Evaluation of glaciogenic seeding condition over the mountains in Utah

Utah has one of the longest running cloud seeding program in the U.S.. The Utah seeding program targeted several mountain ranges from south to north focusing on winter orographic clouds. In this study, all mountain ranges in Utah are considered to evaluate the cloud seeding condition utilizing the high-resolution Weather Research and Forecasting (WRF) data simulated by NCAR for 13 years. The WRF model data are validated against the observations before developing the suitable cloud seeding condition climatology. Since there are several mountain ranges from south to north, we first separated them to 24 mountain ranges and four regions (northern, central, Uinta and southern regions). Then cloud seeding condition is evaluated for each mountain range for 13-years. Then average is calculated for each region to develop the seeding condition climatology.

Temperature near mountain top level and supercooled liquid water are the two important variables that were considered to find the suitable seeding condition. The seeding condition is evaluated during precipitation only and also during non-precipitating periods. These criteria are applied to all mountain ranges separately and developed the climatology. The cloud seeding condition significantly varies from the northern Utah mountain ranges to southern Utah mountains. The suitable condition is observed for longer period over the northern Utah mountains and Uinta mountain while southern mountain range has shorter period for suitable seeding condition. The central Utah mountains are in the middle between northern and southern mountain regions indicating roughly suitable period decreases from north to south in Utah mountain ranges. Monthly variation of seeding condition based on different temperature ranges will also be discussed.