不同物理过程参数化方案对梅雨锋暴雨的敏感性试验

以2005年7月上旬江淮流域的一次梅雨锋暴雨为研究对象,选取WRF模式中Lin和Ferrier两个微物理方案和KF、NKF、Betts-Miller-Janjic三个积云参数化方案,经过组合得到6组方案,进行两重网格嵌套模拟,对数值模拟结果进行分析比较。通过分析得出如下结论：6个方案均能模拟出降水雨带的走向、降水中心,其中Ferri-er和NKF方案及Ferrier和Betts-Miller-Janjic方案模拟的降水强度和分布与实况最接近;在模拟降水量时采用微物理方案Ferrier初始阶段效果好,采用微物理方案Lin在后期效果好;当微物理方案相同时,积云对流参数化方案的变化对垂直速度、假相当位温、相对比湿的反映敏感;粗网格采用一定的积云对流参数化后,可一定程度再现α中尺度特征。     

积云对流参数化方案对梅雨锋暴雨过程模拟的影响

利用MM5模式,选用4种积云对流参数化方案对2002年7月长江流域梅雨锋暴雨过程进行数值试验,讨论了同一水平分辨率下不同参数化方案对降水特征、中尺度特征和云物理特征模拟的影响。结果表明:不同方案对强降水中心落区影响不是很大,但对降水强度有较大影响;4种方案次网格尺度和网格尺度降水对总降水贡献不同;GR和KF方案的闭合假设中考虑次网格尺度湿下沉气流,可一定程度再现一些中尺度特征;4种方案模拟的云物理量特征存在很大差别。     

积云对流参数化对一交梅雨锋暴雨过程影响的模拟检验

应用１９８８年版日本谱模式ＪＳＭ,对比分析了Ａｒａｋａｗａ－Ｓｃｋａｗａ－Ｓｃｈｕｂｅｒｔ、Ｋａｉｎ－Ｆｒｉｔｓｃｈ、ＫｕｏＡｎｔｈｅｓ和Ｇａｄｄ－Ｋｅｅｒｓ等几种积云对流参数化方案在梅雨锋暴雨对流系统模拟中的表现。     

积云对流参数化对一次梅雨锋暴雨过程影响的模拟检验

应用1988年版日本谱模式JSM,对比分析了Arakawa-Schubert、Kain-Fritsch、Kuo-Anthes和Gadd-Keers等几种积云对流参数化方案在梅雨锋暴雨对流系统模拟中的表现.对1988年7月中旬日本九州地区一次梅雨暴雨的模拟结果显示,建立在多种积云簇作用平衡基础上、并刻划了积云内上升和下沉气流作用的Arakawa-Schubert方案表现最佳.结果同时显示,在模式积云对流与模式环境场的相互作用过程中,高质量的初始条件和积云对流参数化方案对理想的中尺度数值模拟都是非常必要的.     

公里尺度分辨率WRF模拟梅雨暴雨对积云对流参数化的敏感性试验研究

本文利用中尺度模式WRF V4.0.2(Weather Research and Forecasting Model,Version 4.0.2)对浙江省两次梅雨锋暴雨过程进行数值模拟,分别选用WSM6和Thompson云微物理方案、YSU和MYJ边界层方案、以及11种对流参数化方案进行试验,探究不同积云对流参数化方案对梅雨锋暴雨的1 km高分辨率预报的影响,结果表明：（1）在对各试验的降水预报评估过程中,使用传统点对点方法和邻域法都能客观表现出各试验的预报水平,而邻域检验法能更客观地评估模式对小范围强降水的预报水平。（2）三类积云对流方案（包括：无积云对流方案、传统积云对流方案和尺度自适应积云对流方案）都能较好地模拟出小雨降水的发生情况,但随着降水强度增强至暴雨、大暴雨量级时,尺度自适应的积云对流方案对降水的预报结果有明显改善。（3）在不同微物理和边界层组合方案下,尺度自适应积云对流方案的模拟结果差异更显著,而传统积云对流方案的模拟结果的效果差异不明显。（4）在1～10 km的“灰色区域”范围内,当网格分辨率逐渐提高到1 km时,尺度自适应积云对流方案较传统积云对流方案对模式的预报结...     

数值天气预报业务模式现状与展望

利用WRF V4.1.3模式和ERA5再分析资料,对2020年7月7日发生在华中地区的一次梅雨锋大暴雨天气过程进行了分析和数值模拟试验,探究了不同垂直和水平分辨率组合对降雨模拟效果的影响,在此基础上考察了3 km水平分辨率时,是否采用积云参数化方案对降雨模拟效果的影响,结果表明：各试验模拟的中低层环流形势、雨团特征、雨带分布基本与实况一致,但不同试验之间也存在一定差异;选定3个降水大值区,分析了逐小时降水演变发现,无论是降水峰值出现时间还是峰值强度,各试验的模拟结果与实况均有较大偏差,其中水平分辨率相同和积云参数化方案相同的试验的结果比较接近;TS、ETS、BS和SAL评分显示,3 km试验的模拟结果总体要优于12 km试验,说明提高模式的水平分辨率可改善降水预报效果;在3 km分辨率时,不考虑积云参数化方案明显降低了预报技巧,且对大暴雨预报的降低程度更大,但对于不同阈值的降水预报,积云参数化方案的影响不同;改变垂直分辨率对预报技巧的影响不如改变水平分辨率和是否使用积云参数化方案显著;3 km水平分辨率的模式中采用积云参数化方案能显著提升对降雨强度的预报技巧。

     

一次梅雨锋暴雨过程数值模拟的云微物理参数化敏感性研究

梅雨锋暴雨中的云微物理过程对降水的演变有着重要影响。本文通过WRF模式（3.4.1版本）,针对2018年6月29～30日一次梅雨锋背景下的暴雨过程进行数值模拟,分别采用了Morrison、Thompson和MY云微物理参数化方案进行对比分析,结果发现:（1）三个方案模拟的背景场在天气尺度上,都与ERA5再分析资料一致,能够模拟出有利于强降水发生的环流场。云微物理过程对梅雨期暴雨的局地环流有着显著影响,不同方案存在明显差异,本次过程中,Thompson方案模拟出更强的局地环流系统变率和上升气流。三个方案的模拟降水均有所夸大,小时降水率始终大于观测值。冰相粒子融化或雨滴搜集云滴的高估可能是造成降水模拟值偏强的重要原因之一,总体来看,Morrison方案的模拟效果相对最优。（2）冰相粒子融化、雨滴搜集云滴是雨滴增长的关键源项,蒸发则是其最重要的汇项。总的来说,雨滴对云滴的搜集量大于冰相粒子融化。但上述过程在不同方案中存在空间上的差异,从而使得模拟降水的空间分布存在差异。（3）Thompson方案中,冰相粒子融化量最大,雨滴蒸发项显著大于其它两个方案,在底层表现得最为明显。同时,该方案水汽凝结效应最强,使得雨滴搜集更多云滴。该方案模拟的雨滴最多,降水最强。该方案中凝华的主要产物为雪,且其在与过冷水碰并增长过程中占主导地位,故模拟的雪最多。（4）Morrison方案中,水汽主要凝华为雪和少量霰（冰晶忽略不计）;Thompson方案中水汽基本凝华为雪,其它冰相粒子极少;MY方案中,水汽主要凝华为雪和冰晶,冰晶总量略少于雪,但显著大于其它方案。（5）云滴在凇附过程中的总体贡献大于雨滴。Morrison和MY方案中,霰粒子搜集云滴增长的量均最大。Morrison方案中,其它凇附过程不同程度发挥作用,而MY方案中,其它凇附过程几乎可忽略不计。并且,霰粒子搜集云滴的增长量大于凝华过程产生的雪粒子总量。贝吉龙及凇附效应的差异,是不同方案中冰相粒子分布差异的关键原因之一。     

梅雨锋暴雨数值模拟中地形的作用

通过WRF模式对2003年7月9日至10日梅雨锋暴雨天气过程在有、无地形情况下数值模拟的结果的分析,探讨了地形对梅雨锋暴雨的影响。研究表明:在有地形的模拟中,模拟的结果较好地再现了梅雨锋降水过程、主要影响系统和梅雨锋的结构;而无地形的模拟中,模拟的雨带偏南,强降水范围偏大,降水系统偏南。地形对梅雨锋暴雨的作用是由于地形减弱了北方冷空气的强度。     

模式垂直分辨率对梅雨锋暴雨数值模拟的影响

利用中尺度数值模式MM5(V3),对2003年7月7日~8日发生在武汉地区的一次梅雨锋暴雨过程进行了数值模拟。采用经过简化处理的基于矢量模的双参数最优化处理方法,对模式大气进行了垂直分层。在水平分辨率不变的情况下,数值模式的垂直分层分别采用25层和36层进行了对比模拟试验。模拟结果表明,水平分辨率达到较高的精度后,粗的垂直分辨率会放大模式中地形的作用,造成数值模拟雨带落区的偏差;要得到比较好的模拟结果,需要相应的提高数值模式的垂直分辨率。水平分辨率与垂直分辨率的不协调,会在水平方向上产生虚假的重力波,影响数值模式的模拟结果。     

\"0907\"长江下游梅雨锋暴雨的数值模拟和诊断分析

利用常规观测资料、卫星TBB资料以及客观再分析资料,对2009年7月6—7日(简称\"0907\")的长江下游梅雨锋暴雨过程进行了数值模拟和天气分析,重点研究了中尺度系统的发生发展机制。结果表明:7月6—7日对流层低层,长江下游北侧存在的一次天气尺度低压,其发展和东移,促使锋生加强,低空急流发生。WRF中尺度模式数值模拟结果显示,在次天气尺度低压的南侧不断形成β中尺度和γ中尺度对流系统。对其中一个β中尺度对流系统的分析研究表明:低空中尺度急流和中尺度辐合首先发生。之后中尺度辐散迅速加强。高层强辐散、低空中尺度急流核和中尺度低涡的相互耦合作用使系统不断发展并东移。高层相对干冷空气的侵入促使系统衰减消亡。     

The sensitivity of numerical simulation of the east asian monsoon to different cumulus parameterization schemes

In this paper, a 5-level spectral AGCM is used to examine the sensitivity of simulated East Asian summer monsoon circulation and rainfall to cumulus parameterization schemes. From the simulated results of East Asian monsoon circulations and rainfalls during the summers of 1987 and 1995, it is shown that the Kuo’s convective parameterization scheme is more suitable for the numerical simulation of East Asian summer monsoon rainfall and circulation. This may be due to that the cumulus in the rainfall system is not strong in the East Asian monsoon region. This paper is supported by the National Key Progranmme “96-908”.     

Global and regional coupled climate sensitivity to the parameterization of rainfall interception

A coupled land?Catmosphere model is used to explore the impact of seven commonly used canopy rainfall interception schemes on the simulated climate. Multiple 30-year simulations are conducted for each of the seven methods and results are analyzed in terms of the mean climatology and the probability density functions (PDFs) of key variables based on daily data. Results show that the method used for canopy interception strongly affects how rainfall is partitioned between canopy evaporation and throughfall. However, the impact on total evaporation is much smaller, and the impact on rainfall and air temperature is negligible. Similarly, the PDFs of canopy evaporation and transpiration for six selected regions are strongly affected by the method used for canopy interception, but the impact on total evaporation, temperature and precipitation is negligible. Our results show that the parameterization of rainfall interception is important to the surface hydrometeorology, but the seven interception parameterizations examined here do not cause a statistically significant impact on the climate of the coupled model. We suggest that broad scale climatological differences between coupled climate models are not likely the result of how interception is parameterized. This conclusion is inconsistent with inferences derived from earlier uncoupled simulations, or simulations using very simplified climate models.     

Simulation of monsoon depressions using MM5: sensitivity to cumulus parameterization schemes

Summary The sensitivity of the simulation of the monsoon depressions to the cumulus parameterization schemes used in a numerical model is studied using the Pennsylvania State University – National Center for Atmospheric Research (PSU-NCAR) model MM5 version 3.6.2. Three different cases of monsoon depressions were studied with a two way interacting domains of 45 km and 15 km resolutions. Two different cumulus parameterization schemes namely Grell (GR) and Kain-Fritsch (KF) were used for the sensitivity study. The model was integrated for 48 hours with the initial and boundary conditions of European Center for Medium Range Weather Forecasting Reanalysis (ERA-40) data. The results show that both the schemes are able to simulate the large scale features of the monsoon depressions realistically. However, both the schemes failed to simulate the exact location of the depression after 24- and 48-hour simulation. The rainfall simulations of both the schemes were very different. The model with the GR scheme tends to over predict the rainfall. The KF scheme could simulate the distribution of the rainfall comparable to the observations. The KF scheme could simulate the maximum observed rainfall but due to locational errors of the simulated depression, the location of the maximum rainfall was not exact. It is also seen that the resolution of the model has a positive impact on the rainfall simulation. The GR and KF schemes were able to realistically simulate the apparent heat sources, but the apparent moisture profile simulated with KF scheme was more comparable to the verifying analysis. The root mean square errors of mean sea-level pressure, temperature, zonal wind and meridional wind were smaller for KF simulation compared to the GR simulation. Permanent affiliation: Center for Development of Advanced Computing, Pune University Campus, Ganeshkhind, Pune-411 007, India.     

Simulating the diurnal cycle of rainfall in global climate models: resolution versus parameterization

The effects of horizontal resolution and the treatment of convection on simulation of the diurnal cycle of precipitation during boreal summer are analyzed in several innovative weather and climate model integrations. The simulations include: season-long integrations of the Non-hydrostatic Icosahedral Atmospheric Model (NICAM) with explicit clouds and convection; year-long integrations of the operational Integrated Forecast System (IFS) from the European Centre for Medium-range Weather Forecasts at three resolutions (125, 39 and 16 km); seasonal simulations of the same model at 10 km resolution; and seasonal simulations of the National Center for Atmospheric Research (NCAR) low-resolution climate model with and without an embedded two-dimensional cloud-resolving model in each grid box. NICAM with explicit convection simulates best the phase of the diurnal cycle, as well as many regional features such as rainfall triggered by advancing sea breezes or high topography. However, NICAM greatly overestimates mean rainfall and the magnitude of the diurnal cycle. Introduction of an embedded cloud model within the NCAR model significantly improves global statistics of the seasonal mean and diurnal cycle of rainfall, as well as many regional features. However, errors often remain larger than for the other higher-resolution models. Increasing resolution alone has little impact on the timing of daily rainfall in IFS with parameterized convection, yet the amplitude of the diurnal cycle does improve along with the representation of mean rainfall. Variations during the day in atmospheric prognostic fields appear quite similar among models, suggesting that the distinctive treatments of model physics account for the differences in representing the diurnal cycle of precipitation.     

Simulation of heavy precipitation episode over eastern Peninsular Malaysia using MM5: sensitivity to cumulus parameterization schemes

A comparative study has been conducted to investigate the skill of four convection parameterization schemes, namely the Anthes–Kuo (AK), the Betts–Miller (BM), the Kain–Fritsch (KF), and the Grell (GR) schemes in the numerical simulation of an extreme precipitation episode over eastern Peninsular Malaysia using the Pennsylvania State University—National Center for Atmospheric Research Center (PSU-NCAR) Fifth Generation Mesoscale Model (MM5). The event is a commonly occurring westward propagating tropical depression weather system during a boreal winter resulting from an interaction between a cold surge and the quasi-stationary Borneo vortex. The model setup and other physical parameterizations are identical in all experiments and hence any difference in the simulation performance could be associated with the cumulus parameterization scheme used. From the predicted rainfall and structure of the storm, it is clear that the BM scheme has an edge over the other schemes. The rainfall intensity and spatial distribution were reasonably well simulated compared to observations. The BM scheme was also better in resolving the horizontal and vertical structures of the storm. Most of the rainfall simulated by the BM simulation was of the convective type. The failure of other schemes (AK, GR and KF) in simulating the event may be attributed to the trigger function, closure assumption, and precipitation scheme. On the other hand, the appropriateness of the BM scheme for this episode may not be generalized for other episodes or convective environments.     

The sensitivity of the tropical circulation and Maritime Continent precipitation to climate model resolution

The dependence of the annual mean tropical precipitation on horizontal resolution is investigated in the atmospheric version of the Hadley Centre General Environment Model. Reducing the grid spacing from about 350 km to about 110 km improves the precipitation distribution in most of the tropics. In particular, characteristic dry biases over South and Southeast Asia including the Maritime Continent as well as wet biases over the western tropical oceans are reduced. The annual-mean precipitation bias is reduced by about one third over the Maritime Continent and the neighbouring ocean basins associated with it via the Walker circulation. Sensitivity experiments show that much of the improvement with resolution in the Maritime Continent region is due to the specification of better resolved surface boundary conditions (land fraction, soil and vegetation parameters) at the higher resolution. It is shown that in particular the formulation of the coastal tiling scheme may cause resolution sensitivity of the mean simulated climate. The improvement in the tropical mean precipitation in this region is not primarily associated with the better representation of orography at the higher resolution, nor with changes in the eddy transport of moisture. Sizeable sensitivity to changes in the surface fields may be one of the reasons for the large variation of the mean tropical precipitation distribution seen across climate models.     

On the sensitivity of mesoscale models to surface-layer parameterization constants

The Colorado State University standard mesoscale model is used to evaluate the sensitivity of one-dimensional (1D) and two-dimensional (2D) fields to differences in surface-layer parameterization constants. Such differences reflect the range in the published values of the von Karman constant, Monin-Obukhov stability functions and the temperature roughness length at the surface. The sensitivity of 1D boundary-layer structure, and 2D sea-breeze intensity, is generally less than that found in published comparisons related to turbulence closure schemes generally.     

2003年江淮梅雨期一次特大暴雨的研究——中尺度对流和水汽条件分析

本文对2003年7月4日-5日江淮梅雨期间的一次特大暴雨过程进行了多尺度的详细分析.环流背景、中尺度对流云团和水汽条件分析表明,这次特大暴雨是在典型梅雨的有利环境背景形势下,由梅雨锋上的中尺度对流系统造成的,地面低压、低层切变线及西南低空急流与这次特大暴雨过程有着密切的关系.强降水中心与中尺度对流云团的关系十分密切,中β尺度云团的生成合并增强,和其中中γ降水系统的存在,导致了降水强度的局地性差异.江淮流域主要表现为经向水汽通量的辐合区,强水汽通量舌与低层高θse的舌区一致,暴雨过程中水汽的快速集中主要是通过风场散度项造成的,局地风场的辐合在水汽快速集中起主要作用.低层充沛的水汽则通过气旋性涡度柱中的强上升气流输送到对流层的中高层.     

Sensitivity of the GCM driven summer monsoon simulations to cumulus parameterization schemes in nested RegCM3

The regional climate model (RegCM3) from the Abdus Salam International Centre for Theoretical Physics has been used to simulate the Indian summer monsoon for three different monsoon seasons such as deficit (1987), excess (1988) and normal (1989). Sensitivity to various cumulus parameterization and closure schemes of RegCM3 driven by the National Centre for Medium Range Weather Forecasting global spectral model products has been tested. The model integration of the nested RegCM3 is conducted using 90 and 30-km horizontal resolutions for outer and inner domains, respectively. The India Meteorological Department gridded rainfall (1° × 1°) and National Centre for Environment Prediction (NCEP)–Department of Energy (DOE) reanalysis-2 of 2.5° × 2.5° horizontal resolution data has been used for verification. The RegCM3 forced by NCEP–DOE reanalysis-2 data simulates monsoon seasons of 1987 and 1988 reasonably well, but the monsoon season of 1989 is not represented well in the model simulations. The RegCM3 runs driven by the global model are able to bring out seasonal mean rainfall and circulations well with the use of the Grell and Anthes–Kuo cumulus scheme at 90-km resolution. While the rainfall intensity and distribution is brought out well with the Anthes–Kuo scheme, upper air circulation features are brought out better by the Grell scheme. The simulated rainfall distribution is better with RegCM3 using the MIT-Emanuel cumulus scheme for 30-km resolution. Several statistical analyses, such as correlation coefficient, root mean square error, equitable threat score, confirm that the performance of MIT-Emanuel scheme at 30-km resolution is better in simulating all-India summer monsoon rainfall. The RegCM3 simulated rainfall amount is more and closer to observations than that from the global model. The RegCM3 has corrected its driven GCM in terms of rainfall distribution and magnitude over some parts of India during extreme years. This study brings out several weaknesses of the RegCM model which are documented in this paper.