两次贵阳机场冬季辐射雾环流背景与边界层特征对比分析

Comparative Analysis of Circulation Background and Boundary Layer Characteristics of Two Winter Radiation Fog Events at Guiyang Airport

摘要: 本文利用贵阳龙洞堡机场的人工观测记录簿、AWOS自动气象观测、ERA5第五代全球大气再分析资料以及微波辐射计资料，选取2026年1月13日(辐射冻雾)和1月17日(非冻辐射雾)两次冬季低能见度过程作为研究对象，从环流背景、边界层热力与层结、地面气象要素这三个方面展开对比分析。分析结果显示，两次过程都出现在高压控制、地面弱风(<2 m·s⁻¹)、低层存在较强逆温且湿度接近饱和的静稳形势下，具备了辐射雾生成所需的典型环流和边界层条件。两次过程的本质差异主要表现在近地面热力状态上；1月13日过程受到更强的高压脊和相对干冷的近地面空气影响，夜间辐射降温使得近地面气温降到了0℃以下(−1.9℃~−1.1℃)，从而形成以冻雾(FZFG)为主的辐射冻雾；而1月17日过程850 hPa湿度更高(79%~87%，与之相比过程1为50%~64%)，近地面气温保持在0℃以上(+1℃~+4℃)，形成了持续时间更长(约4 h，过程1约2 h)、强度更大(最低能见度100 m，过程1为200 m)的非冻辐射雾。由此可以看出，冻雾和非冻辐射雾的区分，主要取决于近地面气温是否能跨越0℃这个阈值，而不是取决于雾的浓度大小。针对ERA5 2 m气温存在暖偏差的问题，本文用人工观测气温替换后重新核算了逆温强度，两次过程的低层逆温均比原估算偏强，但过程1强于过程2的相对关系没有改变；同时基于简化热力方程的量级估算表明，在静风晴夜条件下辐射冷却项比平流项大1~2个量级，是近地面降温的主控因子。此外，在对比中还发现，AWOS器测的2 m气温和跑道视程(RVR)在这一类深厚的辐射雾过程当中，与人工主导观测之间存在系统性的偏差，所以冻雾的起止和判识还是应该以人工主导能见度和人工气温为准。

Abstract: Based on the manual observation records, AWOS automatic weather observations, ERA5 fifth-generation global atmospheric reanalysis data and microwave radiometer data of Guiyang Longdongbao Airport, two winter low-visibility events, i.e., 13 January 2026 (radiation freezing fog) and 17 January 2026 (non-freezing radiation fog), are compared from three aspects: circulation background, boundary layer thermal structure and stratification, and surface meteorological elements. The results show that both events occurred under a stable synoptic situation characterized by high pressure control, weak surface wind (<2 m·s⁻¹), strong low-level temperature inversion and near-saturated humidity, which provided the typical circulation and boundary layer conditions for radiation fog formation. The essential difference between the two events lies in the near-surface thermal state. Affected by a stronger high-pressure ridge and relatively dry-cold near-surface air, the near-surface temperature in the event on 13 January dropped below 0˚C (−1.9˚C~−1.1˚C) due to nocturnal radiative cooling, resulting in radiation freezing fog dominated by FZFG. In the event on 17 January, the 850 hPa humidity was higher (79%~87% vs. 50%~64% in event 1) and the near-surface temperature remained above 0˚C (+1˚C~+4˚C), resulting in a non-freezing radiation fog with longer duration (about 4 h vs. about 2 h) and greater intensity (minimum visibility 100 m vs. 200 m). It can be seen that the distinction between freezing fog and non-freezing radiation fog mainly depends on whether the near-surface temperature crosses the 0˚C threshold, rather than on fog concentration. In view of the warm bias of ERA5 2 m temperature, the inversion intensity is recalculated by using manually observed temperature instead, indicating that the low-level inversion in both events is stronger than the original estimation, while the relative relationship that event 1 is stronger than event 2 remains unchanged. The magnitude estimation based on a simplified thermodynamic equation shows that under calm and clear night conditions, the radiative cooling term is 1~2 orders of magnitude larger than the advection term, and is the dominant factor of near-surface cooling. In addition, it is found that the AWOS measured 2 m temperature and runway visual range (RVR) have systematic deviations from the manual observations in such deep radiation fog events, so the onset/end and identification of freezing fog should still be based on the manually determined dominant visibility and manually observed temperature.