天气形势对四川盆地区域性臭氧污染的影响

本研究结合地面观测资料,ERA5再分析数据和PCT客观分型法,分析了2014~2019年四川盆地区域性O₃污染特征以及天气形势与O₃污染的关系.结果表明,2014~2019年四川盆地O₃区域污染发生频数呈单峰型分布,于2016年达到峰值,且发生区域主要集中在成都平原城市群.在6种典型天气类型中,类型1、2、6为污染型,其海平面气压呈西高东低,四川盆地受低压系统控制.类型3、4为清洁型,其中类型3呈北高南低,且在四川盆地东部存在1个低值中心;类型4呈东高西低,在青藏高原区域有一些小范围的高压中心.在污染型天气形势下,四川盆地的气象条件为温度高、云量低、地面接收到的紫外辐射强、相对湿度低,加速了O₃的生成,再叠加类型1的静风条件不利于污染物扩散;类型2、6盛行的东南气流对O₃及其前体物的输送,造成污染型天气类型发生区域性O₃污染比例明显高于其他几种类型.此外,基于环流分型的预测结果表明环流形势对四川盆地各城市群区域O₃污染影响可以达到其年变化的2倍以上,对整个四川盆地O₃浓度变化的贡献率为34.8%~66.3%.     

Application of ground-based Lidar for studies of the dynamics of ozone in a mountainous basin

A ground-based Differential Absorption Lidar was employed to study the dynamics of atmospheric O3 within the planetary boundary layer of a basin in the 'Fichtelgebirge' mountains, NE Bavaria. In particular, the night-time dynamics of O3 linked to the ground were investigated. The Lidar system measured vertical profiles of O3 up to 1 km above ground. For detailed analysis of the night-time dynamics of ozone, supplementary data from three ground-based stations (measuring mixing ratios of O3 and NO(x), as well as meteorological parameters) are essential. The Lidar results could be evaluated with these data from various altitudes above the basin floor. For the station with the largest (vertical) distance to the ground-based Lidar, the agreement was very good at all times. The Lidar method proved to be useful for examining the spatial distribution of O3. The observed night-time decrease of O3 at the bottom of the basin was due to deposition and to advection of air masses containing less O3 from the mountain slopes.     

区域农业生产脆弱性及干旱诊断分析

以山东区域农业生产作为案例，根据主要作物历年产量波动分析，发现趋势产量年际间变化较为平稳，而气象产量年际间变化幅度较大，说明山东农业生产存在着气候脆弱性。通过对比分析光、温生产潜力和光、温、水生产潜力及气象因子对产量的直接、间接通径系数，得出气象产量主要受降水因索的制约，水分是气候资源组合中的薄弱环节，也是山东农业的主要限制因索。历年作物生长期内降水达不到需水要求的概率为20％～35％。各作物不同生育时段的受旱概率相差较大，最低为7％，高的达50％～85％，这些结果为区域农业生产的减灾防灾提供了依据。     

MODELED REGIONAL CLIMATE CHANGE IN THE HYDROLOGIC REGIONS OF CALIFORNIA: A CO2 SENSITIVITY STUDY1

ABSTRACT: Using a regional climate model (RegCM2.5), the potential impacts on the climate of California of increasing atmospheric CO₂ concentrations were explored from the perspective of the state's 10 hydrologic regions. Relative to preindustrial CO₂ conditions (280 ppm), doubled preindustrial CO₂ conditions (560 ppm) produced increased temperatures of up to 4°C on an annual average basis and of up to 5°C on a monthly basis. Temperature increases were greatest in the central and northern regions. On a monthly basis, the temperature response was greatest in February, March, and May for nearly all regions. Snow accumulation was significantly decreased in all months and regions, with the greatest reduction occurring in the Sacramento River region. Precipitation results indicate drier winters for all regions, with a large reduction in precipitation from December to April and a smaller decrease from May to November. The result is a wet season that is slightly reduced in length. Findings suggest that the total amount of water in the state will decrease, water needs will increase, and the timing of water availability will be greatly perturbed.     

STREAM TEMPERATURE CORRELATIONS WITH AIR TEMPERATURES IN MINNESOTA: IMPLICATIONS FOR CLIMATE WARMING1

ABSTRACT: Air temperatures are sometimes used as easy substitutes for stream temperatures. To examine the errors associated with this substitution, linear relationships between 39 Minnesota stream water temperature records and associated air temperature records were analyzed. From the lumped data set (38,082 daily data pairs), equations were derived for daily, weekly, monthly, and annual mean temperatures. Standard deviations between all measured and predicted water temperatures were 3.5°C (daily), 2.6°C (weekly), 1.9°C (monthly), and 1.3°C (annual). Separate analyses for each stream gaging station gave substantially lower standard deviations. Weather monitoring stations were, on average, 37.5 km from the stream. The measured water temperatures follow the annual air temperature cycle closely. No time lags were taken into account, and periods of ice cover were excluded from the analysis. If atmospheric CO₂ doubles in the future, air temperatures in Minnesota are projected (CCC GCM) to rise by 4.3°C in the warm season (April-October). This would translate into an average 4.1°C stream temperature rise, provided that stream shading would remain unaltered.     

MEASURING EVAPORATION WITH CERAMIC BELLANI PLATE ATMOMETERS1

ABSTRACT: Ceramic atmometers were tested to determine their usefulness for measuring evaporation in water resources applications. Field experiments were used to evaluate the precision, responsiveness to a range of potential evaporation conditions in a forested catchment, and interpretation of water loss of Bellani plate atmometers. The experiments, conducted from April to October in a warm, humid climate in the southeastern United States, indicate that atmometers can be reliable monitoring instruments for estimating potential evaporation. The small size, portability, low internal thermal mass, low cost, and ability to integrate the effect of radiation, air temperature, humidity and windspeed into one direct measurement of potential evaporation, make atmometers a useful instrument for certain water resources applications.     

IMPLICATIONS OF FEEDBACK PROCESSES IN PLANT WATER USAGE AND RESULTING CLIMATE CHANGE1

ABSTRACT: Increased carbon dioxide in the atmosphere has the secondary effect on plants of reducing transpiration. The degree of reduction in transpiration has been studied mostly at the leaf scale and as such, has not taken feedbacks into account that come into play when the plant canopy or the atmosphere as a whole is considered. The objective of this paper is to examine the role of negative feedback processes that act through the dynamics of the canopy and the atmosphere. This is done through the application of two canopy models, one of which is later coupled to a full Atmospheric General Circulation Model (AGCM) called GENESIS. The results suggest that the reduction in transpiration in a double CO₂ environment compared to present day will not be as considerable as the leaf scale experiments suggest ‐ a 7 percent reduction compared to 15 to 57 percent when feedbacks are considered. At the regional scale, precipitation patterns appear to be the primary factor in determining evapotranspiration. The implications for agriculture, in terms of water usage, would therefore not seem to be as acute as the leaf scale experiments depict. Regarding climate change, there is a suggestion that regional water usage may vary from present day values in certain areas.     

江苏省大雾的变化特征及气溶胶对其影响

通过分析近50年江苏长序列大雾日数、持续时间、时空分布规律以及其成因,探讨气溶胶对大雾形成的可能机制.研究结果表明:大雾可能出现在任何时候,但在清晨和秋季出现的频率最多.它们的变化可从该区的季节环流背景特征和雾的形成机理得以解释.年代际大雾日变化大体呈现出抛物线(先升后降)分布特征,而大雾持续时间一直呈波动增长趋势,气象因素不能全部解释其变化特征.气溶胶对大雾形成和持续时间可能有重要影响,气象因素和气溶胶共同作用可解释江苏省年际大雾日变化和大雾持续的变化特征.     

海洋性气候对天津市滨海地区空气质量的影响及预报

对天津市滨海地区污染气象条件与空气质量进行了相关分析研究,并在此基础上建立该地区空气质量统计预报方法,建立的统计方程经过试预报验证,取得良好的预报效果。     

秋季嘉兴PM2.5质量浓度特征分析

利用膜采样、颗粒在线称重方法和维萨拉气象仪对2004和2006年秋季嘉兴大气中ρ(PM_2.5)及气象因子进行了分析.结果表明:2004和2006年秋季ρ(PM2.5)分别为(84.7±62.4)和(89.0±61.5) 　μg/m3;ρ(PM2.5)占ρ(PM₁₀) 比例为42%～69%;ρ(PM_2.5)日均值变化大(16.7～345.7 μg/m3),晴天ρ(PM_2.5)约为阴雨天的2倍.ρ(PM_2.5)日变化分析表明,晴天呈双峰双谷现象,晚高峰(16:00—20:00)ρ(PM_2.5)大于早高峰(06:00—10:00),阴雨天日变化不明显.PM_2.5与相对湿度无显著相关性,但在不同相对湿度下PM_2.5与能见度呈显著的负指数关系.东北风和西北风是观测期内当地的主导风向,ρ(PM2.5)高值出现在西南风方向,重污染天气过程形成原因复杂.