Analysis of Meteorological Grade Characteristics and Causes of Forest Fire Risk in Guangxi from 1981 to 2020
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Abstract:
Based on the GB/T 36743—2018 national standard for forest fire risk meteorological level, we have analyzed the characteristics of forest fire risk meteorological levels at 91 national meteorological stations in Guangxi from 1981 to 2020. We also verified our results using actual forest fire conditions. The areas with high forest fire risk are located in Baise and Chongzuo in the west of Guangxi, and Beihai in the coastal region. The average number of days with high fire risk is less in the northeast of Guangxi. The high fire risk period is from October to December, with the number of high fire risk days during this period accounting for 45.3% of the entire year. Among the four meteorological factors affecting the meteorological level of forest fire risk in Guangxi, precipitation has the greatest impact, followed by temperature. Wind speed and relative humidity have a comparatively lesser impact. We have studied the abnormal characteristics of sea surface temperature and atmospheric circulation of sea level pressure, geopotential height, wind field, and vertical velocity in the middle and lower troposphere using NCEP/NCAR monthly average reanalysis data, NOAA monthly sea surface temperature data, correlation coefficient analysis method, and composite analysis method. We also have examined the causes of the differences in the number of high fire risk days during the high forest fire risk period in Guangxi. The results reveal that the variant interactions between the ocean and the atmosphere, induced by the sea surface temperature in key areas in autumn, lead to differences in precipitation during the high fire risk period in Guangxi. This in turn results in differences in the number of high fire risk days. In autumn, the cold sea surface temperature in the equatorial Middle East Pacific triggers the abnormal cyclone circulation in the Philippines from October to December. The East Asian winter monsoon becomes stronger, and the western Pacific subtropical high is weaker than normal and shifts to the east. Consequently, Guangxi is in a sinking dry air flow area with less precipitation, leading to a higher number of high fire risk days during the high fire risk period. Conversely, the warm sea surface temperature in the equatorial Middle East Pacific in autumn gives rise to the abnormal anticyclone circulation in the South China Sea. The western Pacific subtropical high is stronger, and its ridge point extends westward. The warm and humid southwest airflow is stronger, and Guangxi is in the area of rising humid airflow. This results in more precipitation, thereby reducing the number of high fire risk days during the high fire risk period.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.