北京几次弱降水过程预报失误分析
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摘要
在选取的北京地区2011年冬季至2012年春季9次弱降水过程中,预报员出现了4次空报、2次漏报,预报效果总体不理想。通过对9次过程的预报检验、天气分析和多模式预报对比,得到如下认识:北京地区弱降水过程天气形势复杂多样,按高空大气环流形势可分为两槽一脊型、一槽两脊型、一槽一脊型,按地面天气形势可分为冷锋型、华北锢囚锋型、东风与倒槽型和东风回流型;弱降水过程普遍具有对流层低层水汽条件差或动力抬升弱的特点;对湿层浅薄、饱和层高度高、抬升凝结高度高的弱降水过程,数值模式容易出现空报;而对低层湿度条件好、饱和层高度低、抬升凝结高度低但高空系统弱的降水过程,模式又容易出现漏报;预报员主观预报出现空、漏报主要源于对天气系统的结构及发生发展机理认识不足,对边界层水汽、抬升等关键降水要素缺乏预报订正经验。
The public weather forecasts were not so correct for the time period from winter 2011 to early spring 2012 in Beijing.Of the nine weak precipitation processes(WPPs),four cases were false alarms,two were missed and three were better forecasted.Through the forecast verification,synoptic analysis and comparison of model forecasts for the nine processes,following results are achieved.The synoptic conditions of WPPs in Beijing vary case by case.The weather patterns at 500 hPa can be classified into three categories:patterns of two-troughs one-ridge,one-trough two-ridges and one-trough one-ridge.The surface situation can be classified into four patterns,which are cold front,occluded front in North China,the easterly wind and inverted trough and the eastward returning current.Most WPPs are characterized by poor vapor conditions in lower troposphere or weak dynamic lifting conditions.For the WPP with thinner wet layer,higher vapor saturation layer and higher lifting condensation layer,numerical prediction models tend to give false alarm;for the WPP with favorable vapor condition at low level,lower vapor saturation layer and lower lifting condensation layer,the models are prone to omission.The subjective precipitation forecast errors are mainly because forecasters did not sufficiently understand the structures of the weather systems and their developing mechanisms.Besides,they were lack of correction experiences for the model boundary water vapor and lifting conditions,which are critical factors for rainfalls.
The public weather forecasts were not so correct for the time period from winter 2011 to early spring 2012 in Beijing.Of the nine weak precipitation processes(WPPs),four cases were false alarms,two were missed and three were better forecasted.Through the forecast verification,synoptic analysis and comparison of model forecasts for the nine processes,following results are achieved.The synoptic conditions of WPPs in Beijing vary case by case.The weather patterns at 500 hPa can be classified into three categories:patterns of two-troughs one-ridge,one-trough two-ridges and one-trough one-ridge.The surface situation can be classified into four patterns,which are cold front,occluded front in North China,the easterly wind and inverted trough and the eastward returning current.Most WPPs are characterized by poor vapor conditions in lower troposphere or weak dynamic lifting conditions.For the WPP with thinner wet layer,higher vapor saturation layer and higher lifting condensation layer,numerical prediction models tend to give false alarm;for the WPP with favorable vapor condition at low level,lower vapor saturation layer and lower lifting condensation layer,the models are prone to omission.The subjective precipitation forecast errors are mainly because forecasters did not sufficiently understand the structures of the weather systems and their developing mechanisms.Besides,they were lack of correction experiences for the model boundary water vapor and lifting conditions,which are critical factors for rainfalls.
引文
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谌芸,孙军,徐珺,等,2012.北京721特大暴雨极端性分析及思考(一)观测分析及思考[J].气象,38(10):1255-1266.
董林,符娇兰,宗志平,2012.2011年隆冬北京初雪成因分析[J].气象,38(8):913-920.
符娇兰,马学款,陈涛,等,2017.“16·7”华北极端强降水特征及天气学成因分析[J].气象,43(5):528-539.
郭锐,张琳娜,李靖,等,2012.2010年冬季北京初雪预报难点分析[J].气象,38(7):858-867.
何娜,孙继松,王国荣,等,2014.北京地区预报失误的两次降雪过程分析[J].气象科技,42(3):488-495.
蒋建莹,史历,倪允琪,2005.一次“高影响天气”的弱降雪过程的数值研究[J].应用气象学报,16(2):231-237.
孙继松,梁丰,陈敏,等,2003.北京地区一次小雪天气过程造成路面交通严重受阻的成因分析[J].大气科学,27(6):1057-1066.
孙建华,赵思维,2003.华北地区“12·7”降雪过程的数值模拟研究[J].气候与环境研究,8(4):387-401.
孙军,谌芸,杨舒楠,等,2012.北京721特大暴雨极端性分析及思考(二)极端性降水成因初探及思考[J].气象,38(10):1267-1277.
魏东,廖晓农,杨波,2010.有利环流形势下北京降雪空报原因[J].气象科技,38(2):182-188,281.
赵思雄,孙建华,陈红,等,2002.北京“12·7”降雪过程的分析研究[J].气候与环境研究,7(1):7-21.