西藏改则地区雨季上对流层/下平流层大气垂直结构观测研究

An observational study on the vertical structure of the upper troposphere and lower stratosphere in Gaize of Tibet during the rainy season

中文关键词:  西藏  风速  相对湿度  对流层顶  GPS探空

英文关键词:Tibet  Wind speed  Relative humidity  Tropopause  Radiosonde

中文摘要:

      利用中国第3次青藏高原大气科学试验2014年7-8月改则探空试验期间获取的每天3次观测的探空数据，对该地区对流层大气垂直结构进行了研究。结果表明：改则地区海拔高度17-19 km存在逆温现象；第一对流层顶平均高度16082 m，第二对流层顶平均高度16466 m，前者出现概率远高于后者，两类对流层顶的高度均与其对流层顶的温度、气压成反比。08、14和20时（北京时）的最大风速分别出现在11.8、12.6和12.1 km高度，风速分别为16.2、16.3和15.9 m/s，风向随高度顺时针变化，对应为暖平流，由下层西南风转为上层的东南风，17 km以上高度稳定成东北风，下层主导风为西南风。在约8 km的高度上存在一个最大相对湿度聚集区，从地面开始相对湿度随高度升高而增大（逆湿现象），达到该聚集区后，随高度升高而减小。青藏高原西部雨季对流层顶折叠现象出现概率较低，可能与该季节高空急流或高空锋天气较少有关。

英文摘要:

      By analyzing three-times-daily radiosonde observation data from the third Tibetan Plateau experiment of atmospheric science during July-August 2014, the vertical structure of the troposphere has been investigated. A temperature inversion layer is found at altitudes between 17 and 19 km above sea level. The height of the first tropopause is approximately 16082 m, a little lower than the height (16466 m) of the second tropopause. The frequency of occurrence of the former is much larger than that of the latter,and both are inversely associated with temperature and pressure at the level of the tropopause. The maximum wind speed (08:00,14:00 and 20:00, Beijing time) is 16.2, 16.3 and 15.9 m/s respectively at altitudes of 11.8, 12.6 and 12.1 km, while the wind direction changes clockwise from southwesterly winds in lower levels to southeasterly winds in upper levels in response to the warm advection. The wind direction finally turns to northeasterly above 17 km height. The relative humidity (RH) increases significantly with altitude from ground until about 8 km above ground level (AGL), where RH reaches its peak value and then decreases with increasing altitude. Also, the RH inversion can be observed in lower levels.