Measuring the social and economic performance of catch share programs: Definition of metrics and application to the U.S. Northeast Region groundfish fishery     

《Marine Policy》2014

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阿勒泰地区冬季降水变化特征分析     

白松竹 《沙漠与绿洲气象(新疆气象)》2014,8(1):17-22

利用阿勒泰地区7个地面气象站1961—2011年51a的降水观测资料,运用线性趋势、变差分析、EOF、Molet小波变换、M—K突变检测、R／S分析法,分析了该地区近50a来冬季降水的时空变化特征。结果表明：近50a来,该地区冬季降水量存在自山区向河谷逐渐减少的分布特征,年际变化幅度由东北向西南逐渐减小;在空间分布上以全地区一致型为主,部分年份还呈现东北一西南差异分布。冬季降水量在196l一1968年处于偏多阶段,1968--1982年为偏少阶段,此后呈增多趋势。该地区降水以18a周期变化为主,20世纪70年代中后期出现8a的短周期,在90年代中期出现5a的短周期振荡。冬季降水量的突变特征并不显著。R／S分析表明该地区冬季降水量的增加趋势在未来仍将持续。  相似文献   

Optimising three-band spectral indices to assess aerial N concentration,N uptake and aboveground biomass of winter wheat remotely in China and Germany     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

Remotely and accurately quantifying the canopy nitrogen status in crops is essential for regional studies of N budgets and N balances. In this study, we optimised three-band spectral algorithms to estimate the N status of winter wheat. This study extends previous work to optimise the band combinations further and identifies the optimised central bands and suitable bandwidths of the three-band nitrogen planar domain index (NPDI) for estimating the aerial N uptake, N concentration and aboveground biomass. Analysis of the influence of bandwidth change on the accuracy of estimating the canopy N status and aboveground biomass indicated that the suitable bandwidths for optimised central bands were 37 nm at 846 nm, 13 nm at 738 nm and 57 nm at 560 nm for assessing the aerial N uptake and were 37 nm at 958 nm, 21 nm at 696 nm and 73 nm at 578 nm for the assessment of the aerial N concentration and were 49 nm at 806 nm, 17 nm at 738 nm and 57 nm at 560 nm for the estimation of aboveground biomass. The optimised three-band NPDI could consistently and stably estimate the aerial N uptake and aboveground biomass of winter wheat in the vegetative stage and the aerial N concentration in the reproductive stage compared to the fixed band combinations. With suitable bandwidths, the broadband NPDI demonstrated excellent performance in estimating the aerial N concentration, N uptake and biomass. We conclude that the band-optimised algorithm represents a promising tool to measure the improved performance of the NPDI in estimating the aerial N uptake and biomass in the vegetative stage and the aerial N concentration in the reproductive stage, which will be useful for designing improved nitrogen diagnosis systems and for enhancing the applications of ground- and satellite-based sensors.  相似文献   

Assessing integration of intensity,polarimetric scattering,interferometric coherence and spatial texture metrics in PALSAR-derived land cover classification     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

Synthetic aperture radar (SAR) is an important alternative to optical remote sensing due to its ability to acquire data regardless of weather conditions and day/night cycle. The Phased Array type L-band SAR (PALSAR) onboard the Advanced Land Observing Satellite (ALOS) provided new opportunities for vegetation and land cover mapping. Most previous studies employing PALSAR investigated the use of one or two feature types (e.g. intensity, coherence); however, little effort has been devoted to assessing the simultaneous integration of multiple types of features. In this study, we bridged this gap by evaluating the potential of using numerous metrics expressing four feature types: intensity, polarimetric scattering, interferometric coherence and spatial texture. Our case study was conducted in Central New York State, USA using multitemporal PALSAR imagery from 2010. The land cover classification implemented an ensemble learning algorithm, namely random forest. Accuracies of each classified map produced from different combinations of features were assessed on a pixel-by-pixel basis using validation data obtained from a stratified random sample. Among the different combinations of feature types evaluated, intensity was the most indispensable because intensity was included in all of the highest accuracy scenarios. However, relative to using only intensity metrics, combining all four feature types increased overall accuracy by 7%. Producer’s and user’s accuracies of the four vegetation classes improved considerably for the best performing combination of features when compared to classifications using only a single feature type.  相似文献   

改善MODIS BRDF产品热点效应的方法研究   总被引：3，自引：3，他引：0  

董亚冬  焦子锑  张虎  李佳悦  焦广平  石涵予 《遥感学报》2014,18(4):804-825

核驱动的Ross Thick-LiSparse Reciprocal(RTLSR)双向反射函数(BRDF)模型已广泛地应用于MODIS等星载传感器的业务化产品处理中。但是,对于多年MODIS二向反射产品历史数据,如何基于RTMLSR模型发展一种简单有效快速的方法,进行热点效应的校正是一个迫切需要解决的问题。本文提出了一种简单有效的方法,不需要对观测数据重新反演,直接在现有MODIS二向反射产品的基础上进行热点校正,方便用户对历史MODIS二向反射产品的使用。该方法应用POLDER-3/BRDF数据库和部分经MODIS业务化算法筛选的反射率数据进行验证,并与RTLSR模型和RTMLSR模型的结果进行比较,结果表明:(1)该方法比现有的MODIS业务化RTLSR算法,对热点反射率有明显改善,拟合相对误差平均降低了10.12%;(2)该方法相对于RTMLSR模型在热点反射率拟合效果上差别不大,相对误差相差2.10%;(3)该方法对热点和冷点归一化的植被指数(NDHD)的估算效果有一定程度的改善,相对于RTLSR模型降低了约4.99%,与RTMLSR模型的相对误差相差1.32%,该方法对直接应用现有MODIS BRDF产品,基于热点方向反射率反演植被结构参数(如植被聚集指数)的精度提高有现实应用价值。  相似文献   

一种解码接收机原始二进制数据的方法     

李萌  ;胡绍林 《全球定位系统》2014,(3):59-61

本文对华迅G PS/BD双模接收机输出的原始二进制数据的格式进行了深入讨论,利用M atlab对其输出的二进制数据的解码并提取出观测值、星历等,该方法可以简捷快速的解码出所需要的观测信息。  相似文献   

低精度INS／GPS组合导航大方位失准角初始对准方案     

吴松羽  王可东 《全球定位系统》2014,(6):1-5

在低精度MEMS-IMU和GPS组合导航中,由于IMU的精度问题,无法通过传统的解析方法实现方位失准角的粗对准,造成了大方位失准角问题,从而导致系统的强非线性。通过变换状态量,用方位失准角的两个三角函数代替方位失准角作为状态量,建立了新的线性系统方程。用改进奇异值分解法对新对准系统进行可观测度分析,完成了车载导航试验,结果表明：本初始对准方案在低精度的组合导航中具有很好的对准精度和对准速度。  相似文献   

CMIP5/AMIP GCM simulations of East Asian summer monsoon   总被引：1，自引：0，他引：1  

FENG Jinming  WEI Ting  DONG Wenjie  WU Qizhong  WANG Yongli 《大气科学进展》2014,31(4):836-850

The East Asian summer monsoon （EASM） is a distinctive component of the Asian climate system and critically influences the economy and society of the region.To understand the ability of AGCMs in capturing the major features of EASM,10 models that participated in Coupled Model Intercomparison Project/Atmospheric Model Intercomparison Project （CMIP5/AMIP）,which used observational SST and sea ice to drive AGCMs during the period 1979-2008,were evaluated by comparing with observations and AMIP Ⅱ simulations.The results indicated that the multi-model ensemble （MME） of CMIP5/AMIP captures the main characteristics of precipitation and monsoon circulation,and shows the best skill in EASM simulation,better than the AMIP Ⅱ MME.As for the Meiyu/Changma/Baiyu rainbelt,the intensity of rainfall is underestimated in all the models.The biases are caused by a weak western Pacific subtropical high （WPSH） and accompanying eastward southwesterly winds in group Ⅰ models,and by a too strong and west-extended WPSH as well as westerly winds in group Ⅱ models.Considerable systematic errors exist in the simulated seasonal migration of rainfall,and the notable northward jumps and rainfall persistence remain a challenge for all the models.However,the CMIP5/AMIP MME is skillful in simulating the western North Pacific monsoon index （WNPMI）.  相似文献   

Western Arctic Cyclones and Equilibrium between the Atmospheric Boundary Layer and the Sea Surface     

R. L. Raddatz  R. J. Galley  B. G. Else  T. N. Papakyriakou  M. G. Asplin  L. M. Candlish 《大气与海洋》2014,52(2):125-141

The data-collection campaign for the 2008 International Polar Year–Circumpolar Flaw Lead System Study saw the Canadian Coast Guard Ship (CCGS) Amundsen, a research icebreaker, overwinter in high-concentration unconsolidated sea ice in Amundsen Gulf. Environmental monitoring continued into the open-water season. During this period, the Amundsen registered five relatively deep mean sea-level pressure minima (less than 100?kPa). Three were selected for further analysis based on season and the nature of the underlying ocean or sea-ice surface: (1) a winter pressure minimum over unconsolidated sea ice, (2) a spring pressure minimum which likely contributed to the break-up of the sea-ice cover on Amundsen Gulf, and (3) a summer pressure minimum over open water. The characteristics of these pressure minima and the impact of their passage on the atmospheric boundary layer and on the sea-ice cover as they crossed Amundsen Gulf were examined. Several features were revealed by the analysis. (1) The winter and summer pressure minima were migratory cyclones accompanied by Arctic frontal waves with characteristics very similar to the polar frontal waves associated with the migratory cyclones found at more southerly latitudes, whereas the spring pressure minimum was attributed to an Arctic frontal trough of low pressure with the cyclonic centre remaining south of the Gulf. (2) The passage of the frontal-wave cyclone in winter and the frontal trough of low pressure in spring disrupted the equilibrium that had been established during more settled periods between the atmospheric boundary layer and the mosaic surface (leads, polynyas, and sea ice); however, equilibrium was quickly re-established. (3) In summer, the thermal structure of the lower atmospheric boundary layer persisted through the passage of the frontal-wave cyclone over the open-water surface. (4) The passage of the frontal-wave cyclone in winter and the frontal trough of low pressure in spring modified the mesoscale sea-icescape.  相似文献   

Impact of vegetation feedback on the mid-Pliocene warm climate     

ZHANG Ran  JIANG Dabang 《大气科学进展》2014,31(6):1407-1416

Studying the vegetation feedback during warm periods of the past can lead to better understanding of those in the future.In this study,we conducted several simulations to analyze vegetation feedback during the mid-Pliocene warm period.The results indicate that the main features of vegetation change in the mid-Pliocene were a northward shift of needleleaf tree,an expansion of broadleaf tree and shrub,and a northward expansion of grass,as compared to the pre-industrial period.The global annual mean warming ratio caused by vegetation feedback was 12.1％,and this warming ratio was much larger in northern middle and high latitudes.The warming caused by vegetation change was directly related to the surface albedo change and was further amplified by snow/sea ice-albedo feedback.  相似文献