Diurnal Characteristics of Gravity Waves over the Tibetan Plateau in 2015 Summer Using 10-km Downscaled Simulations from WRF-EnKF Regional Reanalysis

Diurnal variations of gravity waves over the Tibetan Plateau (TP) in summer 2015 were investigated based on high-resolution downscaled simulations from WRF-EnKF (Weather Research and Forecasting model and an ensemble Kalman filter) regional reanalysis data with particular emphasis on wave source, wave momentum fluxes and wave energies. Strong diurnal precipitations, which mainly happen along the south slope of the TP, tend to excite upward-propagating gravity waves. The spatial and temporal distributions of the momentum fluxes of small-scale (10–200 km) and meso-scale (200–500 km) gravity waves agree well with the diurnal precipitation distributions. The power spectra of momentum fluxes also show that the small- and meso-scale atmospheric processes become important during the period of the strongest rainfall. Eastward momentum fluxes and northward momentum fluxes are dominant. Wave energies are described in terms of kinetic energy (KE), potential energy (PE) and vertical fluctuation energy (VE). The diurnal variation and spatial distribution of VE in the lower stratosphere correspond to the diurnal rainfall in the troposphere.

基于WRF - EnKF（天气研究与预报模式和集合卡尔曼滤波）区域再分析数据的高分辨率降尺度模拟，对2015年夏季青藏高原（TP）重力波的日变化进行了研究，特别关注了波源、波动量通量和波能量。主要发生在青藏高原南坡的强降水日变化往往会激发向上传播的重力波。小尺度（10 - 200千米）和中尺度（200 - 500千米）重力波动量通量的时空分布与日降水分布吻合良好。动量通量的功率谱还表明，在最强降雨期间，小尺度和中尺度大气过程变得很重要。向东的动量通量和向北的动量通量占主导地位。波能量用动能（KE）、势能（PE）和垂直波动能（VE）来描述。平流层下层VE的日变化和空间分布与对流层的日降雨相对应。