IPWG U.S. Validation Page



Daily (IPWG) Validation

Swath Statistics

STAR Rainfall Product Cal/Val Center


Project Description


This website disseminates the results of both daily and seasonal validation of STAR rainfall products over the contiguous United States. Daily rainfall amounts are validated relative to the gauge-corrected Multi-Radar/Multi-Sensor System (MRMS), and MRMS radar-only data at 2-minute temporal resolution are used to validate the level-2 swath data (e.g., AMSR2 and ATMS).

Seasonal validation is performed for several NESDIS-generated operational rainfall products (i.e., SCaMPR, MiRS, MSPPS, and the HydroEstimator), which were originally developed by STAR scientists. For comparison, validation also was extended to CMORPH, Merged Microwave, GPI (CPC), TRMM (NASA), NRL Blended, PERSIANN (UC Irvine), and GSMAP (JAXA).

This research effort seeks to provide algorithm developers with feedback on the performance of their products, which will help guide decisions on whether to divert resources toward algorithm improvement or to investigate reasons for recent algorithm behavior (good or poor).

Recent Updates


The website has undergone a complete transformation to ease access and better serve the community. The main page now directly links our various validation activities. Navigation buttons accompany the daily validation images, allowing for easier analysis of consecutive days. Archives now provide access to daily imagery over 60 days old.

The validation procedures were modified to incorporate precipitation estimates from the ATMS instrument. In addition, considerable effort has been expended to streamline and document these procedures. The formatting and quality of the JPSS GCOM AMSR2 and ATMS images have been update. The new AMSR2 images are currently automated and the ATMS images will be automated in the near future.

Times series and histograms were created to compare GPROF2014 rain rates with the Stage IV radar data for January and July 2013. This work was requested by Ralph Ferraro (STAR) to assist algorithm development by his group.

Future Tasks


Seasonal rainfall validation for the ongoing 2016-2017 seasons is being conducted routinely and the new results are posted within one month following each season. The 2017 daily rainfall images will be archived and added to the Daily Validation seection. Work is also being conducted to update the daily validation images. Once these images are completed they will be phased into the "Most Recent" subsection in the Daily Validation Section.

Our Cal/Val efforts are expanding to incorporate several exciting new rainfall estimates, including the JPSS GCOM AMSR-2, MiRS ATMS, NESDIS bRR, Environmental Data Records (EDR) rain rate from SSMI/S, and NASA IMERG.

Present validation activities focus on rainfall validation, and largely exclude validation of snowfall estimates. Several snow products are routinely produced by STAR scientists, and validation of these products is required. We will begin assessing potential sources of reliable snow validation data that can be used to routinely validate snowfall estimates from satellites.

Statistical Maps

Time Series Plots

Precipitation Histograms