福州长乐国际机场春季低能见度天气的分型与物理机制诊断——以2023年三次典型过程为例

Diagnosis of Weather Types and Physical Mechanisms of Low Visibility in Spring at Fuzhou Changle International Airport—Taking Three Typical Processes in 2023 as Examples

摘要: 利用ERA5再分析资料(原始分辨率0.25˚ × 0.25˚，为精细化诊断插值处理为0.1˚ × 0.1˚)及长乐机场地面观测报文，对2023年春季发生的三次典型低能见度天气过程(高压入海回流型、锋前暖区型、均压场静稳型)进行了对比诊断分析。结果表明：(1) 高压入海回流型主要受变性高压南侧偏东气流驱动，海面水汽经地形抬升后在950 hPa以下形成深厚饱和层，导致低云(BKN004)维持；(2) 锋前暖区型由西南低空急流主导，强盛的暖湿平流使得近地层温露差迅速归零(T − Td = 0℃)，形成爆发性平流雾，此类型湿度层深厚且伴有显著的增温特征；(3) 均压场静稳型发生在弱气压梯度背景下，地面微风(<2 m/s)配合夜间辐射降温，在近地层形成逆温封锁，不利于水汽垂直扩散。本研究建立了基于动力场与湿度场配置的预报着眼点，为机场二类盲降保障提供参考。

Abstract: Objective: Low visibility weather, such as fog and low clouds, is a critical factor affecting flight safety and efficiency at coastal airports. Fuzhou Changle International Airport (ZSFZ), located on the southeast coast of China, frequently experiences low visibility events in spring, posing significant challenges to flight operations (e.g., CAT II landings). This study aims to classify the synoptic patterns and reveal the physical mechanisms behind three typical low visibility events in the spring of 2023, providing theoretical support for operational forecasting. Data and Methods: Based on the METAR observations from ZSFZ and the ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) (original resolution 0.25˚ × 0.25˚, interpolated to 0.1˚ × 0.1˚ for fine-scale profile analysis), this paper analyzes the evolution of meteorological parameters including visibility, ceiling, horizontal wind field, vertical velocity, and relative humidity. Results: The study identifies three distinct weather types: (1) High-Pressure Reflux Type (Case of March 24~25, 2023): This event was characterized by a degenerated cold high-pressure system moving eastward into the sea. The diagnostic analysis shows that the easterly airflow transported abundant moisture from the sea to the land. The relative humidity below 950 hPa exceeded 95%, and the topographic uplift effect maintained the low cloud ceiling at approximately 120 meters (BKN004). (2) Pre-frontal Warm Sector Type (Case of February 12, 2023): This type occurred in the warm sector ahead of a frontal cyclone. A strong southwesterly low-level jet was observed at 925 hPa, acting as a “moisture conveyor belt.” The warm and moist advection caused the surface temperature-dew point spread (T-Td) to drop to 0˚C rapidly. (3) Equal Pressure Field/Static Stability Type (Case of April 14~15, 2023): This event occurred under a weak pressure gradient field. The vertical profile indicates that the near-surface wind speed was extremely weak (<2 m/s), and a stable inversion layer trapped moisture near the ground. Conclusion: Different synoptic patterns correspond to distinct dominant physical mechanisms. For the reflux type, forecasters should focus on the persistence of easterly winds; for the warm sector type, the intensity of the southwest jet is key; for the static type, the focus should be on inversion strength.