夏季东亚地区AOD与地面太阳辐射变化的联系及季风环流异常:季节趋势影响   总被引：2，自引：1，他引：1       下载免费PDF全文

孙一  管兆勇  马奋华  夏阳 《大气科学学报》2015,38(2):165-174

利用2000—2013年MODIS-Terra卫星产品提供的气溶胶光学厚度(aerosol optical depth,AOD)资料及NCEP/NCAR再分析资料集,使用奇异值分解(singular value decomposition,SVD)方法,分析了夏季东亚地区AOD与到达地面太阳辐射(downward solar radiation flux,DSRF)相联系的主要模态,并分析了其与夏季风变化的关系。夏季多年平均的AOD分布显示,在东亚地区存在两个AOD大值区(0.9),分别位于山东、河南、河北交界处附近以及苏中部分地区。而在福建、台湾及其附近洋面上,夏季AOD的值小于0.4。地面太阳辐射总体上呈现出由南往北递增的分布。比较发现,AOD与地面太阳辐射的气候分布较为相似。在保留季节趋势的情况下,运用SVD方法对两者进行分解,结果表明东亚地区AOD与地面太阳辐射表现出较好的正相关关系。由于相对于年际变化而言,季节趋势是更为主要的部分,因而这种同相关系可归因于季风活动的季节性进程。利用SVD1左场时间系数进行相关分析发现:6月(2013年除外),当中国东部气溶胶AOD大而地面太阳辐射亦大时,在中国东南部以及日本岛南部地区,由于气流辐合增强和存在较强的上升运动,降水偏多,而由于副高位置偏南,使得中国中东部偏北地区水汽供应偏弱,降水偏少。由于地面净太阳辐射增强,华北部分地区异常增暖。8月,大陆上空AOD为负(时间系数为负),地面太阳辐射减少,北方降水增多而南方降水减少,华北地区有一小范围的异常降温。上述结果表明北方气溶胶明显偏少时,云量增加,降水将增多,且辐射明显减弱;说明夏季风的季节进程对气溶胶、到达地面的太阳辐射变化等具有重要影响。  相似文献   

Modeling of Arctic Sea Ice Variability During 1948–2009: Validation of Two Versions of the Los Alamos Sea Ice Model(CICE)          下载免费PDF全文

WU Shu-Qiang  ZENG Qing-Cun  BI Xun-Qiang 《大气和海洋科学快报》2015,8(4)

The Los Alamos sea ice model(CICE) is used to simulate the Arctic sea ice variability from 1948 to 2009. Two versions of CICE are validated through comparison with Hadley Centre Global Sea Ice and Sea Surface Temperature(Had ISST) observations. Version 5.0 of CICE with elastic-viscous-plastic(EVP) dynamics simulates a September Arctic sea ice concentration(SASIC) trend of –0.619 × 1012 m2 per decade from 1969 to 2009, which is very close to the observed trend(-0.585 × 1012 m2 per decade). Version 4.0 of CICE with EVP dynamics underestimates the SASIC trend(-0.470 × 1012 m2 per decade). Version 5.0 has a higher correlation(0.742) with observation than version 4.0(0.653). Both versions of CICE simulate the seasonal cycle of the Arctic sea ice, but version 5.0 outperforms version 4.0 in both phase and amplitude. The timing of the minimum and maximum sea ice coverage occurs a little earlier(phase advancing) in both versions. Simulations also show that the September Arctic sea ice volume(SASIV) has a faster decreasing trend than SASIC.  相似文献   

西南地区极端降水变化趋势   总被引：7，自引：3，他引：4  

罗玉  范广洲  周定文  华维  李金建 《气象科学》2015,35(5):581-586

利用西南地区90个气象台站1970-2010年逐日降水量资料,依据世界气象组织(WMO)定义的连续5d最大降水量、总降水量、强降水比等6种极端降水指数,采用F检验、11a滑动平均等统计方法,研究了西南地区极端强降水变化趋势的时空变化特征。在时间上,西南地区近41年来冬、春、夏季连续5d最大降水量缓慢波动上升,秋季连续5d最大降水量呈下降趋势;强降水、降水强度及强降水比呈上升趋势,但总降水量和最长持续无降水日数呈减少趋势;另外,各极端降水指数还存在明显的年际、年代际变化。在空间上,西南地区极端降水变化趋势具有显著的地域差异,呈东西或西北东南向梯度变化特征。其中冬季连续5d最大降水量、降水强度、强降水比及最长持续无降水日数,在西南大部分地区呈增加趋势。秋季连续5d最大降水量与总降水量在西南大部分地区呈减少趋势。而春、夏季连续5d最大降水量和强降水的增减区域大致相当。  相似文献   

Cosmological constraints on galaxy cluster structure     

《Astroparticle Physics》2015

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地下水水质评价与预测方法综述     

李扬  窦炳臣  陈振  王学民  原明考 《山东国土资源》2015,31(8)

近年来,地下水水质安全引起了社会广泛的关注,国内外学者开展了大量水质评价与预测研究,本文综合了当前几种广泛应用的水质评价与预测方法,对比了各自的适用性与局限性,展望了今后水质评价与预测发展的趋势,以期为地下水管理、开发利用提供参考依据。  相似文献   

Estimating time-based instantaneous total mortality rate based on the age-structured abundance index   总被引：1，自引：0，他引：1  

王迎宾 《中国海洋湖沼学报》2015,33(3):559-576

The instantaneous total mortality rate(Z) of a fish population is one of the important parameters in fisheries stock assessment. The estimation of Z is crucial to fish population dynamics analysis,abundance and catch forecast,and fisheries management. A catch curve-based method for estimating time-based Z and its change trend from catch per unit effort(CPUE) data of multiple cohorts is developed. Unlike the traditional catch-curve method,the method developed here does not need the assumption of constant Z throughout the time,but the Z values in n continuous years are assumed constant,and then the Z values in different n continuous years are estimated using the age-based CPUE data within these years. The results of the simulation analyses show that the trends of the estimated time-based Z are consistent with the trends of the true Z,and the estimated rates of change from this approach are close to the true change rates(the relative differences between the change rates of the estimated Z and the true Z are smaller than 10%). Variations of both Z and recruitment can affect the estimates of Z value and the trend of Z. The most appropriate value of n can be different given the effects of different factors. Therefore,the appropriate value of n for different fisheries should be determined through a simulation analysis as we demonstrated in this study. Further analyses suggested that selectivity and age estimation are also two factors that can affect the estimated Z values if there is error in either of them,but the estimated change rates of Z are still close to the true change rates. We also applied this approach to the Atlantic cod(G adus morhua) fishery of eastern Newfoundland and Labrador from 1983 to 1997,and obtained reasonable estimates of time-based Z.  相似文献   

Interannual salinity variability of the Northern Yellow Sea Cold Water Mass     

李昂  于非  刁新源 《中国海洋湖沼学报》2015,33(3):779-789

This paper discusses the interannual variability of the Northern Yellow Sea Cold Water Mass(NYSCWM) and the factors that influence it,based on survey data from the 1976–2006 national standard section and the Korea Oceanographic Data Center,monthly E-P flux data from the European Centre for Medium-Range Weather Forecasts,and meridional wind speed data from the International Comprehensive Ocean-Atmosphere Data Set. The results show that:1) the mean salinity of the NYSCWM center has a slightly decreasing trend,which is not consistent with the high salinity center; 2) both the southern salinity front and the halocline of the NYSCWM display a weakening trend,which indicates that the difference between the NYSCWM and coastal water decreases; 3) the Yellow Sea Warm Current intrusion,the E-P flux of the northern Yellow Sea,and the strength of the winter monsoon will affect the NYSCWM salinity during the following summer.  相似文献   

Spatiotemporal variation in the terrestrial vegetation phenology of Iraq and its relation with elevation     

《International Journal of Applied Earth Observation and Geoinformation》2015

Iraq contains the Great Mesopotamian alluvial plain of the Euphrates and Tigris rivers. Its regional vegetation phenological patterns are worthy of investigation because relatively little is known about the phenology of semi-arid environments, and because their inter-annual variation is expected to be driven by uncertain rainfall and varied topography. The aim of this research was to assess and map the spatial variation in key land surface phenology (LSP) parameters over the last decade and their relation with elevation. It is the first study mapping land surface phenology during last decade over the whole of Iraq, and one of only a few studies on vegetation phenology in a semi-arid environment. Time-series of Moderate Resolution Imaging Spectroradiometer (MODIS) normalised difference vegetation index (NDVI) data at 250 m spatial resolution and 8 day temporal resolution, were employed to map the spatial variation in three LSP parameters for the major vegetation types in Iraq during 2001–2012. LSP parameters were defined by inflection points after smoothing the vegetation phenological signals using the Fourier technique. The estimated key LSP parameters indicated that the relatively shorter length of season (LOS) in the north of Iraq resulted from a delayed start of season (SOS). Greater spatial variation occurred in the SOS than end of season (EOS), which may be due to the spatial distribution of rainfall and temperature as a function of elevation. A positive correlation was observed for SOS and EOS with elevation for all major land cover types with EOS producing the largest positive correlation (R² = 0.685, R² = 0.638 and R² = 0.588, p < 0.05 in shrubland, cropland and grassland, respectively). The magnitude of delay in SOS and EOS increased in all land cover types along a rising elevation gradient where for each 500 m increase, SOS was delayed by around 25 or more days and EOS delayed by around 22 or more days, except for grassland. The SOS and EOS also varied temporally during the last decade, particularly the SOS in the lowland, north of the country where the standard deviation was around 80 to 120 days, due mainly to the practice of crop rotation and the traditional biennial cropping system. Thus, the results of this research emphasize the effect of elevation on key LSP parameters over Iraq, for all major vegetation types.  相似文献   

长江源区近44年气候变化的若干统计分析   总被引：11，自引：1，他引：10  

陈芳  马英芳  申红艳  刘秀兰 《气象科技》2007,35(3):340-344

利用长江源区5个气象站44年的气温、降水量资料以及其中2个探空站500hPa露点资料,分析了该地区气候变化趋势、突变等情况。结果表明：近44年来长江源区气温普遍升高,冬季升温幅度较大,夏季增温趋势明显,进入21世纪后,长江源区春季平均气温在降低,夏、秋季平均气温增高较趋缓,而冬季增温加剧的趋势十分明显;年、夏季降水量变化呈微弱减少趋势,而冬、春和秋季降水量呈现出增加趋势,其中春季增幅较大,冬季增湿趋势明显;长江源区年平均气温在20世纪60年代末70年代初就显现出波动回升的趋势,在1986年前后发生了由冷到暖的突变,冬、春季降水量均在20世纪70年代和80年代出现了由少向多的突变。长江源区气候在波动性变暖变干过程中,自1986年起出现了气候转向暖湿的信号,其主要原因在于全球变暖并由此引起的海洋蒸发和陆地蒸散加强,地气水分循环加快,空中水汽输送加强。  相似文献   

Temporal trends of mercury in marine biota of west and northwest Greenland     

Rigét F  Dietz R  Born EW  Sonne C  Hobson KA 《Marine pollution bulletin》2007,54(1):72-80

Temporal trends in mercury concentrations ([Hg]) during the last two to three decades were determined in liver of shorthorn sculpin, ringed seal and Atlantic walrus from northwest Greenland (NWG, 77 degrees N) and in liver of shorthorn sculpin and ringed seal from central west Greenland (CWG, 69 degrees N) during the last decade. Stable-nitrogen (delta(15)N) and carbon (delta(13)C) isotope values were determined in muscle of ringed seals to provide insight into potential trophic level changes through time. Log-linear regressions on annual median [Hg] did not reveal any temporal trend in shorthorn sculpin from CWG and NWG and walrus from NWG. In ringed seals from NWG, an increase in [Hg] of 7.8% per year was observed. When based on delta(15)N-adjusted [Hg] this rate increased to 8.5% but was still non-significant. In ringed seal from CWG no trend was found in [Hg] during the period 1994-2004. However, during the last part of the period (1999-2004) the [Hg] increased significantly. Including tissue delta(15)N values as a covariate had a marked effect on these results. The annual changes in delta(15)N-adjusted [Hg] was estimated to -5.0% for the whole period and 2.2% during the last 5 years compared to -1.3% and 12.4%, respectively, for the non-adjusted [Hg].  相似文献