CFCs及其代用品的全球增温潜能

本文用一维辐射·对流模式系统地研究了现有含氯氟烃气体(CFCs)及其可能代用品的辐射强迫、比地面增温效应和全球增温潜能(GWP).结果发现:大多数提议的代用品的GWP值明显小于现有的CFCs.这主要归因于:(1)它们所产生的辐射强迫和比地面增温效应较小,一般只有CFCs的50％—60％;(2)其大气寿命比CFCs短得多.     

相对湿度对气溶胶辐射特性和辐射强迫的影响

采用已有的气溶胶折射指数等资料 ,计算了在不同的相对湿度条件下硫酸盐气溶胶的辐射特性。结合两种不同化学输送模式 (CTM )的模拟结果及LASGGOALS/AGCM模式 ,模拟估算了考虑相对湿度影响后全球硫酸盐气溶胶的辐射强迫。结果表明 :(1)随着相对湿度的增加 ,硫酸盐气溶胶的质量消光效率因子在短波波段有所减小 ,单次散射反照率仅在长波波段有所增加 ,不对称因子在整个波段均有所增加 ;(2 )用两个CTM资料模拟辐射强迫的结果相差较大 ,其全球平均辐射强迫分别为 - 0 .2 6 8和 - 0 .816W/m2 ;(3)在考虑相对湿度的影响后 ,硫酸盐气溶胶辐射强迫的分布类型与相应干粒子的强迫分布类型基本相同 ,但全球平均的强迫值减少了 6 %左右。     

一维辐射对流模式对云-辐射强迫的数值模拟研究

利用一维辐射－对流气候模式, 详细研究了云量、云光学厚度以及云高等要素的变化对大气顶和地面太阳短波辐射和红外长波辐射通量以及云的辐射强迫的影响, 给出了计算这些物理量的经验拟合公式。结果表明, 云具有极为重要的辐射－气候效应。云量、云光学厚度以及云高即使只有百分之几的变化, 所带来的辐射强迫也可以与大气二氧化碳浓度加倍所产生的辐射强迫（3.75 W/m2）相比拟。例如, 当分别给它们+3%的扰动时, 即取云量变化0.015, 云光学厚度变化0.27, 以及云高变化0.15 km时（在实际的地球大气中, 这种尺度的变化是完全可能发生的）, 那么,可以得到地气系统的太阳短波辐射强迫-3.10 W/m2以及红外长波辐射强迫-1.77 W/m2, 二者之和为-4.78 W/m2, 已经完全可以抵消大气二氧化碳浓度加倍所产生的辐射强迫。但是, 当云量、云光学厚度以及云高向相反方向产生类似扰动时, 所产生的辐射强迫可能极大地放大二氧化碳浓度增加所产生的增强温室效应。因此, 研究结果揭示出, 不管是为了解释过去的气候变化, 还是预测未来的气候变化, 亟待加强在一个变化了的气候环境（例如地面温度升高）下, 云将发生何种变化的研究。     

云辐射强迫效应对热带气旋发展和结构的影响

利用高分辨率中尺度WRF-ARW模式,进行云辐射强迫效应对热带气旋(Tropical Cyclone,TC)发展和结构影响的敏感性试验研究。结果表明,云辐射强迫效应主要通过改变TC云区的辐射分布影响对流活动,进而影响TC的发展和结构。在TC发展阶段,TC内区对流云区云顶的强烈辐射冷却作用和云层内部的辐射增温过程降低了TC中上层的静力稳定度,中下层的变化相对不明显。总体上考虑云辐射效应的试验更易激发出更多更强的对流活动,有利于TC的发展及TC尺度的增大。鉴于云辐射强迫对TC的影响,在TC数值预报中需要更加重视云辐射强迫效应。     

硫酸盐和烟尘气溶胶辐射特性及辐射强迫的模拟估算

利用已有的硫酸盐和烟尘气溶胶折射指数资料，精确计算了这两种气溶胶从太阳短波到红外谱段的辐射特性。然后，在LLNL化学输送模式(CTM)模拟的硫酸盐和烟尘气溶胶资料及改进的气溶胶参数化基础上，在国内首次用GCM估算了这两种气溶胶引起的全球辐射强迫。结果表明:(1)西欧是全球最大的硫酸盐辐射强迫中心，最大值出现在夏季，达-5.0W/m2；(2)烟尘强迫的最大中心出现在夏季的南美和非洲中南部，为4.0W/m2；(3)南半球大陆人为气溶胶的强迫不容忽视；(4)某些地区人为气溶胶的强迫在量值上可与CO2等温室气体引起的强迫相比拟。     

卫星遥感中国海域气溶胶直接辐射强迫

利用搭载在Terra卫星上的CERES和MODIS两颗传感器所提供的大气辐射通量和气溶胶数据,结合Fu-Liou辐射传输模式和SPRINTARS气溶胶模式,对中国海域气溶胶在大气顶的短波直接辐射强迫进行了研究.结果表明:(1)在中国海域,CERES的大气顶短波辐射通量与MODIS在550 nm处气溶胶光学厚度(AOT550)存在着非常好的线性相关关系,相关系数0.9左右,说明中国海域气溶胶对于大气顶的短波辐射通量作用是显著的;(2)利用这一线性相关关系,在中国海域,结合CERES和MODIS两颗传感器数据直接计算获取气溶胶瞬时短波直接辐射强迫(Fs).计算发现Fs具有明显的时间变化规律和空间分布特征:在时间上,Fs具有明显的季节变化,春季最大而夏季最小,秋、冬季介于两者之间.在空间上,Fs具有明显的区域分布特征,等值线沿着海岸线分布,随着离岸距离的增加而减小,这一特征说明陆源气溶胶是中国海域气溶胶的主要来源.同时,在数值上,AOT550与Fs在4个季节中都存在着相当好的负相关关系,说明气溶胶减少了进入大气顶的短波辐射,总体来说是"冷室作用";然后,利用Fu-Liou辐射传输模式计算获得修正因子,将卫星获得的Fs转化为日平均短波直接辐射强迫(Fd),得到中国海域的气溶胶日平均短波直接辐射强迫的分布;最后,利用SPRINTARS气溶胶模式的模拟结果,与上述卫星获得的日平均短波直接辐射强迫进行了比较,两者具有非常好的一致性.     

南京北郊黑碳气溶胶的浓度观测及辐射强迫研究

利用2008年南京大学浦口校区气溶胶采样数据对碳气溶胶的浓度变化特征进行了分析,建立了由气溶胶光学参量计算模块(OPAC)和辐射传输模型(TUV)组成的箱模式,并结合实际观测资料,利用该模式对南京北郊黑碳气溶胶的光学厚度及辐射强迫进行了评估。结果表明:南京北郊黑碳气溶胶(BC)的年平均浓度为6.7±4.6μg/m3,有机碳气溶胶(OC)的年平均浓度为21.3±13.3μg/m3,有机碳与黑碳气溶胶浓度的平均比值为3.4。黒碳气溶胶浓度具有夏季低、冬春季高的特点。由箱模式计算得到的黒碳气溶胶的年均光学厚度为0.07,年均吸收系数为44 Mm–1。白天正午晴空条件下黑碳所造成的最大瞬时地面辐射强迫可达-22.9±14.3 W/m2,在大气层顶造成的最大瞬时辐射强迫为12.5±7.3 W/m2。     

中国地区气溶胶的辐射强迫及其气候响应试验

根据国内测定的排放因子数据和国家、部委及各省市统计年鉴公布的排放源数据,得到的中国大陆的1°×1°网格精度的SO2的排放分布,计算了中国地区人为扰动气溶胶的辐射强迫。应用近期开发的二维能量平衡模式计算了由该种气溶胶所引起的中国地区地面温度变化。模式结果表明,最大辐射强迫和最大地面温度变化都集中在中国的沿海和四川地区。最大辐射强迫达3 W/m2。     

平流层气溶胶的辐射强迫及其气候响应的水平二维分析

利用比较先进的辐射模式计算了平流层气溶胶的辐射强迫,并对之进行了参数化。结果发现平流层气溶胶的辐射强迫的水平分布不仅与其本身的水平变化有关,而且与下垫面的反照率有很大的关系。利用近期开发的二维能量平衡模式模拟了皮纳图博火山气溶胶对地面平衡温度的影响,结果表明:皮纳图博火山至喷发后1年半左右降温达最大,至喷发后第5年降温已很小。     

辐射和积云对流过程对大气辐射通量的影响

基于中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室发展的全球大气环流谱模式(SAMIL-R42L26),研究了澳大利亚气象局研究中心(BMRC)新辐射方案和新Zhang-McFaflane积云对流方案对大气辐射通量模拟的影响.新辐射方案相比原辐射方案在辐射计算光谱分辨率、气体吸收和计算效率等方面作了很多改进,其对大气辐射通量的模拟能力相应提高.在晴空条件下,大气顶出射长波、大气吸收短波和地表入射短波等与观测的偏差较原辐射方案明显减小,尤其是在对流活跃区域.在云天条件下大气辐射通量与观测的偏差也较原辐射方案减小,但其偏差依然较大,这与模式中积云对流参数化方案模拟能力不足引起的辐射通量偏差有关.为此,换用了新Zhang-McFarlane积云对流方案,其结果表明,对流活跃区水汽含量显著增加,原对流方案中偏强的"双赤道辐合带"现象明显减弱,赤道辐合带地区的大气辐射通量偏差有明显减小,在海洋地区晴空大气顶出射长波和地表入射短波的量值及空间分布均接近观测结果,同时大气顶全球平均能量收支的年变化和观测结果趋于一致,其中模拟的伞球年平均大气顶能量收支和观测的偏差不到0.6 W/m2.试验结果同时表明,在未来研究中引入气溶胶分布、调整相关的云物理和陆面过程等物理参数化方案是进一步提高SAMIL-R42L26辐射通最模拟性能的关键.     

Climate change scenarios for precipitation and potential evapotranspiration over central Belgium

In this article, we examine climate model estimations for the future climate over central Belgium. Our analysis is focused mainly on two variables: potential evapotranspiration (PET) and precipitation. PET is calculated using the Penman equation with parameters appropriately calibrated for Belgium, based on RCM data from the European project PRUDENCE database. Next, we proceed into estimating the model capacity to reproduce the reference climate for PET and precipitation. The same analysis for precipitation is also performed based on GCM data from the IPCC AR4 database. Then, the climate change signal is evaluated over central Belgium using RCM and GCM simulations based on several SRES scenarios. The RCM simulations show a clear shift in the precipitation pattern with an increase during winter and a decrease during summer. However, the inclusion of another set of SRES scenarios from the GCM simulations leads to a less clear climate change signal.     

Temperature extremes and wildfires in Siberia in the 21st century: the MGO regional climate model simulation

Possible changes in temperature extremes and wildfires in the 21st century in the regions of Russia are analyzed using a regional climate model (RCM) with high space-time resolution. The IPCC A2 scenario of greenhouse gas and aerosol concentration increase in the atmosphere is used. It is shown that changes in extreme wildfires appear to be in the 21st century most pronounced relative to changes in moderate and high wildfires. In some areas, along with decreased moderate and high wildfires, a significant increase in extreme wildfires is expected. Further studies should be associated both with RCM development, aimed at improving simulation of the wildfire atmospheric condition, and with enlarging the parameter set for wildfire analysis. Not only seasonal mean, but also monthly mean wildfire conditions should be studied, along with the use of statistical methods of model data interpretation to analyze intraseasonal and interannual variability of wildfire characteristics.     

Improved regional scale processes reflected in projected hydrological changes over large European catchments

For the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC), the recent version of the coupled atmosphere/ocean general circulation model (GCM) of the Max Planck Institute for Meteorology has been used to conduct an ensemble of transient climate simulations These simulations comprise three control simulations for the past century covering the period 1860–2000, and nine simulations for the future climate (2001–2100) using greenhouse gas (GHG) and aerosol concentrations according to the three IPCC scenarios B1, A1B and A2. For each scenario three simulations were performed. The global simulations were dynamically downscaled over Europe using the regional climate model (RCM) REMO at 0.44° horizontal resolution (about 50 km), whereas the physics packages of the GCM and RCM largely agree. The regional simulations comprise the three control simulations (1950–2000), the three A1B simulations and one simulation for B1 as well as for A2 (2001–2100). In our study we concentrate on the climate change signals in the hydrological cycle and the 2 m temperature by comparing the mean projected climate at the end of the twenty-first century (2071–2100) to a control period representing current climate (1961–1990). The robustness of the climate change signal projected by the GCM and RCM is analysed focussing on the large European catchments of Baltic Sea (land only), Danube and Rhine. In this respect, a robust climate change signal designates a projected change that sticks out of the noise of natural climate variability. Catchments and seasons are identified where the climate change signal in the components of the hydrological cycle is robust, and where this signal has a larger uncertainty. Notable differences in the robustness of the climate change signals between the GCM and RCM simulations are related to a stronger warming projected by the GCM in the winter over the Baltic Sea catchment and in the summer over the Danube and Rhine catchments. Our results indicate that the main explanation for these differences is that the finer resolution of the RCM leads to a better representation of local scale processes at the surface that feed back to the atmosphere, i.e. an improved representation of the land sea contrast and related moisture transport processes over the Baltic Sea catchment, and an improved representation of soil moisture feedbacks to the atmosphere over the Danube and Rhine catchments.     

计算非均匀地表通量的一种简化PDF及其应用

提出描述地表非均匀特性的简化概率密度函数（PDF），它可代替各种具体的PDF用于求解次网格尺度平均通量而不影响其精度，这种简化PDF可直接加入陆面过程模式方程组中进行陆－气通量交换的数值试验。它对非均匀地表陆面过程参数化具有一定的普适性。本文仅讨论了对称分布的简化计算（非对称分布另文讨论），列举了非均匀分布的观测事实，并以地表净红外辐射通量计算为例，详细验证了应用这种简化PDF的可行性和可靠性。     

SF6气体的辐射强迫和全球增温潜能的研究

IPCC(2007)指出, 六氟化硫(SF6) 作为臭氧消耗物质 (ODSs) 的部分替代物质, 近年来排放量大大增加。它作为控制排放的人造长寿命温室气体之一已经被列入《京都议定书》。但是, 目前在臭氧消耗物质替代品中, 对SF6的辐射强迫和全球增温潜能的研究较少, 而且所用的谱吸收资料陈旧。本文采用最新的分子吸收数据库HITRAN2004中的SF6的吸收截面数据, 利用Shi(1981) 的吸收系数重排法, 建立了SF6的相关k分布的辐射计算方案, 在此基础上研究了SF6在晴空大气下的辐射效率和全球增温潜能, 并首次计算了SF6的全球温变潜能, 与其全球增温潜能进行了比较。本文的研究表明: SF6的辐射效率为0.512 W/m2, 经过大气寿命调整之后的辐射效率为0.506 W/m2, 二者差别不大; 根据IPCC (2007) 给出的排放情景, 到2100年, SF6在大气中的体积分数将达到35×10-12～70×10-12, 引起的相应辐射强迫将在0.004～0.028 W/m2之间变化; 相对于二氧化碳的100年全球增温潜能为2.33×104, 比IPCC(2007)的结果大2.2%; 100年的持续排放的全球增温潜能为2.26×104, 与其他长寿命人造温室气体一道, 其对全球变暖的长期影响不容忽视。     

Dynamics of severe atmospheric droughts in European Russia

Severe atmospheric droughts of different intensity over the southern Russian Plain are studied using the observations and model data during the period of 1936–2100. Spatial distribution, frequency, and duration of droughts are considered. Dynamics of extreme droughts in the 20th century is derived from the meteorological station data. The tendency of drought occurrence in 1991–2000, 2041–2050, and 2091–2100 is obtained from the MGO (Main Geophysical Observatory) regional climate model (RCM). A catalog of severe atmospheric droughts of different intensity is made based on the observations for 1936–2000 and modeling results for 1991–2000. The comparison of the observational and model data has shown that the MGO RCM simulates well the frequency of severe atmospheric droughts.     

Probabilistic forecasting of seasonal drought behaviors in the Huai River basin,China

Results from high resolution 7-km WRF regional climate model (RCM) simulations are used to analyse changes in the occurrence frequencies of heat waves, of precipitation extremes and of the duration of the winter time freezing period for highly populated urban areas in Central Europe. The projected climate change impact is assessed for 11 urban areas based on climate indices for a future period (2021–2050) compared to a reference period (1971–2000) using the IPCC AR4 A1B Scenario as boundary conditions. These climate indices are calculated from daily maximum, minimum and mean temperatures as well as precipitation amounts. By this, the vulnerability of these areas to future climate conditions is to be investigated. The number of heat waves, as well as the number of single hot days, tropical nights and heavy precipitation events is projected to increase in the near future. In addition, the number of frost days is significantly decreased. Probability density functions of monthly mean summer time temperatures show an increase of the 95th percentile of about 1–3 °C for the future compared with the reference period. The projected increase of cooling and decrease of heating degree days indicate the possible impact on urban energy consumption under future climate conditions.     

An approximate energy cycle for inter-member variability in ensemble simulations of a regional climate model

The presence of internal variability (IV) in ensembles of nested regional climate model (RCM) simulations is now widely acknowledged in the community working on dynamical downscaling. IV is defined as the inter-member spread between members in an ensemble of simulations performed by a given RCM driven by identical lateral boundary conditions (LBC), where different members are being initialised at different times. The physical mechanisms responsible for the time variations and structure of such IV have only recently begun to receive attention. Recent studies have shown empirical evidence of a close parallel between the energy conversions associated with the time fluctuations of IV in ensemble simulations of RCM and the energy conversions taking place in weather systems. Inspired by the classical work on global energetics of weather systems, we sought a formulation of an energy cycle for IV that would be applicable for limited-area domain. We develop here a novel formalism based on local energetics that can be applied to further our understanding IV. Prognostic equations for ensemble-mean kinetic energy and available enthalpy are decomposed into contributions due to ensemble-mean variables (EM) and those due to deviations from the ensemble mean (IV). Together these equations constitute an energy cycle for IV in ensemble simulations of RCM. Although the energy cycle for IV was developed in a context entirely different from that of energetics of weather systems, the exchange terms between the various reservoirs have a rather similar mathematical form, which facilitates some interpretations of their physical meaning.     

Impacts of Spectral Nudging on the Sensitivity of a Regional Climate Model to Convective Parameterizations in East Asia

The sensitivity of a regional climate model (RCM) to cumulus parameterization (CUPA) schemes in modeling summer precipitation over East Asia has been investigated by using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (PSU-NCAR MM5). The feasibility of physical ensemble and the effect of interior (spectral) nudging are also assessed. The RCM simulations are evaluated against the NCEP/NCAR reanalysis data and NCEP/CPC precipitation data for three summers (JJA) in 1991, 1998, and 2003. The results show that the RCM is highly sensitive to CUPA schemes. Different CUPA schemes cause distinctive characteristics in the modeling of JJA precipitation and the intraseasonal (daily) variability of regional precipitation. The sensitivity of the RCM simulations to the CUPA schemes is reduced by adopting the spectral nudging technique, which enables the RCM to reproduce more realistic large-scale circulations at the upper levels of the atmosphere as well as near the surface, and better precipitation simulation in the selected experiments. The ensemble simulations using different CUPA schemes show higher skills than individual members for both control runs and spectral nudging runs. The physical ensemble adopting the spectral nudging technique shows the highest downscaling skill in capturing the general circulation patterns for all experiments and improved temporal distributions of precipitation in some regions.     

地球大气透过率及辐射率计算

文章介绍了一种比较简单实用的地球大气的光谱透过率和到达大气层顶的红外辐射率的计算模型,光谱波长从4 μm到∞ μm,吸收气体H2O、CO2、O3的吸收计算采用Elsasser带模式及其经验参数,H2O的连续吸收公式是美国LOWTRAN-6计算程序的水汽连续吸收经验公式。透过率的计算结果与LOWTRAN计算结果相一致。以这种透过率简化模型为基础,建立了辐射传递正演计算模型,开发了相应软件,并用于卫星遥感射出长波辐射的资料处理中,取得了良好结果。