珠江三角洲降水数值预报的初步试验

以广州区域气象中心的实时资料库和大气所的细网格降水数值预报模式为基础,在VAX6220机上建立了珠江三角洲中尺度准业务降水数值预报系统,并从1990年5月20日至6月10日进行了连续22天的试验,对结果的分析表明,系统能稳定及时地提供12小时和24小时的预报产品,对短期降水预报具有一定参考价值。      

陆面特征非均一作用参数化及其对区域气候影响的数值模拟试验

本文首先改进了陆地下垫面特征非均一性的次网格尺度参数化方法，然后利用三维地气耦合的区域气候模式，设计一系列值试验，研究了下垫面特征改变对区域气候环境变化的影响，主要分析了陆地表面特征变化对我国苏南附近地区夏季温度化的影响，结果表明采用地下垫面特征非均一作用的次网格尺度参数化方法对于改进数值模拟结果的质量有一定效果。     

边界层特征量在河南省沙尘天气短期预报中的应用

介绍了利用边界层特征量——摩擦速度和梯度Richardson数制作河南省沙尘天气短期预报的方法.结果表明,该动力学方法更能够从本质上反映沙尘天气产生的机制,定性预报准确率为62.5%.     

MM5对末次盛冰期中国气候的模拟研究Ⅰ:CO2和地球轨道参数的影响

通过模式结果与实况资料和地质记录对比,表明模式系统可以较好地模拟现代气候状况和末次盛冰期气候的变化,特别是降水的变化与地质记录符合得较好.在末次盛冰期和现代气候状况下地球轨道参数的变化对中国地区年平均温度的影响很小,但对不同季节温度变化的作用不同.冬季气温的变化比较显著,不能忽略.CO2浓度在末次盛冰期最低,其混合比为200×10-6,这使得气温降低.CO2的作用也存在明显的季节和区域特征.冬季其影响最大;但夏季其作用较小,甚至出现CO2浓度减少温度增加的现象.产生增温现象的原因是云量发生了变化,使到达地面的太阳辐射增加.这个结果表明云在气候变化中,可能起着非常重要的作用,甚至可以影响某时段和区域温度等要素变化的方向.青藏高原地区对这两个辐射因子变化的响应与中国其他地区相比偏小,原因是该地区的云量高于其他地区.相对现代气候,末次盛冰期地球轨道参数变化对气候的影响小于CO2的作用.但相对于末次盛冰期气候的变化,这两个因子的贡献都是比较小的.CO2对末次盛冰期年平均温度变化的贡献大约为3%-10%.此外,现代和末次盛冰期气候背景下,CO2的作用相同.     

2018年10月乌鲁木齐暴雪过程锋面分析

利用地面常规观测、NCEP/NCAR0.25°×0.25°再分析及风廓线雷达等资料,诊断分析了2018年10月17—18日乌鲁木齐极端暴雪天气过程的锋面特征。结果表明：在欧洲高压脊衰退,中亚长波槽分段东移的背景下,天山北坡强烈锋生并持续近30小时,此次锋生是热力和动力共同作用的,天山附近锋面呈带状准垂直分布,动力锋生激发的次级环流使垂直运动维持发展,为大暴雪提供动力条件; 400～600 hPa西南和地面～850 hpa西北路径输送的水汽,在600～800 hPa强烈辐合,为乌鲁木齐暴雪提供充沛水汽。风廓线雷达监测资料水平风向风速的垂直变化、Cn2能够反映锋生和水汽的演变特征,也从观测事实上证实了锋面对动力抬升及水汽辐合的重要作用。     

Evolution of aerosol vertical distribution during particulate pollution events in Shanghai

A set of micro pulse lidar(MPL)systems operating at 532 nm was used for ground-based observation of aerosols in Shanghai in 2011.Three typical particulate pollution events(e.g.,haze)were examined to determine the evolution of aerosol vertical distribution and the planetary boundary layer(PBL)during these pollution episodes.The aerosol vertical extinction coefficient(VEC)at any given measured altitude was prominently larger during haze periods than that before or after the associated event.Aerosols originating from various source regions exerted forcing to some extent on aerosol loading and vertical layering,leading to different aerosol vertical distribution structures.Aerosol VECs were always maximized near the surface owing to the potential influence of local pollutant emissions.Several peaks in aerosol VECs were found at altitudes above 1 km during the dust-and bioburning-influenced haze events.Aerosol VECs decreased with increasing altitude during the local-polluted haze event,with a single maximum in the surface atmosphere.PM2.5 increased slowly while PBL and visibility decreased gradually in the early stages of haze events;subsequently,PM2.5 accumulated and was exacerbated until serious pollution bursts occurred in the middle and later stages.The results reveal that aerosols from different sources impact aerosol vertical distributions in the atmosphere and that the relationship between PBL and pollutant loadings may play an important role in the formation of pollution.     

高速公路交通事故与气象条件的关系研究

恶劣天气是高速公路交通事故发生的重要诱因。为了解气象条件对高速公路交通事故的影响程度,基于2006—2008年汉宜高速公路交通事故数据,统计分析了该路段交通事故的月际和日变化特征,利用事故率和日交通事故指数区分定义了交通事故频次和灾害严重程度,采用多项式曲线拟合了气象条件与事故指数的关系,确定了事故突发增长的临界气象指标。结果表明:汛期5—9月是汉宜高速公路交通事故高发时期,冬季其次,春季3—4月及秋季10—11月事故发生较少。高速公路交通事故存在明显日变化特征,03—04时和14—17时为事故高发时段。汉宜高速公路交通事故频率主要受中到大雨和夏季高温天气的影响,事故灾害严重程度主要受强降水和冬季低温天气的影响。大风强降水天气条件下的事故率要高于一般强降水条件下的事故率,夏季潮湿、闷热天气条件下的事故率要高于一般高温天气条件下的事故率。当高速公路沿线平均日雨量达到中到大雨时,事故率达到高峰;当沿线平均雨量超过20 mm时,事故灾害突发严重。当公路沿线平均高温超过33℃时,事故率突发增长;0~3℃的低温对事故灾害程度影响较大。     

Changes in wheat potential productivity and drought severity in Southwest China

Theoretical and Applied Climatology - Wheat production in Southwest China (SWC) plays a vital role in guaranteeing local grain security, but it is threatened by increasingly frequent seasonal...     

Estimation of relative humidity based on artificial neural network approach in the Aegean Region of Turkey

The aim of this study is to estimate the monthly mean relative humidity (MRH) values in the Aegean Region of Turkey with the help of the topographical and meteorological parameters based on artificial neural network (ANN) approach. The monthly MRH values were calculated from the measurement in the meteorological observing stations established in Izmir, Mugla, Aydin, Denizli, Usak, Manisa, Kutahya and Afyonkarahisar provinces between 2000 and 2006. Latitude, longitude, altitude, precipitation and months of the year were used in the input layer of the ANN network, while the MRH was used in output layer of the network. The ANN model was developed using MATLAB software, and then actual values were compared with those obtained by ANN and multi-linear regression methods. It seemed that the obtained values were in the acceptable error limits. It is concluded that the determination of relative humidity values is possible at any target point of the region where the measurement cannot be performed.