Simulation of the Indian monsoon using the RegCM3–ROMS regional coupled model

A regional coupled atmosphere–ocean model was developed to study the role of air–sea interactions in the simulation of the Indian summer monsoon. The coupled model includes the regional climate model (RegCM3) as atmospheric component and the regional ocean modeling system (ROMS) as oceanic component. The two-way coupled model system exchanges sea surface temperature (SST) from the ocean to the atmospheric model and surface wind stress and energy fluxes from the atmosphere to the ocean model. The coupled model is run for four years 1997, 1998, 2002 and 2003 and the results are compared with observations and atmosphere-only model runs employing Reynolds SSTs as lower boundary condition. It is found that the coupled model captures the main features of the Indian monsoon and simulates a substantially more realistic spatial and temporal distribution of monsoon rainfall compared to the uncoupled atmosphere-only model. The intraseasonal oscillations are also better simulated in the coupled model compared to the atmosphere-only model. These improvements are due to a better representation of the feedbacks between the SST and convection and highlight the importance of air–sea coupling in the simulation of the Indian monsoon.     

中国业务动力季节预报的进展

利用动力模式开展季节到年际的短期气候预测 ,是目前国际上气候预测的发展方向。自 1996年以来 ,经过 8a多的研制和发展 ,国家气候中心已建立起第 1代动力气候模式预测业务系统 ,其中包括 1个全球大气 海洋耦合模式 (CGCM )、1个高分辨率东亚区域气候模式 (RegCM_NCC)和 5个简化的ENSO预测模式 (SAOMS) ,可用于季节—年际时间尺度的全球气候预测 ;全球海气耦合模式与区域气候模式嵌套 ,可以提供高分辨率的东亚区域气候模式制做季节预测。CGCM对 1982～ 2 0 0 0年夏季的历史回报试验表明 ,该模式对热带太平洋海表面温度和东亚区域的季节预测具有较好的预测能力。RegCM NCC的 5a模拟基本上能再现东亚地区主要雨带的季节进展。利用嵌套的区域气候模式RegCM NCC对 1991～ 2 0 0 0年的夏季回报表明 ,在预报主要季节雨带方面有一定技巧。 2 0 0 1～ 2 0 0 3年 ,CGCM和RegCM NCC的实时季节预报与观测相比基本合理。特别是 ,模式成功地预报了 2 0 0 3年梅雨季节长江和黄河之间比常年偏多的降水。SAOMS模式系统的回报试验表明 ,该系统对热带太平洋海表面温度距平有一定的预报能力 ,模式超前 6～ 12个月的回报与观测的相关系数明显高于持续预报。 1997～ 2 0 0 3年 ,SAOMS多模式集合实时预报与观测的相关系数达到     

区域海气耦合模式对中国夏季降水的模拟

以区域气候模式RegCM3和普林斯顿海洋模式POM为基础,建立了一个区域海气耦合模式,对1963-2002年中国夏季气候进行模拟,重点分析该耦合模式对中国夏季降水的模拟性能以及降水模拟改进的可能原因.结果表明:耦合模式对中国夏季雨带分布的模拟明显优于控制试验(单独的大气模式),对长江流域以及华南降水的模拟性能改进尤为明显,同时耦合模式能够更为真实地刻画中国东部地区汛期雨带的移动.对降水的年际变化分析发现,耦合模式模拟的1963-2002年中国夏季降水年际变率与观测吻合,模拟的夏季长江流域降水与观测降水相关系数达到0.48,模拟的华南夏季降水与观测的相关系数达到0.61,而控制试验结果与观测降水的相关系数均较小.对中国东部长江流域夏季降水与近海海温的相关分析表明,用给定海温驱动的大气模式,并不能正确模拟出中国东部夏季降水与海温的关系,而耦合模式能够较好地模拟出长江流域与孟加拉湾、南海以及黑潮区海温的关系,与GISST(全球海冰和海表温度)和观测降水相关关系一致.对水汽输送通量的分析发现,控制试验模拟的水汽输送路径与NCEP/NCAR再分析资料相比差别较大,耦合模式模拟的来自海洋上的水汽输送强度和路径与NCEP/NCAR再分析资料一致,提高了耦合模式对水汽输送的模拟能力,从而改善了模式对华南以及长江流域降水的模拟.     

Introduction to the Regional Coupled Model WRF4-LICOM: Performance and Model Intercomparison over the Western North Pacific

Regional coupled modeling is one of the frontiers of regional climate modeling, but intercomparison has not been well coordinated. In this study, a community regional climate model, WRF4, with a resolution of 15 km, was coupled with a high-resolution(0.1°) North Pacific Ocean model(LICOM_np). The performance of the regional coupled model,WRF4_LICOM, was compared to that of another regional coupled model, RegCM4_LICOM, which was a coupling of version 4 of the Regional Climate Model(RegCM4) with LICOM_np. The analysis focused on the 2005 western North Pacific summer monsoon rainfall. The results showed that the regional coupled models with either RegCM4 or WRF4 as their atmospheric model component simulated the broad features over the WNP reasonably well. Quantitative intercomparison of the regional coupled simulations exhibited different biases for different climate variables.RegCM4_LICOM exhibited smaller biases in its simulation of the averaged June–July–August SST and rainfall, while WRF4_LICOM better captured the tropical cyclone(TC) intensity, the percentage contributions of rainfall induced by TCs to the total rainfall, and the diurnal cycle of rainfall and stratiform percentages, especially over land areas. The different behaviors in rainfall simulated by the two models were partly ascribed to the behaviors in the simulated western North Pacific subtropical high(WNPSH). The stronger(weaker) WNPSH in WRF4_LICOM(RegCM4_LICOM) was driven by overestimated(underestimated) diabatic heating, which peaked at approximately 450 hPa over the region around the Philippines in association with different condensation–radiation processes. Coupling of WRF4 with LIOCM is a crucial step towards the development of the next generation of regional earth system models at the Chinese Academy of Sciences.     

RegCM-Dust模式对东亚一次沙尘暴天气过程模拟的效果检验

为检验区域气候模式与沙尘模式耦合模式RegCM Dust的性能,以2006年东亚地区一次沙尘暴过程为例,将模拟结果与观测资料进行对比,以检验模式对沙尘天气过程的模拟能力。结果表明：模式对沙尘暴过程的地面风场特征模拟效果较好,总体上重现了大风区的分布;地面沙尘浓度和沙尘光学厚度模拟结果与观测分布总体吻合。模式虽然是区域气候模式与沙尘模式耦合模式,但由于其内核是建立在中尺度数值模式MM4基础上,因此对天气过程尤其是沙尘天气过程具备较好的把握能力,对于沙尘天气过程预测具有良好的应用前景。     

RegCM3模式对中国东部夏季降水的模拟试验

利用最新发布的区域气候模式RegCM3对1998年5—8月中国东部降水进行了模拟试验，考察了模式对降水和大尺度环流系统的模拟能力。结果表明：不同对流性降水方案对不同月份、不同区域的降水模拟效果差别较大，采用Kuo方案和Grell方案时模拟的降水效果要好于BM方案；RegCM3能较成功地再现异常降水的月际尺度变化和空间分布等基本特征；模式还较好地模拟了西太平洋副高脊线的演变过程和两次向北传播的季节内振荡。该模式可应用于中国东部夏季风降水的研究。     

Simulation of China Summer Precipitation Using a Regional Air-Sea Coupled Model

A regional air-sea coupled model based on the regional climate model(RegCM3)and the regional oceanic model POM(Princeton Ocean Model)is developed and a series of experiments are performed to verify the ability of the coupled model in simulating the summer precipitation over China from 1963 to 2002.The results show that the space correlation coefficients between the GISST(Global Ice and Sea Surface Temperature)data and the simulated SST by RegCM3-POM exceed 0.9.Compared with the uncoupled experiments,the coupled model RegCM3-POM has a better performance in simulating the mean summer(June to August)precipitation over China,and the distribution of the rainband in the coupled model is more accurate.The improvement of the rainfall simulation is significant over the Yangtze River Valley and in South China.The rainbelt intraseasoaal evolution over eastern China in summer indicates that the simulation ability of RegCM3-POM is improved in comparison with the uncoupled model.The interannual summer rainfall variation over eastern China simulated by RegCM3-POM is in accordance with observation,while the spatial pattern of the interannual summer rainfall variation in the uncoupled model is inaccurate.The simulated correlation coefficient between the summer rainfall in the uncoupled model RegCM3 and observation is0.30 over the Yangtze River Valley and 0.29 in South China.The coefficient between the rainfall in the coupled RegCM3-POM and observation is 0.48 over the Yangtze River Valley and 0.61 in South China.The RegCM3-POM has successfully simulated the correlation coefficients between summer rainfall in the Yangtze River Valley and SST anomalies of the Bay of Bengal,South China Sea,and the Kuroshio area,whereas the uncoupled model RegCM3 fails to reproduce this relationship.The study further shows that the monsoon circulation and the path of the moisture transport flux simulated by RegCM3-POM are in good agreement with the NCEP/NCAR data.     

A Regional Air--Sea Coupled Model and Its Application over East Asia in the Summer of 2000

A regional air-sea coupled model,comprising the Regional Integrated Environment Model System (RIEMS)and the Princeton Ocean Model(POM)was developed to simulate summer climate features over East Asia in 2000.The sensitivity of the model's behavior to the coupling time interval(CTI),the causes of the sea surface temperature(SST)biases,and the role of air-sea interaction in the simulation of precipitation over China are investigated.Results show that the coupled model can basically produce the spatial pattern of SST,precipitation,and surface air temperature(SAT)with five different CTIs respectively.Also,using a CTI of 3,6 or 12 hours tended to produce more successful simulations than if using 1 and 24 hours.Further analysis indicates that both a higher and lower coupling frequency result in larger model biases in air-sea heat flux exchanges,which might be responsible for the sensitivity of the coupled model's behavior to the CTI. Sensitivity experiments indicate that SST biases between the coupled and uncoupled POM occurring over the China coastal waters were due to the mismatch of the surface heat fluxes produced by the RIEMS with those required by the POM.In the coupled run,the air-sea feedbacks reduced the biases in surface heat fluxes,compared with the uncoupled RIEMS,consequently resulted in changes in thermal contrast over land and sea and led to a precipitation increase over South China and a decrease over North China.These results agree well observations in the summer of 2000.     

Coupling of a regional atmospheric model (RegCM3) and a regional oceanic model (FVCOM) over the maritime continent

Climatological high resolution coupled climate model simulations for the maritime continent have been carried out using the regional climate model (RegCM) version 3 and the finite volume coastal ocean model (FVCOM) specifically designed to resolve regions characterized by complex geometry and bathymetry. The RegCM3 boundary forcing is provided by the EMCWF-ERA40 re-analysis. FVCOM is embedded in the Global MITgcm which provides boundary forcing. The domain of the coupled regional model covers the entire South China Sea with its through-flow, the entire Indonesian archipelago with the Indonesian through-flow (ITF) and includes a large region in the western Pacific and eastern Indian oceans. The coupled model is able to provide stable and realistic climatological simulations for a specific decade of atmospheric–oceanic variables without flux correction. The major focus of this work is on oceanic properties. First, the coupled simulation is assessed against ocean-only simulations carried out under two different sets of air–sea heat fluxes. The first set, provided by the MITgcm, is proved to be grossly deficient as the heat fluxes are evaluated by a two-dimensional, zonally averaged atmosphere and the simulated SST have anomalous cold biases. Hence the MITgcm fluxes are discarded. The second set, the NCEP re-analysis heat fluxes, produces a climatological evolution of the SST with an average cold bias of ~?0.8 °C. The coupling eliminates the cold bias and the coupled SST evolution is in excellent agreement with the analogous evolution in the SODA re-analysis data. The detailed comparison of oceanic circulation properties with the International Nusantara Stratification and Transport observations shows that the coupled simulation produces the best estimate of the total ITF transport through the Makassar strait while the transports of three ocean-only simulations are all underestimated. The annual cycle of the transport is also very well reproduced. The coupling also considerably improves the vertical thermal structure of the Makassar cross section in the upper layer affected by the heat fluxes. On the other hand, the coupling is relatively ineffective in improving the precipitation fields even though the coupled simulation captures reasonably well the precipitation annual cycle at three land stations in different latitudes.     

区域海气耦合模式对华北夏季大气水汽输送模拟结果的检验及其与单独气候模式的比较分析

将区域海气耦合模式RegCM3-POM和区域气候模式RegCM3 40年(1963-2002年)的模拟结果与NCEP/NCAR再分析资料进行对比,检验区域海气耦合模式对中国华北地区夏季大气水汽含量和水汽输送特征的模拟能力,比较耦合模式与单独区域气候模式的差异.结果表明,区域海气耦合模式RegCM3-POM的模拟性能相对于单独区域气候模式RegCM3,大气水汽输送特征的模拟能力有了较大的改进.分析显示两种模式都能够较好地再现东哑地区气候平均夏季大气水汽储量浅红和水汽输送的空间分布特征,而耦合模式对大气水汽输送的模拟更为合理.在对流层中低层更接近观测;耦合模式对中国华北地区夏季平均大气水汽输送通量在垂直方向卜的分布型及水平4个边界水汽输送收支的模拟,相对于单独大气模式有了一定的改进;耦合模式对伴随华北地区夏季早涝的大气水汽异常输送也具有较好的模拟能力,其模拟的水汽输送异常的来源与观测基本一致,尤其是在20°N以北地区,耦合模式结果相对于单独区域气候模式有了很大的改进.但同时耦合模式在低纬度海洋上对气候平均夏季大气水汽含量模拟的偏差比区域气候模式显著;与观测相比,耦合模式对来自孟加拉湾地区的大气水汽输送模拟偏弱,而对西太平洋副热带高压西侧水汽输送模拟偏强,与华北夏季旱涝相联系的水汽输送异常的模拟在低纬度海洋上也存在明显偏差.     

The 1997/ 98 enso cycle and its impact on summer climate anomalies in east asia

l.IntroductionTheENSOeventcanbeconsideredasthemostimp0rtantphenomenonoftheair-seainteractionintheequatoria1Pacific.WhenanENSOeventoccursintheequatorialPacific,severeclimateanomalieswillbecausedinmanyregionsoftheworld(Namias,l976;HorelandWallace,l98l;RasmussonandCarpenter,l982;RasmussonandWallace,l983).Similar-ly,theENS0eventalsohasalargeimpactonclimateanomaliesinEastAsia(WangandZhu,l986;FuandYe,l988).lnrespectoftheimpactofENSOeventonclimateanomaliesinChina,theinvestigationofHuanga…     

Coupling of a Regional Climate Model with a Crop Development Model and Evaluation of the Coupled Model across China

In this study, the CERES(Crop Estimation through Resource and Environment Synthesis) crop model was coupled with CLM3.5, the land module of the regional climate model RegCM4. The new coupled model was named RegCM4_CERES; and in this model, crop type was further divided into winter wheat, spring wheat, spring maize, summer maize, early rice, late rice,single rice, and other crop types based on each distribution fraction. The development of each crop sub-type was simulated by the corresponding crop model separately, with each planting and harvesting date. A simulation test using RegCM4_CERES was conducted across China from 1999 to 2008; a control test was also performed using the original RegCM4. Data on crop LAI(leaf area index), soil moisture at 10 cm depth, precipitation, and 2 m air temperature were collected to evaluate the performance of RegCM4_CERES. The evaluation provided comparison of single-station time series, regional distributions,seasonal variations, and statistical indices for RegCM4_CERES. The results revealed that the coupled model had an excellent ability to simulate the phonological changes and spatial variations in crops. The consideration of dynamic crop development in RegCM4_CERES corrected the wet bias of the original RegCM4 over North China and the cold bias over South China.However, the degree of improvement was minimal and the statistical indices for RegCM4_CERES were roughly the same as the original RegCM4.     

区域海气耦合模式模拟中国夏季降水能力分析

基于OASIS3(Ocean Atmosphere Sea Ice Soil version 3)耦合器,耦合区域气候模式RegCM3(Regional Climate Model version 3)和海洋模式HYCOM(Hybrid Coordinate Ocean Model),建立一个区域海气耦合模式,并通过嵌套方法处理海洋模式的侧边界问题。运用该耦合模式对1982～2001年包括中国在内的东亚地区气候进行连续模拟,重点分析其对中国夏季(6～8月)降水的模拟性能。结果表明:耦合模式基本可以模拟出中国夏季降水的空间分布特征,模拟的降水量值和年际变化在靠近海洋的沿海区域比参照试验有一定程度的改善;能够再现观测夏季降水经验正交函数第一模态(EOF1)的空间分布特征,与观测EOF1的时间相关性也比参照试验有较大提高;前6个模态的组合分析也表明耦合模式对长江中下游、山东半岛、海南岛等区域夏季降水的较大时间尺度气候分量的模拟改善更显著。     

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.     

Interannual to decadal summer drought variability over Europe and its relationship to global sea surface temperature

Interannual to decadal variability of European summer drought and its relationship with global sea surface temperature (SST) is investigated using the newly developed self calibrated Palmer drought severity index (scPDSI) and global sea surface temperature (SST) field for the period 1901–2002. A European drought severity index defined as the average of scPDSI over entire Europe shows quasiperiodic variations in the 2.5–5 year band as well as at 12–13 years suggesting a possible potential predictability of averaged drought conditions over Europe. A Canonical Correlation Analysis between summer scPDSI anomalies over Europe and global SST anomalies reveals the existence of three modes of coupled summer drought scPDSI patterns and winter global SST anomalies. The first scPDSI-SST coupled mode represents the long-term trends in the data which manifest in SST as warming over all oceans. The associated long-term trend in scPDSI suggests increasing drought conditions over the central part of Europe. The second mode is related to the inter-annual ENSO and decadal PDO influence on the European climate and the third one captures mainly the drought pattern associated to Atlantic Multidecadal Oscillation. The lag relationships between winter SST and summer drought conditions established in this study can provide a valuable skill for the prediction of drought conditions over Europe on interannual to decadal time scales.     

基于RegCM3的2006年中国南方夏季持续高温干旱天气的模拟研究

利用区域气候模式RegCM3并行版本,对2006年7—8月发生在中国南方的持续高温干旱气候事件进行了数值模拟试验。通过对模拟结果的对比分析,发现RegCM3能够较好地模拟出2006年夏季盘踞在中国大陆的副热带高压,同时模拟的暖区位置、范围及强度与实况也较接近。相关性检验结果也表明,RegCM3对发生在中国南方的持续高温天气具有一定的模拟能力。     

A study on air–sea interaction on the simulated seasonal climate in an ocean–atmosphere coupled model

This study investigates the effects of air–sea interaction upon simulated tropical climatology, focusing on the boreal summer mean precipitation and the embedded intra-seasonal oscillation (ISO) signal. Both the daily coupling of ocean–atmosphere and the diurnal variation of sea surface temperature (SST) at every time step by accounting for the ocean mixed layer and surface-energy budget at the ocean surface are considered. The ocean–atmosphere coupled model component of the global/regional integrated model system has been utilized. Results from the coupled model show better precipitation climatology than those from the atmosphere-only model, through the inclusion of SST–cloudiness–precipitation feedback in the coupled system. Cooling the ocean surface in the coupled model is mainly responsible for the improved precipitation climatology, whereas neither the coupling itself nor the diurnal variation in the SST influences the simulated climatology. However, the inclusion of the diurnal cycle in the SST shows a distinct improvement of the simulated ISO signal, by either decreasing or increasing the magnitude of spectral powers, as compared to the simulation results that exclude the diurnal variation of the SST in coupled models.     

An evaluation of RegCM3_CERES for regional climate modeling in China

A 20-year simulation of regional climate over East Asia by the regional climate model RegCM3_CERES (Regional Climate Model version 3 coupled with the Crop Estimation through Resource and Environment Synthesis) was carried out and compared with observations and the original RegCM3 model to comprehensively evaluate its performance in simulating the regional climate over continental China. The results showed that RegCM3_CERES reproduced the regional climate at a resolution of 60 km over China by using ERA40 data as the boundary conditions, albeit with some limitations. The model captured the basic characteristics of the East Asian circulation, the spatial distribution of mean precipitation and temperature, and the daily characteristics of precipitation and temperature. However, it underestimated both the intensity of the monsoon in the monsoonal area and precipitation in southern China, overestimated precipitation in northern China, and produced a systematic cold temperature bias over most of continental China. Despite these limitations, it was concluded that the RegCM3_CERES model is able to simulate the regional climate over continental China reasonably well.     

四川盆地夏季降水日变化的数值模拟

利用区域气候模式RegCM3对1991-2004年四川盆地夏季降水进行了数值模拟,通过模拟结果和NCEP/NCAR再分析资料的对比,评估了模式对四川盆地夏季＂夜雨＂现象的模拟能力。结果表明,RegCM3模式能较好地模拟出四川盆地夏季降水的空间分布和日变化规律,四川盆地夏季＂夜雨＂现象的形成与该地区的地形分布有密切关系。...     

Simulation of a Persistent Snow Storm over Southern China with a Regional Atmosphere-Ocean Coupled Model

A regional atmosphere-ocean coupled model,RegCM3-POM,was developed by coupling the regional climate model(RegCM3) with the Princeton Ocean Model(POM).The performance of RegCM3-POM in simulating a persistent snow storm over southern China and the impact of the Madden-Julian oscillation(MJO) on this persistent snow storm were investigated.Compared with the stand-alone RegCM3,the coupled model performed better at reproducing the spatial-temporal evolution and intensity of the precipitation episodes.The power spectral analysis indicated that the coupled model successfully captured the dominant period between 30 and 60 days in the precipitation field,leading to a notable improvement in simulating the magnitude of intraseasonal precipitation variation,and further in enhancing the intensity of the simulated precipitation.These improvements were mainly due to the well-simulated low-frequency oscillation center and its eastward propagation characteristics in each MJO phase by RegCM3-POM,which improved the simulations of MJO-related low-frequency vertical motions,water vapor transport,and the deep inversion layer that can directly influence the precipitation event and that further improved the simulated MJOprecipitation relationship.Analysis of the phase relationship between convection and SST indicated that RegCM3-POM exhibits a near-quadrature relation between the simulated convection and SST anomalies,which was consistent with the observations.However,such a near-quadrature relation was not as significant when the stand-alone RegCM3 was used.This difference indicated that the inherent coupled feedback process between the ocean and atmosphere in RegCM3-POM played an important part in reproducing the features of the MJO that accompanied the snow storm.