比较各地城市火险气象预报因子、方法和等级标准,选取普遍采用的5个气象因子;日最小相对湿度、连续无降水日数对城市火险的贡献最大,指数范围分别为0~40和0~30,日最高温度、日最大风力0~20,日降水量0~-20,综合指数范围一般为0~100进行等间隔划分,得到从低到高5级城市火险气象等级标准。通过两项试验来优化等级划分效果:1)从北到南选取5个城市,比较上述方法与各地方法计算的2001年1、4、7、10月逐日火险等级,经过反复调试,使两套方法计算的等级完全一致和相差一级合计在85%以上;2)统计全国31个中心城市2000~2003年逐日城市火险气象等级5级分布的概率,使之基本符合正态分布。从而得到各气象因子的划分范围、对应城市火险气象指数值以及综合城市火险气象等级标准,给出相应名称和指示意义。

After the comparing of the weather factors,predicting method and ratings standard for urban fire research and operation all over the country,five weather factors are selected for the research: daily minimum relative humidity(index 0-40),number of consecutive days without precipitation(index 0-30),daily maximum air temperature(index 0-20),daily maximum wind strength or velocity(index 0-20) and daily rainfall(index 0-20),and the complex index generally range from 0 to 100 and can be divided to five ratings from low to high.Two experiments are designed to optimize the effect of ratings division: 1) daily fire-danger ratings in four typical months of 2001 for 5 cities from north to south in China are calculated by using above method and local method and compared,and the index with factors are adjusted to make coincidence ratio of two daily rating sequence higher and the correct ratio of ratings ≥85%(supposed that the predicting value has only one or no rating error with actual rating;2) the total number of every rating for thirteen central cities in China from 2000 to 2003 are calculated and made to fit with the normal distribution.Then,the dividing range of weather factors,corresponding urban fire-danger index and ratings are determined,and the ratings are named.