美国第20届气候诊断年会

文章介绍了１９９５年１０月在西雅图召开的美国第２０届气候诊断年会，着重讨论了如下８个问题：气候变暖，ＥＮＳＯ影响，全球降水分析，年代际气候变率，ＥＮＳＯ预测，数值气候预测，统计气候预报及气候模拟。     

美国第19届气候诊断年会

本文介绍了美国第１９届气候诊断年会的内容。     

广西1996年气候影响评价

１９９６年度（１９９５年１２月至１９９６年１１月），各地年平均气温为１６．０－２２．７℃，全区大部比常年偏低０．４－０．７℃；年降水量为９７３．０－２２７７．４毫米，钦州、防城港两市和南宁、玉林两地区南部比常年偏少１－２成，百色地区大部偏我１－２成，其余地区正常；各地年日照时数为１１２１．５－２２６６．５小时，大部分份地区偏少８０－３００小时。１９９６年度主要气候事件及其影响以夏季洪灾害及春季低温     

河南省气候工作发展45年之回顾

河南省气候工作发展４５年之回顾程炳岩（河南省气候中心，郑州．４５０００３）气候工作是气象事业的重要组成部分，也是气象部门为回民经济建设服务的主要内容之一．１９４９年以来，随着新中回河南气囊事业的建立与发展，气候工作也从无到有，其内客日往车窗，技＊手段...     

对“气候”定义的认识

从气候发展的角度，分析了不同时期人们对气候概念的认识，并对此提出了几点看法。     

一种月、季气候资料的处理使用方法

气候作为自然资源和自然环境的组成部分，是人类生存、经济发展和社会进步的基础条件之一。气候资料作为气候的一个分支和基础，对它的分析处理十分重要。气候表征的是一种多年的均值状态，对于这种资料的分析处理有多种方法，从资料的获取、分析处理都存在一定的技巧，最终实现业务应用。文章论述一种计算机软件的编程应用及资料处理输出的过程，其结果可减轻广大天气气候预测人员的劳动强度、提高短期气候预测准确率，且有一定的业务应用意义。     

1994年我国天气气候特点

１９９４年，我国南北大部降水比较丰沛，中部地区降水偏少，北方春末夏初旱、秋旱及江淮流哉伏旱范围较大，部分地区旱情严重。汛期，我国出现南北两条明显多雨带，桂、粤、湘及辽、吉等省（区）部分地区发生严重洪涝灾害。全国大部地区气温偏高，低温冻害轻，东北初霜明显偏晚，对农业生产十分有利；夏季，大部地区出现罕见持续高温。登陆台风明显偏多，危害重，其中浙江受灾最重。风雹灾害轻。总的来看，１９９４年气候年景为一般     

太平机场航空气候特征

根据气候学和统计学原理,对哈尔滨太平国际机场的气象资料进行统计分析,找出该机场的航空气候特征。     

Simulated Influence of Mountainous Wind Farms Operations on Local Climate

Renewable energy sources, especially wind power, were believed to be able to slow down global warming; however, evidence in recent years shows that wind farms may also induce climate change. With the rapid development of wind power industry, the number of wind farms installed in mountains has gradually increased. Therefore, it is necessary to study the impact of wind farms in mountainous areas on local climate. The Suizhou and Dawu wind farms in northern Hubei Province were chosen for the present study on the impact of wind farm operations on the local climate in mountainous areas. The mesoscale meteorological numerical model Weather Research and Forecasting Model (WRF) and the Fitch model, together with turbulence correction factor, were used to simulate wind farm operations and study their effects on local climate. The results showed the characteristics of wind speed attenuation in mountainous wind farms: the amplitude and range of wind speed attenuation were stronger in the nighttime than in the daytime, and stronger in summer than in winter. The surface temperature increased and became more significant in summer. However, a cooling variation was observed above the surface warming center. The height of this center was higher in the daytime than it was in the nighttime. The latent heat flux in the wind farms decreased at night, accompanied by an increase in sensible heat flux. However, these changes were not significant. Some differences were observed between the impact of wind farms on the climate in the plains and the mountains. Such differences are more likely to be related to complex terrain conditions, climate conditions, and the density of wind turbines. The present study may provide support for the development and construction of wind farms in mountainous areas.     

Model Computations of the Impact of Climatic Change on the Windthrow Risk of Trees

The more humid, warmer weather pattern predicted for the future is expected to increase the windthrow risk of trees through reduced tree anchorage due to a decrease in soil freezing between late autumn and early spring, i.e during the most windy months of the year. In this context, the present study aimed at calculating how a potential increase of up to 4°C in mean annual temperature might modify the duration of soil frost and the depth of frozen soil in forests and consequently increase the risk of windthrow. The risk was evaluated by combining the simulated critical windspeeds needed to uproot Scots pines (Pinus sylvestris L.) under unfrozen soil conditions with the possible change in the frequency of these winds during the unfrozen period. The evaluation of the impacts of elevated temperature on the frequency of these winds at times of unfrozen and frozen soil conditions was based on monthly wind speed statistics for the years 1961–1990 (Meteorological Yearbooks of Finland, 1961–1990). Frost simulations in a Scots pine stand growing on a moraine sandy soil (height 20 m, stand density 800 stems ha–1) showed that the duration of soil frost will decrease from 4–5 months to 2–3 months per year in southern Finland and from 5–6 months to 4–5 months in northern Finland given a temperature elevation of 4°C. In addition, it could decrease substantially more in the deeper soil layers (40–60 cm) than near the surface (0–20 cm), particularly in southern Finland. Consequently, tree anchorage may lose much of the additional support gained at present from the frozen soil in winter, making Scots pines more liable to windthrow during winter and spring storms. Critical wind-speed simulations showed mean winds of 11–15 m s–1 to be enough to uproot Scots pines under unfrozen soil conditions, i.e. especially slender trees with a high height to breast height diameter ratio (taper of 1:120 and 1:100). In the future, as many as 80% of these mean winds of 11–15 m s–1 would occur during months when the soil is unfrozen in southern Finland, whereas the corresponding proportion at present is about 55%. In northern Finland, the percentage is 40% today and is expected to be 50% in the future. Thus, as the strongest winds usually occur between late autumn and early spring, climate change could increase the loss of standing timber through windthrow, especially in southern Finland.     

Evaluation of wind resource using numerically optimized data in the southwestern Korean Peninsula

The wind distribution over the Korean Peninsula was analyzed using numerically optimized wind data to reduce the uncertainties in estimating the wind resources. The simulated data were validated by a comparison with surface wind observations and three statistical indexes. According to the simulated surface winds, mesoscale circulation, such as land-sea breeze and mountain-valley winds affect the wind characteristics of the hub height at coastal and inland regions. However, the prevailing winds are strongly associated with the synoptic forcing at the island and mountainous regions, not the regional circulation. On the other hand, the atmospheric stability definitely affects the strength of the daytime and nocturnal wind speed at a hub height. Overall, there was a significant difference between the numerical and logarithmic method to estimate the wind energy at hub height. Moreover, the discrepancy in the wind density estimated using the two methods becomes clear over inland and mountainous areas.     

A Comparison Of Aerosol-Layer And Convective Boundary-Layer Structure Over A Mountain Range During Staaarte '97

The temporal evolution and spatial structure of the aerosol layer (AL) height as observed with an airborne downlooking lidar over the Swiss Alps were investigated with a three-dimensional mesoscale numerical model and a particle dispersion model. Convective boundary-layer (CBL) heights were derived from the mesoscale model output, and the behaviour of surface-released particles was investigated with the particle dispersion model. While a previous investigation, using data from the same field study, equated the observed AL height with the CBL height, the results of the current investigation indicate that there is a considerable difference between AL and CBL heights caused by mixing and transport processes between the CBL and the free atmosphere. CBL heights show a more terrain-following behaviour and are lower than AL heights. We argue that processes causing the difference between AL and CBL heights are common over mountainous terrain and that the AL height is a length scale that needs to be considered in air pollution studies in mountainous terrain.     

A Numerical Study of Precipitation Characteristics over Taiwan Island during the Winter Season

Summary  Two-thirds of the land mass of Taiwan island is mountainous, which affects the airflow and precipitation systems over the island. In this study, we discuss the characteristics of precipitation systems when the prevailing wind direction is from the north-east during winter. Observations indicate that rainfall amounts were higher in northeastern Taiwan (the upstream side of the mountains) and that a rainfall shadow occurred in southwestern Taiwan. Simulation results from a non-hydrostatic model indicate that airflow was deflected in eastern Taiwan, while relatively high (low) pressure areas formed in eastern (western) Taiwan. A higher mixing ratio of rainfall occurred over northeastern Taiwan while lighter rainfall occurred in the eastern, and northwestern areas and the southern tip of Taiwan. This was consistent with the observational data except for the southern tip of Taiwan. Uplift due to the topography near the mountainous areas, as well as low level convergence near the coastal areas (due to the deceleration of an easterly wind in northeastern Taiwan), helped form the mixing ratio of rain. Transportation of the mixing ratio of rainfall, due to low level westward flow and upper level eastward flow, caused it to cover a larger area. The mixing ratio of rainfall formed in the upper mountainous areas in northeastern Taiwan if the upstream moisture content was reduced significantly. A temperature inversion at low levels resulted in a decrease in relative humidity and an increase in stability, requiring that the mixing ratio of rainfall should develop closer to the mountainous areas. If a low level wind blew parallel to the orientation of the mountains (NNE-SSW), a higher mixing ratio of rainfall could occur in the mountainous areas of western Taiwan. Received January 30, 1998 Revised February 19, 1999     

石家庄市风环境容量变化特征及区划研究

利用气象观测、高分辨率城市地理信息、卫星遥感反演及ERA-Interim再分析资料,基于水平风速、混合层高度及地表粗糙度长度指标,利用等权重加权综合评价法和几何间隔分级法,开展了石家庄市风环境容量指标和区划研究,得到风环境容量指数分级阈值和空间分布.结果表明,石家庄市水平风速和大气混合层高度均由西部山区向东南部平原逐渐降低,在西南部山区存在一个高值区,在东南部平原存在一个低值区,且具有明显的季节和日变化特征;石家庄市区和西部山区地表粗糙度长度较大,平原地区较小;风环境容量指标分为低值区、次低值区、中等区、次高值区和高值区5个等级,在空间上石家庄市区及平原地区级别较低,西部和北部山区级别较高,其中石家庄市区、正定东南部、栾城东部、藁城大部分地区及无极西部是风环境容量最低区域,赞皇、高邑、赵县西南部、元氏西部、南部及井陉西南部为最高区域.     

北京降水特征及北京市观象台降水资料代表性

将北京分为城区、郊区、南部山区及北部山区4个区域,利用14个观测站1978—2010年共33年的月降水量资料,分析了不同区域降水年变化和夏季降水特征及其差异。结果表明:各区域年平均降水量存在较大差异,郊区降水量最多 (620 mm),城区与南部山区降水量较少,而北部山区降水量最少 (476 mm);城区与南部山区的年降水量较接近,二者与郊区和北部山区都有显著差异。4个区域的降水量都表现出减少趋势,郊区最明显 (47 mm/10 a),北部山区的减少趋势最小 (0.7 mm/10 a)。对4个区域夏季 (6—9月) 降水量分析发现,城区与南部山区具有较好的一致性,二者与郊区和北部山区具有显著差异。均方根偏差和相关系数的计算结果表明:北京市观象台与城区和南部山区的降水年变化和夏季降水特征差异均不显著,而与郊区和北部山区有显著差异,说明北京市观象台降水资料对城区和南部山区具有最优代表性,而对北部山区和郊区的代表性较差。     

南方夏秋干旱期间的天气气候特征

对40多年来南方的天气气候特征进行了分析,提出了7～9月夏秋干旱期形成干旱的主要天气系统为西太平洋副热带高压.从干燥度和降水的空间分布综合分析,得出了南方最旱区位于湖南、江西中部.广西、贵州、湖南西北和东南山区、江西南部山区、安徽南部山区、福建-浙江沿海交界山区和苏北沿海为湿润区,人工增雨潜力较大.特殊地形所形成的焚风效应是形成湘中干旱不可忽略的原因.为南方夏秋期间对流云降水潜力研究和科学实施人工增雨作业提供一定依据.     

METHODS CALCULATING THE SPATIAL DISTRIBUTION OF AGROCLIMATIC RESOURCES IN MOUNTAINOUS AREAS AND CLIMATIC EFFECTS OF MICROTOPOGRAPHY*

The methods calculating the spatial distribution of agroclimatic resources (temperature,humidity,precipitation,wind speed,etc.) in mountainous areas are presented.The linear model can be used for the mean temperature,accumulated temperature,and the occurrence date and duration of limiting temperature,but the nonlinear model for extreme temperature,humidity,precipitation and wind speed.The climatic effects of topography obtained from the application of these methods in the Shaxi River basin,Fujian Province,are also described.The results show that the methods proposed in this paper may effectively disclose the macro-and micro-variations of spatial distribution of agroclimatic resources in mountainous areas.     

On the micrometeorology of surface hoar growth on snow in mountainous area

Profiles of temperature and humidity are calculated for a snow surface being cooled by outgoing radiation assuming no wind. These suggest that fog would necessarily form to block the cooling and, even in the absence of fog, the diffusion of water vapor to the surface could not account for observed rates of surface hoar growth. Therefore turbulent transfer to an interfacial sublayer with a very large temperature gradient must occur at least intermittently. In mountainous areas, gravity drainage of air over the interfacial sublayer probably accounts for the turbulence since air currents from a regional pressure gradient appear to transfer enough heat to the surface to prevent surface hoar growth. The vapor must diffuse through a 1 mm interfacial sublayer until the crystals reach a sufficient height to interact with the drainage wind.