标量粗糙度对地气交换的影响

为提高地-气间感热和潜热通量的精度,利用Garratt的公式将标量粗糙度Z0T和Z0q引入BATS,对六种不同的植被作对比试验。结果表明:标量粗糙度Z0T和Z0q均远远小于动量粗糙度Z0,约相差3～10个数量级不等。晴天状况下,农作物区Z0/Z0T最小,约103,阔叶林最大,达1010;雨天状况下,各种植被间标量粗糙度的差异减小了。计算的地表温度、感热通量、潜热通量较原BATS的更为合理。     

一个引入近地层的区域气候模式

把近地层引入到NCAR的区域气候模式RegCM2中(简称为RCMC1)，用该模式及1991年梅雨期间的观测资料作了3组模拟试验，并同实况进行了比较。结果表明，在区域气候模式中引入近地层后，能够更合理的模拟出地表及植被同大气之间的感热和潜热通量输送，从而改善模式模拟的月降水及月平均地面温度的分布。l0层的RCMC1比18层RCM具有更优的模拟气候的能力，且一个模式天的计算量节省227s。     

次网格坡地辐射参数化对RegCM4.1模式模拟东亚夏季气候的影响

本研究将次网格坡地辐射参数化方案引入到区域气候模式(RegCM4. 1)中,并研究次网格坡地辐射参数化对RegCM4. 1模拟东亚夏季气候性能的影响。结果表明:RegCM4. 1高估了夏季青藏高原的热源作用,模拟低层偏强的西南季风导致了模拟的中国夏季降水量总体偏大。引入次网格坡地辐射参数化方案后,模式模拟的青藏高原夏季地表太阳辐射通量和长波辐射通量减小分别可达5%和12%以上,夏季减弱的青藏高原热源作用使得低层西南季风减弱,从而改善了模式对中国夏季降水的模拟;而且改善程度自东南向西北递减,在东南地区模拟夏季降水的相对均方根误差减小9%,空间相关系数和Taylor评分分别提高0. 14和0. 08。     

干旱区陆面过程模型参数优化和地气相互作用特征的模拟研究

依据干旱区陆地下垫面观测结果, 对陆面过程模式Common Land Model (CoLM) 中反照率、 粗糙度长度和土壤热力性质3个方面的参数进行了优化, 并按照不同的参数组合形式设计了为加深理解干旱区地气相互作用的控制试验和研究重要参数影响的敏感性试验, 对敦煌戈壁2000年5月～2004年7月的陆面过程进行了离线 (off-line) 数值模拟分析。控制试验结果表明: 优化参数的模式在干旱区得到了更好的模拟性能, 对地表和深层土壤温度、 净短波辐射、 净长波辐射以及感热通量的模拟能力较原模式有了明显的提高。敏感性试验的结果表明: 地表温度在全年对反照率都比较敏感, 春季和夏季更为显著; 粗糙度长度和土壤热力性质分别在春夏和秋冬对地表温度有较大影响; 感热通量对反照率和粗糙度长度在夏半年比较敏感, 而土壤热力性质对感热通量的影响并不明显。对敏感性试验的结果进一步分析发现: 原模式在计算地表温度、 净辐射和感热通量的过程中存在不同形式的误差抵消的现象, 这就会掩盖模式的模拟误差, 优化参数的模式可以更好的反映干旱区地气相互作用的物理过程。针对模式输出的感热通量和地表热通量的分析发现: 感热通量的季节变化明显, 全年都有由地表向上的感热通量输送, 夏季尤为显著; 相对于感热通量而言, 潜热通量量级很小可以忽略不计。夏季, 净辐射的能量大部分以感热通量的形式返回大气, 其余的能量以地表热通量的形式进入土壤并贮存, 夏季土壤为热汇; 冬季, 夏季贮存的能量又由土壤返回大气, 此时土壤为热源。     

藏北高原高寒草甸地表粗糙度对地气通量的影响

利用中国科学院寒区旱区环境与工程研究所那曲高寒气候与环境观测研究站的BJ观测站2012年1 12月大气湍流观测资料及自动气象站观测资料,应用一种独立的确定地表动力学粗糙度Z0m的方法及两种热力学粗糙度Z0h的参数化方案(Z98和Y07),得出了Z0m和Z0h以及附加阻尼kB-1的变化规律。结果表明,Z0m在一定时间尺度(月、季)上存在着波动,Z0h在高原季风前、盛行期、衰退期有不同的日变化和季节变化特征。结合陆面模式CoLM将地表特征参数代入该模式进行数值模拟,初步探讨了地表粗糙度的变化规律及其对地表通量的影响,结果表明,Z0m的动态变化和Z0h参数化方案的改进提高了CoLM模式的模拟性能,模拟的地表通量更接近观测值。     

陆面过程模型CoLM与区域气候模式RegCM3的耦合及初步评估

陆面过程通过影响陆面和大气之间物质（如,水分）和能量的交换影响气候, 其参数化方案对数值天气预报、全球及区域气候模拟有重要影响。本研究利用对生物物理、生物化学过程考虑更全面的陆面模式Common Land Model(CoLM) 替代区域气候模式RegCM3原有的陆面模式BATS, 发展了耦合区域气候模式C－RegCM3; 将其应用于东亚地区典型洪涝年份夏季气候模拟以进行评估, 结果表明新耦合的模式C－RegCM3能合理模拟大尺度环流场、近地表气温和降水的分布特征, 对西北半干旱地区降水模拟比RegCM3有所改进。通过利用区域气候模式C－RegCM3及RegCM3对地表能量和水文过程模拟结果的比较, 发现在半干旱、半湿润过渡区C－RegCM3模拟的潜热增大、感热减小; 模拟的地表吸收太阳辐射差异较明显的地区位于模式模拟的主要雨区; C-RegCM3在上述过渡区模拟的夏季地表土壤湿度比RegCM3偏干, 这与它在过渡区降水模拟偏少、蒸散发模拟偏大相对应, 体现了该模式在半干旱、半湿润过渡带模拟出比RegCM3更明显的局地土壤湿度－降水－蒸散发之间的正反馈作用。     

土壤湿度初始异常对东亚区域气候模拟影响的敏感性试验

利用耦合了CLM3.5陆面模式的区域气候模式RegCM4.0,通过敏感性试验,探讨了人为减小春季初始土壤体积水含量对短期时间尺度东亚夏季气候模拟的可能影响。结果表明:较低的初始土壤湿度场能够明显改变区域的地表能量平衡,引起地表净长波辐射和感热通量的显著增加,进而加强了地表对大气的加热,因而引起东亚大范围地区特别是中国东部、印度北部和中亚地区地表温度、气温的升高。与气温不同,初始土壤湿度场对降水的影响很小而且有较大的不确定性,同时偏暖的下垫面使得对流层中高层出现暖高压异常,但这些影响均不显著。综合来看,土壤湿度初始场的初始异常,对RegCM4.0 模式东亚气候模拟的结果有一定影响,特别是在地表温度、气温和能量平衡方面,应在以后的模拟中加以考虑。     

MM5BATS对东亚夏季气候及其变化的模拟试验

将陆面过程模式BATS耦合到中尺度模式MM5V3中与另一区域气候模式RegCM2一起对1995—2000年夏季东亚的区域气候作了模拟试验,并与实际资料作了比较。模拟试验结果表明：(1)两个模式均能较合理地模拟出6年夏季平均的环流、温度和海平面气压等的变化,MM5BATS的模拟结果要略优于RegCM2的结果;(2)MM5BATS模式较合理地模拟出了6年夏季平均的降水分布,而RegCM2模式的模拟结果偏强;(3)MM5BATS模式较好地模拟出了1997年和1998年夏季环流场的变化,对降水的模拟也比较合理。RegCM2对1997年和1998年降水的模拟基本上都偏强。模拟试验结果还表明,在区域气候模拟中有必要采用更新的模式。     

CMIP6全球气候模式对青藏高原中东部地表感热通量模拟能力评估

利用青藏高原（以下简称高原）气象台站常规观测资料、国家青藏高原科学数据中心的青藏高原地气相互作用过程高分辨率（逐小时）综合观测数据集（2005～2016）、国际耦合模式比较计划第六阶段（CMIP6）的历史模拟试验数据和卫星辐射资料,定量评估了12个全球气候模式对1979～2014年高原中东部地表感热通量的模拟能力,并对其模拟偏差进行了成因分析。结果表明,CMIP6模式可较好地重现高原地表感热通量的年循环和季节平均的空间分布型,但数值较计算感热通量偏低,主要表现为对感热通量大值区严重低估。区域平均而言,12个模式模拟的春季高原中东部感热通量的时间演变序列整体较计算感热通量偏低,其中偏差最大的模式为MIROC6,其多年均值仅为计算值的1/3左右。进一步分析发现多模式模拟的春季高原10 m高度处风速和地气温差分别偏强和偏弱,说明CMIP6模拟的春季高原感热通量偏低可主要归因于地气温差的模拟冷偏差。地气温差的模拟冷偏差在高原中东部地区普遍存在,且地表温度和空气温度均存在明显冷偏差,尤其地表温度偏差更大,这很大程度上可能与CMIP6多模式模拟的春季高原降水偏强有关。     

硫酸盐气溶胶直接辐射效应在线与离线模拟方法的比较

利用区域气候模式RegCM 2与大气化学模式连接的模拟系统 ,比较了硫酸盐气溶胶辐射强迫的在线、离线模拟方法的硫酸盐柱含量、大气顶直接辐射强迫及地表温度响应。发现 :在线与离线模拟方法得到的硫酸盐柱含量、有无反馈大气顶直接辐射强迫和地表温度响应在许多地区有很大差异 ,这种差异在较小区域平均的尺度上更显著 ,在全区域平均尺度上也较为明显 ,是不能被忽略的 ;结果显示从硫酸盐含量到辐射强迫和地表温度响应逐渐加大的差异 ,说明硫酸盐气溶胶的辐射强迫与模拟方法有关 ,显示出较大的不确定性。     

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.     

Effects of crop growth and development on regional climate: a case study over East Asian monsoon area

In this study, the CERES phenological growth and development functions were implemented into the regional climate model, RegCM3 to give a model denoted as RegCM3_CERES. This model was used to represent interactions between regional climate and crop growth processes. The effects of crop growth and development processes on regional climate were then studied based on two 20-year simulations over the East Asian monsoon area conducted using the original regional climate model RegCM3, and the coupled RegCM3_CERES model. The numerical experiments revealed that incorporating the crop growth and development processes into the regional climate model reduced the root mean squared error of the simulated precipitation by 2.2–10.7% over north China, and the simulated temperature by 5.5–30.9% over the monsoon region in eastern China. Comparison of the simulated results obtained using RegCM3_CERES and RegCM3 showed that the most significant changes associated with crop modeling were the changes in leaf area index which in turn modify the aspects of surface energy and water partitions and lead to moderate changes in surface temperature and, to some extent, rainfall. Further analysis revealed that a robust representation of seasonal changes in plant growth and developmental processes in the regional climate model changed the surface heat and moisture fluxes by modifying the vegetation characteristics, and that these differences in simulated surface fluxes resulted in different structures of the boundary layer and ultimately affected the convection. The variations in leaf area index and fractional vegetation cover changed the distribution of evapotranspiration and heat fluxes, which could potentially lead to anomalies in geopotential height, and consequently influenced the overlying atmospheric circulation. These changes would result in redistribution of the water and energy through advection. Nevertheless, there are significant uncertainties in modeling how monsoon dynamics responds to crop modeling and more research is needed.     

作物生长对流域水文过程与区域气候的影响

利用区域气候模式RegCM3以及考虑作物生长过程的耦合模式RegCM3_CERES对东亚区域进行20年模拟,研究作物生长对流域水文过程与区域气候的影响。结果表明：考虑作物生长过程的耦合模式模拟海河流域、松花江流域、珠江流域多年平均降水效果明显改进,在除黑河流域外的各流域模拟的温度负偏差有所减小,其中在海河流域、淮河流域的夏季改进尤为明显。各流域夏季（6、7、8月）月蒸散量最高,其中长江流域、海河流域、淮河流域、珠江流域的夏季月蒸散量基本上在100 mm左右,并且七大流域蒸散发的季节变化趋势跟总降水基本一致。多数流域考虑作物生长过程的耦合模式模拟得出蒸散发减少且进入的水汽增加,导致局地水循环率减小;黑河流域与黄河流域降水有所增加,其他流域均有不同程度的减小。针对长江流域,比较耦合模式RegCM3_CERES与模式RegCM3模拟结果显示,叶面积指数减少1.20 m²/m²,根区土壤湿度增加0.01 m³/m³,进而导致潜热通量下降1.34 W/m²（其中在四川盆地地区减少16.00 W/m²左右）,感热通量增加2.04 W/m²,从而影响到降水和气温。     

A regional climate model downscaling projection of China future climate change

Climate changes over China from the present (1990–1999) to future (2046–2055) under the A1FI (fossil fuel intensive) and A1B (balanced) emission scenarios are projected using the Regional Climate Model version 3 (RegCM3) nests with the National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM). For the present climate, RegCM3 downscaling corrects several major deficiencies in the driving CCSM, especially the wet and cold biases over the Sichuan Basin. As compared with CCSM, RegCM3 produces systematic higher spatial pattern correlation coefficients with observations for precipitation and surface air temperature except during winter. The projected future precipitation changes differ largely between CCSM and RegCM3, with strong regional and seasonal dependence. The RegCM3 downscaling produces larger regional precipitation trends (both decreases and increases) than the driving CCSM. Contrast to substantial trend differences projected by CCSM, RegCM3 produces similar precipitation spatial patterns under different scenarios except autumn. Surface air temperature is projected to consistently increase by both CCSM and RegCM3, with greater warming under A1FI than A1B. The result demonstrates that different scenarios can induce large uncertainties even with the same RCM-GCM nesting system. Largest temperature increases are projected in the Tibetan Plateau during winter and high-latitude areas in the northern China during summer under both scenarios. This indicates that high elevation and northern regions are more vulnerable to climate change. Notable discrepancies for precipitation and surface air temperature simulated by RegCM3 with the driving conditions of CCSM versus the model for interdisciplinary research on climate under the same A1B scenario further complicated the uncertainty issue. The geographic distributions for precipitation difference among various simulations are very similar between the present and future climate with very high spatial pattern correlation coefficients. The result suggests that the model present climate biases are systematically propagate into the future climate projections. The impacts of the model present biases on projected future trends are, however, highly nonlinear and regional specific, and thus cannot be simply removed by a linear method. A model with more realistic present climate simulations is anticipated to yield future climate projections with higher credibility.     

区域气候模式对温室效应引起的中国地区气候变化的数值模拟

利用基于 ＲｅｇＣＭ２的区域气候模式并单向嵌套澳大利亚 ＣＳＩＲＯ Ｒ２１Ｌ９全球海－气耦合模式，进行了温室气体二氧化碳浓度倍增对中国气候变化影响的数值试验研究。控制试验结果表明：区域模式由于具有较高的分辨率，因而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；模式对 ２×ＣＯ２敏感性试验结果表明了在 ＣＯ２浓度倍增情况下，由于温室效应，中国区域的地面气温将有明显升高，降水也将呈增加趋势。     

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.     

Mean, interannual variability and trends in a regional climate change experiment over Europe. I. Present-day climate (1961–1990)

We present an analysis of a multidecadal simulation of present-day climate (1961–1990) over Europe with the regional climate model RegCM nested within the global atmospheric model HadAMH. Climatic means, interannual variability and trends are examined, with focus on surface air temperature and precipitation. The RegCM driven by HadAMH fields is able to reproduce the basic features of the observed mean surface climate over Europe, its seasonal evolution and the regional detail due to topographic forcing. Surface air temperature biases are mostly less than 1–2 °C and precipitation biases mostly within 10–20%. The RegCM has more intense vertical transport of temperature and water vapor than HadAMH, which results in lower surface air temperatures and greater precipitation than found in the HadAMH simulation. In some cases this is in the direction of greater agreement with observations, while in others it is in the opposite direction. The simulation shows a tendency to overestimate interannual variability of temperature and precipitation compared to observations, particularly during summer and over the Mediterranean regions. It is shown that in DJF, MAM and SON the RegCM interannual variability is primarily determined by the boundary forcing from HadAMH, while in JJA the internal model physics and resolution effects dominate over many subregions of the domain, and the RegCM has higher interannual variability than HadAMH. The precipitation trends simulated by the nested modeling system for the period 1961–1990 capture some features of the observed trends, in particular the cold season drying over the Mediterranean regions. Ensembles of simulations are, however, needed for a more robust assessment of the models capability to simulate climatic trends. Overall, this simulation is of good quality compared with previous nested RegCM experiments and will constitute the basis for the generation of climate change scenarios over the European region to be reported in future work.     

初、边值条件对区域气候模拟的影响

利用区域气候模式(RegCM2)对1998年夏季风气候进行了模拟,并就初、边值条件对模拟结果的影响情况进行了讨论,结果表明:该模式可以较好地模拟出月际尺度的气候变化,但对降水异常的模拟还需作进一步完善.通过在几个季节采用不同初始场进行的数值模拟发现,从春季开始的积分其结果对初始场的敏感性较高,初始场的差别会对后期模拟产生明显影响.相对来说,从冬季开始的积分,其对初始场的依赖性较小,初始场的差别会在积分过程中逐渐减小,因而在利用RegCM2进行区域气候模拟时宜从冬季开始.另外,通过对采用不同侧边界嵌套方案的模拟效果进行简单讨论,发现当采用较少的缓冲区(5圈)时,海绵边界对温度、比湿及位势高度的模拟要比指数松弛及流入流出边界好,降水的模拟也要比其他方案好一些,但对风场的模拟则不如指数松弛方案.     

RegCM3 CORDEX东亚试验模拟和预估的中国夏季温度变化

按照CORDEX (COordinated Regional Downscaling Experiment) 计划试验设计要求,利用中国科学院大气物理研究所全球模式FGOALS-g2的数据驱动区域气候模式RegCM3,针对1986~2005年历史气候和2010~2065年RCP8.5排放情景下气候预估,对东亚地区进行了50 km动力降尺度模拟。首先评估了RegCM3模式及驱动模式FGOALS-g2对1986~2005年夏季中国地表气温和极端高温事件的模拟能力,然后比较了两个模式在RCP8.5排放情景下对中国夏季地表气温和极端高温事件预估的变化,重点分析了动力降尺度结果的优势。结果表明,两个模式均能合理再现夏季中国地表气温和极端高温事件的大尺度气候态特征。相对于全球模式,区域模式由于水平分辨率较高,能在刻画地表气温分布的细节上体现出优势。在RCP8.5排放情景下,两个模式预估的三个地表气温指标均显著升高,到21世纪中期 (2046~2065年),两个模式预估的全国平均地表气温增幅相当,气温日较差变化均较小。在FGOALS-g2模式预估中,到21世纪中期,三个地表气温指标的增幅相当,气温日较差没有明显变化,东北和青藏高原的地表气温增幅最大。在RegCM3模式预估中,到21世纪中期,中国大部分地区日最高气温 (Tmax) 增幅大于日最低气温 (Tmin) 增幅,气温日较差增加;而在青藏高原西部,Tmax的增幅较Tmin偏低,气温日较差减小。在RCP8.5排放情景下,两个模式预估的极端高温事件到21世纪中期也显著增加,RegCM3模式预估的极端高温事件全国平均增幅略高于FGOALS-g2模式的预估。在两个模式的预估中,日最高气温最大值 (TXx)、暖昼指数 (TX90p) 和持续暖期指数 (WSDI) 变化的空间分布特征与Tmax相似;和当代相比TX90p增加了60%以上,而WSDI增加了一倍以上。