不同积云对流参数化方案对中国东部降水模拟的对比分析

本文将目前国际上气候模式中应用比较广泛的三种积云对流参数化方案引入到P-σRCM9区域气候模式中,并考察了不同积云对流参数化方案对P-σRCM9区域气候模式模拟中国降水性能的影响.分析发现四种积云对流参数化方案(包括原方案)下模拟的积云对流加热率基本上都呈现出单峰特征,且加热峰值出现在对流层中低层.并发现积云对流参数化方案对冬季降水平均场和年际变率模拟的影响较小,而对夏季降水模拟的影响更加重要.同时注意到Kuo方案和Anthes-Kuo方案模拟的冬、夏季降水平均场和年际变率均较其他两个方案更接近观测.     

积云对流参数化对东亚近海热带气旋活动模拟的影响

基于CWRF高分辨率模式的模拟结果,探讨了8种积云对流参数化方案对1986—2015年间东亚近海热带气旋的路径、频数及强度模拟的影响。结果发现:采用Kain-Fritsch方案模拟的热带气旋活动的空间分布与JTWC统计结果最接近。KF方案模拟的热带气旋生成频数(强度)明显高(强)于其他积云对流参数化方案,而BMJ方案模拟的热带气旋生成频数(强度)明显低(弱)于其他积云对流参数化方案。进一步分析发现,采用优化集合积云参数化方案(ECP)模拟热带气旋频数、ACE指数以及PDI指数的年际变化趋势较好,而采用KF积云对流参数化方案对热带气旋空间分布、频数及强度的模拟总体最优。      

RIEMS中积云对流参数化方案对我国降水的影响

利用区域环境集成系统模式RIEMS选择Kuo-anthes(KA)和Grell(GCC)积云对流参数化方案,进行1991年5～8月敏感性试验,重点考察了区域环境集成系统模式中两种积云对流参数化方案对1991年江淮流域持续性暴雨的模拟能力.结果表明:1)对于200 hPa西风急流的位置和强度来说,采用GCC积云对流参数化方案较采用KA对流参数化方案,RIEMS模式模拟的结果更加接近观测;2)不管模式采用哪种参数化方案,RIEMS模式都能模拟出850 hPa上的水汽输送和流场,但模式模拟的水汽输送都比观测强;3)不管是采用GCC方案还是KA方案RIEMS模式基本上能够模拟出平均气温的空间分布,但对于长江以南地区,模式模拟的温度较观测偏低,对长江以北地区模式模拟的温度偏高.而采用GCC方案模式模拟的温度更加接近观测,并且对大部分地区温度偏差在-1.65～1.5℃;4)对于降水来说,采用GCC方案模式能够较好地模拟降水的空间分布特征以及雨带季节性移动,但模拟的雨带较观测的偏北,大约为1～2纬度.尽管GCC积云对流参数化方案在RIEMS模式中模拟中国地区降水更加接近观测,但由于积云对流参数化在不同水平分辨率下影响模式模拟的效果,因此对利用RIEMS模式进行数值模拟应考虑不同水平分辨下积云对流参数化方案的适用范围.     

两种积云对流参数化方案对1998年区域气候季节变化模拟的影响研究

利用区域气候模式RegCM3,选择Kuo-Anthes积云对流参数化方案和基于FC80假设的Grell积云对流参数化方案,对1998年东亚气候分别进行年尺度模拟,模拟结果对比分析表明:在春、夏季转换时期, 两者模拟的降水形势差别较大, 对江淮、中南和华南地区的夏季降水量模拟差别最为明显。对流层上层模式变量和模式大气质量对积云对流参数化方案的选择不敏感, 而对流层中、下层模式变量对积云对流参数化方案比较敏感。不同积云对流参数化方案对8天时间尺度的天气系统模拟差别比较大。在积云对流比较活跃的夏季,不同参数化方案会导致模式大气出现不同的系统性偏差。由于模式在陡峭地形处动力过程计算方案存在缺陷,在高原与盆地的交界处,模式误差会产生明显的突变。     

MM5模式中不同对流参数化方案的数值模拟

MM5模式中有多种积云参数化方案可供选择,不同参数化方案及分辨率对降水预报有很大影响。本文利用4种积云参数化方案(GR,KF,BM,AK)对辽东半岛一次大暴雨过程进行试验,结果表明,不同的参数化方案,对强降水落点及强度的模拟,结果差别较大。模拟较好的是GR方案,最差的是AK方案;4种积云对流参数化方案模拟的海平面气压场差别较大,其中GR方案模拟出造成2005年第5号台风暴雨的高低压系统和中尺度气旋;粗网格采用一定的积云对流参数化后,可在一定程度再现一些中尺度特征;4种方案由于闭合假设不同,模拟的云物理特征存在很大差别,这种差别对各种天气要素的准确预报会产生一定的影响。     

中国夏季不同强度降水模拟对不同积云对流参数化方案的敏感性研究

利用PσRCM9区域气候模式, 分析了中国夏季不同强度降水模拟对不同积云对流参数化方案的敏感性。结果表明, 采用四种积云对流参数化方案, 模式能够模拟出小雨、 大雨和暴雨的雨量百分比和雨日百分比空间分布的一致性特征, 但不能模拟出中雨雨量百分比和雨日百分比空间分布的相似性, 这是由于模式不能模拟中雨雨量百分比的空间分布形式所致。还发现模拟的我国夏季降水以小雨和中雨为主, 四种积云对流参数化方案均低估了中国夏季大雨和暴雨对总降水的贡献, 尤其是在我国西部、 东北和华北地区更明显。不同积云对流参数化方案下模拟的极端强降水阈值的空间分布形式基本与观测一致, 但强度与观测存在较大差异。相比较而言, Grell方案较Kuo、 Anthes-Kuo和Betts-Mille积云对流参数化方案更适合中国东南部地区夏季极端强降水的模拟。     

热带大气季节内振荡数值模拟对积云对流参数化方案的敏感性

利用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(LASG)的大气环流模式(SAMIL-R42L9)研究了热带大气季节内振荡(MJO)的模拟对积云对流参数化方案的敏感性,结果表明两种对流参数化方案——湿对流调整方案(MCA)和Zhang-McFarlane(1995年)方案对MJO的模拟能力有明显的差异。MCA方案较好地模拟出了MJO的基本特征,包括季节内的时间尺度和向东的传播。Zhang-McFarlane(1995年)对流方案模拟的MJO振幅非常弱,而且缺乏连续的传播特征,在MJO的演变过程中弱的低层水汽辐合使MJO难以维持和传播。两种不同的对流参数化方案产生的非绝热加热垂直廓线明显不同,Zhang-McFarlane(1995年)方案产生的非绝热加热强度在对流层各层过于一致,没有明显的最大加热层,而且平均的加热强度太弱,这是该方案难以模拟出合理的MJO的主要原因之一。因此,模式对热带大气季节内振荡的模拟能力很大程度上依赖于所使用的积云对流参数化方案,当积云参数化方案改变时模式模拟的MJO也发生明显变化,而非绝热加热廓线是对流参数化方案影响MJO模拟的一个重要影响因子。3种不同的非绝热加热垂直分布的敏感性试验表明,当最大的加热层位于对流层中低层尤其是对流层中层时,更容易产生出与观测较为接近的季节内的扰动,而当最大加热位于对流层高层时,更易于激发出西传的扰动。     

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...     

Validation for a tropical belt version of WRF: sensitivity tests on radiation and cumulus convection parameterizations

对基本气候态和降水日变化的分析是检验模式模拟性能、理解模式误差来源的重要手段。为了评估出对热带气候模拟效果较好的物理参数化方案组合,本文应用WRF带状区域模式,主要比较了四种积云对流参数化方案:NewTiedtke、Kain-Fritsch、newSAS、Tiedtke,和两种辐射参数化方案:RRTMG和CAM,对热带带状区域的气候模拟结果。研究表明:使用NewTiedtke积云对流参数化方案和RRTMG辐射方案的试验,表现出对气温、降水及降水日变化等综合性最好的模拟性能;NewTiedtke积云对流参数化方案能模拟出较好的降水空间分布和降水日变化位相分布特征;与RRTMG辐射方案相比,CAM辐射方案会使温度模拟偏低,特别是陆地上更明显,这种陆地上的冷偏差可能主要来源于Tmin的模拟偏冷。     

不同云微物理参数化方案对冰雹模拟的影响

在利用WRF模式模拟2015年7月29日内蒙古中部地区一次典型冷涡天气系统影响下的冰雹过程基础上,初步探讨积云(KF、BMJ、GD、G3)和微物理(Lin、WSM6、GM、NT、MYDM7)参数化方案对冰雹模拟结果的影响。液态和固态降水粒子质量浓度时间变化受微物理与积云参数化方案共同影响,水汽、能量以及动力条件主要受积云参数化方案影响。综合考虑不同等级降水的TS评分和呼和浩特市两次对流过程的模拟效果,4种积云参数化方案中,KF表现最优,其次是G3和GD方案,BMJ的模拟效果较差。5种微物理方案中Lin和WSM6模拟效果较好,其中WSM6-KF模拟的降水粒子质量浓度的时间变化、水汽和能量条件以及动力条件的效果最优。     

The Vertical Structures of Atmospheric Temperature Anomalies Associated with El Nio Simulated by the LASG/IAP AGCM： Sensitivity to Convection Schemes

The vertical structures of atmospheric temperature anomalies associated with El Nio are simulated with a spectrum atmospheric general circulation model developed by LASG/IAP (SAMIL). Sensitivity of the model’s response to convection scheme is discussed. Two convection schemes, i.e., the revised Zhang and Macfarlane (RZM) and Tiedtke (TDK) convection schemes, are employed in two sets of AMIP-type (Atmospheric Model Intercomparison Project) SAMIL simulations, respectively. Despite some deficiencies in the up...     

Water Vapor and Cloud Radiative Forcings over the Pacific Ocean Simulated by the LASG/IAP AGCM: Sensitivity to Convection Schemes

Characteristics of the total clear-sky greenhouse effect (GA) and cloud radiative forcings (CRFs), along with the radiative-related water vapor and cloud properties simulated by the Spectral Atmospheric Model developed by LASGIAP (SAMIL) are evaluated. Impacts of the convection scheme on the simulation of CRFs are discussed by using two AMIP (Atmospheric Model Inter-comparison Project) type simulations employing different convection schemes: the new Zhang-McFarlane (NZH) and Tiedtke (TDK) convection schemes. It shows that both the climatological GA and its response to El Nio warming are simulated well, both in terms of spatial pattern and magnitude. The impact of the convection scheme on GA is not significant. The climatological longwave CRF (LWCRF) and its response to El Nio warming are simulated well, but with a prominently weaker magnitude. The simulation of the climatology (response) of LWCRF in the NZH (TDK) run is slightly more realistic than in the TDK (NZH) simulation, indicating significant impacts of the convection scheme. The shortwave CRF (SWCRF) shows large biases in both spatial pattern and magnitude, and the results from the TDK run are better than those from the NZH run. A spuriously excessive negative climatological SWCRF over the southeastern Pacific and an insufficient response of SWCRF to El Nio warming over the tropical Pacific are seen in the NZH run. These two biases are alleviated in the TDK run, since it produces vigorous convection, which is related to the low threshold for convection to take place. Also, impacts of the convection scheme on the cloud profile are discussed.     

Spring Arctic Oscillation-East Asian summer monsoon connection through circulation changes over the western North Pacific

In the present study the links between spring Arctic Oscillation (AO) and East Asian summer monsoon (EASM) was investigated with focus on the importance of the North Pacific atmospheric circulation and sea surface temperature (SST). To reduce the statistical uncertainty, we analyzed high-pass filtered data with the inter-annual time scales, and excluded the El Ni?o/Southern Oscillation signals in the climate fields using a linear fitting method. The significant relationship between spring AO and EASM are supported by the changes of multi-monsoon components, including monsoon indices, precipitation, and three-dimensional atmospheric circulations. Following a stronger positive spring AO, an anomalous cyclonic circulation at 850?hPa appears in southeastern Asia and the western North Pacific in summer, with the easterly anomalies spanning from the Pacific to Asian continent along 25°N?C30°N and the westerly anomalies south of 15°N. At the same time, the summer western North Pacific subtropical high becomes weaker. Consistently, the positive precipitation anomalies are developed over a broad region south of 30°N stretching from southern China to the western Pacific and the negative precipitation anomalies appear in the lower valley of the Yangtze River and southern Japan. The anomalous cyclone in the western North Pacific persisting from spring to summer plays a key role in modulating EASM and monsoon precipitation by a positive air-sea feedback mechanism. During spring the AO-associated atmospheric circulation change produces warmer SSTs between 150°E?C180° near the equator. The anomalous sensible and latent heating, in turn, intensifies the cyclone through a Gill-type response of the atmosphere. Through this positive feedback, the tropical atmosphere and SST patterns sustain their strength from spring to summer, that consequently modifies the monsoon trough and the western North Pacific subtropical high and eventually the EASM precipitation. Moreover, the SST response to AO-circulation is supported by the numerical simulations of an ocean model, and the anomalous atmospheric circulation over the western North Pacific is also reproduced by the dedicated numerical simulations using the coupled atmosphere?Cocean model. The observation evidence and numerical simulations suggest the spring AO can impact the EASM via triggering tropical air-sea feedback over the western North Pacific.     

Identifying Global Monsoon Troughs and Global Atmospheric Centers of Action on a Pentad Scale

Using two datasets of global pentad grid precipitation and global 850 hPa geopotential height during 1979-2007, this study identified global monsoon troughs and global atmospheric centers of action (ACAs) on a pentad scale. The global monsoon troughs consist of planetary-scale monsoon troughs and peninsula-scale monsoon troughs. Forced by seasonal variations in solar radiation, the inter-tropical convergence zones (ITCZs) represent the planetary-scale monsoon troughs, which are active and shift over the tropical North Pacific, the tropical North Atlantic, and the tropical South Indian oceans. The peninsula-scale monsoon troughs are originated from regional land-sea topography and varied with contrasts in seasonal land-sea surface temperatures and precipitation. During the boreal summer, five peninsula-scale troughs and one planetary-scale trough are distributed in the Asia-Northwest Pacific (NWP) region. In total, 22 troughs, nine monsoon troughs, and 19 ACAs in the lower troposphere were identified. Relevant ACAs may be useful in constructing regional monsoon and circulation indices.     

An investigation of QBO signals in the east Asian and Indian monsoon in GCM experiments

Observations have shown that the monsoon is a highly variable phenomenon of the tropical troposphere, which exhibits significant variance in the temporal range of two to three years. The reason for this specific interannual variability has not yet been identified unequivocally. Observational analyses have also shown that EI Niño indices or western Pacific SSTs exhibit some power in the two to three year period range and therefore it was suggested that an ocean-atmosphere interaction could excite and support such a cycle. Similar mechanisms include land-surface-atmosphere interaction as a possible driving mechanism. A rather different explanation could be provided by a forcing mechanism based on the quasi-biennial oscillation of the zonal wind in the lower equatorial stratosphere (QBO). The QBO is a phenomenon driven by equatorial waves with periods of some days which are excited in the troposphere. Provided that the monsoon circulation reacts to the modulation of tropopause conditions as forced by the QBO, this could explain monsoon variability in the quasi-biennial window. The possibility of a QBO-driven monsoon variability is investigated in this study in a number of general circulation model experiments where the QBO is assimilated to externally controlled phase states. These experiments show that the boreal summer monsoon is significantly influenced by the QBO. A QBO westerly phase implies less precipitation in the western Pacific, but more in India, in agreement with observations. The austral summer monsoon is exposed to similar but weaker mechanisms and the precipitation does not change significantly.     

大气环流模式SAMIL模拟的夏季全球加热场和东亚夏季风

各国科学家一直致力于从理论和数值模拟上对季风系统进行全面地研究。本文根据“热力适应”理论, 从分析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的最新版本大气环流谱模式(SAMIL2.4.7) 对全球非绝热加热场的模拟性能出发, 分析并解释了SAMIL对东亚夏季风 (EASM) 子系统的模拟情况。通过与再分析资料Reanalysis-2 ( NCEP/DOE AMIP-II Reanalysis ) 对比分析发现, SAMIL能很好地模拟出夏半球副热带地区加热场的四叶型分布 (LOSECOD), 但模拟的各加热场在强度上存在一定的偏差, 主要表现在感热加热在大陆上普遍偏高, 而潜热加热在印度半岛两侧、西太平洋地区(尤其在南北纬10°) 偏高, 赤道带、中南半岛、中国南海等地区偏弱。而对EASM子系统的分析发现, SAMIL能很好地模拟南亚高压; 较好地模拟西太平洋副热带高压的主体, 但西太平洋 (30°N附近) 潜热偏强使得模拟的副高强度偏强、 西伸脊点过于偏西; 模式也能较好地抓住夏季西风急流的两个中心, 但中纬度潜热、 感热的模拟偏弱造成急流两中心风速均小于Reanalysis-2资料 10 m/s左右。进一步的讨论可知, 造成感热和潜热偏差的主要原因是模式中云参数化方案和积云对流参数化方案的不足, 改进模式中相关的物理参数化方案将是SAMIL后续发展的首要工作。     

The MJO in an AGCM with three different cumulus parameterization schemes

The Madden–Julian oscillation (MJO) is simulated using an AGCM with three different cumulus parameterization schemes: a moist convective adjustment (MCA) scheme, the Zhang–McFarlane (ZM) mass-flux scheme, and the Tiedtke scheme. Results show that the simulated MJO is highly dependent on the cumulus parameterization used. Among the three cumulus parameterizations, only the MCA scheme produces MJO features similar to observations, including the reasonable spatial distribution, intraseasonal time scales and eastward propagation. Meanwhile, the amplitude is too large and the eastward propagation speed too fast than observations and the relationship between precipitation and low-level wind anomaly is unrealistic with enhanced convection occurring within easterly anomalies instead of westerly anomalies as in observations. The over-dependence of precipitation on boundary convergence produced by the MCA scheme is presumably responsible for this unrealistic phase relation in the simulation. The other two schemes produce very poor simulations of the MJO: spectral power of westward propagation is larger than that of eastward propagation in zonal wind and precipitation, indicating a westward propagation of the intraseasonal variability.The mean state and vertical profile of diabatic heating are perhaps responsible for the differences in these simulations. The MCA scheme produces relatively realistic climate background. When either ZM or Tiedtke scheme is used, the observed extension of westerly winds from the western Pacific to the dateline is missing and precipitation over the equatorial region and SPCZ is dramatically underestimated. In addition, diabatic heating produced by both ZM and Tiedtke schemes are very weak and nearly uniform with height. The heating profile produced by the MCA scheme has a middle-heavy structure with much larger magnitude than those produced by the other two schemes. In addition, a very unrealistic boundary layer heating maximum produced by the MCA scheme induces too strong surface convergence, which perhaps contributes to the too strong intraseasonal variability in the simulation.     

亚澳季风异常与ENSO准四年变化的联系分析

分析了赤道地区纬向风的年际变化特征，以及亚澳季风与ENSO在各个位相的联系。结果表明：赤道纬向风变化与中东太平洋海温变化在准四年周期上是强烈耦合的；在El Eino期间东亚冬季风弱，夏季风强，而南亚夏季风弱，反之，在La Nina期间东亚冬季风强，夏季风弱，而南亚夏季风强；东亚地区的异常北风有利于西太平洋西风异常爆发，使得东太平洋海温升高，但只有随后在中东太平洋出现持续性西风异常，El Nino才能发展，其中来自太平洋中部的异常北风（并不是来自东亚大陆地区）和南太平洋中部的异常南风的辐合对中东太平洋出现持续性西风异常起重要的作用，尤其是澳大利亚东北部的季风异常的影响更为显。     

The Annual Modes of Tropical Precipitation Simulated by the LASG/IAP Coupled Ocean-Atmosphere Model FGOALS_s1.1

This paper evaluates the performance of a coupled general circulation model FGOALS_s1.1 developed by LASG/IAP in simulating the annual modes of tropical precipitation.To understand the impacts of air-sea coupling on the annual modes,the result of an off-line simulation of the atmospheric component of FGOALS_s1.1,i.e.,LASG/IAP atmospheric general circulation model SAMIL,is also analyzed.FGOALS_s1.1 can reasonably reproduce major characteristics of the annual mean precipitation.Nonetheless,the coupled model shows overestimation of precipitation over the equatorial Pacific and tropical South Pacific,and underestimation of precipitation over the northern equatorial Pacific.The monsoon mode simulated by FGOALS_s1.1 shows an equatorial anti-symmetric structure,which is consistent with the observation.The bias of the coupled model in simulating monsoon mode resembles that of SAMIL,especially over the subtropics.The main deficiency of FGOALS_s1.1 is its failure in simulating the spring-fall asymmetric mode.This is attributed to the false phase of sea surface temperature anomaly (SSTA) annual cycleover the equatorial central-castern Pacific and Indian Ocean,which leads to the bias of the Walker circulation over the equatorial Pacific and the anti-Walker circulation over the Indian Ocean in boreal spring and fall.In addition,the domains of the western North Pacific monsoon and Indian monsoon simulated by the coupled model are smaller than the observation.The study suggests that the bias of the fully coupled oceanatmosphere model can only be partly attributed to the bias of the atmospheric component.The performance of FGOALS-s1.1 in simulating the annual cycle of equatorial SST deserves further improvement.     

Boreal summer continental monsoon rainfall and hydroclimate anomalies associated with the Asian-Pacific Oscillation

With the twentieth century analysis data (1901–2002) for atmospheric circulation, precipitation, Palmer drought severity index, and sea surface temperature (SST), we show that the Asian-Pacific Oscillation (APO) during boreal summer is a major mode of the earth climate variation linking to global atmospheric circulation and hydroclimate anomalies, especially the Northern Hemisphere (NH) summer land monsoon. Associated with a positive APO phase are the warm troposphere over the Eurasian land and the relatively cool troposphere over the North Pacific, the North Atlantic, and the Indian Ocean. Such an amplified land–ocean thermal contrast between the Eurasian land and its adjacent oceans signifies a stronger than normal NH summer monsoon, with the strengthened southerly or southwesterly monsoon prevailing over tropical Africa, South Asia, and East Asia. A positive APO implies an enhanced summer monsoon rainfall over all major NH land monsoon regions: West Africa, South Asia, East Asia, and Mexico. Thus, APO is a sensible measure of the NH land monsoon rainfall intensity. Meanwhile, reduced precipitation appears over the arid and semiarid regions of northern Africa, the Middle East, and West Asia, manifesting the monsoon-desert coupling. On the other hand, surrounded by the cool troposphere over the North Pacific and North Atlantic, the extratropical North America has weakened low-level continental low and upper-level ridge, hence a deficient summer rainfall. Corresponding to a high APO index, the African and South Asian monsoon regions are wet and cool, the East Asian monsoon region is wet and hot, and the extratropical North America is dry and hot. Wet and dry climates correspond to wet and dry soil conditions, respectively. The APO is also associated with significant variations of SST in the entire Pacific and the extratropical North Atlantic during boreal summer, which resembles the Interdecadal Pacific Oscillation in SST. Of note is that the Pacific SST anomalies are not present throughout the year, rather, mainly occur in late spring, peak at late summer, and are nearly absent during boreal winter. The season-dependent APO–SST relationship and the origin of the APO remain elusive.