南极半岛及附近地区大风天气及其预报

南极半岛及附近地区经常出现大风天气,它是影响该地区的主要天气现象.造成大风的主要天气系统是极地气旋.极地气旋的强弱、移速和路径的不同,对南极半岛及附近地区的影响也不同.而周围的环境流场也是形成大风的重要因素.所以,分析天气形势背景,对做好该地区大风天气现象的预报是十分重要的.本文利用1985年1月到1987年10月中国南极长城站接收的智利南极弗雷气象中心播发的南半球地面传真天气图,北京气象中心绘制的南半球地面和500hPa高空天气图资料,结合长城站的地面气象观测资料,对影响南极半岛及附近地区的大风天气过程进行了分析和研究.主要根据地面天气图上的天气形势归纳为四种类型:(1)强极地高压型;(2).强副热带高压型;(3)南美大陆高压型;(4)副热带高压脊线南伸型.同时,结合分析结果提出了预报南极半岛及附近地区大风天气的思路.     

天气动力学组合因子在MOS降水预报中的应用

利用我国的数值产品ＨＬＡＦＳ格点场资料,结合内蒙古地区降水系统的天气动力学演变特征,构造出能反映降水系统的天气动力学发展机制的结构特征因子,采用ＭＯＳ方法建立预报方程。用较短的样本资料建立ＭＯＳ预报方程,提高了ＭＯＳ预报方程的预报能力和适应性。试验结果表明,该ＭＯＳ预报方程计算稳定并具有很好的预报能力和效果,易于业务化。     

1996年岁末沪宁线持续五天大雾的原因探讨

1996年12月27-31日江苏境内发生了持续五天的大雾。本文普查了天气图,分析了产生雾的天气形势特征,并进行了一些物理量的计算,制作了时空分布和垂直剖面图,重点分析了它的形成和长时间维持的原因,对冬季辐射雾的预报有一定参考价值。     

Synoptic Situations and Pollutant Concentrations in Fog Water Samples from the Milešovka Mt.

This contribution presents the results of chemical analyses of the fog and/or cloud water samples, which were collected at the Mileovka Mt. during the years 2000 and 2001. The study aims mainly at proving the dependence of pollutant concentration on the direction of the atmospheric steering flow. It is evident that the highest mean pollutant concentration in fog water appeared at the steering flow from south or at the flow with an east component. The lowest pollutant concentrations were reported during the synoptic situations with considerable west component of the steering flow. Furthermore, we compare the characteristic values of pollutant concentrations from the Mileovka Mt. with similar results from other sites abroad.     

2016年12月至2017年2月T639、ECMWF及日本模式中期预报性能检验

对2016年12月至2017年2月T639、ECMWF及日本（文中简称JP）数值模式的中期预报产品进行了分析和检验。结果表明：3个模式对亚洲中高纬环流形势的调整和演变均具有较好的预报性能,其中ECMWF模式预报效果最好。3个模式对850 hPa温度的转折性变化趋势均有较好的预报能力,对南方地区温度变化的预报能力优于北方地区;T639模式对北方地区的温度预报存在整体偏低的误差,而JP模式对南方地区的温度预报整体偏高,ECMWF预报综合效果最好。对于2017年2月影响全国的寒潮天气过程中地面冷高压的预报,T639模式对地面冷高压中心强度的预报效果优于ECMWF和JP模式,ECMWF模式对高压中心位置预报较为准确,T639和JP模式对高压中心位置预报均存在明显偏差。     

1949—2015年北上热带气旋特征

利用1949—2015年CMA STI热带气旋(TC：Tropical Cyclone)最佳路径数据集、NCEP25°×25°再分析资料及常规资料,对北上TC特征进行研究。结果表明：1949—2015年进入北上定义区的TC共计91个,占西北太平洋（包含南海）TC总数41%,年平均14个;进入定义区最早5月,最晚9月,最多8月,但7月北上几率最大。依据TC运动形态特征将北上TC路径分为转向北上和直接北上两大类,其中转向北上TC转向之后路径与转向点密切联系,这对北上TC路径预报有重要意义。北上TC生成源地主要在8°~25°N,122°~155°E,不同路径北上TC源地纬度、经度分布有差异,源地偏北的TC未来转向点偏北和直接北上的可能性大。北上TC一般在定义区外20°N左右达到生命史最大强度,进入定义区后强度大多减弱为热带风暴,强度越强减弱速度越快;进入影响区后发生变性的TC明显增加。北上TC路径与西太平洋副热带高压的主体位置、形态和强度有关,副高西端高脊的引导气流决定北上TC未来路径是转向还是北上,西脊点的位置决定北上TC未来转向点的位置。不同路径北上TC暴雨和大风天气区分布存在差异,中纬转向、高纬转向和直接北上路径是造成北方强烈降水和大风的主要路径。     

A probabilistic description of the wind over Liverpool Bay with application to oil spill simulations

Surface winds from the UK Meteorological Office mesoscale (12 km grid) atmospheric model have been used to define the wind at a location in Liverpool Bay during 1997–2001. Winds from the SW (centred on 240°) with a speed of about 10 m/s (20 knots) were the most frequent, although weaker winds from the SE were also common. The wind spectra were red in character and showed no evidence for a peak at the synoptic (2–5 day) time scale; however, a zero-up-crossing analysis suggested a dominant periodicity at 3.1 days, and at this time scale the winds were spatially coherent over a distance of 300 km. A wind direction transition matrix was derived to quantify the probability with which the wind changed between two specified directions. This information was then used with an estimate of the mean duration of a wind event to compute a stochastic wind time series that contained a similar energy level, periodicity, and direction variability to the archived wind data. The archived and stochastic winds were then used in 1000 oil spill contingency simulations during which estimates of the mean and minimum times taken for oil to reach the coastline, and the percentage of the oil impacting selected sites were computed. The stochastic winds provided more realistic results, when compared against those derived using the wind archive, than those obtained using a wind rose representation of the winds. The derivation and use of a stochastic wind time series has application to a range of modelling studies.     

Analysis of the Characteristics of the Low-level Jets in the Middle Reaches of the Yangtze River during the Mei-yu Season

Here, we analyze the characteristics and the formation mechanisms of low-level jets(LLJs) in the middle reaches of the Yangtze River during the 2010 mei-yu season using Wuhan station radiosonde data and the fifth generation of the European Centre for Medium-Range Weather Forecasts(ERA5) reanalysis dataset. Our results show that the vertical structure of LLJs is characterized by a predominance of boundary layer jets(BLJs) concentrated at heights of 900–1200 m.The BLJs occur most frequently at 230...     

中国近海大风的天气学分型

利用2010—2014年地面观测站（包括288个海岛站、380个沿海气象站、28个浮标站、37个船舶站、53个气象观测塔、13个海上平台站、9个沿海风廓线仪等）和高空气象观测站资料,采用天气学分型和统计分析方法,对2010—2014年285次中国近海6级及以上大风天气个例进行了分析,将近海的大风天气过程归纳为冷空气型、温带气旋型和热带气旋型3种类型。其中冷空气型又分为小槽东移型、小槽发展型和横槽转竖型;温带气旋型又分为东海气旋型、黄渤海气旋型和蒙古气旋型。这些分型可为海上大风预报预警提供天气学背景参考依据。