谈城市绿地生态效应

城市绿地作为“城市的肺”，一直受到城市规划和建设者的关注。早在20世纪初，城市绿地的研究就受到了有关学者和城市决策者的重视，但多局限于对绿地美学效应的研究，而绿地结构和大气生态的相关性研究却比较晚。近年来，有关这方面的研究受到了挑战。一方面通过园林绿化来缓解城市气候效应、改善城市环境质量，已为园林科技工作者和城市决策者所推崇；另一方面，城市规模的日益扩大，使城市土地寸土寸金，可用于绿化的土地愈来愈少，成本也愈来愈高，尤其是老城改造中的绿地规划难度更大。

低纬高原城市冬季南北朝向室内温湿特征的初步分析

通过对低纬城市——昆明冬季室内、外气温观测资料的分析,探讨了不同天气下南北朝向室内的气温、湿度特征。得出昆明地区冬季各种天气状况下室内最低气温和日均气温的增温效应均十分显著,与庭院相比,南向室内的增温幅度为7.7～10.0 ℃和4.6～5.8 ℃;北向室内为4.6～7.0 ℃和1.3～4.4 ℃;最高气温南向室内高于室外,而北向室内一般低于室外。另外,建筑物不但可维持较高的室内温度,而且减缓了室内气温的变化幅度,不论南向室内还是北向室内,气温日较差均小于室外,变幅仅为室外的40 %～48 %(南向)和20 %～30 %(北向),且最高气温出现时间比室外约迟2小时,显示了建筑物内温度变化的惰性。研究还得出南向室内的相对湿度均小于北向,南北差异以晴天最大,阴天最小。室内相对湿度的日变化特征为夜间湿度大,变化小,昼间湿度小,变化大。以上结果可为低纬城市气候的深入研究,建筑的合理设计提供科学基础。

关注城市气候改善人居环境

长期以来，人类一向与大自然和谐共处、相安无事。但自工业革命以来，人类大量燃烧煤和石油向地球大气排放巨量的废气，大气温室效应己使全球发生气候变暖、极冰融化、海平面上升等难以逆转的环境效应。与此同时，日益剧烈的人类活动还使城市环境发生了显著变化，派生出诸如“热岛”、“灰霾岛”、“乡村风”等城市气候效应，严重困扰居民的日常生活。因此，关注城市气候，改善居住环境，已经引起社会各界的高度重视。

THERMAL EFFECTS OF BUILDING′S EXTERNAL SURFACES IN CITY——Characteristics of Heat Flux into and out of External Wall Surfaces

This study examined the thermal effects of building′s external wall surfaces, using observational data of spatial-temporal distribution of surface temperature, air temperature, and heat flux into and out of external surface. Results indicate that external wall surface temperature and nearby air temperature vary with the change of orientation, height and season. In general, the external wall surface temperature is lower near the ground, and is higher near the roof, than nearby air temperature. But north wall surface temperature is mostly lower than nearby air temperature at the same height; south wall surface temperature during the daytime in December, and west wall surface temperature all day in August, is respectively higher than nearby air temperature. The heat fluxes into and out of external wall surfaces show the differences that exist in the various orientations, heights and seasons. In December, south wall surface at the lower sites emits heat and north wall surface at the higher sites absorbs heat. In April, all external wall surfaces, emit heat near the ground and absorb heat near the roof. In August, west wall surface all day emits heat, and other wall surfaces just show the commensurate behavior with that in April.

Observed Climate Change in East China during 1961-2007

By using in situ daily observations in East China during 1961-2007 and NCEP reanalysis data, the methods of statistical analyses, urban minus rural and observation minus reanalysis, it is revealed that the observed climate change and surface warming in East China were mainly induced by urbanization. The results show that East China has experienced two warmer periods of 1930s and 1980s in the past century; from 1951 to 2007, the regional mean temperature increased at a rate of 0.14℃ per decade; heat waves happened in urban center more frequently, and local climate showed a warming and dry trend; there was no significant linear trend in regional mean precipitation in the past 50 years. Urbanization was a crucial element for the regional warming; about 44% of the warming was due to heat island effect in the mega city.

IMPACT OF URBANIZATION IN DIFFERENT REGIONS OF EASTERN CHINA ON PRECIPITATION AND ITS UNCERTAINTY

Climate effect caused by urbanization has been an indispensable anthropogenic factor in the research on regional climate change.Based on daily precipitation data,possible effects of precipitation on the development of three city groups in eastern China are discussed.With three classification methods(TP,PD and MODIS land cover),urban and rural stations are identified.The main findings are as follows.Climate effects caused by urbanization are different from place to place.In 1960 to 2009,the urbanization brought more precipitation to the Yangtze River Delta and Pearl River Delta city groups but had no obvious effect on the precipitation of the Beijing-Tianjin-Tangshan city group.The difference of precipitation is slight between urban and suburban areas during slow period of the urbanization from 1960 to 1979.It is more evident in the rapid period(1980 to 2009) that urbanization has positive effects on precipitation in every city group.The difference of precipitation between urban and rural stations is sensitive to the ways of distinguishing rural from urban area,which may cause uncertainties in 1960 to 1979,while it is very different in 1980 to 2009 in which urbanization favors more precipitation in all city groups and their differences in precipitation are not sensitive to the division methods.

A ＂Trojan＂ in Climatic Change： The Urban Effect

This paper sets out the preliminary results of an experimental research plan aimed at analysing the thermal processes inherent to the urbanisation effect. Although this effect is undeniable, the extent of its impact is a matter of controversy. The results obtained in this study show both the nature of the phenomenon and its considerable magnitude. Failure to take this process into account might seriously bias any analysis of thermal evolution, the cornerstone of the climate change hypothesis.

A climatic environmental performance assessment method for ecological city construction:Application to Beijing Yanqi Lake

In contrast to the input perspective for evaluating planning metrics, this research takes the climatic environmental output effects as the starting point for assessing ecological city construction. Based on approaches such as observation data analysis, meteorological model simulation, and remote sensing, a set of climatic environmental performance assessment methods is developed and established. These methods mainly focus on surface ventilation assessment and urban thermal environment assessment. With the Yanqi Lake ecological development demonstration area located in Huairou district, Beijing as an example, the assessment of the local climatic environment before and after the construction are conducted, and relevant policy suggestions for urban planning and construction are presented. The results show that after development, the ventilation capacity will decrease overall and the ventilation potential index will decrease from 0.53 to 0.44. While this is not a large reduction, and is still at a favorable level, the ventilation potential in some local areas will markedly decrease. Furthermore, the thermal environment will become poorer to some extent; the urban heat island(UHI) area and intensity will increase compared with the current situation;continuous heat islands may occur in local areas; the UHI potential index of the core area will rise from 0.0878 to 0.1217(still a favorable level).Therefore, urban surfaces should be carefully developed and arranged during planning. It is suggested that the negative impacts of large areas of urban construction on the local climatic environment in the Yanqi Lake could be mitigated by 1) strengthening the airflow by introducing fresh,cold, northwesterly air via constructed ventilation corridors, 2) increasing the number of ecological cold sources, particularly for water bodies and green belts to prevent the UHI in the southern region of Yanqi Lake from becoming linked with each other, and 3) considering a pre-program before sub-domain and building planning to obtain optimum building locations. Different construction standards should be developed for different ventilation potential and UHI intensity levels. For strong heat island areas, land areas should be reserved to serve as cold sources.