陇东黄土高原冰雹的气候特征及预报

利用陇东1971～2000年的冰雹资料,分析了冰雹的气候特征,归纳了产生冰雹天气过程的3种主要环流背景.     

典型农牧交错区农牧业气候资源区划与减灾——以内蒙古赤峰市巴林左旗为例

通过对巴林左旗农业资源和生产现状的调查与分析，采用相关分析和回归分析等方法，建立了气候因子空间分布模型和产量与主要气象要素关系模型，分析确定出了对农牧业生产布局有重要影响的区划指标；应用1：25万地理信息数据和GIS分析技术，实现了该地区农牧业气候资源的区划，并利用聚类分析方法进行了验证，提出了减灾对策。为有效开发利用巴林左旗的农业气候资源，合理布局农、牧、林业生产，降低灾害的威胁提供科学参考。     

Impacts of Climatic Change On Peatland Hydrochemistry; A Laboratory-Based Experiment

A laboratory simulation of a reduction in water table height that could be anticipated from current climate change models, resulted in a change in the efficiency with which a valley-bottom wetland acted as a sink/source of nutrients. Effects were confined to the upper 10 cm of the profile, but since this depth has the greatest hydraulic conductivity, it was noted that the effects of hydrochemical changes therein would be readily transferred to receiving waterbodies. Marked changes in leachate chemistry were observed, including increases in nitrate and sulphate concentrations, while concentrations of phenolics, dissolved organic carbon, potassium, iron and ammonium decreased. These changes have implications for the quality and productivity of waters draining wetlands.     

CHARACTERISTICS AND CONTRIBUTING CAUSES OF AN ABNORMAL FREQUENCY OF FLOOD-PRODUCING RAINSTORMS AT CHICAGO1

ABSTRACT: Major hydrometeorological factors pertinent to defining and understanding the hydrologic characteristics of urban and other small-basin storms were investigated using data from a continuous 44-year operation of a recording raingage network in Chicago. Factors included: the frequency distribution of basin mean rainfall and its relation to storm maximum precipitation; the spatial distribution characteristics of each storm, including storm rainfall reduction factors which are widely used in hydrologic design problems; and weather-related causes related to the frequency and intensity of severe rainstorms in the Chicago area in recent years. Results have indicated that urban mean rainfall frequencies were overestimated in earlier studies in which they were derived from point/areal mean rainfall ratios obtained from much shorter records on rural networks. Reduction factors were found to vary between urban and rural storm systems due to urban-related effects. Two factors were found to be potential contributors to the characteristics of severe rainstorm occurrences at Chicago. These include urban-induced rain enhancement and an upward climatic trend in the occurrence of heavy rainfall events during the sampling period. Study results should be generally applicable to other large urban areas in the Midwest and other regions of similar precipitation climate.     

气候遥感解译法在区域气候研究中的应用

运用遥感手段进行气候资源普查和生态气候类型的划分,是现代应用气候的一种新的研究方法,也是遥感技术应用的一个新领域。研究实践证明,遥感技术对于下垫面气候研究具有独特的功能,特别是对地方气候分析提供了新的内容和手段。本文以内蒙古兴安盟科右中旗和突泉县为列,对气候遥感解译法进行初步分析和概述,以促进该研究法在区域气候研究中更广泛地推广和应用。     

GENERATION OF SYNTHETIC AND MISSING CLIMATIC DATA FOR PUERTO RICO1

ABSTRACT: Climatic data such as temperature, solar radiation, relative humidity, and wind speed have been widely used to estimate evapotranspiration. Moat of the solar radiation data and portions of the relative humidity data are either not available or missing from the records in Puerto Rico. Depending upon the availability and data characteristics of records, three methods (including a regression technique, an averaging of historical data, and a regional average) were used to generate missing data, and a time series analysis was used to synthesize a series of climatic data. The limitations and applicability of each method are discussed. The results showed that the time series analysis method can be successfully used to synthesize a series of monthly solar radiations for several stations. The regression technique and the regional average can be successfully applied to generate missing monthly solar radiation data. The regression technique and the averaging of historical data have been satisfactorily used to interpolate missing monthly relative humidity. The explained variance (R²) varied from 0.68 to 0.88, which are both significant at the 0.05 level of significance.     

CLIMATIC VARIATION AND SURFACE WATER RESOURCES IN THE GREAT BASIN REGION1

ABSTRACT: There is mounting evidence that increasing amounts of atmospheric carbon dioxide may lead to significant changes in global climate during the next century. The possible effects of such climatic changes on surface runoff in the Great Basin Region of the western United States has been investigated by applying water balance models to four watersheds in Nevada and Utah. The most probable change, a 2°C increase in average annual temperature coupled with a 10 percent decrease in precipitation, would reduce runoff from 17 to 28 percent of the present mean, with drier basins showing the greatest change. Decreasing precipitation by 25 percent causes runoff reductions of 33 to 51 percent. Equivalent changes to a cooler and wetter climate show corresponding increases in runoff of approximately the same magnitude, but such a shift is not considered likely. Based on projected water requirements for the year 2000, a change to a warmer and drier climate would cause severe water shortages in many parts of the Great Basin.     

基于状态空间法的大型气候环境实验室热负荷仿真模型

目的建立可用于大型气候环境实验室初期设计热负荷计算的方法和模型,对实验室的热负荷进行计算,为制冷系统选型提供依据。方法通过分析实验室的组成结构和热负荷来源,基于状态空间法建立各部分的热负荷计算方法,在Simulink中搭建以制冷量为输入参数的实验室热负荷计算仿真模型,对实验室空载降温过程进行仿真。结果该仿真模型可以快速对实验室热负荷进行计算,并且可以方便地增减热负荷模块,实验室在降温过程中热负荷达3500 k W以上,地板结构的热负荷占到了总热负荷50%以上。结论热负荷计算结果可应用于空调系统和制冷系统的设计和选型,以及控制策略的优化。     

Impact of Grazing Intensity during Drought in an Arizona Grassland

Abstract:  The ecological benefits of changing cattle grazing practices in the western United States remain controversial, due in part to a lack of experimentation. In 1997 we initiated an experimental study of two rangeland alternatives, cattle removal and high-impact grazing, and compared grassland community responses with those with more conventional, moderate grazing practices. The study was conducted in a high-elevation, semiarid grassland near Flagstaff, Arizona (U.S.A.). We conducted annual plant surveys of modified Whittaker plots for 8 years and examined plant composition shifts among treatments and years. High-impact grazing had strong directional effects that led to a decline in perennial forb cover and an increase in annual plants, particularly the exotic cheatgrass ( Bromus tectorum L.). A twofold increase in plant cover by exotic species followed a severe drought in the sixth year of the study, and this increase was greatest in the high-impact grazing plots, where native cover declined by one-half. Cattle removal resulted in little increase in native plant cover and reduced plant species richness relative to the moderate grazing control. Our results suggest that some intermediate level of cattle grazing may maintain greater levels of native plant diversity than the alternatives of cattle removal or high-density, short-duration grazing practices. Furthermore, episodic drought interacts with cattle grazing, leading to infrequent, but biologically important shifts in plant communities. Our results demonstrate the importance of climatic variation in determining ecological effects of grazing practices, and we recommend improving conservation efforts in arid rangelands by developing management plans that anticipate this variation.     

PAH Levels and Profiles in the Suspended Particulate Matter in Zagreb through Four Seasons

This paper presents the analysis of polycyclic aromatic hydrocarbons (PAHs) measured in all four seasons in suspendedparticulate matter (SPM) collected with a high-volume sampler on one measuring site in the northern part of Zagreb. About 30 samples of SPM were analysed for each season, including workdays and weekends and there were no differences amongst them. The concentrations of all PAHs were highest in winter andlowest in summer. The spring PAH concentrations were lower thanthe autumn ones, as the spring had more sunny and warm days. Theprofiles of PAH/BaP at the measurement sites showed that the mainsource of PAHs in spring and summer was traffic while asubstantial amount of autumn and winter PAHs, besides traffic,came from heating.