北京降水特征及北京市观象台降水资料代表性

Characteristics of Precipitation in Beijing and the Precipitation Representativeness of Beijing Weather Observatory

  • 摘要: 将北京分为城区、郊区、南部山区及北部山区4个区域,利用14个观测站1978—2010年共33年的月降水量资料,分析了不同区域降水年变化和夏季降水特征及其差异。结果表明:各区域年平均降水量存在较大差异,郊区降水量最多 (620 mm),城区与南部山区降水量较少,而北部山区降水量最少 (476 mm);城区与南部山区的年降水量较接近,二者与郊区和北部山区都有显著差异。4个区域的降水量都表现出减少趋势,郊区最明显 (47 mm/10 a),北部山区的减少趋势最小 (0.7 mm/10 a)。对4个区域夏季 (6—9月) 降水量分析发现,城区与南部山区具有较好的一致性,二者与郊区和北部山区具有显著差异。均方根偏差和相关系数的计算结果表明:北京市观象台与城区和南部山区的降水年变化和夏季降水特征差异均不显著,而与郊区和北部山区有显著差异,说明北京市观象台降水资料对城区和南部山区具有最优代表性,而对北部山区和郊区的代表性较差。

     

    Abstract: In order to investigate annual variations and characteristics of summer precipitation, Beijing is divided into four areas according to different land use and topographic height: The urban area (UA), suburban area (SA), north mountainous area (NMA), and south mountainous area (SMA). Results of cluster analysis based on monthly precipitation amount during 33 years verify the reasonability of the regional division. Using observed monthly rain-gauge measurements from 14 meteorological stations in Beijing, differences among four areas are investigated. Significant annual mean precipitation differences are observed among four areas, with the maximum precipitation amount observed in SA (620 mm), followed by UA and SMA, and the minimum precipitation amount observed in NMA (476 mm). In UA and SMA, the precipitation amount is similar, presenting a significant difference from SA and NMA. Precipitation amount in all the four areas shows a decreasing trend, with the highest decreasing rate observed in SA (47 mm/10 a), which passes the significance test at a significance level of 0.06, and the lowest decreasing rate observed in NMA (0.7 mm/10 a). Summer precipitation which accounts for 79.1% of the annual total amount in four areas is analyzed. Results show that UA and SMA have similar features, yet being significantly different from those in SA and NMA.Differences in precipitation between Beijing Weather Observation (BWO) and four areas are also investigated, and results show that BWO isn’t significantly different from UA and SMA in both annual and summer precipitation amount, but differences between BWO, NMA and SA are significant. Upon comparison of the statistics of root-mean-square error and correlation coefficient of precipitation between BWO and four areas, consistent results are obtained, which reveals that the representativeness of precipitation in BWO is good for UA and SMA, but is poor for NMA and SA. As a result, it suggests that some other stations should be selected in suburban and north mountainous areas to represent the characteristics of precipitation there. Together with BWO, these stations may better reflect the characteristics of precipitation variations over Beijing metropolitan area.

     

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