Characteristics Of Radiosonde-observed Wind,temperature And Humidity At South Pole In The Past 30 Years

As the coldest continent on the earth,Antarctica plays an important role in the research of global climate change due to its special geographical location and ecological environment.The vertical profiles and trends of temperature and wind at the South Pole up to 30 km above mean sea level?amsl?were investigated by radiosonde data collected from 1987 to 2017.Combined with reanalysis data,the extreme temperatures in winter at about 5 km were studied.The characteristics of humidity variation from the surface to 10 km amsl during 2005 to 2017 were also analyzed.The main conclusions were as following:?1?During an average year between 1987 and 2017,the highest?lowest?temperature in the troposphere was approximately-25??-60??in December?July?at a height of about 500m above the surface?at the surface?.The coldest layer was around 21 km in winter,reaching-90?.A temperature inversion layer above the surface was found during the whole year,while the inversion layers at about 10 km amsl mostly disappeared during spring and winter.General warming trends of annual mean temperature were found in the troposphere,at the rate of0.3?/decade near the surface.For the layer average from the surface to 10 km amsl,the increasing trend was most obvious in autumn,reaching 0.55?/10a.?2?The EOF analysis of the number of days with extreme high and low temperature in winter indicated the multiple characteristics of the spatial patterns.Antarctic oscillation was the main factor for the change of extreme events in the first mode.The positive?negative?phase of the first EOF mode of extreme high temperature events showed a decrease?increase?in the number of days,and the variation of days with extreme low temperature was opposite.The composite analysis also showed that during the positive phase of the SAM index,there are few extreme warm days and more extreme cold days.The number of days with extreme high temperature in the northeast of Antarctica increased with the strengthen of wind,while in the west Antarctica,the increase of wind speed may result in the low temperature.When the sea surface temperature in the Nino3.4 region increased,the number of days with extreme low temperatures increased significantly in most area of the Antarctic.?3?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 occurred in higher levels.The wind speed near surface was frequently in 2-10 m/s range.Around 6-9 km above mean sea level a tropopause jet up to 25 m/s was observed.In the upper stratosphere,strong winds larger than 30 m/s sometimes appeared.The correlation coefficient between seasonal/yearly wind speed and temperature gradient was negative?positive?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.?4?Most of the water vapor was confined in the lowermost 3 km of the atmosphere with a maximum of over 0.3 g·kg^-1 in December at a 200 m height above surface,and the specific humidity had the similar characteristic of annual cycle and inversion layers as the temperature.Above 6 km amsl,the specific humidity remained almost invariant due to its small moisture content.From the surface to 10 km amsl,the specific humidity averaged had the relatively obvious trend of about 0.006 g·kg^-1/decade in spring.