Relationships for Deriving Thunderstorm Anvil Ice Mass for CCOPE Storm Water Budget Estimates

Abstract

Relationships between radar reflectivity and ice water content are derived from pendmtions into thundemonn anvils in Montana on seven days during the Cooperative Convective Precipitation Experiment (CCOPE), using aircraft data and radar reflectivity, based upon an approach which minimizes the errors in converting measured crystal size to mass. Other sources of error do exist, particularly when measurements are taken in the vicinity of convective cells. The effects of truncation of the measured size spectrum due to sampling volume limitations are discussed. Ice water content (IWC) values predicted from the curves for most of the cases investigated are about the same for a given value of the radar reflectivity factor. Derived curves differ significantly in some cases from those applied to thunderstorm anvils in the past. A sensitivity study is performed to develop an improved mass-diameter relationship for anvil crystals. The choice of Z-IWC relationship has a major effect upon the estimate of the mass transported into the anvil, as demonstrated from one of the cases where wind fields were measured using Doppler radar.