1987-2017年间南极点大气风温垂直结构及趋势变化特征

本文基于1987—2017年南极点的无线电探空数据，研究了地面至30 km海拔高度的气温、风向和风速的垂直分布及变化趋势.多年平均的逐月数据表明，气温在各高度上均具有显著的季节变化，南半球夏季（冬季）对流层低层温度最高达-25℃（最低达-60℃），分别出现于1月（7月）地面以上约500 m（近地面）.近30年来，年平均地面气温呈0.3℃/10a的增加趋势，增温趋势总体上随高度增加而减缓，至对流层上层的气温变化趋势为负，约为-0.25℃/10a.对于对流层整层平均气温，秋季上升趋势在四季中最为明显，达0.55℃/10a，而年平均气温的趋势约为0.3℃/10a.近地面全年盛行东北风，风速大多在2~10 m·s^-1范围内；对流层的低层（高层）为西北风（西南风），在海拔6~9 km处，对流层急流可达25 m·s^-1；而平流层低层（高层）为南风（东南风），最大风速可超过30 m·s^-1.风速和温度梯度变化特征在地面至10 km（10~30 km）高度段表现为负相关（正相关）.近30年近地面呈现北风增加东风减少的趋势，而高空南风减少，东风和北风增多.对流层整层平均风速显示，各季节平均风速均呈增加趋势，并且与温度类似，秋季的增加趋势最显著，达0.59 m·s^-1/10a，而春季趋势最为平缓，仅0.05 m·s^-1/10a.对流层整层年平均风速的线性趋势为0.24 m·s^-1/10a，地面年平均风速呈0.05 m·s^-1/10a的增加趋势.

Vertical structures and trends of atmospheric temperature and wind during 1987-2017 at the South Pole

The vertical profiles and trends of temperature, wind direction and wind speed up to 30 km altitude are investigated by using the radiosonde data collected over the South Pole during the period from 1987 through 2017. The multi-year averaged data showed that the temperature had a significant seasonal variation with the highest (lowest) temperature in southern hemisphere summer (winter). The highest (lowest) temperature in the lower troposphere was approximately -25℃ (-60℃) in January (July) at a height of about 500 m above the surface (at surface). The annual mean temperature showed a warming trend of 0.3℃ per decade at surface, but the trends kept decreasing with increasing height, and turned to negative (-0.25℃/decade) in the upper troposphere. For the height averaged temperature in the whole troposphere, the most apparent increasing trend occurred in autumn, reaching 0.55℃/decade, while the yearly averaged temperature had a trend of about 0.3℃/decade. Throughout all the seasons there were the dominant northerlies to easterlies close to the surface, north-westerlies (westerlies to southerlies) at lower (upper) troposphere, and southerlies (southerlies to easterlies) in lower (upper) stratosphere. Near surface more northerlies and less easterlies were recorded, and less southerlies but more easterlies and northerlies occurred in higher levels. The wind speed near surface was frequently in 2~10 m·s^-1 range. Around 6~9 km above mean sea level a tropopause jet up to 25 m·s^-1 was observed. In the upper stratosphere, strong winds larger than 30 m·s^-1 sometimes appeared. The correlation coefficient between seasonal/yearly wind speed and temperature gradient was negative (positive) over South Pole at the height section of surface -10 km (10~30 km). The seasonal and height averaged wind speed of the whole troposphere showed increasing trends in the recent 30 years, and similar to temperature, the most significant trend occurred in autumn, reaching 0.59 m·s^-1/decade, while the mildest trend appeared in spring with a value of only 0.05 m·s^-1/decade. For the yearly and height averaged wind speed of the whole troposphere, there was an increasing trend of 0.24 m·s^-1/decade. The annual mean surface wind speed increased at a rate of 0.05 m·s^-1/decade.