271
12
Precipitation Estimate
Using NEXRAD GroundBased Radar Images
Validation, Calibration,
and Spatial Analysis
Xuesong Zhang
CONTENTS
12.1 Introduction .................................................................................................. 272
12.2 Literature Review ......................................................................................... 273
12.2.1 NEXRAD Precipitation Products .................................................... 273
12.2.2 Validation and Calibration of NEXRAD Precipitation Images
Using Rain Gauge Data .................................................................... 274
12.3 Overview of the NEXRAD Validation and Calibration Software ............... 276
12.3.1 Features of NEXRAD-VC ............................................................... 276
12.3.2 NEXRAD Calibration Algorithms in NEXRAD-VC ..................... 277
12.3.2.1 Bias Adjustment ................................................................ 278
12.3.2.2 Ordinary Kriging .............................................................. 278
12.3.2.3 Simple Kriging .................................................................. 279
12.3.2.4 Regression Kriging ........................................................... 279
12.3.2.5 Kriging with External Drift .............................................. 281
12.3.2.6 Simple Kriging with Varying Local Means ..................... 282
12.3.2.7 Semivariogram Model ....................................................... 282
12.3.3 Accuracy Evaluation Coefficients .................................................... 283
12.4 Case Study 1: Comparing NEXRAD Precipitation Data with Rain
Gauge Observations ..................................................................................... 285
12.4.1 Performance of NEXRAD in a Mountainous Region versus
Southern Plains ................................................................................ 285
12.4.2 Performance of NEXRAD in Warm Season versus Cold Season ... 287
12.4.3 Effect of Subgrid Heterogeneity on NEXRAD Performance .......... 288
12.4.4 NEXRAD Performance for Hourly and Daily Temporal Scales ..... 291
12.5 Case Study 2: Calibrating NEXRAD Precipitation DATA Using Rain
Gauge Observations ..................................................................................... 291
12.5.1 Little River Experimental Watershed (LREW) ............................... 292
12
Precipitation Estimate
Using NEXRAD GroundBased Radar Images
Validation, Calibration,
and Spatial Analysis
Xuesong Zhang
CONTENTS
12.1 Introduction .................................................................................................. 272
12.2 Literature Review ......................................................................................... 273
12.2.1 NEXRAD Precipitation Products .................................................... 273
12.2.2 Validation and Calibration of NEXRAD Precipitation Images
Using Rain Gauge Data .................................................................... 274
12.3 Overview of the NEXRAD Validation and Calibration Software ............... 276
12.3.1 Features of NEXRAD-VC ............................................................... 276
12.3.2 NEXRAD Calibration Algorithms in NEXRAD-VC ..................... 277
12.3.2.1 Bias Adjustment ................................................................ 278
12.3.2.2 Ordinary Kriging .............................................................. 278
12.3.2.3 Simple Kriging .................................................................. 279
12.3.2.4 Regression Kriging ........................................................... 279
12.3.2.5 Kriging with External Drift .............................................. 281
12.3.2.6 Simple Kriging with Varying Local Means ..................... 282
12.3.2.7 Semivariogram Model ....................................................... 282
12.3.3 Accuracy Evaluation Coefficients .................................................... 283
12.4 Case Study 1: Comparing NEXRAD Precipitation Data with Rain
Gauge Observations ..................................................................................... 285
12.4.1 Performance of NEXRAD in a Mountainous Region versus
Southern Plains ................................................................................ 285
12.4.2 Performance of NEXRAD in Warm Season versus Cold Season ... 287
12.4.3 Effect of Subgrid Heterogeneity on NEXRAD Performance .......... 288
12.4.4 NEXRAD Performance for Hourly and Daily Temporal Scales ..... 291
12.5 Case Study 2: Calibrating NEXRAD Precipitation DATA Using Rain
Gauge Observations ..................................................................................... 291
12.5.1 Little River Experimental Watershed (LREW) ............................... 292