Characteristics of Precipitation Cloud System in Northeast China Cold Vortex at Changbai Mountain Foothills

Abstract

Utilizing the microwave radiometer data and hourly rainfall data in Jilin Cloud Physics Field Scientific Test Base, CMA, the precipitation cloud system in Northeast China cold vortex at the Changbai Mountain foothills is analyzed. Rainfall events are divided into heavy precipitation, moderate intensity precipitation, and weak precipitation. Assisted by ERA5 reanalysis data, results show that the middle and high clouds appear first by 6 hours before the precipitation occurrence at the Changbai Mountain foothills. Water vapor and cloud water are both important for the occurrence and maintenance of heavy precipitation induced by Northeast China cold vortex. The cloud liquid water appears approximately with the height of 5-6 km by 4 hours before the precipitation induced by Northeast China cold vortex. Two hours before precipitation, the cloud descendes sharply. During one hour after the three types precipitation occurrence, the vapor density respectively leap to 13-14 g·m-3, 9-12 g·m-3, and 7-9 g·m-3 below 1 km height. Integrated water vapor during three types of precipitation increase to 5.8 cm, 4.2 cm, and 3.5 cm, respectively. The water vapor increases 5 hours before the occurrence of strong precipitation below 6 km height. The vapor density increases to 12-14 g·m-3 below 1 km height. There is cloud liquid water with 1.0-1.6 g·m-3 at the height of 5-6 km in the temperature layers of -5--10 ℃, which contributes to the formation of ice and snow crystals. Six hours before the heavy precipitation, moderate intensity precipitation, and weak precipitation, the integrated cloud liquid water are 4.2-4.8 mm, 3.0 mm, 2.3 mm, respectively. There are middle and high clouds in the temperature layers of -6 ℃ and -16 ℃. The height of cloud base drops sharply from 5.5-7 km to the ground, while the relative humidity drops sharply. These characteristics continue until the beginning of heavy rainfall. For moderate and weak precipitation induced by Northeast China cold vortex, there is middle cloud before the precipitation, and the cloud liquid water is 0.4-0.8 g· m-3 at the height of 5-6 km. However, there is no characteristic of water vapor jumping or relative humidity decreasing.Through the study of these physical quantity characteristics, indicators with indicative and predictive significance for precipitation induced by Northeast China cold vortex have been established.

Keywords

• microwave radiometers
• precipitation
• statistical analysis