Building a Multi-Satellite Passive-Microwave Hail Retrieval and Climatology

Satellite-borne observations of hail provide a means to construct globally uniform hail climatologies. We leverage the sensitivity of passive-microwave radiometers to scattering by hail, particularly in the channels from 10 to 89 GHz to create a satellite-borne passive microwave hail retrieval. This sensitivity has been used to develop hail proxies for the last several decades. We then apply this retrieval to multiple satellites to construct robust, near-global climatologies of hail.

We employ 17+ years of Tropical Rainfall Measuring Mission (TRMM) precipitation feature data to construct a multi-frequency passive-microwave hail retrieval trained on surface hail reports in the United States. We then extend our hail retrieval to the Global Precipitation Measurement (GPM), Advanced Microwave Scanning Radiometer for EOS (AMSR-E), and the Advanced Microwave Scanning Radiometer 2 (AMSR2) passive-microwave datasets.

We employ a histogram-adjustment method to account for different frequencies used across multiple satellites and differing footprint sizes before applying the hail retrieval. The climatologies are gridded and normalized to account for the satellites' different orbits and inclinations, which affect sampling and diurnal biases. Limited diurnal sampling by the sun-synchronous satellites carrying AMSR-E and AMSR2 will have to be accounted for before merging the AMSR-based climatologies with those from TRMM and GPM. Once we establish a uniform assessment of the probability of hail from each of these four platforms, ultimate goals are to construct near-global climatologies from 1998 to the present, and then to leverage the longstanding passive-microwave dataset that extends back to the late 1980's.