The Numerical Simulation on Atmospheric Transport and Dispersion of the Spray Atomized from Flood Discharging by Hydropower Station over Complex Terrain

Summary  A three-dimensional, nonhydrostatic numerical model with high spatial resolution, in which a simple energy closure scheme is employed, has been developed to simulate the spray dispersion over complex terrain. The evaporation, condensation, and dispersion of the spray and moisture are taken into account in model equations. The term of latent heat due to phase transformation is considered in detail to account for its effects on the temperature field and airflow. As an application of the model, the spray concentration and air relative humidity are calculated under neutral condition. The results indicate that under the neutral condition, the spray is transported to about 0.6 km downwind from the source, and its effects on the air humidity reach a further distance of 0.9 km downwind from the source. Attention is given to the dependence of the results upon the various factors influencing the simulation, such as the intensity of the source, the atmospheric stratification, and the dynamic factor of the terrain. Some numerical tests were carried out to provide extra insight to the effects of these factors. It has been demonstrated that the simulation results such as relative humidity and temperature are sensitive to these factors, especially to the thermal stratification. Under unstable conditions, the effects of the spray source increase significantly, and the variation extent of the temperature, relative humidity and flow field is larger than that under neutral condition. The effects of dynamic and thermal factors on the air flow field are discussed through the comparison of the modeling results over complex terrain and flat terrain. Received June 8, 1998 Revised April 17, 1999     

气候变化对中国东北地区典型城市办公建筑能耗的影响

利用中国东北地区三个典型城市（哈尔滨、长春和沈阳）1961—2019年的气温、相对湿度等气象资料和TRNSYS软件模拟的能耗资料,分析了气候变化对东北地区办公建筑设计气象参数的影响,研究了气候变化对办公建筑能耗的影响及其影响因子。结果表明：与1961—1990年相比,近30 a（1991—2019年）东北地区三个城市的办公建筑室外设计计算参数,即供暖室外计算温度、冬季空调室外计算温度和夏季空调室外计算温度均有所升高,且夏季空调室外计算温度升幅低于其他两个设计参数,三个城市供暖室外计算温度分别升高了2.1℃、1.7℃和0.2℃;1961—2017年三个城市办公建筑冬季供暖能耗均呈减少趋势,夏季制冷能耗均呈增加趋势,年总能耗呈减少趋势;哈尔滨和长春的变化速率大于沈阳,三个城市的办公建筑年总能耗减少速率分别为5.02 MJ·m^-2/10 a、6.15 MJ·m^-2/10 a和1.99 MJ·m^-2/10 a。气温是影响东北地区城市办公建筑能耗的主要气象因子,分别可以解释三个城市冬季供暖能耗95%、96%和93%的变化和夏季制冷能耗72%、71%和72%的变化;气温每升高1℃,三个城市的冬季采暖能耗将分别减少20.6 MJ·m^-2、21 MJ·m^-2和18.9 MJ·m^-2,夏季制冷能耗将分别增加15.1 MJ·m^-2、16.1 MJ·m^-2和18.8 MJ·m^-2,年总能耗将分别减少5.5 MJ·m^-2、4.9 MJ·m^-2和0.1 MJ·m^-2。     

Temperature stratification of the lower atmosphere over Moscow

Features of diurnal and annual cycles and of seasonal changes of temperature stratification in the lower 800-m air layer over Moscow are discussed on the basis of analysis of long-term data of acoustic (sodar) observations at Moscow State University (MSU). Of about 34 000 separate hours of height-time sweep of echo signal during 1988–2003, refined estimates are presented of occurrence frequencies of surface and elevated inversions, unstable stratification, etc., in Moscow. On the basis of long series of hourly sodar data and surface weather observations at MSU, special features of temperature stratification are considered under extremely low and high values of air temperature, wind speed, and relative humidity. A review is presented of existing data on temperature stratification in central Russia for the whole period of aerological observations; results of acoustic sounding are compared against the data obtained using other techniques.     

青藏高原冬季平均温度、湿度气候特征的REOF分析

通过对青藏高原123个测站, 1961~1998年冬季 (12月至翌年2月) 平均温度、相对湿度资料做气候特征分析, 得到32°~33°N附近地区可能是高原南北温湿变化的分水岭, 以北主要受干冷空气影响, 以南主要受暖湿空气影响。用方差极大正交旋转EOF (即REOF) 方法对以上资料进行分析, 可以将青藏高原温度、相对湿度进行分型、分区, 并对各区的温度、相对湿度特征进行分析。结果表明, 近40年来, 各区的温度总趋势是在波动中逐步升高的。增温时段主要出现在1978~1981年及1983年至今。1983年开始的增温, 是近40年来最强的一次, 增温幅度大且持续时间长, 但从90年代开始增温幅度及范围出现波动。从温度线性倾向来看, 东部高原增温幅度从南到北存在“大—小—大”的现象。高原大部分地区湿度变化总趋势是在波动中逐步增湿的, 但高原北界以变干为主。从80年代后期至今高原进入显著增湿阶段, 但从90年代中后期开始增湿幅度及范围出现波动。从湿度线性倾向来看东部高原增湿幅度从南到北存在逐步减小现象, 甚至祁连山地区出现变干现象。     

利用采暖/制冷度日分析建筑能耗变化的适用性评估

采暖/制冷度日与建筑能耗有显著线性关系,被认为是最简单可靠的衡量能源需求的指标,但其适用性还缺乏全面的评估。通过模拟1961-2009年天津市办公、商场以及不同节能水平的居住建筑能耗,分析了能耗与采暖/制冷度日的关系,确定其反映能耗变化的适用性。结果表明：采暖期办公及商场建筑的热负荷与采暖度日的相关性达到极显著水平（P<0.01）,决定系数（R2）分别为0.99和0.97;制冷期冷负荷与制冷度日的关系尽管也达到极显著水平,但决定系数仅分别为0.64和0.55;不同节能水平居住建筑热负荷与采暖度日极显著相关,决定系数均在0.99以上。研究认为：采暖度日可以反映办公、商场及居住建筑的热负荷特征,用于分析气候变化对能耗的影响是可行的;但制冷度日不能完全反映办公及商场建筑冷负荷的变化,仅可分别解释冷负荷变化的64%和55%,单纯用制冷度日研究能耗变化是不够全面的。通过分析能耗与气候要素的关系发现,冬季采暖期能耗主要受气温的影响,而夏季制冷能耗受气温和湿度的共同影响。     

1998年7月21日武汉暴雨小尺度动力特征的数值模拟研究

利用三维完全弹性积云数值模式,模拟了1998年7月21日武汉暴雨期间强降水积云的发生、发展过程.着重分析了积云动力学特征以及近地层散度场、水汽通量等对积云降水的发展、维持的贡献.结果表明,特殊的温、湿层结配置是这次强降水对流云发生的主要原因,而近地层高温、高湿气体源源不断地向云体输送,是强降水积云长时间维持的能量来源.合适的上下层风切变,特别是近地层逆向云体风速的存在,使得云体移动前方下层高温、高湿气体向云内输送,云后部伴随降雨而出现的干冷出流迅速流出,上层高空急流的存在,为积云顶部出流在更大范围扩散提供了条件.散度场、水汽通量场的分布及演变,也进一步证明了上述结论.     

The contribution of moisture to heat stress in a period of global warming: the case of the Mediterranean

This study deals with potential changes in the relative humidity associated with global warming and their implications on heat stress along the coastal region of the Mediterranean in the summer season. It is based on the assumption that the regional warming will enhance the lower-level stability due to the thermal inertia of the sea with respect to its overlying air. The enhanced stability implies more effective trapping of the near surface moisture, and as a result—further increase of the relative humidity. The marine boundary layer over the Mediterranean is modeled. The central feature of the model is the marine inversion capping the marine moist air, which intensity is positively correlated with the stability. Simple calculations indicate that if the temperature increases, while the stability remains unchanged, the near-surface relative humidity would not be affected. But, an increase in the stability would result in an increase in the near-surface relative humidity. This prediction is validated through observed trends of the respective fields, using the NCEP/NCAR reanalysis data and soundings from the eastern Mediterranean. The results are consistent in indicating an increase in the near-surface temperature, the lower-level stability and the relative humidity over the eastern part of the Mediterranean, but not in its western part. The results for the eastern Mediterranean support the expectation for an aggravation of heat stress beyond that imparted by the temperature rise.     

土壤湿度异常对区域短期气候影响的数值模拟试验

用区域气候模式 (RegCM_NCC) 对江淮流域地区春季初始土壤湿度异常导致的区域气候效应进行了数值模拟分析, 结果表明:土壤湿度异常变化对区域降水的影响非常显著, 土壤湿度的正异常使得异常区域内降水增大, 地面空气增湿、蒸发加大, 与此相应, 地表气温迅速降低, 土壤湿度的负异常有与之相反的结果, 这种区域气候响应是通过改变地表辐射平衡及地-气系统能通量而实现的; 区域土壤湿度异常对短期气候的影响在一个月之内较明显, 它的影响可持续至以后的几个月, 但强度逐渐减弱; 区域土壤湿度异常的气候响应不仅仅局限于异常区域内部, 而且可以通过次级环流影响到其他区域的降水、温度等变化。     

Seasonal trends of climate change in the Yangtze Delta and its adjacent regions and their formation mechanisms

Summary Based on the monthly mean values of 10 meteorological elements from 53 surface weather stations in the Yangtze Delta and its adjacent areas during 1961–1997, the part played by linear climate trends has been analyzed to explore the characteristics of the regional climate change. The results show that the annual air temperature, and maximum and minimum air temperatures, have all increased rapidly in the Yangtze Delta, but there has been a reverse trend in its adjacent areas, i.e., the air temperatures have gradually decreased. Thus the Yangtze Delta emerges as a regional heat island in relation to its adjacent areas. The regional heat island consists of several urban heat sub-islands in southern Jiangsu Province and northern Zhejiang Province, including Shanghai, Wuxi, Changshu, Nanjing, Hangzhou and Ningbo. It appears most obvious in winter and least obvious in summer. An intensity of the regional heat island is defined, and it is shown that the variation of the heat island is positively correlated to the economic development of the region, and is assumed to be related with the increased consumption of energy due to economic development. The results of a climatological analysis of the other annual meteorological elements have indicated the tendency that the soil temperature of the Yangtze Delta has a weak cooling process, its precipitation has evidently increased, sunshine duration and visibility have apparently decreased, and the trend centers appear mainly in the cities. All these phenomena imply that air pollution and aerosols increase with economic development, leading to a cooling mechanism, which in turn suppresses the enhancement of the heat island caused by increasing consumption of energy. On the other hand, an intensified heat island also makes convection and precipitation increase. For the adjacent areas whose economic development is less intense than the Yangtze Delta, a weak cooling appeared there because their heat island caused by increasing consumption of energy resources could not offset the cooling due to aerosols. It can be seen from satellite images that the increase of aerosols in the Yangtze Delta is more obvious than its adjacent areas. By use of a three-region nested mesoscale model, a series of simulations are made with no-forcing and forcing of the optical depth of aerosol and the heating due to energy consumption by human activities. The results of the analysis and the simulation coincide very well. The simulations support the above-mentioned mechanisms of the regional heat island in the Yangtze Delta of China.     

An assessment of boundary-layer air mass characteristics associated with topographically-induced local wind systems

Measured and derived meteorological parameters are used to examine the changes in air mass associated with local winds of differing origin. Research conducted explores the usefulness of wet bulb potential temperature, equivalent potential temperature, virtual potential temperature and relative humidity as indicators of air mass change during sea breeze, foehn wind and nocturnal drainage flow events. The complex interactions between these different topographically-induced wind systems in South Canterbury, New Zealand, provide an environment in which marked changes in air mass characteristics are common. Results demonstrate that under a considerable range of boundary-layer conditions, measured wet bulb potential temperature when used in conjunction with windspeed and direction enables quick and accurate determination of air mass origin. Relative humidity was also found to respond closely to changes in local air mass type, but its dependence on air temperature makes it a less reliable indicator.     

Effects of climate change on building energy consumption in cities

Summary Sensitivity of building-energy consumption to changing urban environments is examined by simulating building energy loads in hypothetical urban settings. A modified version of an algorithm developed by the U.S. Army Construction Engineering Research Laboratory is used to evaluate energy requirements. Energy loads for two buildings of interest are estimated for changing climatic conditions (air temperature) as well as changing environments around the building. An isolated building and a building surrounded by several other buildings are considered.Results indicate that climate warming may lead to energy savings in a wide range of climates while savings also depend on the nature of the building and its use. In cool climates, climate warming forces net energy-load decreases through reductions of the winter heating loads. For example, a one-degree increase in annual air temperature in Duluth led to a 10 kWh decrease in net energy loads for a small office building. In warm climates, urbanization tends to accelerate energy consumption although shadowing may contribute significantly to decreases in summer cooling loads. In Phoenix, annual mean daily net energy loads decreased by about 10 kWh due to shadowing for the same office building. Even in relatively cool regions, summer cooling-load reductions caused by shadowing are effective.With 12 Figures     

An assessment of the potential impact of a downward shift of tropospheric water vapor on climate sensitivity

This work uses an energy balance climate model (EBCM) with explicit infrared radiative transfer, parametrized tropospheric temperature and humidity profiles, and separate stratosphere, troposphere, and surface energy balances, to investigate claims that a downward redistribution of tropospheric water vapor in response to surface warming could serve as a strong negative feedback on climatic change. A series of sensitivity tests is carried out using: (1) a variety of relationships between total precipitable water in the troposphere and temperature; (2) feedbacks between surface temperature and the vertical distribution of tropospheric water vapor at low latitudes; and (3) feedback between surface temperature or meridional temperature gradient and lapse rate. Fixed relative humidity (RH) enhances the global mean surface temperature response to a CO₂ doubling by only 50% compared to fixed absolute humidity, giving a response of 1.8 K. When water vapor is assumed to be redistributed downward between 30°S–30°N such that a 1 K surface warming reduces total precipitable water above 600 hPa by 10%, the global mean surface air temperature response is reduced to 1.2 K. Assuming a stronger downward redistribution in relation to surface temperature change has a rapidly diminishing marginal effect on global mean and tropical surface temperature response, while slightly increasing the warming at high latitudes due to the parametrized dependence of middle-to-high latitude lapse rate on the meridional temperature gradient. A modest downward water vapor redistribution, such that absolute humidity in the upper troposphere at subtropical latitudes is constant as total precipitable water increases, can reduce the tropical temperature sensitivity to less than 1 K, while increasing the equator-to-pole amplification of the surface air temperature response from a factor of about three to a factor of four. However, it is concluded that whatever changes in future GCM response might occur as a result of new parametrizations of subgrid-scale processes, they are exceedingly unlikely to produce a climate sensitivity to a CO₂ doubling of less than 1 K even if there is a strong downward shift in the water vapor distribution as climate warms. Received: 23 February 1998 / Accepted: 1 November 1999     

Restoration of an inner-city stream and its impact on air temperature and humidity based on long-term monitoring data

Spatiotemporal changes in air temperature and humidity associated with the restoration of an inner-city stream in Seoul, Korea, are investigated based on long-term monitoring data. The Cheonggye stream, covered under a concrete structure for 46 years, was restored in 2005 and runs 5.8 km eastward through a central region of Seoul. Long-term monitoring of the air temperature and relative humidity was made along the stream throughout the restoration and across the stream after the restoration. The area along the stream had a higher air temperature than the entire metropolitan area. The temperature anomaly between the monitoring area and the surrounding metropolitan area was 0.13^oC lower on average at the center of the stream after the restoration. The stream's effect on the air temperature was also evident in the temperature distribution along a street traversing the stream. The relative and specific humidities were increased due to the restoration. The restored stream modified the nearby urban climate in the opposite direction compared to urbanization. The results could be used as a model case in mitigating urban climate by a stream in future urban planning practices.     

人工控制气象条件降低高炉焦比

高炉冶炼的重要能耗指标－焦比，存在着明显的季节性变化，而这种变化近似于某些气象要素的季节性变化。经分析发现绝对湿度与焦比的关系最为密切，通过试验，发现可以运用脱湿鼓风这种人工控制气象条件的方法降低焦比，为高炉创造四季如冬的最佳工艺环境，同时产生很大的经济效益。     

Detailed spatial modeling of temperature in Moscow

A computer complex is described developed for the detailed temperature forecasting in large megalopolises. It consists of the global and microclimatic models implementing the modeling of the thermal regime within Moscow. To increase the modeling quality, an improved technique is proposed of computation of temperature characteristics within the urban canyon. A spatial resolution of output modeling data reaches 500 m. A comparison with the station data demonstrates that the accuracy of air temperature simulation in Moscow and in its nearest vicinities is quite satisfactory.     

广东“回南天”现象分析及其预报

利用室内地板温度、气温、露点、湿度,以及NCEP 1°×1°分析数据等资料,对2012年广东2—3月冬春过渡季节"回南天"(高湿天气)的5次个例的天气形势、气象要素特征和物理变化过程进行了分析。结果表明:冷空气影响结束后,广东上空迅速转受暖湿空气控制,当室外空气露点高于室内物体温度时"回南天"现象就会产生;"回南天"是出现在冷暖急转的天气背景下的;冬春季节当持续控制广东的冷高压脊快速减弱,同时925hPa上有明显的偏南气流时,预报员就要考虑是否会出现"回南天"现象;气温快速回升,露点高于室内物体温度是"回南天"出现的必要条件,要重点分析未来露点的变化;"回南天"有两种结束方式,即冷性结束和暖性结束。     

城市中水体布局对大气环境的影响

城市下垫面状况在很大程度上决定城市大气物理环境的特征。在城市区域增加湿地等自然地表有利于城市的减温增湿,促使局地流场发生变化,改善局地微气象条件以及大气物理环境。城市规划大气物理环境多尺度数值模拟系统为城市规划大气物理环境定量评估提供了有效的模拟工具。利用该系统中的城市尺度模式模拟了水体布局为集中型和分散型,水体面积占有率分别为4%、8%、12%和16%条件下,城市大气温度、湿度、风速、城市大气扩散条件的变化及其对城市大气环境的影响,利用北京市城市水体气象观测数据,分析了水体周边和商业区、交通区温、湿度的差异,并对模式模拟结果进行了验证,揭示了城市水体布局对城市大气物理环境影响的可能机制。模拟和观测结果显示,城市水体布局会对城市微气象环境产生一定影响。无论分散型或集中型布局,城市水体面积的增加,都在一定程度上使城市气温降低、湿度增加、平均风速增大。比较而言,分散型水体布局对城市区域微气象环境的影响更为显著。     

桂北山区两次突发性大暴雨触发及维持机制分析

利用常规观测资料、区域自动站资料、柳州多普勒雷达资料以及ERA5再分析资料对2020年6月24日(“6·24”过程)和7月9日(“7·9”过程)广西柳州元宝山地区先后出现的突发性局地大暴雨过程进行了分析, 探讨这两次过程的触发因子。结果表明: 在低层偏南暖湿气流持续输送的前提下, 元宝山脉动力抬升进一步增强了山脉附近垂直上升运动; 白天大量积聚的能量导致热力条件非常不稳定, 地面中尺度辐合线及局地地形形成的中尺度辐合中心和大尺度环流的配合致使对流系统先在元宝山脉南侧触发起来, “列车效应”以及高效率、低质心的降雨系统使得小时雨强和累积雨量极大; 两次过程与850 hPa西南气流风速脉动密切相关, 高温高湿的暖湿气流在元宝山地区强烈辐合为暴雨增幅提供了有利条件, 有利于强降水在柳州北部地区维持; “6·24”过程近地层有弱冷空气侵入, 低层水汽饱和、中高层有干冷空气卷入; “7·9”过程近地层没有冷空气侵入, 湿层深厚, 整层为高温高湿的环境。     

Estimating heat fluxes by merging profile formulae and the energy budget with a variational technique

A variational technique (VT) is applied to estimate surface sensible and latent heat fluxes based on observations of air temperature, wind speed, and humidity, respectively, at three heights (1 m, 4 m, and 10 m), and the surface energy and radiation budgets by the surface energy and radiation system (SERBS). The method fully uses all information provided by the measurements of air temperature, wind, and humidity profiles, the surface energy budget, and the similarity profile formulae as well. Data collected at Feixi experiment station installed by the China Heavy Rain Experiment and Study (HeRES) Program are used to test the method. Results show that the proposed technique can overcome the well-known unstablility problem that occurs when the Bowen method becomes singular; in comparison with the profile method, it reduces both the sensitivities of latent heat fluxes to observational errors in humidity and those of sensible heat fluxes to observational errors in temperature, while the estimated heat fluxes approximately satisfy the surface energy budget. Therefore, the variational technique is more reliable and stable than the two conventional methods in estimating surface sensible and latent heat fluxes.     

An investigation of the Iranian climatic changes by considering the precipitation, temperature, and relative humidity parameters

The present study tends to describe the survey of climatic changes in the case of the eastern and central areas of Iran and, to some extent, the northern parts. The monthly and yearly change trends in the minimum, maximum and mean temperatures, relative humidity, and the precipitation were surveyed for 26 synoptic stations in Iran during a 55-year period. The study was carried out by using the ??-Kendall test. The results showed the same temperature changes for the centrally located stations as the eastern and northern ones. Most of the stations in Zagros showed no significant temperature changes. A significant decrease in the precipitation was seen in summer in different stations. Most of the eastern and centrally located stations showed a decrease in relative humidity trend, while this condition was not recorded in Zagros and northern part of Iran. The present results also showed that the upward trend of minimum air temperature had an effect in increasing the mean air temperature in the stations with temperature ascending trend. This effect of minimum temperature was significantly more than that of the maximum temperature, which could be the result of increasing the amount of greenhouse gases and the reflection of received thermal energies, from land through the night. This increase in the temperature and a decrease in relative humidity would cause an increase in the evaporation of the received precipitation.