西安机场冬半年逆温层与主导能见度的对应关系统计分析

Statistical Analysis of the Correspondence between Inversion Layer and Prevailing Visibility at Xi’an Airport in Winter-Half Year

摘要: 利用EC 0.25˚ × 0.25˚再分析资料，提取2021年1月~2025年12月期间每年冬半年共509个观测日、世界时15~02时共2588条逆温层记录，按天气现象将样本分为三类：总体情况、降水类(RA/SN)和高湿度类(BR/FG，不含RA/SN)，分析逆温层的时间变化特征及其与主导能见度的对应关系。结果表明：① 冬半年逆温层出现频次呈“12月~1月双峰、10月与3月双谷”特征，12月和1月分别达576和588个时次，合计占45.0%；41.2%的逆温层位于近地层(950 hPa以下)，中低层(775~875 hPa)逆温平均厚度最大(772 m)。② 降水类样本(n = 118)逆温层最厚(672.0 m)、梯度最弱(0.126℃/100 m)、层底最高(1244 m)，且能见度与厚度、梯度、层底高度的相关性均不显著(|Spearman ρ| ≤ 0.10, p > 0.28)，提示降水环境下能见度主要受降水过程控制，逆温层结构不是主要决定因素。③ 高湿度类样本(n = 714)中，主导能见度与逆温层厚度呈显著负相关(Spearman ρ = −0.168, p < 0.001)，与层底高度呈弱负相关(ρ = −0.103, p < 0.01)，与梯度呈弱正相关(ρ = +0.077, p < 0.05)；<0.5 km浓雾对应“厚而低”的逆温结构(厚度767 m、层底高度751 m)，FG样本能见度中位数仅350 m，逆温厚度达755.0 m。④ 两类低能见度天气的逆温结构明显不同：降水类呈“厚弱高远”型，高湿度类呈“较低较薄”型并随厚度增加而能见度下降，在航空气象低能见度预报中应区分天气背景进行诊断。

Abstract: Based on EC 0.25˚ × 0.25˚ reanalysis data, a total of 2 588 inversion-layer records were extracted for winter-half years from January 2021 to December 2025, covering 509 observation days at 15:00~02:00 UTC. Samples were classified into three groups according to weather phenomena: all cases, precipitation cases (RA/SN), and high-humidity cases (BR/FG, excluding RA/SN). Temporal variations of inversion layers and their correspondence with prevailing visibility were analyzed. The results show that: ① The frequency of winter-half-year inversions presents a bimodal pattern in December-January and double-valley pattern in October and March, with 576 and 588 hourly occurrences in December and January respectively, accounting for 45.0 % in total. 41.2 % of inversions occur in the near-surface layer (below 950 hPa), and inversions in the mid-lower level (775~875 hPa) have the largest mean thickness (772 m). ② For precipitation samples (n = 118), inversions are the thickest (672.0 m), with the weakest lapse-rate gradient (0.126˚C/100 m) and the highest base height (1244 m). No significant correlations are found between visibility and inversion thickness, gradient or base height (|Spearman ρ| ≤ 0.10, p > 0.28), indicating that visibility under precipitation conditions is mainly governed by precipitation processes rather than inversion-layer structure. ③ In high-humidity samples (n = 714), prevailing visibility is significantly negatively correlated with inversion thickness (Spearman ρ = −0.168, p < 0.001), weakly negatively correlated with base height (ρ = −0.103, p < 0.01), and weakly positively correlated with gradient (ρ = +0.077, p < 0.05). Dense fog with visibility < 0.5 km corresponds to “thick and low-base” inversion structures (thickness 767 m, base height 751 m). For FG samples, the median visibility is merely 350 m with an inversion thickness of 755.0 m. ④ Distinct inversion-layer structures exist for the two low-visibility weather types: precipitation cases feature “thick, weak-gradient and high-base” inversions, whereas high-humidity cases show relatively “low and thin” inversions, with visibility decreasing as inversion thickness increases. Weather backgrounds should be differentiated in diagnostic work for aeronautical meteorological low-visibility forecasting.