Factors Influencing Diurnal Variations of Cloud and Precipitation in the Yushu Area of the Tibetan Plateau
Factors Influencing Diurnal Variations of Cloud and Precipitation in the Yushu Area of the Tibetan Plateau
复制标题
DOI：
10.1007/s13351-022-1167-6
复制
发表时间：
2022-04
影响因子：
3.2
通讯作者：
Bangjun Cao;S. Lyu;Yu Zhang;Xianyu Yang;Boliang Li;Lijuan Yuan;Meilin Li
中科院分区：
文献类型：
--
作者：
Bangjun Cao;S. Lyu;Yu Zhang;Xianyu Yang;Boliang Li;Lijuan Yuan;Meilin Li
利用云雷达、地面观测资料和欧洲中期天气预报中心再分析v5（ERA 5）资料，对青藏高原玉树地区夏季夜间降水的影响因子进行了研究。比较了非降水日和降水日的云顶高度、云底高度和液态水含量。结果表明，玉树地区降水日的平均对流层高度白天在10 km以下，夜间在10 km以上，最大值出现在北京时间23时。CBH与露点扩展同相。降水强度和CTH与LWC同步。ERA 5的小时平均降水强度和对流有效位能在2100 BT达到最大值，比观测值提前3 h。无降水日中午有下降运动，降水日夜间有上升运动。此外，低层（5000米以下）水平风向从早到晚呈顺时针旋转。风切变发生在大气中层，伴随着副热带西风急流在高层。200 ~ 500 hPa的水平风速差与LWC呈正相关，从而有助于高空云的形成。
Using the cloud radar, ground observations, and ECMWF Reanalysis v5 (ERA5) data, we investigate the factors influencing nighttime precipitation during summer in the Yushu area of the Tibetan Plateau (TP). The cloud top height (CTH), cloud base height (CBH), and liquid water content (LWC) are compared between non-precipitation and precipitation days. The results show that the average CTH on precipitation days in Yushu is below 10 km above ground level (AGL) in the daytime, whereas it exceeds 10 km AGL at night, with the maximum at 2300 BT (Beijing Time). The CBH is in-phase with the dewpoint spread. The precipitation intensity and CTH are in-phase with the LWC. The hourly averaged precipitation intensity and convective available potential energy in ERA5 reach their maximums at 2100 BT, which is 3 h ahead of their observed counterparts. There is descending motion in the mid day on non-precipitation days, whereas there is ascending motion at night on precipitation days. In addition, the horizontal wind direction in the lower level (below 5000 m) shows clockwise rotation from morning to night. Wind shear occurs in the mid level of the atmosphere, accompanied by a subtropical westerly jet in the upper level. The difference in horizontal wind speed between 200 and 500 hPa is positively related to the LWC, thereby contributing to the formation of upper-level cloud.