of hydrological models (Jayakrishnan et al., 2004). Problems with rainfall measurements by gauge were documented in several studies (e.g., Legates and DeLiberty, 1993; Finnerty et al., 1997).

Weather radar measurements of precipitation, which provide precipitation data with much higher spatial resolution compared to rain gauges, have served meteorology for over 40 years and hydrology around 20 years (Krajewski and Smith, 2002). The installation of the Next Generation Weather Radar (NEXRAD) system across the United States in the early to mid 1990s by National Weather Service (NWS), which includes more than 160 WSR-88D (Weather Surveillance Radar-1988 Doppler) radars, has revolutionized the NWS forecast and warning programs through improved detection of severe wind, rainfall, hail, and tornadoes (Fulton, 2002). NEXRAD has two series of products: Levels 2 and 3, and Stages II, III, and IV (Fulton, 2002; Jayakrishnan et al., 2004; Xie et al., 2005, 2006). The Multisensor Precipitation Estimator (MPE), developed by the NWS Office of Hydrology in March 2000, is a product that merges rainfall measurements from rain gauges, and rainfall estimates from NEXRAD and Geostationary Operational Environmental Satellite (GOES) products. The NWS West Gulf River Forecast Center (WGRFC) switched from Stage III to MPE as the preferred precipitation estimation program in October 2003, and ended Stage III in December, 2004.  Thus, since January 1, 2005, only MPE has been produced and distributed by the WGRFC (Greg Story, personal communication, April 2005).

In spite of better spatial representation of rainfall variability by radar compared with rain gauge networks, there are limitations of radar estimates due to data contamination and uncertainty issues (Smith et al., 1996; Legates, 2000; Xie et al., 2006; Wang et al. 2008). In particular, radar rainfall overestimation is caused by the presence of hail, large raindrops, or melting; underestimation occurs due to small raindrops, dry ice, attenuation, truncation error, and beam blockage. Minimizing these errors has been one of the major tasks in radar meteorology for decades (Schmid & Wuest, 2005).


The goals of the LRSG group for the rainfall and modeling study, supported by NASA, NOAA, and USGS, are to:

(1) validate the Stage III or MPE products and document their possible errors,

(2) study the spatial-temporal variation of rainfall in one radar cell using high dense raingauge network,

(3) use NEXRAD rainfall and MODIS bio-physical states to predict runoff for ungauge basins, and use NEXRAD rainfall as a forcing for hydrological and ecological modeling for the Texas coastal region, and

(4) perform flash-flooding forecasting for the Central Texas region, the most flash-flood prone region in North America.



Project Title Funding Source
Developing and applying an integrated multi-scale Earth system modeling framework to study the impacts of changing climate, local weather, and land use and watersheds and downstream coastal ecosystems NASA Interdisciplinary Science Program
Better understanding NEXRDA Level II reflectivity using a network of four double-gauge platforms in a single radar cell NOAA UCAR/COMET program
Using satellite data and fully coupled regional hydrologic, ecological and atmospheric models to study complex coastal environmental processes NASA Interdisciplinary Science Program
Enhanced short-term hydrometeorological forecasting NOAA MSI program
Validating DSP precipitation product using 50 GBRA rain gauge rainfall NOAA UCAR/COMET program
Validation of remotely sensed precipitation using rain gauge data in the Texas Hill Country USGS/TexasView Remote Sensing Consortium
NEXRAD radar rainfall downscaling A subcontract from New Mexico Institute of Mining and Technology (funded by the New Mexico WRRI)




(*first author student, **first author postdoc/visiting professor)


Wang, X., Y. Chen, L. Song, X. Chen, H. Xie, and L. Liu, 2013. Analysis of lengths, water areas and volumes of the Three Gorges Reservoir at different water levels using Lnadsat images and SRTM DEM data. Quaternary International, doi: 10.1016/j.quaint.2013.03.041 (link).

Wang, X., H. Xie, N. Mazari, J. Zeitler, H. Sharif, and Weldon Hammod, 2013. Evaluation of the near-real time NEXRAD DSP Product in the evolution of heavy rain events on the Upper Guadalupe River Basin, Texas. Journal of Hydroinformatics. doi: 10.2166/hydro.2012.016 (link).

*Mazari, N., H. Xie, J. Zeitler, and H. Sharif, 2013. Validation of the NEXRAD DSP product with a dense gauge network. Journal of Hydrological Engineering. Vol 18:156-167, doi: 10.1061/(ASCE)HE.1943-5584.0000676 (link)

Sharif, H. O., S. Chintalapudi, A. Elhassan, H. Xie, and J. Zeitler, 2013. Physically-Based Hydrological Modeling of the 2002 Floods in San Antonio, Texas. Journal of Hydrological Engineering. Vol. 18: 228-236: doi:10.1061/(ASCE)HE.1943-5584.0000475 (link)

Xie, H., X. Zhang, B. Yu, and H. Sharif, 2011. Performance evaluation of interpolation methods for incorporating rain gauge measurements into NEXRAD precipitation data: A case study in the Upper Guadalupe River Basin. Hydrological Processes. Vol 25(24): 3711-3720. doi:10.1002/hyp.8096 (link)

*Schnur, M., H. Xie, and X. Wang, 2010. Estimating root zone soil moisture at distant sites using MODIS NDVI and EVI in a semi-arid region of southwestern USA. Ecological Informatics. Doi: 10.1016/j.ecoinf.2010.05.001 (link)

Sharif, H. O., A. A. Hassan, S. Bin-Shafique, H. Xie, and J. Zeitler, 2010. Hydrologic Modeling of an Extreme Flood in the Guadalupe River in Texas. J. of American Water Resources Association, 46(5): 881-891, DOI: 10.1111/j.1752-1688.2010.00459.x (link).

Sharif, H. O., L. Sparks, A. A. Hassan, J. Zeitler, and H. Xie, 2010. Application of a distributed hydrologic model to the November 17, 2004 Flood of Bull Creek Watershed, Austin, Texas. J. of Hydrologic Engineering Vol 15(8):651-657, DOI: 10.1061/(ASCE)HE,1943-5584.0000228 (link).

**Guan, H., J.L. Wilson, H. Xie, 2009, A cluster-optimizing regression-based approach for precipitation spatial downscaling in mountainous terrain. Journal of Hydrology, Vol 375: 578-588, doi:10.1016/j.jhydrol.2009.07.007 (link)

**Guan, H., H. Hsu, O. Makhnin, H. Xie, and J. Wilson, 2009. Examination of selected atmospheric and orographic effects on monthly precipitation of Taiwan using the ASOADeK model. International Journal of Climatology, Vol 29 (8): 1171-1181, doi:10.1002/joc.1762 (link)

*Weissling, B.P., H. Xie, and K. Murray, 2009. Evaluation of NRCS curve number and MODIS time series proxies for antecedent moisture condition. Civil Engineering and Environmental Systems, Vol.26 (1): 85-101, doi: 10.1080/10286600802005356 (link).

*Weissling, B. and H. Xie, 2009. MODIS biophysical states and NEXRDA precipitation in statistical evaluation of antecedent moisture condition and streamflow. Journal of the American Water Resources Association, 45(2): 419-433, DOI: 10.1111/j.1752-1688.2009.00300.x, (link)

*Weissling B. and H. Xie, 2008. Proximal watershed validation of a remote sensing-based streamflow estimation model. Journal of Applied Remote Sensing. Vol. 2, 023549, DOI:10.1117/1.3043664  (link) (pdf).

*Wang, X., H. Xie, H. Sharif, and J. Zeitler, 2008. Validating NEXRDA MPE and Stage III precipitation products for uniform rainfall on the Upper Guadalupe River Basin of the Texas Hill Country. Journal of Hydrology, Vol. 348(1-2): 73-86, doi: 10.1016/j.jhydrol.2007.09.057 (pdf)

*Weissling, B.P., H. Xie, and K.E. Murray, 2007. A multitemporal remote sensing approach to parsimonious streamflow modeling in a southcentral Texas watershed, USA. Hydrology and Earth System Sciences Discussions, 4, 1-33 (a discussion paper).

Xie, H., X. Zhou, J. Hendrickx, E. Vivoni, H. Guan, Y. Tian, and E. Small, 2006, comparison of NEXRAD Stage III and gauge precipitation estimates in central New Mexico , Journal of the American Water Resources Association, 42(1): 237-256 (pdf)

Xie, H., X. Zhou, E. Vivoni, J. Hendrickx, and E. Small, 2005, GIS Based NEXRAD Precipitation Database: automated approaches for data processing and visualization , Computers and Geosciences, Vol.31 (1), pp 65-76 (pdf).



(Presentations or proceedings)


*Mazari, N., H. Xie, X. Wang, J.W. Zeitler, and H. Sharif, 2009. Validation of NEXRAD DSP product with high accuracy rain gauges network. 34th Conference on Radar Meteorology, October 5-9, Williamsburg, VA.

*Yu, B., X. Zhang, H. Xie, 2008. Using geostatistical methods to improve radar rainfall estimates accuracy. AGU Fall meeting, San Francisco, CA, December 15-19.

Sharif, H., S. Chintalapudi, X. Wang, H. Xie, and J.W. Zeitler, 2008. Hydrometeorological analysis of flooding events in San Antonio, TX. AMS 88th annual meeting, New Orleans, LA, January 20-24.

*Mazari, N., H. Xie, H., Sharif, J. Zeitler, 2007. NEXRAD reflectivity derived rainfall estimates comparison with measurement from collocated rain gauges. AGU Fall meeting, San Francisco, CA, December 10-14. (link)

*Guan, H., H. Xie, and J. L. Wilson, 2007. A physically-based multivariate-regression approach for downscaling NEXRAD precipitation in mountainous terrain. 33rd Conference on Radar Meteorology,  Cairns, Queensland, Australia. August 6-10, 2007. (link)

*Weissling, BP, H. Xie, 2007. Streamflow prediction in ungaged watersheds: statistical modeling with remote sensing. AMS 87th annual meeting, San Antonio, TX, January 14-18 (link)

*Wang, X., H Xie, H Sharif, 2007. The impact of local and global climate variation/change on extreme weather events in the south central Texas. AMS 87th annual meeting, San Antonio, TX, January 14-18 (link)

*Weissling, BP, H Xie, 2006. A multitemporal remote sensing approach to streamflow prediction and flood vulnerability forecasting. AGU Fall meeting, San Francisco, CA, December 11-15.(link)

*Wang, X and H. Xie, 2006. Comparison of the NEXRAD MPE and Stage III precipitation products in Texas Hill country. SWAAG annual meeting, Norman, OK, October 26-28.

*Wang X., H Xie, 2006. Comparison of the NEXRDA MPE and Stage III precipitation products in Texas Hill Country. UTSA 2006 student conference on Engineering, Science and Biotechnology, October 20.

**Guan, H., J.L.Wilson, E.E. Small, 2006. Partitioning of evaporation and transpiration in semiarid ecosystems using a dual-source surface energy model (TEVT). AGU Joint Assembly. Baltimore, MD, May 23-26 (link)

**Guan, H., H.Xie, H. Hsu, O. Makhnin, J.l. Wilson, 2006. ASOADek application of gauge-based precipitation records in Taiwan and its hydroclimatic implications. AGU Joint Assembly. Baltimore, MD, May 23-26 (link)

**Guan, H., H.Xie, and J.L.Wilson, 2006. A physically-based multivariate-regression appraoch for downscaling NEXRAD precipitation in mountainous terrain. AGU Joint Assembly. Baltimore, MD, May 23-26.(link)

Xie, H. and X. Wang, 2006. Comparison of NEXRAD Stage III and MPE precipitation products with constraints from high quality and density of raingauge networks in the Upper Guadalupe River Basin, Central Texas. AAGU Joint Assembly. Baltimore, MD, May 23-26.(link)

Xie, H., X.Zhou, J.M,Hendrickx, and H.Guan, 2006. Evaluation of NEXRDA Stage III precipitation data over Sevilleta National Wildlife Refuge: a semiarid region in Central New Mexico. AGU Joint Assembly. Baltimore, MD, May 23-26. (link)

Wang, X. and H. Xie, 2006.Validation of the new NEXRAD precipitation product - Multisensor Precipitation Estimator (MPE) - in Texas Hill Country. AAG Annual Meeting. Chicago, IL, March 7-11.

Xie, H. and X. Wang, 2005. Validation of NEXRAD Stage III (or MPE) precipitation in Texas Hill Country and the variability of the estimates between Texas Hill Country and Central New Mexico. The 32nd Conference on Radar Meteorology, Albuquerque, NM, October 24-28

**Guan, H., H. Xie, and J. Wilson, 2005. A physical-based parsimonious approach for spatial disaggregation of NEXRAD precipitation in mountainous terrain. The 32nd Conference on Radar Meteorology, Albuquerque, NM, October 24-28.

Xie, H., E. Vivoni, X. Zhou, and J. Hendrickx, 2005. Rainfall climatology of the monsoon season in New Mexico: Observations from NEXRAD Stage III (1996-2003), AMS Annual Conference (85th), January 9-13, San Diego, California.

Scanlon, B., M. Musgrove, A. Sansom, H. Xie, B. Wilcox, J. Sharp, C. Alexander, B. Vieux, R.Jackson, S. Archer, K. Keese, R. Reedy, 2004. Unique Aspects of proposed San Antonio/Guadalupe Hydrologic Observatory in Texas, AGU Fall Meeting, December 13-17, San Francisco, California.

Scanlon, B., M. Musgrove, A. Sansom, H. Xie, J. Sharp, Z. Yang, 2004. Potential advances in quantifying water cycle in karst system using hydrologic observatory approach, GSA Annual Conference, November 7-10, Denver, Colorado.

Xie, H., G. R. Keller, and X. Zhou, 2004. GIS-based automated time-series remote sensing data conversion and information retrieval, GSA Annual Conference, November 7-10, Denver, Colorado.


Last Updated: October, 2013