中文摘要：

利用2011年12月至2012年3月中国科学院黄河源区气候与环境综合观测研究站提供的玛曲站的观测资料,通过对比分析三次积雪过程及其前期无雪时的近地层气象要素特征,研究了积雪对大气温度层结特征的影响。观测结果表明：降雪前降温较快,由冷空气过境引发的降雪过程可使2.35 m高处日最高、最低气温24 h降低10℃,雪后气温回升较慢,平均速率为2.5℃·d^-1。温度梯度值白天为负值、夜晚为正值,7.17 m以下温度梯度绝对值较大,平均为0.4℃·m^-1,7.17-18.15 m温度梯度绝对值较小,其值不足0.2℃·m^-1,到18.15 m绝对值减小到0.05℃·m^-1;当地表有积雪覆盖时,早上温度随高度减小的变化趋势出现时间比无雪覆盖时落后1 h,傍晚温度随高度增大的变化趋势较之提前1 h出现。积雪可减小白天气温分布范围,第二次积雪过程由于风速较大减小较明显。除晴天11：00—16：00 4.2-7.17 m,积雪存在将减小各层温度梯度绝对值;晴天11：00—16：00 4.2-7.17 m温度梯度绝对值比2.35-4.2 m偏大,当有积雪覆盖时偏大幅度明显增大,出现这种异常主要是受4.2 m偏暖的影响,这种偏暖现象可能是由观测场内外下垫面植被覆盖不同而引起的温度平流所致,当风速较大时,将破坏这种平流作用,不同高度温度趋于一致。

英文摘要：

Using the observation data at Maqu station in integrated climate and environment observation station from Chinese Academy of Sciences from December 2011 to March 2012. The research station is located at Hequ horse farm of the southwest of Maqu County in Gansu Province. It＇s elevation is 3423 meteors,it＇s called the first bend of the YellowRiver. Its unique location makes the climate cold in winter,the surface of the ground is mainly dominated by alpine meadowand alpine grassland. The three-snowcover process was analyzed,analyzing the different characteristics of the meteorology elements of the near surface between the snowcover and no snowcover,observation results showthat： The snowfall process caused by cold air crossing makes the highest and lowest temperature of a day in 2. 35 m decrease 10 ℃ in one day,temperature rise slowly after the snowfall,the average rate is 2. 5 ℃ every day. The temperature gradient value is negative in the daytime and positive in the night,the absolute value of temperature gradient is larger below7. 17 meteors,and the value of 7. 17 - 18. 15 meteors is smaller,its value is less than 0. 2 ℃ · m^-1,the absolute value of 18. 15 meteors is decreased to0. 05 ℃ ·m^-1. When the surface is covered with snow,the change trend＇s appearance in the morning that temperature decreases with height is one hour later than no snowcover,in the evening,the trend of the temperature increases with the increasing of height is one hour ahead. Snowcover reduce distribution range of temperature during the day,the reduction of second snowprocess is the most obvious because the large wind speed. In addition to 4. 2 - 7. 17 meteors for 11： 00—16： 00 on sunny days,snowcover will decrease the absolute value of temperature gradient in each layer. The absolute value of the 4. 2 - 7. 17 meteors temperature gradient in the sunny days is larger than 2. 35 - 4. 2 meteors during the period of 11： 00—16： 00,and the partial large amplitude increase when there is snowcover,it may be caused by the