A five‐year radar climatology of convective precipitation for New Jersey

Abstract

AbstractA radar climatology of convective precipitation for New Jersey during the summer season (May‐September) was developed using manually digitized radar (MDR) data from four local radar sites. Convective precipitation frequencies were determined by tabulating occurrences of echo intensity levels equal to 2 or more for each of 63 grid boxes located in and around New Jersey. Convective precipitation frequencies over a 5‐year period (1978–1982) were plotted by grid box, and isopleths of duration and intensity level were constructed. The distribution of the frequency of occurrence of convective activity was examined for thunderstorm (level 3 or more) occurrence and severe thunderstorm (level 5 or more) occurrence. The highest convective frequencies occurred over south‐eastern Pennsylvania while the greatest frequency of more intense convection occurred over south‐central New Jersey. An analysis of variance (ANOVA) was performed on the data set to determine the relative variability of convective precipitation in the grid. Year‐to‐year and week‐to‐week variability was high whilst intergrid‐box variability was low. Duncan's multiple range test (DMRT) was applied to compare individual years to each other, and individual weeks to each other. When grid boxes were assigned to four climatological regions and DMRT applied, some regions were found to be significantly different from one another. No significant differences were found between grid boxes within each region. There was no interaction between grid regions and years as differences in mean convective activity between regions remained generally constant from year to year. The distribution of convective activity over New Jersey was found to be determined by local climatological factors while the total frequency from year to year was determined by the mean synoptic pattern.