美国中尺度气象学与九十年代天气预报服务现代化——中美中尺度气象研讨会

第二届中美中尺度气象会议于1990年9月19—21日在美国科罗拉多州博尔德市召开。国家气象局、中科院大气所、北京大学、南京大学、上海市气象局和湖北省气象局共12名代表与会。该研讨会按中美大气科学技术协议每两年召开一次,在两国交替举行,它的首届会议于1988年9月5—7日在北京举行,美方以当时的 NCAR 主任 Anthes 为团长的12人代表团参加了首届会议,成员也是来自NCAR、NOAA 和一些大学。会议主要有两个任务:相互交流中尺度气象研究、应用、业务方面的最新成果;回     

地面对晴空大气热辐射结构的影响

本文利用1987年美国FIFE资料及1986年6月TIPMEX资料,并利用大气长、短波一维辐射传输数值模式,计算了晴空大气状态下地面辐射参数(地面热辐射温度、地表反照率等)对大气长波冷却率、短波加热率廓线的影响。结果表明,地球表面对大气边界层内的热辐射结构影响很大,特别是在高原地区这种影响尤其显著。     

CHARACTERISTICS OF ATMOSPHERIC EXTINCTION-TO-BACKSCATTERING RATIO IN RUBY LIDAR MEASUREMENTS

In this paper the dependence of the ratio k (the atmospheric extinction-to-backscattering ratio) upon the aerosol refractive index and size distribution is theoretically studied in ruby lidar measurements. An empirical expression for the ratio k is then established. Moreover the effect of molecular scattering on the ratio k is discussed.     

THE PHOTODISSOCIATION COEFFICIENTS OF OZONE AND OXYGEN IN THE CLOUDY TURBID ATMOSPHERE

In this paper, the effects of clouds with different albedos at different altitudes as underlying surface on the photodissociation coefficients of oxygen and ozone in the turbid atmosphere, where the multi-scattering of molecules and aerosols is considered, have been investigated. In addition, the effects of doubling the ozone concentration in the tropopausc due to the atmospheric motion on the photodissociation coefficients of ozone and oxygen are also studied.     

GRADIENT MEASUREMENTS OF METHANE FLUX IN LIN''''AN RICE PADDIES

From July to September of 1990,CH_4 flux measurements were made in Lin'an rice paddies using gradient profiletechniques.Some characteristics of the turbulence structure under the stable conditions have been verified in the surfacelayer according to the in situ measurements.The semi-empirical turbulent parameters β_m,β_h and β_c and their changeswith the stability parameter Ri are given.Observed results indicate that CH_4 flux in the rice-paddy is mainly decided bythe methnogenesis and the process of CH4 transport from internal soils to the atmosphere,and that the CH_4 verticaltransfer is depressed in the stable surface layer.The CH_4 flux shows that its obvious diurnal changes,and the meanCH_4 flux are higher in nighttime and lower in daytime,and the peaks appear at about 2000 BST at night and 0300 BSTin the early morning,respectively.The mean value of CH_4 flux is about 4.18±2.3 mg/m~2 h.     

20世纪80年代中国地区大气气溶胶光学厚度的平均状况分析

利用中国北京等 41个甲种日射站 1 979～ 1 990年太阳直接辐射日总量和日照时数等资料 ,配合同期 TOMS version - 7臭氧观测资料 ,反演了 41个站逐年、逐月 0 .75μm大气气溶胶的平均光学厚度值 (Aerosol Optical Depth,AOD) ,据此分析了 1 2 a来中国大气气溶胶的变化和时空平均分布特征。结果表明 :中国大气气溶胶光学厚度 AOD的多年平均分布是以四川盆地为中心向四周减少 ,南疆盆地和长江中游武汉附近为另两个大值中心 ;长江中下游大部分地区、山东半岛以及广东沿海等 ,AOD值亦较大 ;而东北大部、西北大部、云南和福建沿海等地 AOD较小。AOD各月平均分布有所不同。中国绝大部分地区春季 AOD值最大 ,最小值则各地不同。 1 979～ 1 990年 ,青藏高原、四川盆地西部、贵州北部、长江中下游大部分地区、山东半岛和南疆盆地西部等 ,AOD呈增长趋势。而东北地区、西北地区大部、云贵高原和广西西部以及华东沿海等地 AOD呈减小势态。中国地区 AOD的季节变化曲线大体可分为单峰、一峰一谷、两峰一谷和多峰等 4种类型     

CHARACTERISTICS OF VEGETATION COVER,ROUGHNESS AND ALBEDO DISTRIBUTION OVER CHINA

To build land surface dataset for climate model,with application of remote sensing techniqueas well as the Geographic Information System(GIS),the data of surface type,roughness andalbedo over China in 1997 were retrieved,resolutions being 10 km×10 km.Based on these data,an analysis is conducted on the geographic distributions and seasonal variations of surfacevegetation cover and roughness as well as albedo over China.Results show that surface vegetationcover is mainly located to the south of Yangtze River,in Southwest and Northeast China andsparse vegetation cover is in the Northwest.The variation of land surface cover affects thevariations of land surface roughness and albedo.High albedo occurred in the north of XinjiangAutonomous Region,the north of Northeast China and the Qinghai-Xizang Plateau in winter,incorrespondence with the location of snow cover.For most part of China,surface roughness decreases and albedo increases in winter,while theroughness increases and the albedo decreases in summer,which could mainly result from landsurface cover(snow cover and vegetation cover)and soil moisture changes.This shows that thegeographic distribution and seasonal variation of the albedo are almost opposite to those of theroughness,in agreement with theoretical results.Temporally,the amplitude of surface roughnesschange is quite small in comparison with the roughness itself.     

对流云降水过程中地形作用的数值模拟

该文利用地形追随坐标三维云模式，对湖北的一次对流降水过程进行了平坦地面和理想斜坡地形的模拟试验。结果发现平坦地面模拟的回波强度、最大降水强度和累积降水都与实况有相当的差距。理想地形的对流过程虽然不能模拟出对流群中多单体的生消过程，但最大降水强度和累积降水都比平坦地面的大，更接近实测结果。模拟试验表明，在地形坡度较大时，会产生较强的上升气流，从而使系统对流发展旺盛，产生较大的降水和较强的回波。所以在模拟山区和丘陵地带的对流系统时，采用地形坐标并考虑地形将会改善模式的模拟结果。     

MEASUREMENTS AND MODEL SIMULATIONS OF SURFACE OZONE VARIATIONS AT DIFFERENT BACKGROUND CONCENTRATIONS OF THE PRECURSORS

Ozone photochemical production and loss in very different environments at Waliguan baselinestation and Lin'an background station were simulated by using the measurement data and photo-chemical box model.The results show that net ozone photochemical production rate is negative,about 0.5 ppb/d,at Waliguan baseline sation,because of very low precursor concentrations.Butat Lin'an background station,the net photochemical ozone production is positive,about 2—3 ppb/h.which is very closed with the measurement at Lin'an.That means ozone production was con-trolled by photochemical reactions at Lin'an background station,because of the higher precursorconcentrations.The net destruction rate,at Waliguan Mt.,is not large,so that future increase inanthropogenic emission of reactive nitrogen will lead to larger production rates of steady-state O_3concentration.     

用卫星和雷达资料进行大范围降水估计

利用日本 GMS 卫星的展宽数字云图资料(Stretched Visible and Infrared Spin Scan Radiome-ter)和中国气象科学研究院的 Doppler 雷达资料,综合卫星和雷达资料进行大范围降水估计的研究。首先把卫星和雷达资料从各自的坐标系中变换到公共坐标系——双标准纬线(30°N 和60°N)Lambert 投影坐标系中,以雷达资料作为判断降水的标准,统计得到降水概率与红外亮度温度及可见光反照率的相关矩阵。然后再把这一相关矩阵应用到一定的卫星探测的大范围中,得出降水区域分布的估计结果。用该方法对1989年7月23日和8月16日两个个例进行了估计计算。