Main Detrainment Height of Deep Convection Systems over the Tibetan Plateau and Its Southern Slope

Abstract

Deep convection systems (DCSs) can rapidly lift water vapor and other pollutants from the lower troposphere to the upper troposphere and lower stratosphere. The main detrainment height determines the level to which the air parcel is lifted. We analyzed the main detrainment height over the Tibetan Plateau and its southern slope based on the CloudSat Cloud Profiling Radar 2B_GEOPROF dataset and the Aura Microwave Limb Sounder Level 2 cloud ice product onboard the A-train constellation of Earth-observing satellites. It was found that the DCSs over the Tibetan Plateau and its southern slope have a higher main detrainment height (about 10–16 km) than other regions in the same latitude. The mean main detrainment heights are 12.9 and 13.3 km over the Tibetan Plateau and its southern slope, respectively. The cloud ice water path decreases by 16.8% after excluding the influences of DCSs, and the height with the maximum increase in cloud ice water content is located at 178 hPa (about 13 km). The main detrainment height and outflow horizontal range are higher and larger over the central and eastern Tibetan Plateau, the west of the southern slope, and the southeastern edge of the Tibetan Plateau than that over the northwestern Tibetan Plateau. The main detrainment height and outflow horizontal range are lower and broader at nighttime than during daytime.

摘要

深对流系统能够快速的将对流层下层的水汽和污染物输送到对流层上层和平流层下层, 其主要溢出高度则决定了气块被深对流抬升后影响环境场的高度. 基于A-train卫星编队中的CloudSat和Aura两颗卫星对青藏高原及其南坡深对流的联合观测, 本文对深对流在青藏高原及其南坡的主要溢出高度以及出流对环境场冰水含量的影响进行了综合的分析研究. 主要的结论如下: 通过CloudSat CPR对云雷达回波的观测发现青藏高原及其南坡的深对流相比同纬度的其他地区有较高的主要溢出高度, 深对流出流云砧分布在10–16 km. 平均的主要溢出高度在青藏高原及其南坡分别为12.9和13.3 km. 具有较高出流高度和较大出流范围的深对流则主要分布在青藏高原的中东部以及高原南坡. 夜间发生的深对流相比白天出流高度较低但是出流范围更大. 结合Aura MLS对冰水含量的观测也表明在深对流出流过程中环境场冰水含量的最大增加层也发生在178hPa (约13km). 深对流对气候态的平均冰水路径有显著影响, 去除深对流的影响后, 夏季平均冰水路径将减少16.8%.