5—10月全球热带和副热带200hPa多年平均环流的研究(二)——行星风系

北半球夏半年逐月200 hPa主要风系的分析表明: (1)北半球夏季副热带急流的两个中心分别位于亚洲和北美上空.纬度在45°N附近.另外在中东太平洋和中东大西洋热带地区存在高空西风.盛夏前者成为明显的独立风系. (2)北半球夏季高空东风急流具有三个中心,分别位于也门.印度半岛南部和马来西亚上空.前两个中心的变化明显地与南亚季风活动有关,最后一个中心则稳定少变. (3)南半球冬季最强的西风带位于大洋洲上空,最大值在大洋洲东岸. (4)200 hPa全球有四个跨赤道的质量交换区.其中沿100°E和印度洋的质量交换最强,它们与亚洲季风活动密切有关.     

安全射界图技术在人工影响天气指挥系统中的应用

为了进一步提高人工影响天气作业的安全性,利用雷达回波外推TREC、TITAN技术和安全射界图技术,生成人工影响天气预警产品、建议产品。利用雷达外推30min、60min产品与作业点最大射程的位置关系,输出作业预警产品。利用当前回波与作业点的位置关系,生成对空射击的仰角、方位角信息,利用安全射界技术进行筛选,生成实时、客观的作业建议产品,以此进行决策指挥,避免了人工决策安全射区可能出现的误差,达到了安全、高效作业的目的。     

上海地区盛夏高温分布和热岛效应的初步研究

根据1997～1998年的7～8月高温加密观测资料和卫星遥感资料,应用自然正交函数分解技术(EOF),对上海地区盛夏高温分布的气候平均场和第一特征场进行了分析.上海地区盛夏平均高温场分布具有显著的城市热岛效应特征.作者详细讨论了市区建成面积、土地利用类别、人口密度和人为热等都市化因素对热岛效应范围和强度的影响,并做出定量的估计,提出了缓解城市热岛效应的若干对策.第一特征场分析表明,风向是影响上海地区热岛效应范围和强度变化的最主要的气象因子.     

首都北京及周边地区大气、水、土环境污染机理与调控原理

在国家科技部大力支持、中国气象局统一部署下,项目首席徐祥德与项目总顾问周秀骥及项目专家组共同部署了BECAPEX(北京环境大气监测)2002年现场科学试验计划,并提出科学数据分析研究重点与卫星、遥感信息等多学科技术的综合应用研究计划与实施方案.本项目在2002年现场观测资料分析与理论研究方面取得了重要进展.     

2004/2005年冬季强寒潮事件的等熵位涡分析

利用2004年12月1日—2005年2月28日的NCAR/NCEP逐日再分析资料,对2004年12月22日—2005年1月1日的强寒潮事件进行等熵位涡分析。结果表明:这次强寒潮事件的强冷空气来自欧亚北部和北极地区的高纬平流层下部与对流层上部。在寒潮爆发前期,高位涡强冷空气传播到贝加尔湖南侧,并被来自低纬度的低位涡空气所切断,在欧亚地区形成北部低位涡(阻塞高压)南部高位涡(低涡)的偶极型环流。随着低位涡的减弱消亡,高位涡强冷空气沿高原北侧向东南方向移动,当高位涡中心移到中国东部地区,高位涡空气柱在垂直方向上强烈向下伸展,使得气柱的气旋性涡度加强,东亚大槽迅速加深,引起寒潮的爆发。进一步分析表明,高位涡中心向南、向下传播过程中,等熵面上高位涡中心附近气流在其西侧和北侧地区沿等熵面下沉,引起上述地区低层西伯利亚高压迅速发展,导致强寒潮爆发。     

商丘暴雨日及分布特征研究

对商丘国家观象台1954-2005年月报表中挑取的符合暴雨日条件的142个样本分析,结果表明:商丘暴雨日具有明显的季节性,频发于7、8月份;暴雨日年平均2.73个;日暴雨量最大(193.3 mm)不超过200 mm;最长连续暴雨日数不超过2日;连续暴雨日降水量累计(223.9 mm)不超过250 mm;1 h最大降水量不超过70 mm。暴雨日的年代际变化特征明显,20世纪80年代后暴雨日出现较晚,60-90年代的暴雨日数递减,90年代后有增加趋势;大暴雨日数自60年代起有逐步增加趋势。暴雨日对月、年降水量有显著贡献,4-9月暴雨日对月降水量的贡献很大,且从4月到7月暴雨日的贡献呈递增趋势。一年内暴雨日出现5次时,当年的年雨量为偏多年份。     

Observational study of surface ozone at an urban site in East China

In this study, we present the observational data of near surface ozone and some meteorological parameters during 2004, at an urban site (36°42′ N, 117°08′ E, 34.5 m a.s.l.) of Jinan, China. Hourly ozone concentrations exceeding the standard value of China, 100 ppbv, were observed for 65 h (in 23 days) from April to October, and values exceeding US NAAQS (National Ambient Air Quality Standard) for 1 h ozone, 120 ppbv, were observed for 15 h (in 7 days) from late May to early July. Ozone formation presented the phenomenon of “weekend effect”, especially in summer. Monthly variation of ozone coincided with temperature except for July and August. The low ozone levels in July and August may be due to the short sunshine duration and much rainfall during this period. Among these meteorological parameters, daily averaged ozone shows a significant correlation with temperature (r = 0.66) in the year and with relative humidity (r = − 0.75) in summer. Throughout the year, high ozone concentrations were mainly associated with the wind from 180 to 247.5°, while high ozone concentration seemed to have no obvious correlation with a given wind direction in summer. An anomalous nocturnal high ozone episode during 23–25 May 2004 was investigated. Growth fractions of ozone during the nighttime episode were 62.2% and 71.1% for 23 and 24 May, respectively. Synoptic analysis shows that favorable synoptic condition had presumably elevated the background ozone level in this region. Backward trajectory analysis shows that the increase of ozone concentration and the relatively constant high ozone concentrations during the night of May 23 might originate from the transport of ozone rich air mass above boundary layer. Transport of ozone from Yangtze Delta and East Central China might be a significant process for the high ozone level during night May 24 at Jinan.     

A mechanism for Atlantic multidecadal variability in the Kiel Climate Model

Atlantic Multidecadal Variability (AMV) is investigated in a millennial control simulation with the Kiel Climate Model (KCM), a coupled atmosphere–ocean–sea ice model. An oscillatory mode with approximately 60 years period and characteristics similar to observations is identified with the aid of three-dimensional temperature and salinity joint empirical orthogonal function analysis. The mode explains 30 % of variability on centennial and shorter timescales in the upper 2,000 m of the North Atlantic. It is associated with changes in the Atlantic Meridional Overturning Circulation (AMOC) of ±1–2 Sv and Atlantic Sea Surface Temperature (SST) of ±0.2 °C. AMV in KCM results from an out-of-phase interaction between horizontal and vertical ocean circulation, coupled through Irminger Sea convection. Wintertime convection in this region is mainly controlled by salinity anomalies transported by the Subpolar Gyre (SPG). Increased (decreased) dense water formation in this region leads to a stronger (weaker) AMOC after 15 years, and this in turn leads to a weaker (stronger) SPG after another 15 years. The key role of salinity variations in the subpolar North Atlantic for AMV is confirmed in a 1,000 year long simulation with salinity restored to model climatology: No low frequency variations in convection are simulated, and the 60 year mode of variability is absent.     

极地和赤道热状况异常与我国及湖北省严寒关系的分析

本文对1952-1986年期间我国几次特大严寒的环流背景及发生规律作了分析和探讨,认为:严寒是一个大范围的天气现象,严重严寒往往涉及全国甚至欧亚范围,严寒的发生与大气环境的异常分布有关,导致严寒发生的前期因子是极地和赤道大范围热状况异常.     

湿润气候区无资料站点土壤湿度插补及预报试验

利用前期降水指数法(API)并结合水量平衡方程提出一种土壤湿度的初始化方案,将所建模型用于湿润气候区无资料站点的土壤湿度插补与预报试验,证明其应用的可行性。