中国区域气溶胶对东亚夏季风的可能影响（I）：硫酸盐气溶胶的影响

利用NCAR的新一代GCM CAM3.0模式离线耦合一个气溶胶同化系统,模拟研究了中国区域硫酸盐气溶胶的直接气候效应对东亚夏季风及其降水的影响。结果显示：中国区域硫酸盐气溶胶引起全球平均的直接辐射强迫为-0.25 W/m²,中国内陆约25°N以北普遍降温,而海表温度升高。由此导致海陆温差缩小,东亚夏季风强度减弱,中国地区季风降水明显减少,而尤以积云降水减少起主要作用。硫酸盐气溶胶对中国地区的对流活动起抑制作用。     

中国区域气溶胶对东亚夏季风的可能影响(Ⅰ):硫酸盐气溶胶的影响

利用NCAR的新一代GCM CAM3.0模式离线耦合一个气溶胶同化系统,模拟研究了中国区域硫酸盐气溶胶的直接气候效应对东亚夏季风及其降水的影响.结果显示:中国区域硫酸盐气溶胶引起全球平均的直接辐射强迫为-0.25 w/m2,中国内陆约25°N以北普遍降温,而海表温度升高.由此导致海陆温差缩小,东亚夏季风强度减弱,中国地区季风降水明显减少,而尤以积云降水减少起主要作用.硫酸盐气溶胶对中国地区的对流活动起抑制作用.     

RegCM3引入气溶胶间接气候效应模拟效果对比

利用2006年区域气候模式RegCM3和Streets气溶胶排放源清单,在原模式中引入间接气候效应模块,改进云降水方案,对硫酸盐气溶胶的时空分布、辐射强迫效应进行了模拟研究。结果表明：硫酸盐气溶胶辐射强迫有明显季节变化;直接效应使地表温度降低,冬春季大值区出现在四川盆地,夏季大值区出现在华北平原。对降水的影响,主要表现在西南—东北水汽输送带上降水减少;其间接气候效应主要表现在使南方地区温度上升、北方地区温度下降;珠江流域和黄河流域降水减少,长江流域和东北地区降水增加。总的来说,直接效应大于间接效应。     

中国区域气溶胶对东亚夏季风的可能影响（I）：硫酸盐气溶胶的影响

 利用NCAR的新一代GCM CAM3.0模式离线耦合一个气溶胶同化系统,模拟研究了中国区域硫酸盐气溶胶的直接气候效应对东亚夏季风及其降水的影响。结果显示：中国区域硫酸盐气溶胶引起全球平均的直接辐射强迫为-0.25 W/m²,中国内陆约25°N以北普遍降温,而海表温度升高。由此导致海陆温差缩小,东亚夏季风强度减弱,中国地区季风降水明显减少,而尤以积云降水减少起主要作用。硫酸盐气溶胶对中国地区的对流活动起抑制作用。     

中国区域气溶胶对东亚夏季风的可能影响(Ⅱ)：黑碳气溶胶及其与硫酸盐气溶胶的综合影响

利用NCAR的新一代GCM CAM3.0模式耦合一个气溶胶同化系统,研究了中国区域黑碳气溶胶的直接气候效应。结果显示,中国区域黑碳气溶胶引起全球平均辐射强迫为0.13 W/m2,导致除了青藏高原和广西以外的中国大部分地区降温,其中东北、四川和内蒙古中北部降温最显著。由此造成海陆温差缩小,气压差降低,从而总体上使东亚夏季风减弱。但与硫酸盐气溶胶的影响相比,黑碳气溶胶使季风减弱的程度较小,长江中下游地区的降水有所增加。黑碳气溶胶加强了中国东南部地区的对流活动,这与硫酸盐气溶胶的作用相反。同时,探讨了中国区域硫酸盐和黑碳气溶胶的综合直接气候效应。结果表明,硫酸盐和黑碳气溶胶的综合作用与仅有硫酸盐气溶胶的情形十分相似,降水变化的区域也和硫酸盐的保持一致。     

中国区域气溶胶对东亚夏季风的可能影响(Ⅱ)：黑碳气溶胶及其与硫酸盐气溶胶的综合影响

 利用NCAR的新一代GCM CAM3.0模式耦合一个气溶胶同化系统,研究了中国区域黑碳气溶胶的直接气候效应。结果显示,中国区域黑碳气溶胶引起全球平均辐射强迫为0.13 W/m2,导致除了青藏高原和广西以外的中国大部分地区降温,其中东北、四川和内蒙古中北部降温最显著。由此造成海陆温差缩小,气压差降低,从而总体上使东亚夏季风减弱。但与硫酸盐气溶胶的影响相比,黑碳气溶胶使季风减弱的程度较小,长江中下游地区的降水有所增加。黑碳气溶胶加强了中国东南部地区的对流活动,这与硫酸盐气溶胶的作用相反。同时,探讨了中国区域硫酸盐和黑碳气溶胶的综合直接气候效应。结果表明,硫酸盐和黑碳气溶胶的综合作用与仅有硫酸盐气溶胶的情形十分相似,降水变化的区域也和硫酸盐的保持一致。     

人为气溶胶对中国东部冬季风影响的模拟研究

采用美国国家大气研究中心(NCAR)的公共大气模式CAM5.1研究了人为气溶胶排放增加对中国东部冬季风的影响,同时通过对比中国东部地区不同人为气溶胶排放源的敏感性试验结果,探讨了人为硫酸盐、黑碳及总人为气溶胶(硫酸盐+黑碳)增加对东亚冬季风的影响。结果表明:冬季硫酸盐气溶胶排放增加的直接和第一间接效应减少了到达地表的短波辐射通量,引起了陆地地表和对流层低层降温,海平面气压升高,增加了海陆间气压梯度,使得东亚冬季风增强。其第二间接效应导致中国南部大尺度降水率减少;黑碳气溶胶排放增加导致到达地表的短波辐射通量减少和大气中短波辐射通量增加,其半直接效应部分抵消了直接效应,故地表温度变化微小且不显著。加热的对流层低层导致中国南部对流活动和对流降水率增加;总人为气溶胶排放增加导致的大气温度变化表现为弱的降温作用,引起中国北部对流和大尺度降水率减少,而南部对流降水率增加。总人为气溶胶和黑碳气溶胶排放增加是导致中国北(南)部的东亚冬季风增强(减弱)的重要因素。     

硫酸盐气溶胶对全球水循环因子的影响

  利用卫星资料进一步检验了CAM3.0模式对云的模拟能力,该模式可以较好地再现全球云的分布和季节变化的主要特征。在硫循环过程与辐射和动力过程之间双向耦合的情况下,探讨了硫酸盐气溶胶直接气候效应对水循环过程的影响。模式较好地模拟了硫酸盐气溶胶的浓度和分布变化。硫酸盐气溶胶对水循环因子的影响在不同季节和区域是不同的,其中,北半球夏季的影响最大,这是因为北半球夏季硫酸盐浓度最高。纬向平均的云量、降水和水汽的变化形势大部分相似,存在比较密切的联系。     

我国硫酸盐气溶胶气候效应的数值模拟

气溶胶的气候效应近年来备受关注。区域气候模式能够在有限的计算资源下取得更高的分辨率,成为一种研究区域气候的有力工具。本文使用意大利国际理论物理中心(ICTP)开发的区域气候模式(Reg CM3),对2008年12月~2009年11月我国硫酸盐气溶胶的时空分布及其直接气候效应进行了模拟。研究表明受大气环流影响,硫酸盐气溶胶空间分布在夏季分布最广,而其最大平均季度柱浓度出现在四川盆地,达到了27mg·m-2。受特殊地形的影响,四川盆地上空在全年一直维持着高浓度的硫酸盐。硫酸盐气溶胶对直接辐射强迫与其柱浓度的分布有很好的相关性。直接辐射强迫在夏季分布最广,其数值达到了-2.99W·m-2,全年平均为-2.4W·m-2。硫酸盐的直接气候效应造成了地面气温下降,在夏季达到了-0.26℃,全年平均为-0.09℃。直接气候效应对降水总体表现为微弱的抑制作用,但不同区域,不同季节差异较大。     

CAM3.0模式中东亚气溶胶浓度变化的直接效应及全球海面温度年代际变化对东亚夏季降水的影响研究

利用CAM3.0气候模式模拟研究东亚地区气溶胶浓度增长以及1976/1977年前后发生的海温年代际变化对东亚夏季降水场的影响及其机制。采用四组试验:即对东亚区域(100~150 °E,20~50 °N)分别进行的单独加倍黑碳气溶胶浓度、单独加倍硫酸盐气溶胶浓度、同时加倍这两种气溶胶浓度的三组关于气溶胶直接气候效应的试验及全球海温在1976/1977前后发生变化的海温年代际变化试验,来比较、探讨海温年代际变化和东亚地区气溶胶浓度增加对东亚夏季降水的影响机制。结果表明,无论是海温年代际变化还是各种气溶胶的浓度加倍,都能导致我国出现长江以北地区降水减少-东南沿海地区降水增加的“南涝北旱”的降水异常分布型。但两者在洋面上空降水的迥异表现及东亚低层风场的不同变化,显示其具有不同的异常降水机制。比较三类气溶胶浓度增加的试验结果发现:在单独硫酸盐气溶胶浓度增加试验中,东亚中部出现最显著的中下层大气降温、异常下沉气流以及降水减少;而在黑碳气溶胶试验中,出现在东亚中部的异常下沉气流强度减弱且位置偏南;在同时增加两类气溶胶浓度时,降水异常分布与单独黑碳气溶胶浓度增加所导致的降水异常相近,但强度减小。      

MODELING THE EFFECTS OF ANTHROPOGENIC SULFATE IN CLIMATE CHANGE BY USING A REGIONAL CLIMATE MODEL

1 INTRODUCTION Being an important composition of the atmosphere, aerosol attracts increasing attention from the scientific community in recent years, together with the radiative forcing it causes and effects it imposes on the climate system. The anthropogenic aerosol affects the climate both directly and indirectly. The climate is directly affected when solar shortwave radiation is scattered and absorbed in what is known as the 搖mbrella effect? which can be dated back to as early as mor…     

CLIMATE CHANGE DUE TO GREENHOUSE EFFECTS IN CHINA AS SIMULATED BY A REGIONAL CLIMATE MODEL-PART I:EVALUATION OF THE MODEL SIMULATIONS*

Impacts of greenhouse effects(2×CO₂) on climate change over China as simulated by a regional climate model have been investigated.The model was based on RegCM2 and is nested in one-way mode within a global coupled atmosphere-ocean model(CSIRO R₂₁L₉ AOGCM).Two multi-year simulations,the control run with normal CO₂ concentration and the sensitivity run with doubled CO₂ concentration are conducted. As Part I of the publications,results of control run of the CSIRO,i.e.its simulation of present climate in China,are analyzed briefly.It shows that the model can basically reproduce the surface air temperature and precipitation pattern over China.Therefore,its outputs can be used to drive the regional model. Analysis of control run of RegCM shows that with a high resolution,the model improves the simulations of surface air temperature and precipitation in China as compared to the CSIRO model, especially for the precipitation.The spatial correlation coefficient between simulated and observed annual temperature increased from 0.83 in the CSIRO to 0.92 in the RegCM and for annual precipitation from 0.48 in the CSIRO to 0.65 in the RegCM.A similar improvement in the RegCM compared to the CSIRO was found in all simulated months.The main improvement for surface temperature is that RegCM can simulate the fine scale structure of temperature caused by topography.RegCM greatly improved the spatial distribution of precipitation by eliminating the virtual precipitation center in central China,which was simulated by many other GCMs.The precipitation simulated by RegCM in North and Northwest China is smaller than that by CSIRO, which makes it closer to the observation.     

温室效应引起的中国区域气候变化的数值模拟Ⅰ:模式对中国气候模拟能力的检验

使用RegCM2区域气候模式单向嵌套澳大利亚CSIRO R21L9全球海-气耦合模式,进行了CO2加倍对中国区域气候变化影响的数值试验研究,分析了控制试验(1×CO2)即模式对中国当代气候的模拟情况.首先给出了全球模式控制试验在中国地区的结果,分析表明它对中国区域的地面气温和降水具有一定的模拟能力,其结果可以用来制作驱动区域气候模式的初始场和侧边界.对RegCM2 5 a时间长度控制试验积分结果的分析与检验表明,区域气候模式由于具有较高的分辨率和较完善的物理过程,它对中国区域地面气温和降水的模拟效果较全球模式有了较大提高,如它模拟的各月气温与实况的相关系数全年12个月的平均由全球模式的0.83提高到0.92,降水由0.48提高到0.65.     

Modelling climate change impacts on maize growth and development in the Czech Republic

Summary The crop growth model CERES-Maize is used to estimate the direct (through enhanced fertilisation effect of ambient CO₂) and indirect (through changed climate conditions) effects of increased concentration of atmospheric CO₂ on maize yields. The analysis is based on multi-year crop model simulations run with daily weather series obtained alternatively by a direct modification of observed weather series and by a stochastic weather generator. The crop model is run in two settings: stressed yields are simulated in water and nutrient limited conditions, potential yields in water and nutrient unlimited conditions. The climate change scenario was constructed using the output from the ECHAM3/T42 model (temperature), regression relationships between temperature and solar radiation, and an expert judgement (precipitation). Results: (i) After omitting the two most extreme misfits, the standard error between the observed and modelled yields is 11%. (ii) The direct effect of doubled CO₂: The stressed yields would increase by 36–41% in the present climate and by 61–66% in the 2 × CO₂ climate. The potential yields would increase only by 9–10% as the improved water use efficiency does not apply. (iii) The indirect effect of doubled CO₂: The stressed yields would decrease by 27–29% (14–16%) at present (doubled) ambient CO₂ concentration. The increased temperature shortens the phenological phases and does not allow for the optimal development of the crop. The simultaneous decrease of precipitation and increase of temperature and solar radiation deepen the water stress, thereby reducing the yields. The reduction of the potential yields is significantly smaller as the effect of the increased water stress does not apply. (iv) If both direct and indirect effects of doubled CO₂ are considered, the stressed yields should increase by 17–18%, and the potential yields by 5–14%. (v) The decrease of the stressed yields due to the indirect effect may be reduced by applying earlier planting dates. Received March 9, 2001 Revised September 25, 2001     

Annual and seasonal climate and climatic changes in the Canadian prairies simulated by the CCC GCM

Abstract

As part of a study on the effects of climatic variability and change on the sustainability of agriculture in Alberto, the modelling performance of the second‐generation Canadian Climate Centre GCM (general circulation model) is examined. For the region in general, the simulation of 1 × CO₂ mean temperature is generally better than that for mean precipitation, and summer is the season best modelled for each variable. At the scale of individual grid squares, DJF (December, January, February) (temperature) and JJA (June, July, August) (precipitation) are the seasons best modelled. The GCM‐simulated increases in mean annual temperature resulting from a doubling of CO₂ are of the order of 5 to 6°C in the Prairie region, with much of this increase resulting from substantial warming in the winter and spring. Increases in mean annual precipitation are of the order of 50 to 150 mm (changes of +5 to +15%), with the greatest changes again occurring in winter and spring. As far as the limited GCM run durations allow, temperature and precipitation variance generally show no significant changes from a 1 × CO₂ to a 2 × CO₂ climate. Increased precipitation in winter and spring does not result in greater snow accumulations owing to the magnitude of warming; and significant decreases in soil moisture content occur in summer and fall. The resulting effects on the growing season and moisture regime have the potential to affect agricultural practices in the area.     

Characterizing the annual-mean climatic effect of anthropogenic CO<Subscript>2</Subscript> and aerosol emissions in eight coupled atmosphere-ocean GCMs

This work examines the spatial patterns of the transient response of mean annual temperature and precipitation to CO₂ (or CO₂ plus aerosol or aerosol proxy) radiative forcing in eight coupled AOGCMs, generally for the period 1900–2099. Response patterns are characterized using empirical orthogonal functions (EOFs) and the quasi-EOFs of Harvey and Wigley (the first qEOF field, discussed here, is given by the correlation between local year-by-year temperature changes and the global mean temperature change). The first temperature EOF accounts for 80–95% of the space-time variation of the CO₂ run in all of the models, and is almost identical to qEOF₁ of the temperature response or to the temperature change pattern averaged over the last 30 years of the simulations. EOF₁ accounts for 80–95% of the space-time variation in the CO₂+aerosol runs in six of the eight models. The CO₂ response patterns of different models are highly correlated with one another (R ² generally >0.5), and are also highly correlated with the CO₂+aerosol response patterns (R ² 0.85 in all except one model). The difference between CO₂ and CO₂+aerosol runs can be represented by EOF₁ of the year-by-year differences, by qEOF₁ of the year-by-year differences, or by the difference in temperature averaged over the last 30 years of each run. In models where these representations are highly correlated with each other, they are also highly correlated with CO₂ EOF₁. In other cases, aerosol EOF₁ is modestly to highly correlated with control EOF₁ (i.e.: the year-by-year differences between CO₂ and CO₂+aerosol runs are dominated by internal variability), while aerosol qEOF₁ and the 30-year difference are highly correlated with each other. For all models, the decadal mean temperature change can be closely replicated by scaling the CO₂ EOF₁ pattern based on the global mean temperature changes (RMSE for the last decade is <6% of the RMS temperature change for CO₂ runs, <8% for CO₂+aerosol runs). The first EOF of the precipitation response to increasing CO₂ accounts for only 10–30% of the space-time variation, and is generally highly correlated (R ² up to 0.85) with control EOF₁. In all of the models, there is an increase in precipitation in the ITCZ and a decrease in bands at or near 30°S and 30°N. In many models there is an El Niño-like response, including a substantial decrease in precipitation over the Amazon. Global-mean precipitation increases in all models due to CO₂ forcing, but aerosols appear to have a disproportionally large effect in suppressing the increase compared to their effect in suppressing the warming. There is evidence in some models that the non-absorbing aerosols considered here reduce summer monsoon rainfall compared to the changes that would be expected based on the globally averaged effect of aerosols on precipitation. When regional precipitation changes over time are predicted by scaling a fixed precipitation-change pattern with the global mean temperature change, the global mean RMSE in the predicted change in decadal-mean precipitation is 25–35% of the global RMS precipitation changes by the end of the simulation.     

Climate Change Impacts and Adaptation Strategies in Spring Barley Production in the Czech Republic

The crop model CERES-Barley was used to assess the impacts of increased concentration of atmospheric CO₂ on growth and development of the most important spring cereal in Central and Western Europe, i.e., spring barley, and to examine possible adaptation strategies. Three experimental regions were selected to compare the climate change impacts in various climatic and pedological conditions. The analysis was based on multi-year crop model simulations run with daily weather series obtained by stochastic weather generator and included two yield levels: stressed yields and potential yields. Four climate change scenarios based on global climate models and representing 2 × CO₂ climate were applied. Results: (i) The crop model is suitable for use in the given environment, e.g., the coefficient of determination between the simulated and experimental yields equals 0.88. (ii) The indirect effect related to changed weather conditions is mostly negative. Its magnitude ranges from ?19% to +5% for the four scenarios applied at the three regions. (iii) The magnitude of the direct effect of doubled CO₂ on the stressed yields for the three test sites is 35–55% in the present climate and 25–65% in the 2 × CO₂ climates. (iv) The stressed yields would increase in 2 × CO₂ conditions by 13–52% when both direct and indirect effects were considered. (v) The impacts of doubled CO₂ on potential yields are more uniform throughout the localities in comparison with the stressed yields. The magnitude of the indirect and direct effects ranges from ?1 to ?9% and from +31 to +33%, respectively. Superposition of both effects results in 19–30% increase of the potential yields. (vi) Application of the earlier planting date (up to 60 days) would result in 15–22% increase of the yields in 2 × CO₂ conditions. (vii) Use of a cultivar with longer vegetation duration would bring 1.5% yield increase per one extra day of the vegetation season. (viii) The initial water content in the soil water profile proved to be one of the key elements determining the spring barley yield. It causes the yields to increase by 54–101 kg.ha^?1 per 1% increase of the available soil water content on the sowing day.     

North Atlantic cyclones in CO2-induced warm climate simulations: frequency, intensity, and tracks

The effect of CO₂-induced climate change on the North Atlantic storm and cyclone tracks in winter is analysed using time slice experiments of the Hamburg atmospheric general circulation model (ECHAM3) with triangular truncation at wave number 42 (T42) and 19 levels. The sea surface temperature (SST) and sea ice boundary conditions for these experiments are taken from a transient Intergovernmental Panel on Climate Change (IPCC) scenario A run of ECHAM1/LSG at the times where the 1×CO₂ (control run), the 2×CO₂ and the 3×CO₂ concentrations are reached. Using a cyclone identification and tracking scheme, we detect the low pressure systems as relative minima in the 1000 hPa geopotential height field and connect them to cyclone tracks. The results of the Eulerian analysis of the storm track using filtered variances and the Lagrangian analysis of the cyclone trajectories from the three climate runs are discussed and compared with each other. In the 2×CO₂ experiment, the storm track shifts eastward, whereas the cyclone density shifts northeastward. In the 3×CO₂ experiment the storm track shows a southeastward shift, whereas the cyclone density shifts northward. The variability of the cyclone tracks is determined by a cluster analysis of their relative trajectories considering the first three days of the cyclones. The relative cyclone tracks are grouped into stationary, zonal and northeastward travelling cyclones. This analysis provides a method to assess the model quality and to detect changes of the cyclone trajectories in different climates. In the 2×CO₂ (but not in the 3×CO₂) run the occupation number of northeastward cyclones increases. Received: 27 January 1998 / Accepted: 19 May 1998     

PROJECTIONS OF CLIMATE CHANGE FOR THE CZECH REPUBLIC

The paper deals with a selection of the climatological baseline, GCM validity and construction of the climate change scenarios for an impact assessment in the Czech territory. The period of 1961–1990 has been selected as the climatological baseline. The corresponding database includes more than 50 monthly mean temperature and precipitation series, and 16 time series of daily meteorological data that contain also the solar radiation data. The 1× CO₂ outputs produced by four GCMs, provided by the CSMT (GISS, GFD30, GFD01, and CCCM), were compared with observed temperature and precipitation conditions in western and central Europe with a particular attention devoted to the Czech territory. The GCM ability to simulate annual cycles of temperature, precipitation and radiation was thoroughly examined. The GISS and CCCM were selected as a basis for constructing climate change scenarios as they simulated reasonably the observed patterns. According to the GISS variant, 2× CO₂ climate assumes a higher winter and lower summer warming, and an increase in annual precipitation amounts. A dangerous combination of the summer temperature increase and declining precipitation amounts is a specific feature of the CCCM scenario. An incremental scenario for temperature and precipitation is based on the combination of prescribed changes in both annual means and annual courses.     

Internal Variability as a Cause of Qualitative Intermodel Disagreement on Anthropogenic Climate Changes

Summary The qualitative agreement of two climate models, HADCM2 and ECHAM3, on the response of surface climate to anthropogenic climate forcing in the period 2020 – 2049 is studied. Special attention is paid to the role of internal climate variability as a source of intermodel disagreement. After illustrating the methods in an intermodel comparison of simulated changes in June–August mean precipitation, some global statistics are presented. Excluding surface air temperature, the four-season mean proportion of areas in which the two models agree on the sign of the climatic response is only 53 – 60% both for increases in CO₂ alone and for increases in CO₂ together with direct radiative forcing by sulphate aerosols, but somewhat larger, 59 – 70% for the separate aerosol effect. In areas where the response is strong (at least twice the standard error associated with internal variability) in both models, the agreement is better and the contrast between the different forcings becomes more marked. The proportion of agreement in such areas is 57 – 75% for the response to increases in CO₂ alone, 64 – 84% for the response to combined CO₂ and aerosol forcing, and as high as 88 – 94% for the separate aerosol effect. The relatively good intermodel agreement for aerosol-induced climate changes is suggested to be associated with the uneven horizontal distribution of aerosol forcing. Received December 2, 1998 Revised May 5, 1999