风场变形误差对北京降水记录及变化趋势的影响  被引量:4

Effects of gauge under-catch on precipitation observation and long-term trend estimates in Beijing area

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作  者:郑祚芳[1,2] 任国玉 

机构地区:[1]中国气象局北京城市气象研究所,北京100089 [2]中国地质大学环境学院大气科学系,湖北武汉430074 [3]国家气候中心中国气象局气候研究开放实验室,北京100081

出  处:《水科学进展》2017年第5期662-670,共9页Advances in Water Science

基  金:国家自然科学基金资助项目(41575010;41505102)~~

摘  要:风场变形误差是降水观测误差最主要的来源之一,其不仅影响观测值的准确性,也可能导致长期降水变化趋势中隐含虚假成分。结合北京地区20个气象站点1976—2015年逐日观测资料及前人研究成果,评估了风场变形误差对降水记录及其长期变化趋势的影响,结果表明:(1)近40年来北京地区平均降水捕获率为90%~95%,上升趋势较明显,但空间分布不均匀。城市化进程导致的风速减小是近10年来北京城、乡降水捕获率差异加大的主要原因。(2)北京地区风场变形误差存在明显的年际及季节差异。近40年来年均降水量订正值为23.1 mm,观测值较实际降水量年均低估了4.0%。订正后年均降水强度从实测的7.9 mm/d增加到8.3 mm/d,年降水量的下降速率从34.4 mm/10 a变为37.0 mm/10 a,观测值将降水强度低估了约4.8%,且将降水量的下降趋势低估了约7.0%。(3)对于强度越大的降水过程,风场变形引起的观测误差也越明显。对比发现,城市站点的风场变形误差年际振幅要大于乡村站点,弱降水过程中乡村站点的低估比城市站点明显,对大雨及以上强降水过程则相反,城市站点的低估比乡村站更显著。Among all of the uncertainties of precipitation records,the gauge under catch effect is one of the most important error sources. It not only affects the accuracy of the observational value and area-averaged precipitation calculation,but also leads to a false estimate of the long-term trends of the precipitation for any sites and regions. An accurate evaluation of the gauge under-catch effect is thus of great significance for understanding long-term change of precipitation and its possible causes and impacts. Based on observational data of daily precipitation and daily mean wind speed from 20 meteorological stations in Beijing area during the period 1976—2015,the effects of gauge under-catch on precipitation records and the estimates of the long-term precipitation trends were evaluated,and the urbanization effect on near-surface mean wind speed change was also discussed. The results showed that the mean values of precipitation catch rate ranged from 90% to 95% over last 40 years,but they had a significant upward trend and a heterogeneous spatial distribution with larger catch rates in urban area than in rural area. The urbanization process,which led to a lower wind speed in urban area,was the main reason for the observed difference of the under catch rates between the urban and rural stations especially after 2006. The effects of under catch differed among years and seasons significantly. In the past 40 years,the measured area-averaged annual precipitation was 552. 2 mm,while the under catch adjusted area-averaged annual precipitation was 575. 3 mm,with an average absolute error of 23. 1 mm and an average relative error of 4. 0%. The area-averaged precipitation intensity before and after the under catch adjustment were 7. 9 mm/d and 8. 3 mm/d respectively. The downward trends of the area-averaged annual precipitation for the past 40 years changed from-34. 4 mm/10 a for the pre-adjusted data to-37. 0 mm/10 a for the aft-adjusted data. Therefore,the original observed values underestimated the daily precipitation i

关 键 词:风速 捕获 测量误差 降水记录 变化趋势 北京 

分 类 号:P49[天文地球—大气科学及气象学]

 

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