Relationships between lightning flash rates and passive microwave brightness temperatures at 85 and 37 GHz over the tropics and subtropics

Abstract

[1] Using 13 years of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager observations, the precipitation features are defined by grouping contiguous raining regions over the tropics and subtropics. The lightning flash rate in each precipitation feature is determined using the TRMM Lightning Imaging Sensor. Relationships are investigated between lightning flash rate and minimum brightness temperature of each feature, as well as the area with low brightness temperatures at 85 and 37 GHz wavelengths in the precipitation features. These relationships are treated separately on a 4° × 4° grid between 36°S and 36°N. Consistent with earlier studies, the systems over land have more flashes and higher probabilities of lightning than those over ocean given the same brightness temperatures at 85 and 37 GHz. The minimum 37 GHz brightness temperature in the precipitation feature is found to be a good indicator of the probability of lightning. However, the area of low brightness temperatures of the precipitation features is better correlated with the lightning flash rates than the minimum brightness temperature. This implies that the flash rate is not as highly correlated to the maximum convective intensity of the thunderstorm. It is the total amount of ice passing through the mixed phase region in the convective core(s) that better correlates to the area-total flash rates. Over some land regions, high correlations between flash rate and the area of low brightness temperature at 85 and 37 GHz are established. However, there are large regional variations of these relationships.