1979—2013年ERA-Interim资料的青藏高原低涡活动特征分析
An objective analysis of the Tibetan Plateau vortexes based on the ERA-interim reanalysis data: 1979-2013
-
摘要: 为分析青藏高原低涡活动特征,利用1979—2013年ERA-Interim再分析资料500 hPa高度场,基于气旋客观识别和追踪算法得到青藏高原及其附近地区低涡路径,同时利用客观分析方法对500 hPa温度场进行分析得到低涡的冷暖性质,从而得到一套青藏高原低涡活动的资料。对高原低涡的频次、强度、持续时间、地理位置和移出高原等特征分析结果表明,35年间青藏高原上活动的系统主要为高原低涡,年均约53个,其中,年均6.7个高原低涡移出青藏高原;高原低涡持续时间从少至多呈指数减少,强度和冷暖性质的出现频次均呈正态分布,初生的高原低涡以暖涡居多,占81%。高原低涡发生且强度较大主要在青藏高原的汛期(5—9月),高原低涡源地主要在西藏那曲地区西部和阿里地区北部,消亡地主要位于源地高频中心东侧的唐古拉山地区和青海西部当曲河流域,高原低涡的消亡可能受地形影响。近35年来高原低涡生成频次呈不显著减少趋势(-2个/(10 a));移出高原低涡数(-1.4个/(10 a))和高原低涡移出率(-2.3%/(10 a))均显著减少。Abstract: An objective dataset of the Tibetan Plateau vortexes (TPV) from 1979 to 2013 is obtained from the ERA-Interim reanalysis dataset using an objective identifying and tracking method and the objective method to determine the vortexes warm/cold characteristics. The TPV's frequency, intensity, lifetime, initial and the dissipation location outgoing from the Tibetan Plateau are analyzed using this TPV dataset. The vortexes activities over the Tibetan Plateau are mainly TPVs which formed about 53 per year, and averagely 6.7 TPVs move out of the plateau. The TPVs' duration decreases exponentially with their frequencies of occurrence, with the frequency distributions of TPVs' intensity and warm/cold characteristics showed a normal distribution, in which about 81% of the primary TPVs appears with the warm eddy. Most of the TPVs (esp. ones with stronger intensity) occur in the Tibetan Plateau's rainy season which is from May to September. Most of TPVs are initially located in the eastern Nagqu and northern Ngari of the Tibet Autonomous Region, and dissipated near the Danggula Mountains and the Dangqu River Basin of western Qinghai Province that is located east of the TPVs initial locations. The TPVs dissipation locations indicate that the dissipation of the TPVs may be impacted by the Tibetan Plateau terrain. In recent 35 years, the TPVs occurrence frequency was decreasing with an insignificantly trend (-2 /(10 a)), and both the outgoing TPVs number (-1.4 /(10 a)) and TPVs' outgoing rate (-2.3%/(10 a)) decreased significantly.