Analysis of Recording Raingage Data for the Israeli II Experiment. Part II: Differential Day and Night Effects of Cloud Seeding

Abstract

This paper reports separate analyses of daytime and nighttime precipitation based on data from recording raingages of the second Israeli randomized experiment. These analyses seemed important because there are a number of hypotheses on the differential effects of AgI seeding during the day and at night, and because about half of the seeding of this experiment was done at night. Our findings are unfortunately equivocal because of the large variability of the date which had to be broken down by categories of modal cloud-top temperatures and 12-b (day/night) periods. The increase of precipitation efficiency that had been noticed (on 24-h data) to occur in the −12° to −21°C window appears to have been larger at night, but the difference is not significant. The increase in the number of rain events for warmer clouds may have been only a daytime effect, but again, the present data are not conclusive.