风向的统计方法研究

在核安全分析和环境影响评价中，必须使用到的是小时气象数据。对自动气象站小时风向的计算方法和小时数据如何统计，地面气象规范中和核安全导则中还没有定论，因此本文对小时风向统计方法展开讨论。目前小时风向值的计算方法有算术平均法、滑动平均法、矢量平均法和频率最高法，针对算术平均法和滑动平均法对经过0°的风向统计容易出现误差，本文提出对此的修正方法并对4种计算方法进行了比较。结果表明：文中过零风向修正方法简便准确，小时数据统计方法为正点前10min数据时，修正算术平均法更可靠，但该方法对风速为零时的判断容易出现误差，因此在小风、静风频率高的地方推荐矢量平均法。关于小时数据的划分方法，美国核管会RG1.23与我国核安全导则及地面气象规范中的规定不同，因此文中利用实测资料对不同小时数据统计方法所得结果比较，分析表明，取整点前或其他时段的10min和15min的数据进行平均的风向相关矩阵一致性为97.87%；取4个15min平均值的平均或6个10min数据平均值的平均作为小时值的风向相关矩阵一致性为99.96%，这两种统计方法与取10min和15min的一致性为86.00%，相对较差；取60min时段的平均值作为小时值则与其余方法一致性最差。

Study on the statistical method of wind direction

In nuclear safety analysis and environmental impact assessment, hourly weather data must be used. However, the calculation method and the statistic method of hourly wind direction from automatic weather stations have not been defined as normal rules in the corresponding regulations similar to “ground observational criterion” and “nuclear safety guide” in China, so the statistical method of the hourly wind direction was discussed in this paper. Four methods were often used to the calculation of average wind direction, including the methods of an arithmetic mean, a sliding average, a vector average and a highest frequency. The first two methods were modified since they produce the error when wind direction across 0° was calculated. The results indicate that the modified method for wind direction across 0° is simple and accurate. The modified arithmetic mean method is more reliable when the data 10-min ahead normal hours are used as the hourly data of wind direction. However, it is easy to produce error using this method when wind speed is zero. Thus, a vector average method is recommended when the frequency of light wind and calm is high. The hourly wind direction statistic methods from “RG1.23 guide” presented by U.S and from “nuclear safety guide” and “ground observational criterion” in China differ each other, so the results from the above methods are compared with the observational data by using the same calculation algorithm. Using the wind direction with a 10-min average and a 15-min average before normal hours or other period of time as the hourly wind direction, the consistency of correlation matrix is 97.87%; using average of each 15-min value in one hour or average of each 10-min value in one hour as the hourly wind direction, their consistency is 99.96%. The consistency between the two classification methods and the method of average of a 10-min and a 15-min in one hour is only 86.00 %. Using a 60-min average as the hourly wind direction, the consistency is the worst among all methods.