Ensemble data assimilation in a simple coupled climate model: The role of ocean-atmosphere interaction     

刘征宇  武术  张绍晴  刘赟  容新尧 《大气科学进展》2013,30(5):1235-1248

A conceptual coupled ocean-atmosphere model was used to study coupled ensemble data assimilation schemes with a focus on the role of ocean-atmosphere interaction in the assimilation. The optimal scheme was the fully coupled data assimilation scheme that employs the coupled covariance matrix and assimilates observations in both the atmosphere and ocean. The assimilation of synoptic atmospheric variability that captures the temporal fluctuation of the weather noise was found to be critical for the estimation of not only the atmospheric, but also oceanic states. The synoptic atmosphere observation was especially important in the mid-latitude system, where oceanic variability is driven by weather noise. The assimilation of synoptic atmospheric variability in the coupled model improved the atmospheric variability in the analysis and the subsequent forecasts, reducing error in the surface forcing and, in turn, in the ocean state. Atmospheric observation was able to further improve the oceanic state estimation directly through the coupled covariance between the atmosphere and ocean states. Relative to the mid-latitude system, the tropical system was influenced more by ocean-atmosphere interaction and, thus, the assimilation of oceanic observation becomes more important for the estimation of the ocean and atmosphere.  相似文献   

Central Scandinavian winter precipitation variability during the past five centuries reconstructed from Pinus sylvestris tree rings     

HANS W. LINDERHOLM  DELIANG CHEN 《Boreas: An International Journal of Quaternary Research》2005,34(1):43-52

Using Scots pine ( Pinus sylvestris L.) tree-ring data, winter (September-April) precipitation variability in west central Scandinavia was reconstructed for the past five centuries. The main growth-limiting factor for pine growing in the studied area is summer temperature, but there is an additional influence of precipitation. Using principal components analysis on three tree-ring-width chronologies, a time series was yielded that contained information on winter precipitation (P_w). Using tree rings, only a small part (20%) of the interannual P_w variability could be explained. However, better agreement between the modelled and measured P_w data on semi-decadal time scales (45% variance explained) suggests that tree-ring data from the west-central part of Scandinavia contain useful information on those time scales. The driest winters, disregarding the absolute beginning of the record, were found at the beginning of the 18th century; the last half of the 20th century seems to be the wettest, at least for the past 400 years. Since our precipitation reconstruction agrees fairly well with previously published precipitation proxies, it is suggested that tree rings may add useful information to future multi-proxy reconstructions.  相似文献   

中国降雪气候学特征   总被引：18，自引：1，他引：17  

刘玉莲  任国玉  于宏敏 《地理科学》2012,(10):1176-1185

利用逐日地面降雪观测资料,分析中国25oN以北范围内降雪量、降雪日数、雪带分布和各强度降雪的气候学特征,得到以下结论:①雪季长度与年降雪日数在东部呈纬向分布,大兴安岭北部最长(>210 d),长江以南最短(常年无雪或偶尔降雪);在西部青海省南部和西藏自治区北部最长(>300 d),滇、川、藏交界处及新疆自治区北部较长,南疆较短(<60 d)。年降雪量东南部最少,东北和西北北部较多(>30 mm),青海和西藏降雪量最多(>60 mm)。平均降雪强度江淮一带最大。②根据雪季降雪频次划分中国的雪带,东北大部、内蒙自治区东部、新疆北部、青藏高原大部、秦岭等地区为常年多雪带;长江以南的滇南、四川盆地、江浙沿海等地区为永久无雪带;其余地区为常年降雪带和偶尔降雪带。③不同区域各级降雪日数占总降雪日数的比例都是暴雪日数最少,大雪日数其次,小雪日数最多;但中雪降雪量占总降雪量的比例在东北北部、华北、西北、新疆、东南、青藏高原东部等区域仅高于小雪降雪量,而在黄-淮地区仅次于暴雪降雪量。④降雪年内分配在东北北部、西北、新疆、青藏高原东部等地区都呈双峰型,最多雪时节在早冬和晚冬、早春,隆冬时节并不是降雪最多时间,黄-淮和东南地区呈单峰型,东南地区峰值更陡。⑤总降雪日数和除暴雪外的各等级降雪日数与地理位置关系较明显,在中国东部主要随着纬度升高增加,在中国西部随海拔高度增加而增加;随着纬度升高,东部和西部的总降雪强度都减小,西部的小雪强度也减小。  相似文献   

夏季西太平洋副热带高压的不同类型与中国汛期大尺度旱涝的分布   总被引：8，自引：2，他引：6  

赵俊虎  封国林  杨杰  支蓉  王启光 《气象学报》2012,70(5):1021-1031

利用历史数据,研究了西太平洋副热带高压指数的特征,证实脊线指数和西伸脊点指数可以较好地描述西太平洋副热带高压,同时也指出这两个指数的年际和年代际变化及其不同的配置,是造成中国夏季降水时空分布和旱涝异常的复杂性、多变性的主要原因之一。据此,将西太平洋副热带高压西伸脊点指数和脊线指数的距平投影到二维平面上,对西太平洋副热带高压进行了分类,并对其各种类型下中国夏季降水进行了合成分析,发现夏季西太平洋副热带高压西伸脊点和脊线不同配置下中国夏季降水的总体分布具有明显的规律性:在西太平洋副热带高压脊线偏北的情况下,夏季降水总体表现出南北两条雨带;在西太平洋副热带高压脊线正常的情况下,夏季降水总体表现为北多南少,长江以北降水偏多;在西太平洋副热带高压脊线偏南的情况下,夏季降水总体表现为南多北少,长江流域及其以南地区降水偏多;上述3种情况下西伸脊点越偏西,降水范围越大。此外,通过计算1951—2010年各年夏季降水实况与其西太平洋副热带高压所属年份夏季降水合成的距平相关系数,发现同一类型下各年夏季降水与其合成分布总体相似,说明了西太平洋副热带高压位置对中国降水具有明显的影响,同时也说明此种分类具有一定的合理性。最后,通过对9种西太平洋副热带高压类型下北半球夏季500hPa高度场和850hPa风场距平分别进行合成,对不同西太平洋副热带高压类型下中国夏季降水的大尺度环流背景和可能机理进行了分析。  相似文献   

山西沙尘天气的相关气候因子分析及预测模型的建立     

刘瑞兰  任国玉  吴占华 《干旱气象》2009,27(2):111-117

对山西沙尘天气与蒙古国的降水、我国北方积雪日数、青藏高原积雪日数和表征气候异常变化信号的大气-海洋环流因子SOI指数的关系进行了分析,揭示了全球准周期性变化对沙尘天气趋势的主导性作用.得出蒙古国西部前一年降水对山西省的沙尘天气具有较好的指示性;青藏高原前一年冬季积雪日数和山西省的年沙尘日数呈较好的负相关性;当前冬青藏高原积雪日数多时,山西省少沙尘,反之,多沙尘.就我国北方特别是山西省上游地区的积雪日数而言,指示性比较强的区域分布在内蒙古、甘肃、新疆.这些区域内某些站点前一年冬季的平均积雪日数多时,山西省少沙尘,反之,多沙尘.此外,山西沙尘还与SOI指数有显著的滞后2 a的正响应关系,与SOI有滞后两年正相关的站点主要分布在中东部和东北部.在要素相关分析的基础上,综合各类因子制作了山西省沙尘预测模型,以期为沙尘天气的短期预测工作提供一些参考依据.  相似文献   

SF6气体的辐射强迫和全球增温潜能的研究   总被引：1，自引：0，他引：1  

吴金秀  肖稳安  张华 《大气科学》2009,33(4):825-834

IPCC(2007)指出, 六氟化硫(SF6) 作为臭氧消耗物质 (ODSs) 的部分替代物质, 近年来排放量大大增加。它作为控制排放的人造长寿命温室气体之一已经被列入《京都议定书》。但是, 目前在臭氧消耗物质替代品中, 对SF6的辐射强迫和全球增温潜能的研究较少, 而且所用的谱吸收资料陈旧。本文采用最新的分子吸收数据库HITRAN2004中的SF6的吸收截面数据, 利用Shi(1981) 的吸收系数重排法, 建立了SF6的相关k分布的辐射计算方案, 在此基础上研究了SF6在晴空大气下的辐射效率和全球增温潜能, 并首次计算了SF6的全球温变潜能, 与其全球增温潜能进行了比较。本文的研究表明: SF6的辐射效率为0.512 W/m2, 经过大气寿命调整之后的辐射效率为0.506 W/m2, 二者差别不大; 根据IPCC (2007) 给出的排放情景, 到2100年, SF6在大气中的体积分数将达到35×10-12～70×10-12, 引起的相应辐射强迫将在0.004～0.028 W/m2之间变化; 相对于二氧化碳的100年全球增温潜能为2.33×104, 比IPCC(2007)的结果大2.2%; 100年的持续排放的全球增温潜能为2.26×104, 与其他长寿命人造温室气体一道, 其对全球变暖的长期影响不容忽视。  相似文献   

Simulations of the Tropical Intraseasonal Oscillation by the Atmospheric General Circulation Model of the Beijing Climate Center   总被引：1，自引：0，他引：1       下载免费PDF全文

DONG Min  WU Tongwen  WANG Zaizhi  ZHANG Fang 《Acta Meteorologica Sinica》2010,24(5):571-583

The performance of BCC (Beijing Climate Center) AGCM 2.0.1 (Atmospheric General Circulation Model version 2.0.1) in simulating the tropical intraseasonal oscillation (TIO) is examined in this paper.The simulations are validated against observation and compared with the NCAR CAM3 (Community Atmosphere Model version 3) results.The BCC AGCM2.0.1 is developed based on the original BCC AGCM (version 1) and NCAR CAM3.New reference atmosphere and reference pressure are introduced into the model.Therefore,the origi...  相似文献   

GTS的温盐资料在BCC_GODAS中的同化结果分析   总被引：2，自引：0，他引：2       下载免费PDF全文

刘向文  李维京  吴统文  肖贤俊 《应用气象学报》2010,21(5):558-569

分析了从GTS(全球无线通讯系统)获得的2002-2007年海洋温盐观测资料在国家气候中心第2代全球海洋资料同化系统(BCC_GODAS 2.0)中的同化结果。与SODA(简易海洋同化数据)资料的比较表明:GTS中的海洋温盐资料同化对模式温盐场的改进之处主要表现在混合层暖区的范围和中心强度、温跃层中温度槽脊的深度、温跃层附近的温度梯度以及盐度高、低值区的范围和中心强度等方面,同化后全球温盐场的均方根误差得到一定程度的降低。挑选位于不同海区的单点温盐廓线与ARGO(地转海洋学实时观测阵)观测作了进一步比较,结果表明:大多数情况下,同化后温盐廓线的均方根误差得到明显降低,模拟的温盐垂向分布特征也更为准确。与TAO(热带大气海洋观测网)资料的比较也同样表明:同化后的温盐场特征会得到一定程度改善。  相似文献   

Trends in graded precipitation in China from 1961 to 2000   总被引：3，自引：0，他引：3  

符娇兰  钱维宏  林祥 《大气科学进展》2008,25(2):267-278

Daily precipitation rates observed at 576 stations in China from 1961 to 2000 were classified into six grades of intensity, including trace （no amount）, slight （≤ 1 mm d^-1）, small, large, heavy, and very heavy. The last four grades together constitute the so called effective precipitation （〉 1 mm d^-1）. The spatial distribution and temporal trend of the graded precipitation days are examined. A decreasing trend in trace precipitation days is observed for the whole of China, except at several sites in the south of the middle section of the Yangtze River, while a decreasing trend in slight precipitation days only appears in eastern China. The decreasing trend and interannual variability of trace precipitation days is consistent with the warming trend and corresponding temperature variability in China for the same period, indicating a possible role played by increased surface air temperature in cloud formation processes. For the effective precipitation days, a decreasing trend is observed along the Yellow River valley and for the middle reaches of the Yangtze River and Southwest China, while an increasing trend is found for Xinjiang, the eastern Tibetan Plateau, Northeast China and Southeast China. The decreasing trend of effective precipitation days for the middle- lower Yellow River valley and the increasing trend for the lower Yangtze River valley are most likely linked to anomalous monsoon circulation in East China. The most important contributor to the trend in effective precipitation depends upon the region concerned.  相似文献   

Interdecadal change in the connection between Hadley circulation and winter temperature in East Asia   总被引：5，自引：0，他引：5  

周波涛  王会军 《大气科学进展》2008,25(1):24-30

Based on NCEP/NCAR reanalysis data, the interdecadal variability of Hadley circulation （HC） and its association with East Asian temperature in winter are investigated. Results indicate that the Northern Hemisphere winter HC underwent apparent change in the 1970s, with transition occurring around 1976/77. Along with interdecadal variability of HC, its linkage to surface air temperature （SAT） in East Asia also varied decadally, from weak relations to strong relations. Such a change may be related to the interaction between HC and the atmospheric circulation system over the Philippines, which is associated with the East Asian winter monsoon （EAWM）. Before the 1970s, the connection between HC and the anticyclonic circulation around the Philippines was insignificant, but after the late 1970s their linkage entered a strong regime. The intensification of this connection may therefore be responsible for the strong relations between HC and East Asian winter temperatures after the late 1970s.  相似文献