夏季青藏高原地面热源和高原低涡生成频数的日变化

通过1981—2010年NCEP/NCAR再分析资料,分析出夏季青藏高原地面热源具有强烈的日变化,白天高原是强热源,夜间高原地面转变为弱热汇,日较差可达420 W·m~(-2),呈由西向东递减分布。其中地面感热和潜热加热的日变化均十分明显,日较差分别可达300 W·m~(-2)和200 W·m~(-2);感热加热的日变幅由西北向东南递减,而潜热加热由南向北递减。同时,利用人工识别的高原低涡数据集初步分析了夏季高原低涡生成频数的日变化,发现夜间生成的高原低涡频数略高于白天,其中00 UTC的低涡源地主要在西藏那曲和林芝(工布江达),12 UTC低涡源地主要在西藏那曲和青海玉树。

The Diurnal Variation of the Surface Heat Source on the Tibetan Plateau and The Generating Frequency of Tibetan Plateau Vortex in summer

The diurnal variation of the surface heat source on the Tibetan Plateau (TP) in summer is analyzed using the NCEP/NCAR reanalysis data from 1981 to 2010. The results show that the surface heat source over the TP with a strong diurnal variation, the TP is a strong heat source during the day, and is a weak heat sinks at night. The diurnal difference of the surface heat source is up to 440 W?m_-2, and it shows that a decreasing distribution from the west to the east on the TP. There is obvious diurnal variation of the surface sensible heat flux and the latent heat flux. The diurnal difference of the surface heat flux is up to 320 W?m_-2, and there is a decreasing distribution from the northwest to the southeast on the TP. The diurnal difference of the latent heat flux is up to 220 W?m_-2, and there is a decreasing distribution from the south to the north on the TP. Meanwhile, the Tibetan Plateau Vortex (TPV) dataset for artificial recognition is used to analysis the diurnal variation of the generating frequency of TPV, and it shows that there is a higher frequency in the day, but lower at night. Naqu and Linzhi are the main generating sources of the TPV at 00UTC,Naqu and Yushu are the main generating sources of TPV at 12UTC.There is a lagging time relationship between the generating frequency of TPV and the strength of the surface heating over the TP.