Modeling of spatial distributions of farmland density and its temporal change using geographically weighted regression model   总被引：1，自引：1，他引：0  

Haitao Zhang  Long Guo  Jiaying Chen  Peihong Fu  Jianli Gu  Guangyu Liao 《中国地理科学(英文版)》2014,24(2):191-204

This study used spatial autoregression（SAR） model and geographically weighted regression（GWR） model to model the spatial patterns of farmland density and its temporal change in Gucheng County,Hubei Province,China in 1999 and 2009,and discussed the difference between global and local spatial autocorrelations in terms of spatial heterogeneity and non-stationarity. Results showed that strong spatial positive correlations existed in the spatial distributions of farmland density,its temporal change and the driving factors,and the coefficients of spatial autocorrelations decreased as the spatial lag distance increased. SAR models revealed the global spatial relations between dependent and independent variables,while the GWR model showed the spatially varying fitting degree and local weighting coefficients of driving factors and farmland indices（i.e.,farmland density and temporal change）. The GWR model has smooth process when constructing the farmland spatial model. The coefficients of GWR model can show the accurate influence degrees of different driving factors on the farmland at different geographical locations. The performance indices of GWR model showed that GWR model produced more accurate simulation results than other models at different times,and the improvement precision of GWR model was obvious. The global and local farmland models used in this study showed different characteristics in the spatial distributions of farmland indices at different scales,which may provide the theoretical basis for farmland protection from the influence of different driving factors.  相似文献   

Evolution and spatial patterns of spheres of urban influence in China   总被引：2，自引：1，他引：1  

Kaiyong Wang  Yu Deng  Daowei Sun  Tao Song 《中国地理科学(英文版)》2014,24(1):126-136

This article presents the findings of a study of the spheres of urban influence with regard to all cities in China（not including Hong Kong,Macau and Taiwan Province of China）in the years 1990,2000 and 2009.An optimized gravity model with comprehensive time distance was used to carry out a detailed analysis of the spatial patterns of Chinese spheres of urban influence and the spatial characteristics of urban agglomerations.Such urban agglomerations are characterized by high density population and a developed economy,which are also considered as the national competition unit.This paper initially identifies four spatial patterns of urban agglomerations based on the spatial layout of city groups during their evolution.Some basic characteristics of urban agglomerations are outlined,including the number of cities,the size of cities and the functions of urban centers.These characteristics are examined by using statistical methods and Geographic Information System（GIS）.The main findings from this research are that the development stages and structures of urban agglomerations in China vary significantly.It is also clear that the stages and evolution of spatial patterns are strongly affected and dominated by both policy and location factors.  相似文献   

秋冬季远距离台风海南岛暴雨特征及概念模型     

郑艳  符式红  赵付竹 《气象研究与应用》2014,(4):11-15

通过对1960-2013年在越南登陆或登陆前停编后海南岛出现暴雨的秋冬季台风历史个例的分析,结果表明：秋冬季台风中有47%是南海台风,台风登陆越南或在登陆前停编时的纬度介于11.3°N-20.6°N之间,其中15.0°N-15.9°N最多（23.5%）,而19.0°N-19.9°N没有满足条件的台风;秋冬季暴雨出现的主要时段为9月下旬-10月下旬,其中10月中旬暴雨日最多（23.8%）;秋冬季暴雨落区集中在海南岛东部、中部和北部内陆地区,琼中县最多（12.7%）,西部沿海地区明显偏少;秋冬季暴雨的主要影响系统是热带低值系统（台风或低压环流）、东路或西路冷空气;低空急流和暴雨落区密切相关,暴雨区一般位于低空急流左前侧和切变线南侧;海南岛东北部暴雨偏东风低空急流位于两广南部;东中部暴雨偏东风低空急流位于两广南部至海南岛北部;西南部暴雨东南东风低空急流位于海南岛北部,同时南海存在西南风低空急流;西北部暴雨两广南部有东北东风低空急流;全岛性暴雨两广南部至南海中部为广阔的偏东风低空急流区。  相似文献   

The effect of the wintertime Arctic Oscillation on springtime vegetation over the northern high latitude region   总被引：1，自引：0，他引：1  

Mee-Hyun Cho  Gyu-Ho Lim  Hyo-Jong Song 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(1):567-573

The winter Arctic Oscillation (AO), a major source of climate variability in the Northern Hemisphere, affects winter and the subsequent spring climate over northern high latitude. Such effects are evident even in the 1st eigenmode of the normalized difference vegetation index (NDVI). The impacts of the winter AO is a dipole pattern between Eurasia and North America; positive (negative) values of the winter AO induce warmer (cooler) and high (low) vegetation activity in the following spring over Eurasia (North America). Regarding the time-lagged response of vegetation, the sea surface temperature (SST) and snow cover contribute to maintaining the large-scale circulation anomaly associated with the AO.  相似文献   

渤海风暴减水特征及其对深水航路影响的数值模拟     

傅赐福  付翔  吴少华  于福江  董剑希 《海洋学报》2014,36(3):30-38

利用环渤海9个沿岸站近10a潮位资料分析渤海海域的风暴减水特征,结果表明:渤海年均出现50cm和100cm风暴减水分别超过30d和6d,每年的9月至翌年4月份风暴减水最为频繁;建立了一套精细化天文潮-风暴潮耦合模型用于渤海深水航路的潮位预报,各站天文潮模拟验证的平均均方根误差为18.5cm,由此计算得到航路代表点的潮汐特征值并作潮汐预报;后报模拟了近10a重大风暴减水过程,模拟与实测吻合较好,说明该耦合模型可为该航路的潮位预报提供有益参考。  相似文献   

覆盖中国沿海地区的精细化台风风暴潮模型的研究及适用   总被引：1，自引：1，他引：0  

刘秋兴  董剑希  于福江  傅赐福  李明杰 《海洋学报》2014,36(11):30-37

精细化风暴潮预报是目前风暴潮预报重点发展方向之一,本文首次建立起了一个覆盖整个中国沿海地区的精细化台风风暴潮数值模型,克服了以往分区域数值模型的不足,该模型在中国沿海地区的分辨率达到300m左右。模型采用了并行计算,并对2012年和2013年灾害性台风风暴潮过程进行了数值检验,计算精度和计算所用时间都能够满足业务化运行的要求。本文同时还根据中国气象局、美国国家气象局等5家主要台风预报机构给出的24h台风预报,对2013年度灾害性台风风暴潮过程进行了24h数值预报检验,检验结果表明:根据中国气象局台风登陆前24h预报可以得到更准确的风暴潮预报结果,其预报结果优于其他各家预报结果。该结论可以为今后的台风风暴潮预报中台风路径的选取提供重要的参考。  相似文献   

鲜浒苔稀硫酸水解产糖工艺研究   总被引：1，自引：1，他引：0  

冯大伟  姜鹏  李富超  秦松  赵瑾  陈华新 《海洋科学》2014,38(12):29-33

分别用质量分数为0.6%、1.0%、1.4%、1.8%、2.2%的稀硫酸在121℃高温高压的条件下水解鲜浒苔30、60、90 min,浒苔水解残留物再用纤维素酶酶解,用DNS法测定上述各步骤中的还原糖产量。结果表明,浒苔总糖含量为67.2%。稀硫酸水解工艺中,硫酸质量分数为1.8%、水解90 min,浒苔还原糖转化率最高,达59.9%,每克干质量浒苔可产生447.0 mg还原糖。稀硫酸水解残留物纤维素酶酶解工艺中,浒苔还原糖转化率较低,在硫酸质量分数为0.6%、水解时间为60 min时还原糖转化率出现最大值,仅为6.5%。结果显示浒苔稀硫酸水解产还原糖效果显著,但并不能促进纤维素酶酶解。浒苔糖化可单独采用稀硫酸水解工艺,本实验条件下的最佳工艺条件为1.8%硫酸水解90 min。本研究探索了浒苔糖化工艺条件,对后续的浒苔燃料乙醇发酵研究具有一定的参考意义。  相似文献   

对流层气溶胶的直接气候效应对平流层的影响   总被引：1，自引：1，他引：0       下载免费PDF全文

宋刘明  刘煜  朱彬  李维亮 《应用气象学报》2014,25(1):83-94

通过WACCM-3模式中气溶胶光学厚度与卫星资料的对比发现,模式可以很好地再现全球气溶胶的主要分布特征,但在一些区域还存在数值上的差异。利用数值试验研究对流层气溶胶的直接气候效应对平流层气候的影响,结果表明:对流层气溶胶对平流层气候有明显影响,平流层化学过程在这一影响中起重要作用,而对流层气溶胶对平流层辐射的影响不是其直接气候效应对平流层影响的主要原因。其机制可能是对流层气溶胶改变对流层的辐射平衡,影响对流层的温度和大气环流,进而影响行星波的上传,使得平流层气候发生变化;影响区域主要位于高纬度和极地地区,南半球的变化比北半球大,温度变化最大达10 K,纬向风变化最大可达12 m/s,臭氧体积分数最多减少0.8×10-6。  相似文献   

Tropospheric Wet Refractivity Tomography Based on the BeiDou Satellite System简     

WANG Xiaoying  WANG Xianliang  DAI Ziqiang  KE Fuyang  CAO Yunchang  WANG Feifei  and SONG Lianchun 《大气科学进展》2014,31(2):355-362

This paper presents a novel approach for assessing the precision of the wet refractivity field using BDS （BeiDou navigation satellite system） simulations only,GPS,and BDS＋GPS for the Shenzhen and Hongkong GNSS network.The simulations are carried out by adding artificial noise to a real observation dataset.Instead of using the δ and σ parameters computed from slant wet delay,as in previous studies,we employ the Bias and RMS parameters,computed from the tomography results of total voxels,in order to obtain a more direct and comprehensive evaluation of the precision of the refractivity field determination.The results show that：（1） the precision of tropospheric wet refractivity estimated using BDS alone （only 9 satellites used） is basically comparable to that of GPS; （2） BDS＋GPS （as of current operation） may not be able to significantly improve the data＇s spatial density for the application of refractivity tomography; and （3） any slight increase in the precision of refractivity tomography,particularly in the lower atmosphere,bears great significance for any applications dependent on the Chinese operational meteorological service.  相似文献   

Investigation of Uncertainties of Establishment Schemes in Dynamic Global Vegetation Models简     

SONG Xiang  ZENG Xiaodong 《大气科学进展》2014,31(1):85-94

In Dynamic Global Vegetation Models （DGVMs）, the establishment of woody vegetation refers to flowering, fertiliza- tion, seed production, germination, and the growth of tree seedlings. It determines not only the population densities but also other important ecosystem structural variables. In current DGVMs, establishments of woody plant functional types （PFTs） are assumed to be either the same in the same grid cell, or largely stochastic. We investigated the uncertainties in the competition of establishment among coexisting woody PFTs from three aspects： the dependence of PFT establishments on vegetation states; background establishment; and relative establishment potentials of different PFTs. Sensitivity experi- ments showed that the dependence of establishment rate on the fractional coverage of a PFT favored the dominant PFT by increasing its share in establishment. While a small background establishment rate had little impact on equilibrium states of the ecosystem, it did change the timescale required for the establishment of alien species in pre-existing forest due to their disadvantage in seed competition during the early stage of invasion. Meanwhile, establishment purely fiom background （the scheme commonly used in current DGVMs） led to inconsistent behavior in response to the change in PFT specification （e.g., number of PFTs and their specification）. Furthermore, the results also indicated that trade-off between irtdividual growth and reproduction/colonization has significant influences on the competition of establishment. Hence, further development of es- tablishment parameterization in DGVMs is essential in reducing the uncertainties in simulations of both ecosystem structures and successions.  相似文献