A new method in determining potential region of precipitation enhancement above coastal land

Abstract

To ensure the effectiveness of the operation of artificial precipitation enhancement, a potential region for the operation should be determined in advance. As cloud microphysical measurements needed for the determination of the potential region of cloud seeding are not available before the operation of routine precipitation enhancement, a new method based on the growth process of ice crystal is put forward for determining the potential region using the numerical weather prediction model output. The ice supersaturation, accumulated water vapor within minus temperature layer (≥9 mm), and upward water vapor transportation are adopted as criteria to determine the potential time, height and region of cloud seeding, and the real-time radar images are applied to make decisions on the seeding commanding. The criteria and Doppler radar images are studied in a case of precipitation enhancement characterized by significant water vapor supply from the north part of a tropical cyclone in the northwest Pacific, which shows that the ocean plays a crucial role in the advection transportation of water vapor to the potential region of the coastal area. The study presents a new method to determine the potential region of precipitation enhancement using macro-physical quantities under ice crystal growth environment. The method possesses a clear physical significance and can be readily applied with the required and easily predicted parameters.