共查询到20条相似文献，搜索用时 31 毫秒
1.
Simulation of the east asian summer monsoon using a variable resolution atmospheric GCM 总被引：6，自引：0，他引：6
The East Asia summer monsoon (EASM) is simulated with a variable resolution global atmospheric general circulation model (GCM) developed at the Laboratoire de Météorologie Dynamique, France. The version used has a local zoom centered on China. This study validates the model's capability in reproducing the fundamental features of the EASM. The monsoon behaviors over East Asia revealed by the ECMWF reanalysis data are also addressed systematically, providing as observational evidence. The mean state of the EASM is generally portrayed well in the model, including the large-scale monsoon airflows, the monsoonal meridional circulation, the cross-equatorial low-level jets, the monsoon trough in the South China Sea, the surface cold high in Australia, and the upper-level northeasterly return flow. While the performance of simulating large-scale monsoonal climate is encouraging, the model's main deficiency lies in the rainfall. The marked rainbelt observed along the Yangtze River Valley is missed in the simulation. This is due to the weakly reproduced monsoonal components in essence and is directly related to the weak western Pacific subtropical high, which leads to a fragile subtropical southwest monsoon on its western flank and results in a weaker convergence of the southwest monsoon flow with the midlatitude westerlies. The excessively westward extension of the high, together with the distorted Indian low, also makes the contribution of the tropical southwest monsoon to the moisture convergence over the Yangtze River Valley too weak in the model. The insufficient plateau heating and the resulting weak land-sea thermal contrast are responsible for the weakly reproduced monsoon. It is the deficiency of the model in handling the low-level cloud cover over the plateau rather than the horizontal resolution and the associated depiction of plateau topography that results in the insufficient plateau heating. Comparison with the simulation employing regular coarser mesh model reveals that the local zoom technique improves, in a general manner, the EASM simulation. 相似文献
2.
Effects of model resolution and subgrid-scale physics on the simulation of precipitation in the continental United States 总被引：4，自引：0，他引：4
J. P. Iorio P. B. Duffy B. Govindasamy S. L. Thompson M. Khairoutdinov D. Randall 《Climate Dynamics》2004,23(3-4):243-258
We analyze simulations of the global climate performed at a range of spatial resolutions to assess the effects of horizontal spatial resolution on the ability to simulate precipitation in the continental United States. The model investigated is the CCM3 general circulation model. We also preliminarily assess the effect of replacing cloud and convective parameterizations in a coarse-resolution (T42) model with an embedded cloud-system resolving model (CSRM). We examine both spatial patterns of seasonal-mean precipitation and daily time scale temporal variability of precipitation in the continental United States. For DJF and SON, high-resolution simulations produce spatial patterns of seasonal-mean precipitation that agree more closely with observed precipitation patterns than do results from the same model (CCM3) at coarse resolution. However, in JJA and MAM, there is little improvement in spatial patterns of seasonal-mean precipitation with increasing resolution, particularly in the southeast USA. This is because of the dominance of convective (i.e., parameterized) precipitation in these two seasons. We further find that higher-resolution simulations have more realistic daily precipitation statistics. In particular, the well-known tendency at coarse resolution to have too many days with weak precipitation and not enough intense precipitation is partially eliminated in higher-resolution simulations. However, even at the highest resolution examined here (T239), the simulated intensity of the mean and of high-percentile daily precipitation amounts is too low. This is especially true in the southeast USA, where the most extreme events occur. A new GCM, in which a cloud-resolving model (CSRM) is embedded in each grid cell and replaces convective and stratiform cloud parameterizations, solves this problem, and actually produces too much precipitation in the form of extreme events. However, in contrast to high-resolution versions of CCM3, this model produces little improvement in spatial patterns of seasonal-mean precipitation compared to models at the same resolution using traditional parameterizations. 相似文献
3.
Impact of Horizontal Resolution and Cumulus Parameterization Scheme on the Simulation of Heavy Rainfall Events over the Korean Peninsula 总被引：1，自引：0，他引：1
In this paper, we present the results from high-resolution numerical simulations of three heavy rainfall events over the Korean Peninsula. The numerical results show that the prediction accuracy for heavy rainfall events improved as horizontal resolution increased. The fine-grid precipitation fields were much closer to the real precipitation fields in the case of large synoptic forcing over the Korean Peninsula. In the case of large convective available potential energy and weak synoptic forcing, it seems that even when using a high resolution, the models still showed poor performance in reproducing the observed high precipitation amounts. However, activation of the cumulus parameterization scheme in the intermediate resolution of 9 km, even at a grid spacing of 3 km, had a positive impact on the simulation of the heavy rainfall event. 相似文献
4.
5.
The fifth-generation Pennsylvania State University/NCAR Mesoscale Model Version 3 (MM5V3) was used to simulate extreme heavy rainfall events over the Yangtze River Basin in June 1999. The effects of model's horizontal and vertical resolution on the extreme climate events were investigated in detail. In principle, the model was able to characterize the spatial distribution of monthly heavy precipitation. The results indicated that the increase in horizontal resolution could reduce the bias of the modeled heavy rain and reasonably simulate the change of daily precipitation during the study period. A finer vertical resolution led to obviously improve rainfall simulations with smaller biases, and hence, better resolve heavy rainfall events. The increase in both horizontal and vertical resolution could produce better predictions of heavy rainfall events. Not only the rainfall simulation altered in the cases of different horizontal and vertical grid spacing, but also other meteorological fields demonstrated diverse variations in terms of resolution change in the model. An evident improvement in the simulated sea level pressure resulted from the increase of horizontal resolution, but the simulation was insensitive to vertical grid spacing. The increase in vertical resolution could enhance the simulation of surface temperature as well as atmospheric circulation at low levels, while the simulation of circulation at middle and upper levels were found to be much less dependent on changing resolution. In addition, cumulus parameterization schemes showed high sensitivity to horizontal resolution. Different convective schemes exhibited large discrepancies in rainfall simulations with regards to changing resolution. The percentage of convective precipitation in the Grell scheme increased with increasing horizontal resolution. In contrast, the Kain-Fritsch scheme caused a reduced ratio of convective precipitation to total rainfall accumulations corresponding to increasing horizontal resolution. 相似文献
6.
区域和全球模式的嵌套技术
及其长期积分试验 总被引：7，自引：0，他引：7
将区域模式嵌入澳大利亚CSIRO (Commonwealth Scientific and Industrial Research Organization）的全球模式中,并将其应用于区域模式的长期气候积分试验。模拟结果表明,当区域与全球模式嵌套时,边界吸收问题十分重要,由区域模式得到的高分辨率大尺度环流形式在边界上必须与全球模式提供的强迫一致,同时区域模式必须给出基于模式内部物理过程产生的高分辨信息。因此,在嵌套过程中,必须仔细考虑缓冲区的设置,使大尺度强迫与中尺度特征充分混合,既保持区域模式内外的一致性,又使区域内部中尺度强迫物理过程得到充分发展。将区域模式与澳大利亚CSIRO的9层21波三角形截断谱模式嵌套后,完成了连续3年的区域气候模式积分。模拟结果表明,由于区域模式较好地刻划了区域尺度的地形、下垫面和海岸线分布等的细节特征,模拟的区域气候特征比全球模式有较大的改进,尤其是对季风降水的模拟,区域模式明显改进了全球模式的模拟结果。 相似文献
7.
利用高分辨率的区域气候模式 (RegCM_NCC) 对南海夏季风爆发进行模拟研究。研究表明:该模式对积云对流参数化方案的选择十分敏感, 其中以Kuo积云参数化方案为最好, 可以比较成功地模拟出南海夏季风的爆发时间、爆发前后高、低层风场的剧烈变化以及季风与季风雨带的向北推进。然而该方案对于雨量和副热带高压位置的模拟, 与观测相比尚存在一定的偏差, 主要表现为副热带高压位置模拟偏北、偏东; 南海地区的降水量模拟偏少、降水范围偏小。此外, 采用4种参数化方案 (Kuo, Grell, MFS, Betts-Miller) 集成的结果在某种程度上要优于单个方案的结果, 这种改善主要体现在对南海地区季风爆发后降水的模拟上。 相似文献
8.
通过对1998年南海季风爆发过程中大尺度风场、温度场、厚度场、地面气压场以及视热源与视水汽汇的演变分析研究了对流活动对大尺度场的作用,结果表明:大尺度环流与中尺度对流活动之间可能存在着一种正反馈机制。在季风爆发早期,大尺度背景与中尺度对流活动的关系主要表现为前者为季风爆发以及中尺度对流活动的发生提供有利的天气和动力条件;季风爆发后期持续的大范围中尺度对流活动反过来会对大尺度环流存在明显的反馈作用。由对流活动强烈发展产生的凝结潜热释放在南海北部造成了显著的大气加热,使对流层中上层出现一明显的加热中心,这导致:(1)南海上空经向温度梯度由高层向低层发生反向,形成北高南低的温度梯度,从而使大尺度环流发生季节性改变;(2)相应南海北部地面气压不断加深,形成宽广的季风槽和明显的减压区,促使副热带高压从南海地区最后撤离;(3)随着中低层低压环流的不断发展,对流系统和降水区进一步加强并向南扩展,有利于南海季风在南海中、南部地区爆发和维持;(4)季风槽的加深使其南侧的季风气流与水汽输送进一步加强,促使季风爆发过程达到盛期。 相似文献
9.
利用NCEP再分析资料及台站和格点降水量资料分析了华南季风降水与周边大气环流的关系,并由此建立了反映6月华南降水强度的季风指数,这一季风指数利用菲律宾及其以东与华南850 hPa涡度差定义。华南季风指数具有很好的区域代表性,华南季风指数与亚洲格点日降水量的主要正相关区集中在华南。华南季风指数可以很好地描述华南降水的年际变化和极端年份,季风指数强 (弱) 的年份也是华南降水偏多 (少) 的年份,极端的华南季风指数年份对应极端的华南降水年份。华南季风指数高与低年份对应的华南降水量差值通过了0.01的显著性检验。在年代际尺度上,季风指数强 (弱) 的年代与华南降水偏多 (少) 的年代有很好的对应关系。华南季风指数包含了西南季风、副热带高压以及中高纬度西风槽等各影响系统的信息,可在业务上使用。 相似文献
10.
11.
12.
Pichelli Emanuela Coppola Erika Sobolowski Stefan Ban Nikolina Giorgi Filippo Stocchi Paolo Alias Antoinette Belu&#;i&#; Danijel Berthou Segolene Caillaud Cecile Cardoso Rita M. Chan Steven Christensen Ole B&#;ssing Dobler Andreas de Vries Hylke Goergen Klaus Kendon Elizabeth J. Keuler Klaus Lenderink Geert Lorenz Torge Mishra Aditya N. Panitz Hans-Juergen Sch&#;r Christoph Soares Pedro M. M. Truhetz Heimo Vergara-Temprado Jesus 《Climate Dynamics》2021,56(11):3581-3602
This paper presents the first multi-model ensemble of 10-year, “convection-permitting” kilometer-scale regional climate model (RCM) scenario simulations downscaled from selected CMIP5 GCM projections for historical and end of century time slices. The technique is to first downscale the CMIP5 GCM projections to an intermediate 12–15 km resolution grid using RCMs, and then use these fields to downscale further to the kilometer scale. The aim of the paper is to provide an overview of the representation of the precipitation characteristics and their projected changes over the greater Alpine domain within a Coordinated Regional Climate Downscaling Experiment Flagship Pilot Study and the European Climate Prediction system project, tasked with investigating convective processes at the kilometer scale. An ensemble of 12 simulations performed by different research groups around Europe is analyzed. The simulations are evaluated through comparison with high resolution observations while the complementary ensemble of 12 km resolution driving models is used as a benchmark to evaluate the added value of the convection-permitting ensemble. The results show that the kilometer-scale ensemble is able to improve the representation of fine scale details of mean daily, wet-day/hour frequency, wet-day/hour intensity and heavy precipitation on a seasonal scale, reducing uncertainty over some regions. It also improves the representation of the summer diurnal cycle, showing more realistic onset and peak of convection. The kilometer-scale ensemble refines and enhances the projected patterns of change from the coarser resolution simulations and even modifies the sign of the precipitation intensity change and heavy precipitation over some regions. The convection permitting simulations also show larger changes for all indices over the diurnal cycle, also suggesting a change in the duration of convection over some regions. A larger positive change of frequency of heavy to severe precipitation is found. The results are encouraging towards the use of convection-permitting model ensembles to produce robust assessments of the local impacts of future climate change.
相似文献13.
《Dynamics of Atmospheres and Oceans》2007,43(1-4):30-58
A cloud-resolving model is configured to span the full meridional extent of the tropical atmosphere and have sufficient zonal extent to permit the representation of tropical cloud super-clusters. This is made computationally feasible by the use of anisotropic horizontal grids where one horizontal coordinate direction has over an order of magnitude finer resolution than the other direction. Typically, the meridional direction is chosen to have the coarser resolution (40 km grid spacing) and the zonal direction has enough resolution to ‘permit’ crude convective squall line ascent (1 km grid spacing). The aim was to run in cloud-resolving model (CRM) mode yet still have sufficient meridional resolution and extent to capture the equatorial trapped waves and the Hadley circulation. The large-scale circulation is driven by imposed uniform tropospheric cooling in conjunction with a fixed sea surface temperature distribution. At quasi-equilibrium the flow is characterized by sub-tropical jetstreams, tropical squall line systems that form eastward-propagating super-clusters, tropical depressions and even hurricanes.Two scientific issues are briefly addressed by the simulations: what forces the Hadley circulation and the nature of stratospheric waves appearing in the simulation. It is found that the presence of a meridional sea surface temperature gradient is not sufficient on its own to force a realistic Hadley circulation even though convection communicates the underlying temperature gradient to the atmosphere. It is shown in a simulation that accounts for the observed time and zonal-mean momentum forcing effect of large-scale eddies (originating in middle latitudes) that the heaviest precipitation is concentrated near the equator in association with moisture flux convergence driven by the Trade winds.A spectral analysis of the stratospheric waves found on the equator using the dispersion relation for equatorially-trapped waves provides strong evidence for the existence of a domain-scale Kelvin wave together with eastward and westward propagating inertia-gravity waves. The eastward-propagating stratospheric waves appear to be part of a convectively coupled wave system travelling at about 15 ms−1. 相似文献
14.
High-resolution modelling of the Antarctic surface mass balance, application for the twentieth, twenty first and twenty second centuries 总被引：1，自引：1，他引：0
Cécile Agosta Vincent Favier Gerhard Krinner Hubert Gallée Xavier Fettweis Christophe Genthon 《Climate Dynamics》2013,41(11-12):3247-3260
About 75 % of the Antarctic surface mass gain occurs over areas below 2,000 m asl, which cover 40 % of the grounded ice-sheet. As the topography is complex in many of these regions, surface mass balance modelling is highly dependent on horizontal resolution, and studying the impact of Antarctica on the future rise in sea level requires physical approaches. We have developed a computationally efficient, physical downscaling model for high-resolution (15 km) long-term surface mass balance (SMB) projections. Here, we present results of this model, called SMHiL (surface mass balance high-resolution downscaling), which was forced with the LMDZ4 atmospheric general circulation model to assess Antarctic SMB variability in the twenty first and the twenty second centuries under two different scenarios. The higher resolution of SMHiL better reproduces the geographical patterns of SMB and increase significantly the averaged SMB over the grounded ice-sheet for the end of the twentieth century. A comparison with more than 3200 quality-controlled field data shows that LMDZ4 and SMHiL reproduce the observed values equally well. Nevertheless, field data below 2,000 m asl are too scarce to efficiently show the added value of SMHiL and measuring the SMB in these undocumented areas should be a future scientific priority. Our results suggest that running LMDZ4 at a finer resolution (15 km) may give a future increase in SMB in Antarctica that is about 30 % higher than by using its standard resolution (60 km) due to the higher increase in precipitation in coastal areas at 15 km. However, a part (～15 %) of these discrepancies could be an artefact from SMHiL since it neglects the foehn effect and likely overestimates the precipitation increase. Future changes in the Antarctic SMB at low elevations will result from the competition between higher snow accumulation and runoff. For this reason, developing downscaling models is crucial to represent processes in sufficient detail and correctly model the SMB in coastal areas. 相似文献
15.
次网格对流参数化效果对水平分辨率的敏感生试验 总被引：3，自引：0，他引：3
使用单向嵌套的五层有限域模式进行了次网格对流参数化效果对水平分辨率的敏感性试验.使最细网格覆盖主要降水区,并依次嵌套.设计了四种水平分辨率不同的网格,其水平格距分别为381,190.5,95.25及47.625km.对同一降水个例使用上述各种网格分别作了24小时累计降水量预报(积分48小时)试验.结果表明:(1)总降水量(降水最大值及等面积平均最大值)随网格距的减小而增大.当水平格距减小为50km左右时,便可以很好地预报出一般天气尺度降水的落区及雨量分布;(2)随水平分辨率的提高,次网格对流凝结对总降水的 相似文献
16.
南海夏季风槽的年际变化和影响研究 总被引：7，自引：1，他引：7
南海夏季风槽是南海夏季风的重要组成部分，它的活动不仅对大气环流和气候有明显影响，其本身也具有明显的年际变化特征。首先定义了一个描写南海夏季风槽强度的指数，然后分别对强、弱南海夏季风槽年的例子进行了合成分析。分析结果表明，对应强、弱不同的南海夏季风槽年份，在大气环流背景、对流活动以及海温背景场方面都有很明显的区别，说明南海夏季风槽的异常不是偶然的，有其十分明显的大背景。合成分析的结果还表明，南海夏季风槽的强弱异常不仅对中国夏季降水有重要影响，还会通过遥相关过程影响北半球的其他区域。 相似文献
17.
Assessment of the WRF model in reproducing a flash-flood heavy rainfall event over Korea 总被引：4，自引：0，他引：4
This study examines the ability of the cloud-resolving weather research and forecasting (WRF) model to reproduce the convective cells associated with the flash-flooding heavy rainfall near Seoul, South Korea, on 12 July 2006. A triply nested WRF model with the highest resolution of 3-km horizontal grid spacing was integrated with conventional analysis data. The WRF model simulated the initiation of isolated thunderstorms, and the formation of a convective band, cloud cluster, and squall line at nearly the right time. The corresponding precipitation simulation was also reasonably reproduced in its distribution, although the amount was underestimated. A sensitivity experiment that excludes the orography over the peninsula revealed that orographic forcing over the peninsula is responsible for about 20% increase in precipitation over the heavy rainfall region. It was identified that in addition to the up-lifting local orographic forcing to the west of the mountain range in South Korea, anticyclonic circulation due to the presence of the Gaema Heights in North Korea contribute to the confinement of convective activities in the heavy rainfall region. 相似文献
18.
A cloud-resolving model is configured to span the full meridional extent of the tropical atmosphere and have sufficient zonal extent to permit the representation of tropical cloud super-clusters. This is made computationally feasible by the use of anisotropic horizontal grids where one horizontal coordinate direction has over an order of magnitude finer resolution than the other direction. Typically, the meridional direction is chosen to have the coarser resolution (40 km grid spacing) and the zonal direction has enough resolution to ‘permit’ crude convective squall line ascent (1 km grid spacing). The aim was to run in cloud-resolving model (CRM) mode yet still have sufficient meridional resolution and extent to capture the equatorial trapped waves and the Hadley circulation. The large-scale circulation is driven by imposed uniform tropospheric cooling in conjunction with a fixed sea surface temperature distribution. At quasi-equilibrium the flow is characterized by sub-tropical jetstreams, tropical squall line systems that form eastward-propagating super-clusters, tropical depressions and even hurricanes.Two scientific issues are briefly addressed by the simulations: what forces the Hadley circulation and the nature of stratospheric waves appearing in the simulation. It is found that the presence of a meridional sea surface temperature gradient is not sufficient on its own to force a realistic Hadley circulation even though convection communicates the underlying temperature gradient to the atmosphere. It is shown in a simulation that accounts for the observed time and zonal-mean momentum forcing effect of large-scale eddies (originating in middle latitudes) that the heaviest precipitation is concentrated near the equator in association with moisture flux convergence driven by the Trade winds.A spectral analysis of the stratospheric waves found on the equator using the dispersion relation for equatorially-trapped waves provides strong evidence for the existence of a domain-scale Kelvin wave together with eastward and westward propagating inertia-gravity waves. The eastward-propagating stratospheric waves appear to be part of a convectively coupled wave system travelling at about 15 ms−1. 相似文献
19.
尺度适应(scale-aware)的物理过程是现代数值预报发展的一种趋势,本文针对GRAPES_Meso(Global/Regional Assimilation and Prediction Enhanced System)模式没有考虑物理过程尺度适应的现状,首先在KFeta(Kain-Fritsch Eta)积云对流参数化方案中引进了尺度适应过程,对该方案的对流时间尺度、格点垂直速度以及夹卷率进行了基于尺度适应参数化的改进。为研究尺度适应KFeta方案与原KFeta方案对不同分辨率模式模拟结果的影响,选取了一次华南飑线过程进行数值模拟和影响分析。结果表明:在3 km、5 km、10 km、20 km水平分辨率的GRAPES_Meso模式中,尺度适应KFeta方案相比原方案,对降水强度及落区分布的模拟有一定的正效果,随着模式水平分辨率提高,次网格降水减少、格点降水增多、对流层中低层夹卷略有增强,对原来存在的对流层高层及低层偏冷的偏差有一定的改进,对流活跃区域的上升气流强度、云中水凝物含量更符合真实的天气系统演变。综合来看,改进后的方案更适用于高分辨率数值预报模式,该研究结果可以为尺度适应对流参数化方案的应用及数值模式强降水预报性能的优化提供有益的参考。 相似文献
20.
Squall lines and supercells cause severe weather and huge damages in the territory of Croatia and Hungary. These long living events can be recognised by radar very well, but the problem of early warning, especially successful numerical forecast of these phenomena, has not yet been solved in this region. Two case studies are presented here in which dynamical modelling approach gives promising results: a squall line preceding a cold front and a single supercell generated because of a prefrontal instability. The numerical simulation is performed using the PSU/NCAR meso-scale model MM5, with horizontal resolution of 3 km. Lateral boundary conditions are taken from the ECMWF model. The moist processes are resolved by Reisner mixed-phase explicit moisture scheme and for the radiation scheme a rapid radiative transfer model is applied. The analysis nudging technique is applied for the first two hours of the model run. The results of the simulation are very promising. The MM5 model reconstructed the appearance of the convective phenomena and showed the development of thunderstorm into the supercell phase. The model results give very detailed insight into wind changes showing the rotation of supercells, clearly distinguish warm core of the cell and give rather good precipitation estimate. The successful simulation of convective phenomena by a high-resolution MM5 model showed that even smaller scale conditions are contained in synoptic scale patterns, represented in this case by the ECMWF model. 相似文献