Analysis and Forecasting Methods of Heavy Fog Weather in Zhongwei City in Recent Years
[Purposes]This paper aims to improve the predictive ability of forecasters for low visibility weather"fog".[Methods]Using fog day observation data from four meteorological stations in Zhongwei City from 2000 to 2021,the spatiotemporal distribution characteristics of fog were analyzed.In addition,combined with daily reanalysis data from NCEP/NCAR during the same period,the circulation back-ground and physical characteristics of fog in Zhongwei City were analyzed,and the forecast indicators for fog in Zhongwei City were summarized.[Findings]The results showed that the distribution of foggy days in Zhongwei City decreased from north to south,and the annual foggy days remained relatively stable in fluctuations;In the foggy days of Zhongwei City,the upper 500 hPa is basically a west-northwest airflow,850～700 hPa is a southerly airflow,and the ground is a uniform pressure field.The relative humidity at 850 hPa is relatively large,the ground humidity is close to saturation,and the vertical wind shear is also relatively small.Due to the stable atmospheric stratification at high altitude,the horizontal movement of the ground is not strong,and the energy exchange between high and low altitude is suppressed,which is conducive to the formation and maintenance of foggy weather.[Conclusions]Based on the characteris-tics of the fog day element field in Zhongwei City,the following forecast indicators for fog are obtained:①ground wind speed at each station at 08:00 the next day is predicted to be≤4 m/s;②it is predicted that the cloud cover at each station will not exceed 30%at 8 am the next day;③it is predicted that at 08:00 the next day,the T ground temperature at each station-T 850 hPa≤0℃;④it is predicted that the next day with 850 hPa T-Td≤3℃;5.Forecast the maximum relative humidity of the next morning to be≥90%;⑥At 14:00 on the same day,the relative humidity≥60%;⑦Forecast that the lowest temperature in the morning of the next day will not exceed the dew point temperature at 2 pm on the same day;⑧it is predicted that the Tmin of the next morning≤the Td at 2 pm of the previous day.
NETL
NSTL
万方数据
