胡宁,符娇兰. 2021. 北京一次冬季极端降水过程中相态转换成因及预报误差分析[J]. 气象学报, (0):-, doi:10.11676/qxxb2021.019
北京一次冬季极端降水过程中相态转换成因及预报误差分析
Analysis of cause of precipitation type transition and model forecast errors for an extreme winter precipitation event
投稿时间:2020-06-11  修订日期:2020-11-16
DOI:10.11676/qxxb2021.019
中文关键词:  极端降水,降水相态,零度层高度,模式预报误差
英文关键词:Extreme precipitation, Precipitation type, height of 0℃ level, Model forecast errors
基金项目:
作者单位邮编
胡宁 国家气象中心 100081
符娇兰 国家气象中心 100081
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中文摘要:
      [资料和方法]应用各种常规和非常规观测资料、以及再分析资料[目的]对2020年2月13日夜间至14日白天北京地区一次极端雨雪过程的成因进行了分析,并重点探讨了模式降水相态预报误差及其原因。[结果]结果表明:(1)本次降水过程中,低涡系统深厚,强度异常偏强,移速慢,影响时间长,导致北京地区部分站点降水持续了12h左右。异常偏强东南风急流向北京西部山前输送水汽,配合与急流相伴的较强低空切变形成的对称不稳定,产生高降水率的斜升对流性降水。较长的降水时间以及冬季夜间罕见的高降水率共同造成了此次极端日降水。(2)北京凌晨零度层高度和地面温度下降缓慢,北京西部处于两股冷空气间的暖舌中,冷空气从东路入侵造成北京东部降温时间较西部早,且降温辐度较大,导致零度层高度呈西高东低形势,故转雪时间东部早于西部。(3)模式预报的东路冷空气较观测偏强偏早,降水的对流性也显著弱于观测,导致其预报的凌晨地面气温较观测偏低,零度层高度下降过快,从而过早预报转雪时间,高估了降雪量和积雪深度,[结论]利用非常规温度观测对模式温度廓线预报误差进行检验,可为订正模式相态转化时间预报偏差提供依据。
英文摘要:
      Based on the conventional and unconventional observational data, and the reanalysis data,A case study of the February 2020 mixed rain-snow storm over Beijing was conducted, targeting at the mechanism for the formation of the extreme precipitation, as well as model precipitation type forecasting error and its cause. The result indicates that: (1) the slow moving of the extremely strong and deep low vortex result in the persistence of the precipitation event as long as 12h. The anomalous southeast jet not only transport water vapor to the east of the mountainous area in western Beijing, but also bring about strong vertical shear forming the symmetric instability, which result in slantwise convective precipitation with high precipitating efficiency rarely occurring in winter night. Both factors conjunctively contribute to this extreme rain-snow event. (2) In the early morning of Beijing, the 0℃ level height and surface temperature decrease slowly. The cold air mass from the Northeast Hebei exerts earlier and stronger influence on eastern Beijing, resulting in lower 0℃ level height and thus the earlier rain-snow phase transition in eastern Beijing. (3) The model predicted cold air mass from Northeast Hebei exerting earlier and stronger influence on Beijing than that in observation, causing a stable straitiform precipitation with convection significantly weaker than observation. The model predicted lower surface temperature, more rapid decreasing of 0℃ level height than that in observations, thus predicted earlier rain-snow transition, higher snowfall and snow depth. Verifying the model predicted temperature profile with unconventional observations could be beneficial to the adjusting of model forecasting error in precipitation type transition.
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