Meteorological disasters represent the direct or indirect damagy for life and property of the people, national economy and development of society, as well as some national defense construction. It comes as one of the primary disasters of natural ones, including weather disaster, climate disaster and secondary and derivative disasters of meteorological disasters. China is one of the few countries that suffer a heavy loss due to those meteorological disasters. Since April 1st, 2010, the Regulations for the Defense of Meteorological Disasters has been put into effect.
Generally, weather disaster, climate disaster, secondary and derivative meteorological disasters are included in meteorological disasters. During which, the weather and climate disasters, is direct attributed to the typhoon (tropical storm, strong tropical storm), heavy rain (or snow), thunderstorms, hail, wind, sand, tornado, dense fog (or thick fog), high temperature, low temperature, an unbroken spell of wet weather, sleet, frost, icing (or ice accreting), cold-air, drought, dry hot wind, heatwaves, floods, waterlogging and some other factors. The secondary and derivative refer to those disasters that caused by the meteorological disasters, such as landslides, debris flows, storm surges, forest fires, acid rain and air pollution. Meteorological disasters are of many kinds, and they have some other characteristics, such as having a wide spreading range, a long duration, a high frequency, a significant chain reaction often and not happening solely, as well as a serious damage.
The meteorological classification of catastrophic weather levels is solely for the purpose of observation and forecasting, and these levels are not related to the actual levels of meteorological disasters. It has been pointed out that the magnitude of the storm has nothing to do with the occurrence of disasters. The same problem is found in the classification of fog. On the highway, when the visibility is less than 200 m, the speed of cars must be limited, and when less than or equal to 50 m, the highway will be closed. However, there is no visibility of 50 m in the meteorological observations specification, which results in the lack of historical data for the visibility level of 50 m, which is an important source of information for the risk zone of the fog. Fortunately, where the visibility automatic observer is installed can obtain the observation data of all kinds of visibility observations, which lay the foundation for the forecast and risk assessment of fog.
Therefore, it is unfavorable to classify the disastrous weather scale as the classification standards of meteorological disasters.
In fact, there is only one principle for classifying meteorological disasters: disaste ausing principle. The grade of meteorological disasters should be the level at which disasters occur, that is, the occurrence of a certain level of meteorological conditions will result in this level of disaster.
For example, the classification of wind power should be determined based on the wind force that the ship, vehicle and house can withstand; the level of wave should be divided according to the windbreak prevention capacity of the breakwater; The visibility level should be determined according to the needs of highway management; and the level of agricultural meteorological disasters should be determined based on the degree of damage to the crop. Besides, about some meteorological disasters that cause damage to artificial engineering, the critical meteorological conditions for them should be studied according to engineering design standards and should be used as criteria for meteorological disasters. For example, the classification of wire ice coverings should be based on the design standards of the electric power sector; snow pressure rating shall be determined according to the design standard of agriculture facilities and so on. The advantage of this classification is that the level of meteorological disasters is closely linked with the grade and risk assessment of meteorological disaster forecasts. When a certain level of meteorological conditions is predicted, some kind of disaster may occur. When the forecasted minimum temperature is below -7℃/-9℃/-11℃, citrus may suffer from mild/medium/serious freezing injury. This is the case that weather forecast is turned into disaster prediction.
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