Precipitation Characteristics of Natural and Seeded Cumulus Clouds in the Asir Region of Saudi Arabia
AbstractThis study presents the typical meteorological conditions and radar-derived precipitation characteristics of developing cumulus congestus clouds over the Asir region of southwest Saudi Arabia. Radar response variables were analyzed to see if there were differences between clouds seeded using AgI at various stages of development, and carefully selected similar natural clouds that formed nearby and at approximately the same time. Three groups of seeded clouds were studied: Group I consisted of 28 clouds seeded at a time without any radar echo, and 43 natural clouds for comparison purposes. Group II consisted of 21 clouds seeded when the radar echo was >0 dBZ but <20 dBZ, and 44 natural clouds for comparison purposes. Group III consisted of 13 clouds seeded when the initial radar echo was >30 dBZ, and 19 natural clouds for comparison purposes. In all three groups, there was a positive association between the seeding and greater maximum radar reflectivity (ZMAX) and maximum precipitation flux (MAX FLUX). The biggest differences between groups was for clouds with ZMAX >50 dBZ and MAX FLUX >100 m^3/s. The greatest seeding effects were observed for clouds that were seeded prior to the appearance of a radar echo. Further research is required to determine the effects on precipitation when seeding clouds that merge with a pre-existing cell.
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