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Multiscale Hydrologic Remote Sensing: Perspectives and Applications
to estimate daily spatial precipitation in 2003. These results show the potential of
calibrating NEXRAD data using the rain gauge observation with the aid of specific
interpolation schemes. Zhang and Srinivasan (2010) compared the performance of
BA, regression kriging (RK), and SKlm for incorporating rain gauge observations
into NEXRAD. Their results show that SKlm performs best among these methods.
12.3 OVERVIEW OF THE NEXRAD VALIDATION
AND CALIBRATION SOFTWARE
GIS is a powerful tool for facilitating geospatially related research, including spatial
interpolation of climate data and analysis of storm kinematics (Tsanis and Gad 2001;
Zhang and Srinivasan 2009). Xie et al. (2005) developed a program for automated
processing of NEXRAD Stage III data using Arc Macro Language. Hardegree et
al. (2008) modified the NWS source code to provide decoding and georeferencing
tools. Hydro-NEXRAD is a web-based software for obtaining historical customized NEXRAD-based radar precipitation maps (products) from some 40 WSR-88D
radars covering mainly the central and eastern United States (Krajewski et al. 2011).
Customized basin-centered NEXRAD products can be requested from HydroNEXRAD at http://hydro-nexrad.net/hydronexrad_v0.7/index.html. Recently, Zhang
and Srinivasan (2010) have developed the NEXRAD-VC software for automated
processing and calibrating NEXRAD data for hydrologic and ecological modeling
(Sexton et al. 2010; Srinivasan et al. 2010).
12.3.1 featuReS of nexRad-vc
NEXRAD-VC is an extension of ArcGIS 9.x to facilitate spatial precipitation estimation (Figure 12.1). Its major advantage is the provision of a user-friendly means
of deriving precipitation data from the compressed binary format of NEXRAD and
incorporate rain gauge observations to improve the accuracy of the NEXRAD data.
The following are the major features of NEXRAD-VC.
1. Few requirements on input data preparation. Users of NEXRAD-VC only
need to prepare rain gauge shapefiles, precipitation records for each rain
gauge in text format and hydrologic unit (e.g., subbasin) shapefiles. In addition, users need to download NEXRAD data in NetCDF or compressed
binary file format, which will be sequentially read by NEXRAD-VC and
transformed into ArcGIS grid format.
2. Automatic projection transformation. NEXRAD-VC provides an automatic
projection transformation function to spatially match the rain gauge and
hydrologic unit shapefiles with NEXRAD data. NEXRAD data in NetCDF
and compressed binary formats are in the HRAP grid coordinate system
with a polar stereographic projection true at 60°N, 105°W. In most cases,
rain gauge and hydrologic unit maps are in some projected coordinate systems. The automatic projection transformation function of NEXRAD-VC
can save time by transforming the NEXRAD data to the projection of the
rain gauge and hydrologic unit maps.
Multiscale Hydrologic Remote Sensing: Perspectives and Applications
to estimate daily spatial precipitation in 2003. These results show the potential of
calibrating NEXRAD data using the rain gauge observation with the aid of specific
interpolation schemes. Zhang and Srinivasan (2010) compared the performance of
BA, regression kriging (RK), and SKlm for incorporating rain gauge observations
into NEXRAD. Their results show that SKlm performs best among these methods.
12.3 OVERVIEW OF THE NEXRAD VALIDATION
AND CALIBRATION SOFTWARE
GIS is a powerful tool for facilitating geospatially related research, including spatial
interpolation of climate data and analysis of storm kinematics (Tsanis and Gad 2001;
Zhang and Srinivasan 2009). Xie et al. (2005) developed a program for automated
processing of NEXRAD Stage III data using Arc Macro Language. Hardegree et
al. (2008) modified the NWS source code to provide decoding and georeferencing
tools. Hydro-NEXRAD is a web-based software for obtaining historical customized NEXRAD-based radar precipitation maps (products) from some 40 WSR-88D
radars covering mainly the central and eastern United States (Krajewski et al. 2011).
Customized basin-centered NEXRAD products can be requested from HydroNEXRAD at http://hydro-nexrad.net/hydronexrad_v0.7/index.html. Recently, Zhang
and Srinivasan (2010) have developed the NEXRAD-VC software for automated
processing and calibrating NEXRAD data for hydrologic and ecological modeling
(Sexton et al. 2010; Srinivasan et al. 2010).
12.3.1 featuReS of nexRad-vc
NEXRAD-VC is an extension of ArcGIS 9.x to facilitate spatial precipitation estimation (Figure 12.1). Its major advantage is the provision of a user-friendly means
of deriving precipitation data from the compressed binary format of NEXRAD and
incorporate rain gauge observations to improve the accuracy of the NEXRAD data.
The following are the major features of NEXRAD-VC.
1. Few requirements on input data preparation. Users of NEXRAD-VC only
need to prepare rain gauge shapefiles, precipitation records for each rain
gauge in text format and hydrologic unit (e.g., subbasin) shapefiles. In addition, users need to download NEXRAD data in NetCDF or compressed
binary file format, which will be sequentially read by NEXRAD-VC and
transformed into ArcGIS grid format.
2. Automatic projection transformation. NEXRAD-VC provides an automatic
projection transformation function to spatially match the rain gauge and
hydrologic unit shapefiles with NEXRAD data. NEXRAD data in NetCDF
and compressed binary formats are in the HRAP grid coordinate system
with a polar stereographic projection true at 60°N, 105°W. In most cases,
rain gauge and hydrologic unit maps are in some projected coordinate systems. The automatic projection transformation function of NEXRAD-VC
can save time by transforming the NEXRAD data to the projection of the
rain gauge and hydrologic unit maps.