Microphysical Fingerprinting of Extreme Rainfall Over Taiwan's Central Mountain Range

The knowledge of what drives extreme precipitation events is invaluable to forecasting and warnings, especially in mountainous regions with potentially isolated populations. Mountainous Taiwan is an ideal location for studying these extreme events because it has an abundance of available moisture for frequent heavy rainfall. In this moist environment, microphysical processes can be studied to better understand what is causing heavy rainfall, including how mountainous terrain impacts those processes. We utilized dual-polarization radar data collected in the 2022 PRECIP field campaign to investigate if there is a difference in the dominating microphysical process at different elevations in the mountains through a technique known as fingerprinting. Each individual microphysical process has a unique radar signature that can be seen when observing how precipitating hydrometeors change vertically with height. To address our research question, we used data from a heavy precipitation event during PRECIP (May 25-27, 2022) and separated the radar data into three elevation groupings for the top 99th percentile of rainfall rates in each group. We then used the microphysical fingerprinting technique to determine the dominant process in each elevation grouping for extreme precipitation. We found that as you go higher up in terrain elevation, the dominating microphysical process shifts from coalescence (a process wherein hydrometeors collide with each other and coalesce into larger hydrometeors) to breakup (a process wherein hydrometeors break apart into smaller hydrometeors), which supports our hypothesis that terrain elevation effects the dominating microphysical process. These findings motivate extending this technique to the entirety of PRECIP’s radar dataset to see if the dominant processes in each elevation grouping are different depending on the intensity or type of storm, or other limiting factors that have yet to be explored.