国民核生化灾害防护国家重点实验室Fan Zhang团队报道了中国东北低空急流的特征及其形成机制。该项研究成果发表在2024年6月4日出版的《大气科学进展》上。

据研究人员介绍，本研究使用第五代欧洲中期天气预报中心25km分辨率的再分析数据，分析了1957年至2021年暖季(6月至9月)和冷季(12月至3月)中国东北地区的低空急流(LLJs)。

LLJs出现在两个显著的区域：寒冷季节分布在沿大兴安岭的背风侧翼，温暖季节分布在中国东北中部。环境环流和地形之间错综复杂的相互作用决定了LLJ的分布、海拔、风向、昼夜循环和季节变化。暖季时，西南LLJ在925hPa处盛行，冷季时，西北LLJ在875hPa处更强、更频繁。

对昼夜模式的分析揭示了冷暖季节LLJ的独特行为。在暖季，LLJ发生的单峰出现在午夜左右，与之相反的是，在冷季，LLJ在午夜前不久出现的频率最高，且在早晨还有一个次峰。动量收支分析确立了这两种不同昼夜变化的机制。在这两个季节，LLJs的昼夜变化主要由惯性震荡和山谷环流所驱动。而在冷季早晨观测到的次峰，则是低层大气与复杂地形之间的(热)动力相互作用的结果。

附：英文原文

Title: Characteristics and Formation Mechanisms of Low‐Level Jets in Northeastern China

Author: Shu Hailong, Fan Zhang, Yu Du, Yue Wang, Huichuang Guo, Zhen Song, Qinghong Zhang

Issue&Volume: 2024-06-04

Abstract: This study examines low-level jets (LLJs) across Northeastern China during both warm (June to September) and cold seasons (December to March) from 1957 to 2021, using fifth generation European Centre for Medium-Range Weather Forecasts reanalysis data with 25-km resolution. LLJs manifest in two prominent regions: one along the leeward flank of the Greater Khingan Mountains in the cold season and another at the center of Northeastern China in the warm season. The intricate interplay between ambient circulation and terrain shapes LLJ distribution, altitudes, wind directions, diurnal cycles, and seasonal diversities. During the warm season, prevailing southwesterly LLJs are found at 925 hPa, while the cold season features stronger and more frequent northwesterly LLJs at 875 hPa. Analysis of the diurnal patterns reveals distinctive behaviors of LLJs between the cold and warm seasons. During the warm season, the single peak in LLJ occurrence emerges around midnight, conversely, in the cold season, LLJs are most frequent shortly before midnight with an additional sub-peak in the morning. A momentum budget analysis establishes mechanisms underlying these two distinct diurnal variations. In both seasons, the diurnal variation of LLJs is predominately driven by inertial oscillation and mountain-valley circulation. However, the sub-peak observed in the cold-season morning arises from the (thermo-)dynamic interaction between the low-level atmosphere and complex terrain.

DOI: 10.1007/s00376-024-3209-8

Source: http://www.iapjournals.ac.cn/aas/en/article/doi/10.1007/s00376-024-3209-8viewType=HTML