Rain Rate and Water Content in Hurricanes Compared with Summer Rain in Miami, Florida

Abstract

AbstractLiquid water content (g m−3), precipitation rate (mm h−1), and radar reflectivity (dBZ) are inferred from cross sections of particle images obtained by aircraft. Each dataset is presented in a probability format to display changing functional relationships for the selected intervals. The probability of intercepting a given quantity during a flight provides guidance in required instrument sensitivity together with the frequency of precipitation and liquid water content events for given rainfall totals. These data are compared with surface rain rate obtained over two years in the May–October warm seasons in Miami, Florida, with a Hotplate rain gauge. The warm season Miami surface rain-rate probability distribution is similar to the 2005 hurricane rain-rate distribution. Rain rates > ~120 mm h−1 were responsible for over one-half of the accumulation, even though lighter rain dominated by time. Hurricane rainfall is somewhat more intense than the normal surface convective rainfall in that 10% of the 1977–2001 (old) hurricane rain rates exceeded 20 mm h−1, whereas only 10% of the surface rain rates exceeded only ~10 mm h−1. The shape of the rain-rate probability distributions from the 2005 (recent) hurricane data was nearly identical to the probability distribution of rain rates in the Miami data. The radar reflectivity distributions were similar, whose 90% level was about 45 dBZ for the old storms and about 35 dBZ for the 2005 storms. These data clearly show the low bias of the 2005 hurricane data caused by the systematic avoidance of heavy precipitation.