利用COSMIC掩星资料分析青藏高原地区对流层顶季节变化特征

根据WMO(1957)对流层高度的判别方法,利用2007—2013年COSMIC掩星资料计算了对流层高度,并用无线电探空资料对结果进行检验,分析了青藏高原地区对流层顶季节变化特征。结果表明,COSMIC掩星资料和无线电探空资料判定的对流层高度具有很高的线性相关关系,相关系数高达0.976,平均值偏差为0.448 km,均方根误差为0.672 km。受热力学因素影响,青藏高原对流层顶在夏季最高,在冬季和春季最低。从冬季到夏季,对流层顶断裂带的位置也逐渐北抬。春季、冬季和秋季,受赤道热源影响,从低纬到高纬,在对流层中低层中等熵面逐渐抬升、水汽混合比逐渐下降。夏季,在热源引起的深对流和季风产生的水平输送作用下,青藏高原上空出现了水汽的高值区。

Seasonal variation of the tropopause height over the Tibetan Plateau derived from COSMIC Radio Occultation data

Global Positioning System Radio Occultation (GPS RO) measurements are particularly suitable for the study of tropopause characteristics, due to their high measurement accuracy at the tropopause height.In this study, COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) occultation data from 2007 to 2013 were used to calculate the tropopause heights over the Tibetan Plateau according to the WMO (1957) tropospheric height discriminant method, then radiosonde data were used to examine the results.In addition, the height characteristics of the troposphere over the Tibetan Plateau and the distribution of water vapor in the troposphere were analyzed.The results showed that there was a high linear correlation between the tropopause heights detected by the COSMIC occultation data and radiosonde data over the Tibetan Plateau.The correlation coefficient was as high as 0.976, average deviation was 0.448 km, and root mean square error was 0.672 km.Influenced by thermodynamic factors, the tropopause over the Tibet Plateau is highest in summer and lowest in winter and spring.From winter to summer, the position of the tropopause break area gradually moves northward.In spring, winter and autumn, affected by the equatorial heat source, the entropy surface from low to high latitude rises, with the water vapor mixing ratio decreasing gradually in the middle and lower troposphere.In summer, under the effect of the deep convection caused by the heat source and horizontal transport caused by the monsoon, a high value area of water vapor appears over the Qinghai Tibet Plateau.