我国西南地区秋季降水年际变化的空间差异及其成因

使用1980～2010年全国站点降水资料、ERA-Interim再分析环流资料、哈德莱海表温度资料,运用聚类分析和旋转经验正交函数分解,对西南地区的秋季降水按照其年际变化规律进行分区,进而分析影响各区域降水变化的物理过程和机理。结果表明:西南地区被分为东、西两个区域。西南东、西区域秋季降水的年际变化、显著周期、旱涝异常年份、相关的环流系统都有明显差异。西南东部秋季降水主要与热带海温异常有关,受低纬度环流影响。当赤道东太平洋为暖海温异常,热带印度洋为西正东负的偶极子型海温异常时,分别激发出西北太平洋反气旋和孟加拉反气旋,共同向西南东部输送水汽,造成西南东部降水偏多。西南西部降水在秋季三个月份与不同的环流形势对应:9月降水由中南半岛反气旋输送的暖湿气流决定;10月降水受高原以东反气旋环流和孟加拉湾低槽共同影响;11月降水主要受中高纬环流异常的影响,与斯堪的纳维亚遥相关存在显著负相关。     

ENSO对印度洋偶极子与中国秋季降水关系的影响

利用1950--1999年Hadley中心全球海温资料、NCEP／NCAR再分析资料和中国气象局整编的160站降水资料，通过讨论印度洋偶极子（IOD）独立发生时及IOD与ENSO联合发生时中国秋季降水的差异，研究了ENSO对IOD与中国秋季降水关系的影响。结果表明：仅有IOD发生时，其正位相年使得中国西南地区和黄河流域的秋季降水出现正异常，而当IOD与ENSO伴随出现时，IOD正位相年和E1Nino使得中国西南地区秋季降水正异常区域维持并向东扩展，还使得黄河流域秋季降水转为负异常。此外分析了ENSO改变IOD与中国秋季降水关系的环流成因。     

前期热带太平洋、印度洋海温异常对长江流域及以南地区6月降水的影响

利用NCEP/NCAR提供的1951—2000年全球月平均海表温度距平资料及中国160个测站的月降水资料,采用相关关系分析、合成分析方法,研究了前期热带太平洋、印度洋海温异常对长江流域及以南地区6月降水的影响。结果表明:(1)Nino3指数与印度洋偶极子指数(IODI)有明显的季节变化,且两者同期相关关系随季节不同,以秋季的相关关系最好,相关系数达0.523,并且这时两种指数的强度也较大。作秋季ENSO和印度洋偶极子同时发生年至次年6月的时间序列,发现两事件存在2月左右的位相差,IODI在9—10月达到峰值,Nino3指数在12月达到峰值。说明在相关最好的秋季两事件并不是完全同步的;(2)前期秋季Nino3指数、印度洋偶极子指数及新定义的同时考虑两种指数的一个综合指数—IODN3这3种指数与中国6月降水的相关系数分布有相似特征,主要表现为相关显著区都在长江流域及以南地区。3种指数与降水的相关中,以IODN3与降水相关关系最为显著,显著区范围也最大;(3)前期秋季El Nio和印度洋偶极子正位相同时发生年6月的500 hPa位势高度、垂直速度、水汽输送等异常分布与其前期秋季反位相年6月的异常分布有相反的特征,表明海温异常对长江流域及以南地区降水有重要影响,对应该地区6月降水偏多或偏少;(4)前期秋季El Nio和印度洋偶极子正位相同时发生使菲律宾反气旋加强和维持,形成有利于降水的环流形势。     

印度洋偶极子和华西秋雨的关系

利用统计方法对印度洋偶极子(Indian Ocean Dipole,IOD)与华西秋雨的关系进行分析。结果发现:(1)相对于IOD的季节锁相特征,华西秋雨与印度洋偶极子指数(Indian Ocean Dipole Index,IODI)相关性也呈现相应的变化特征:春、夏季正相关发展、范围扩大;秋季稳定且正相关性较高,与夏季时滞相关较为一致;前期冬季减弱并呈反相关关系。(2)对印度洋偶极子时期异常环流场、水汽场以及射出长波辐射(Outgoing Longwave Radiation,OLR)场特征分析发现,IOD正位相年,500 h Pa高度场距平在冬、春季为负异常,春、秋季西太平洋副热带高压偏强、偏北,且夏季华西区域受中层异常浅槽的西南气流影响,850 h Pa经向风合成在冬、春季以负异常为主,夏、秋季转为正异常,且华西区域秋季为异常气旋性环流控制,赤道印度洋低空东风异常,这些异常环流都利于华西区域降水偏多,并对偶极子的延续起到作用。(3)正位相年,冬、春季华西大部区域为水汽辐散区,夏、秋季四川东北部及黔渝大部为水汽辐合区,水汽输送依靠孟湾西南气流和西太平洋副热带高压外围的偏东气流完成。(4)对应于印度洋海温正(负)异常,秋季华西区域上空的热状况异常分布将使其大气对流增强(减弱)。因此,夏季IOD异常位相为华西秋雨预报提供了一个有用的前期信号,而秋季IOD正位相则对华西秋雨的发生发展起到较好的延续作用。     

热带印度洋-太平洋海温主模态对中国南部秋季降水异常的影响

基于HadISST逐月海温数据,对热带印度洋-太平洋海区海温场主模态及其组合进行了研究。结果表明：三种类型的El Niño事件中,东部型（EP）和对称中部型（CPⅠ）发展年,热带印度洋东部及海洋性大陆降水为负异常,印-太海区Walker环流减弱,赤道印度洋为东风异常,根据Bjerknes反馈,东印度洋海温负异常,易形成正位相印度洋偶极子（Positive Indian Ocean Dipole,PIOD）事件;而非对称中部型（CPⅡ）与印度洋偶极子（Indian Ocean Dipole,IOD）事件无相关性。进一步对印-太海区海温场主模态及其组合与中国南部秋季降水异常的关系进行分析发现,独立EP型、独立CPⅠ型、EP与PIOD组合型及CPⅠ与PIOD组合型四种模态下,在赤道印度洋及热带太平洋暖湿气流的作用下,中国东南部秋季降水呈正异常,其中独立EP型、独立CPⅠ型和CPⅠ与PIOD组合型对中国东南部的局地水汽净输入以自西向东的纬向贡献为主,而EP与PIOD组合型由于西太平洋副热带高压的异常西伸,水汽沿副高西南边缘向北输送进入中国东南部,对中国东南部的局地水汽净输入以经向贡献为主。CPⅡ型El Niño事件发展年,中国南部大部分地区秋季降水异常偏少;独立PIOD事件发展年,中国西南部地区秋季降水表现为正异常,而东南部呈负异常。     

印度洋偶极子对东亚季风区天气气候的影响

利用NCEP/NCAR 40年再分析资料和中国科学院大气物理研究所的IAPAGCM-Ⅱ大气环流模式,分析和模拟了印度洋偶极子对东亚季风区天气气候的影响.结果表明,印度洋偶极子对东亚季风区天气气候,特别是夏季,影响显著.印度洋正偶极子位相期间,东亚地区的西南季风爆发偏晚,强度增强,我国大陆降水增多;而印度洋负偶极子位相期间,东亚地区的西南季风爆发偏早,强度减弱,我国的东南部地区有丰富的降水.     

赤道东太平洋海温异常期间印度洋偶极子对东亚季风区影响的数值模拟

利用中科院大气所的IAP AGCM-Ⅱ大气环流模式，模拟了在存在和没有赤道东太平洋海温异常影响下，印度洋偶极子对东亚季风区天气气候的影响。结果表明：后者东亚地区西南季风的爆发偏晚，南海夏季风增强，此时我国大陆降水偏多；而前者西南季风的爆发将更偏晚，南海夏季风减弱，此时华北降水偏少；赤道东太平洋海温异常和印度洋偶极子有协同作用。     

2018年秋季我国气候异常及成因分析

2018年秋季我国气候异常特征总体表现为：气温呈“东高西低”的分布;东部降水呈“南北多、中间少”的分布,其中内蒙古中东部、东北、江南南部和华南大部地区降水异常偏多,而华北至江南北部降水异常偏少,且江南和西南地区降水出现明显的季节内反向分布转变特征。异常成因分析表明,秋季欧亚中高纬度槽脊活动频繁,冷空气活跃,西太平洋副热带高压较常年同期偏强偏西,脊线季节内南北波动较大,西南水汽输送偏强,导致我国东部降水南北多、中间少。进一步研究表明,海温异常是影响2018年秋季我国气候异常的最主要外强迫因子,季节内El Ni〖AKn~D〗o由中部型向东部型发展,热带印度洋海温偶极子正位相持续,副热带南印度洋偶极子正位相发展。秋季后期El Ni〖AKn~D〗o影响增强,东亚副热带大气环流发生明显的季节内响应。因此,El Ni〖AKn~D〗o和印度洋海温的演变及其对东亚环流的影响,加上欧亚中高纬环流异常的季节内调整,二者共同导致了我国南方地区降水出现明显的东西反向的季节内变化。     

黄河流域秋季降水及环流对ENSO和IOD的响应分析

利用1961-2011年NCEP/NCAR再分析资料和黄河流域54站降水资料,通过讨论印度洋偶极子IOD独立发生时及IOD与ENSO联合发生时黄河流域秋季降水的差异,研究了秋季降水及环流对ENSO和IOD的响应情况.结果表明:1)仅有IOD发生时,其正位相年使得黄河流域的秋季降水相应为正异常.2)当IOD与ENSO伴随出现时,无论IOD是正位相年还是负位相年,只要和El Nino同时发生,黄河流域秋季降水都表现为负异常;和La Ni-na同时发生时,黄河流域秋季降水都表现为正异常.有无ENSO发生,IOD与秋季降水的关系有很大差异.3)欧亚中纬度地区500 hPa高度东高西低距平场形势和850 hPa黄河流域中下游南风距平异常,是黄河流域秋季降水正异常的主要环流成因.4)依据秋季海温与夏季海温相关性,可以把夏季ENSO和IOD异常信号特征作为先兆信号之一来预测秋季降水趋势.     

两类厄尔尼诺事件发展年秋季印度洋海温异常特征对比

基于1951—2010年逐月海气多要素观测资料,对比分析了两类厄尔尼诺事件发展年秋季印度洋的海温异常及大气响应特征,探讨了印度洋偶极子的发生与两类厄尔尼诺事件特征的可能联系。结果表明,两类厄尔尼诺事件的发展年均会出现印度洋偶极子,但出现的概率不同:大多数东部型厄尔尼诺事件都会伴有正位相印度洋偶极子发生;而仅一半的中部型厄尔尼诺事件期间会出现正位相印度洋偶极子的异常海温型,且强度较弱。从印度洋偶极子与两类厄尔尼诺事件的物理联系上看,东部型厄尔尼诺事件期间,印度洋偶极子的发生与其强度联系密切:印度洋偶极子发生在东部型厄尔尼诺事件较强期间,两者通过海洋大陆的异常强下沉运动及大范围负异常降水相联系;东部型厄尔尼诺事件偏弱时并无印度洋偶极子出现,海洋大陆异常下沉运动及负异常降水很弱。然而,中部型厄尔尼诺事件期间印度洋偶极子的发生与其强度并无显著的关系,而与太平洋高海温区的位置存在一定的可能联系:在有印度洋偶极子发生的中部型厄尔尼诺事件发展年秋季,热带太平洋异常高海温区的位置相对偏东,海洋大陆出现显著下沉运动和大范围负异常降水,热带东印度洋为大范围强异常东风控制;但无印度洋偶极子发生的中部型厄尔尼诺事件时,热带太平洋高海温区位置相对偏西,极弱的海洋大陆下沉支对热带印度洋异常海温作用非常有限。     

VARIABILITY OF INTER-ANNUAL RELATIONSHIP BETWEEN INDIAN OCEAN DIPOLE AND HUAXI REGION’S AUTUMN PRECIPITATION

The moving-window correlation analysis was applied to investigate the relationship between autumn Indian Ocean Dipole (IOD) events and the synchronous autumn precipitation in Huaxi region, based on the daily precipitation, sea surface temperature (SST) and atmospheric circulation data from 1960 to 2012. The correlation curves of IOD and the early modulation of Huaxi region’s autumn precipitation indicated a mutational site appeared in the 1970s. During 1960 to 1979, when the IOD was in positive phase in autumn, the circulations changed from a “W” shape to an ”M” shape at 500 hPa in Asia middle-high latitude region. Cold flux got into the Sichuan province with Northwest flow, the positive anomaly of the water vapor flux transported from Western Pacific to Huaxi region strengthened, caused precipitation increase in east Huaxi region. During 1980 to 1999, when the IOD in autumn was positive phase, the atmospheric circulation presented a “W” shape at 500 hPa, the positive anomaly of the water vapor flux transported from Bay of Bengal to Huaxi region strengthened, caused precipitation ascend in west Huaxi region. In summary, the Indian Ocean changed from cold phase to warm phase since the 1970s, caused the instability of the inter-annual relationship between the IOD and the autumn rainfall in Huaxi region.     

全球贸易隐含碳变化及其影响分析

基于最新的GTAP8 (Global Trade Analysis Project）数据库,使用投入产出法,分析了2004年到2007年全球贸易变化下南北集团贸易隐含碳变化及对全球碳排放的影响。结果显示,随着发展中国家进出口规模扩张,全球贸易隐含碳流向的重心逐渐向发展中国家转移。2004年到2007年,发达国家高端设备制造业和服务业出口以及发展中国家资源、能源密集型行业及中低端制造业出口的趋势加强,该过程的生产转移导致全球碳排放增长4.15亿t,占研究时段全球贸易隐含碳增量的63%。未来发展中国家的出口隐含碳比重还将进一步提高。贸易变化带来的南北集团隐含碳流动变化对全球应对气候变化行动的影响日益突出,发达国家对此负有重要责任。     

Retrieval of outgoing longwave radiation from COMS narrowband infrared imagery

Hourly outgoing longwave radiation(OLR) from the geostationary satellite Communication Oceanography Meteorological Satellite(COMS) has been retrieved since June 2010. The COMS OLR retrieval algorithms are based on regression analyses of radiative transfer simulations for spectral functions of COMS infrared channels. This study documents the accuracies of OLRs for future climate applications by making an intercomparison of four OLRs from one single-channel algorithm(OLR12.0using the 12.0 μm channel) and three multiple-channel algorithms(OLR10.8+12.0using the 10.8 and 12.0 μm channels; OLR6.7+10.8using the 6.7 and 10.8 μm channels; and OLR All using the 6.7, 10.8, and 12.0 μm channels). The COMS OLRs from these algorithms were validated with direct measurements of OLR from a broadband radiometer of the Clouds and Earth's Radiant Energy System(CERES) over the full COMS field of view [roughly(50°S–50°N, 70°–170°E)] during April 2011.Validation results show that the root-mean-square errors of COMS OLRs are 5–7 W m-2, which indicates good agreement with CERES OLR over the vast domain. OLR6.7+10.8and OLR All have much smaller errors(～ 6 W m-2) than OLR12.0and OLR10.8+12.0(～ 8 W m-2). Moreover, the small errors of OLR6.7+10.8and OLR All are systematic and can be readily reduced through additional mean bias correction and/or radiance calibration. These results indicate a noteworthy role of the6.7 μm water vapor absorption channel in improving the accuracy of the OLRs. The dependence of the accuracy of COMS OLRs on various surface, atmospheric, and observational conditions is also discussed.     

Information for Authors

AIMS AND SCOPE
Atmospheric and Oceanic Science Letters （AOSL） publishes short research letters on all disciplines of the atmosphere sciences and physical oceanography. Contributions from all over the world are welcome.     

Our Warmest Thanks to AAS Reviewers 2014

正The editorial office of Advances in Atmospheric Sciences(AAS),on behalf of all AAS editors,would like to publicly acknowledge the people listed below who served as reviewers for the journal daring 1 September 2013 to 24 August 2014.We recognize that the time and work of the reviewers is the most important resource in academic publishing.The quality of our journal depends in a crucial way upon the reviewing process and therefore all reviewers'time and efforts taken to sustain the quality of the journal are greatly appreciated.     

Data selection using support vector regression

Geophysical data sets are growing at an ever-increasing rate, requiring computationally efficient data selection(thinning)methods to preserve essential information. Satellites, such as Wind Sat, provide large data sets for assessing the accuracy and computational efficiency of data selection techniques. A new data thinning technique, based on support vector regression(SVR), is developed and tested. To manage large on-line satellite data streams, observations from Wind Sat are formed into subsets by Voronoi tessellation and then each is thinned by SVR(TSVR). Three experiments are performed. The first confirms the viability of TSVR for a relatively small sample, comparing it to several commonly used data thinning methods(random selection, averaging and Barnes filtering), producing a 10% thinning rate(90% data reduction), low mean absolute errors(MAE) and large correlations with the original data. A second experiment, using a larger dataset, shows TSVR retrievals with MAE < 1 m s-1and correlations 0.98. TSVR was an order of magnitude faster than the commonly used thinning methods. A third experiment applies a two-stage pipeline to TSVR, to accommodate online data. The pipeline subsets reconstruct the wind field with the same accuracy as the second experiment, is an order of magnitude faster than the nonpipeline TSVR. Therefore, pipeline TSVR is two orders of magnitude faster than commonly used thinning methods that ingest the entire data set. This study demonstrates that TSVR pipeline thinning is an accurate and computationally efficient alternative to commonly used data selection techniques.     

Temporal vulnerability in hazardscapes: Flood memory-networks and referentiality along the North Carolina Neuse River (USA)

Social models of population vulnerability to disasters increasingly include the notion that vulnerability has a strong temporal component. While this temporality is typically conceptualized as objective (making vulnerability “dynamic,” “multiscalar,” and/or “historical”), it consistently fails to acknowledge that among stakeholders managing hazardscapes temporality is also a social process in which subjective experience of time may play a role in creating situations of population vulnerability. This paper proposes that the temporal situatedness of a population relative to past hazard events and the quality with which stakeholders engage hazard memory-chains combine to significantly influences its vulnerability to natural hazards. It is proposed that this temporal vulnerability is characterized by shared, population level potential for surprise and can be evaluated by exploration of time-series depth and temporal reference points in historical ecological narratives and documents. Based on ethnohistoric research conducted from 2002 to 2006 in flood-prone eastern North Carolina (USA), it is illustrated how temporal vulnerability was relatively higher in the Neuse River watershed located at the City of Kinston than surrounding watersheds. Due to the combination of factors including the damming of the Neuse River in the 1980s, outdated official floodplain maps, relatively unmonitored floodplain development, the stochastic timing of flood events (placing the last major flood more than a generation away), technological optimism, and turnover of floodplain officials and residents, local stakeholders were seriously misinformed about the space-time risks involved both before and after the disaster of Hurricane Floyd (1999) happened. To deal with this inconsistency, the temporal rarity of Hurricane Floyd as a “500-year event” has been motivated and embraced by many in an effort to continue life-as-is. The paper proposes that the concept of temporal vulnerability is further explored and used as key dimension in the vulnerability sciences.     

An assessment of the predictability of the East Asian Subtropical Westerly Jet based on TIGGE data

The predictability of the position, spatial coverage and intensity of the East Asian subtropical westerly jet(EASWJ) in the summers of 2010 to 2012 was examined for ensemble prediction systems(EPSs) from four representative TIGGE centers,including the ECMWF, the NCEP, the CMA, and the JMA. Results showed that each EPS predicted all EASWJ properties well, while the levels of skill of all EPSs declined as the lead time extended. Overall, improvements from the control to the ensemble mean forecasts for predicting the EASWJ were apparent. For the deterministic forecasts of all EPSs, the prediction of the average axis was better than the prediction of the spatial coverage and intensity of the EASWJ. ECMWF performed best, with a lead of approximately 0.5–1 day in predictability over the second-best EPS for all EASWJ properties throughout the forecast range. For probabilistic forecasts, differences in skills among the different EPSs were more evident in the earlier part of the forecast for the EASWJ axis and spatial coverage, while they departed obviously throughout the forecast range for the intensity. ECMWF led JMA by about 0.5–1 day for the EASWJ axis, and by about 1–2 days for the spatial coverage and intensity at almost all lead times. The largest lead of ECMWF over the relatively worse EPSs, such as NCEP and CMA, was approximately 3–4 days for all EASWJ properties. In summary, ECMWF showed the highest level of skill for predicting the EASWJ, followed by JMA.     

汉江流域极端水文事件时空分布特征

利用1960-2012年汉江流域15个气象站点的日降雨资料和3个水文站同时期日径流资料,分析了9个极端降雨指数的空间分布规律,运用广义极值分布（GEV）、Gamma分布两种极值统计模型对各站点的最大1 d降雨、最大3 d降雨极值样本进行拟合,遴选描述降雨极值分布规律最优概率模型,进而推算给定重现期下的降雨设计值,并分析其空间分布规律;选用Gumbel、Clayton和Frank这3种Copula函数建立降雨-洪量极值联合分布模型,优选最合适的Copula函数,由此计算给定重现期下的洪量设计值。结果表明：GEV分布模型能更好地模拟降雨极值序列,不同重现期下的降雨极值在空间上均呈西低东高的特征;3种Copula函数中,Frank Copula函数能更好地拟合降雨-洪量相关关系,由此推求的洪量设计值大于单变量拟合设计值。