庐山云雾及降水的日、季节变化和宏微观物理特征观测研究

An observational study of diurnal and seasonal variations, and macroscopic and microphysical properties of clouds and precipitation over Mount Lu, Jiangxi, China

中文关键词:  庐山  云雾和降水  日和季节变化  宏微观物理特征

英文关键词:Mount Lu  Clouds  Fog and precipitation  Diurnal and seasonal variations  Macroscopic and microphysical properties

中文摘要:

      庐山云雾观测站2015年重新开始观测试验。利用2015年11月—2018年2月庐山云雾试验站观测的云物理资料和九江站的雷达资料，统计研究了庐山云雾及降水的日、季节变化和宏微观物理特征。结果表明，庐山强降水多发生在夏季，降水强度超过100 mm/h，而云雾天多发生在秋冬春季，最高云和雾天数达25 d/月，最低能见度仅20 m，东北风有利于水汽的冷却凝结。云雾辐射影响下的日最低温度出现在09时前后，即云雾消散前。利用雷达资料对降水分类，庐山秋冬季层状云、积层混合云和对流云降水分别占29%、44%和27%，春夏季的对流云和积层混合云降水分别占83%和17%。与城市降水和雾相比，庐山降水的中、小雨滴多，云雾滴谱的数浓度较低，双峰结构显著，且谱较宽。随着云内降水量级的增大，雨滴的数浓度和尺度不断增加，更易于启动碰并机制，使小于11 μm和大于30 μm云雾滴减少，导致11 μm的峰值更为显著。降雪期间的小云雾滴较为丰富，固态降水更容易通过凇附过程消耗大的过冷云滴。

英文摘要:

      The Mount Lu (Lushan) observational station of clouds and fog was restarted in 2015. Characteristics of clouds and precipitation are investigated based on observations collected at Mount Lu station from November 2015 to February 2018, including microphysics properties of clouds/fog and precipitation of 15 months in cold and warm seasons. Statistical results suggest that heavy precipitation over the Mount Lu is frequent in summer with maximal daily precipitation exceeding 100 mm. Clouds and fog occur frequently in autumn, winter and spring. The maximum number of clouds and fog reaches 25 days per month with the lowest visibility of about 20 m. Affected by radiative effects of clouds and fog in the morning, the minimum temperature in the diurnal variation of temperature occurs at about 09:00 (local sun time), right before the dissipation of clouds and fog. Based on analysis of radar data, stratiform precipitation, stratiform precipitation with embedded convection and convective precipitation account for 29%, 44% and 27% of the total precipitation in the autumn and winter, respectively; convective precipitation and stratiform precipitation with embedded convection account for 83% and 17% of the total precipitation in the spring and summer, respectively. Compared with precipitation in urban areas, more small and medium size raindrops are found for precipitation over Mount Lu. Compared with that in urban areas, clouds and fog over Mount Lu are characterized by smaller number concentration, more significant bimodal feature and wider spectra. As the precipitation within clouds increases, both the number concentration and the size of raindrops increase, which makes it easier to initiate the collision and aggregation process, leading to reduction in cloud droplets smaller than 11 μm and larger than 30 μm. As a result, the peak at 11 μm becomes more significant. During snowing period, small cloud droplets are abundant, and the solid-phase precipitation consumes large freezing cloud droplets through the riming process.