基于时序MODIS NDVI的黑河流域土地覆盖分类研究

归一化植被指数(NDVI)是植被生长状态及植被覆盖度的最佳指示因子,其时序数据也已成为基于生物气候特征开展大区域植被和土地覆盖分类的基本手段。基于时序NDVI数据的土地覆盖分类,即通过提取NDVI时间信号所包含的植被生物学参数,构建起一个包含植被生物学信息的分类特征空间。利用2006年重建得到的MODIS NDVI 16天合成时间序列数据,并结合1 km分辨率的DEM数据、野外实地调查资料等辅助数据,综合分析了不同土地覆盖类型对应的时序NDVI谱线及其第一、二谐波的特征阈值,建立决策树对黑河流域的土地覆盖开展分类研究。结果表明,基于时序MODIS NDVI谱线特征的决策树分类精度为78%,Kappa系数为0.74。利用1 km时序MODIS NDVI时间序列获得较为准确的黑河流域土地覆盖类型是可行的。     

Applied geophysics for cover thickness mapping in the southern Thomson Orogen

Abstract

Potentially mineralised Paleozoic basement rocks in the southern Thomson Orogen region of southern Queensland and northern New South Wales are covered by varying thicknesses of Mesozoic to Cenozoic sediments. To assess cover thickness and methods for estimating depth to basement, we collected new airborne electromagnetic (AEM), seismic refraction, seismic reflection and audio-frequency magnetotelluric data and combined these with new depth to magnetic basement models from airborne magnetic line data and ground gravity data along selected transects. The results of these investigations over two borehole sites, GSQ Eulo 1 and GSQ Eulo 2, show that cover thickness can be reliably assessed to within the confidence limits of the various techniques, but that caveats exist regarding the application of each of the disciplines. These techniques are part of a rapid-deployment explorers’ toolbox of geophysical techniques that have been tested at two sites in Australia, the Stavely region of western Victoria, and now the southern Thomson Orogen in northern New South Wales and southern Queensland. The results shown here demonstrate that AEM and ground geophysics, and to a lesser extent depth to magnetic source modelling, can produce reliable results when applied to the common exploration problem of determining cover thickness. The results demonstrate that portable seismic systems, designed for geotechnical site investigations, are capable of imaging basement below 300 m of unlithified Eromanga Basin cover as refraction and reflection data. The results of all methods provide much information about the nature of the basement–cover interface and basement at borehole sites in the southern Thomson Orogen, in that the basement is usually weathered, the interface has paleotopography, and it can be recognised by its density, natural gamma, magnetic susceptibility and electrical conductivity contrasts.     

喀斯特生态脆弱区猫跳河流域土地利用/覆被变化研究

LUCC是当前国际全球变化研究的前沿和热点领域,喀斯特生态脆弱区的土地利用/覆被变化是国际LUCC研究中的薄弱环节。以贵州中部的典型喀斯特流域——猫跳河流域为例,通过详实的地面调查,以1973年的Landsat-MSS影像、1990年和2002年的Landsat-TM影像为数据源,在RS、G IS、GPS为核心的"三S"集成技术支撑下,应用单一土地利用动态度、单一土地利用转入率和转出率、综合土地利用动态度、土地利用度以及土地覆被变化空间指数等指标,定量研究了该流域在过去30 a间的土地利用/覆被的变化特征。研究表明:(1)研究区的土地覆被类型主要以耕地、灌草地、灌木林以及有林地为主;(2)1970年代以来,土地利用/覆被变化剧烈,各地类之间的变化幅度存在较大差别,水田、灌木林、其他林地、灌草地等地类先减后增,旱地和裸岩地先增后减,有林地、水域、城镇建设用地、农村居民点、交通工矿用地等持续增加;⑶1973~1990年的土地利用动态度和土地利用度均比1990~2002年大,前一时期的裸岩地明显增加,土地利用具有明显的不可持续性,进入1990年后,裸岩地缩减,流域生态环境质量趋于好转;⑷伴随着分布面积在平面空间上的张缩,各地类的平均分布高程和坡度在垂直方向上也出现了相应的变化。     

基于DEnKF方法的考虑次网格变异性的MODIS雪盖同化

基于通用陆面模型(CoLM)和确定性集合卡尔曼滤波算法发展了一个考虑模型次网格变异性的MODIS雪盖同化方案,提高雪深模拟的估计精度。利用北疆阿勒泰地区5个气象站点2007年11月至2008年4月逐日雪深观测数据对同化结果进行了验证。结果表明,该同化方案不需要对MODIS雪盖观测数据进行扰动,能明显提高雪深模拟的精度。另外,雪深同化结果与地面观测雪深具有一致的时间变化趋势,能准确地反映积雪深度在各个不同时段的变化特性。     

东北典型林区雪深反演算法的验证与分析

积雪对自然环境和人类活动都有极其重要的影响。积雪参数（雪面积、雪深和雪水当量）反演对水文模型和气候变化研究有着实际的意义。然而,目前森林区的雪深遥感反演精度一直有待于进一步提高。东北地区是我国最大的天然林区和重要的季节性积雪区之一,本文利用FY3B卫星微波成像仪（MWRI）L1级亮温数据和L2级雪水当量数据,以及东北典型林区野外实测雪深数据,对Chang算法、NASA 96算法和FY3B雪深业务化反演算法进行了验证与分析。结果表明：在东北典型林区的雪深反演中,Chang算法和NASA 96算法反演的雪深波动都比较大,当森林覆盖度f≤0.6时,NASA 96算法表现比较好,均方根误差值在3种算法中较小,但当f >0.6时,NASA 96算法失真严重。当考虑纯森林像元（f=1）时,Chang算法低估了雪深47%。当f≤0.3时,FY3B业务化算法始终优于Chang算法。整体上,FY3B业务化算法相对稳定,具有较高的精度。     

可吸入颗粒物(PM10)浓度时空变异性及影响因素分析

本文以厦门市为例,首先对PM10平均浓度数据进行趋势性、周期性和空间变异性进行分析,然后分析了气温、降水强度、降水日数、风向等气候因子对PM10浓度变化在时间上的影响,同时使用了交叉相关分析的方法对月平均降水日数和PM10大气污染指数(API)为优(PM10浓度<0.05mg/m3)的月内天数百分比的相关性进行分析,最后利用从遥感影像获取的地表覆盖数据,分析了土地利用类型与局部PM10年平均浓度的关系。分析结果表明：厦门市PM10浓度年内变化无明显的上升和下降的趋势,但有显著的周期性,分别为3、7和29天,气候因素对PM10浓度的变化有显著的影响,其中月平均降水日数对API为优的月内天数百分比的影响有明显的滞后性,滞后周期大约为3个月,局部PM10年均浓度与该地区的土地覆盖类型有明显的相关性,并且植被覆盖的比例越大,该地区的PM10年平均浓度就越小。     

黄河三角洲新生湿地土地覆被演替图谱

本文根据黄河三角洲新生湿地盐生、湿生、中生以及人工等不同生境的生态景观类型 ,将本区土地覆被类型分为 9类 ,即研究区海域、滩涂、柽柳 -翅碱蓬群落、獐毛 +白茅群落、芦苇 +荻群落、有林地、天然河流与人工水体、耕地和居民工矿用地。从遥感影像数据 (包括LandsatTM432、CBERS 1CCD432 )和专题矢量数据中提取了 1 984、 1 991、 1 996和 2 0 0 0年四期土地覆被数据 ,采用区域质心函数计算四个时期 9类覆被的分布重心 ,并合成土地覆被重心演替过程图谱 ,通过图谱分析 ,归纳出湿地植被演替的三种模式 ,即陆进模式、海退模式以及人类活动影响模式 ,为认识新生湿地植被演替规律以及人类活动的影响、制定湿地保护措施提供参考依据。     

Individual and combined effects of land use/cover and climate change on Wolf Bay watershed streamflow in southern Alabama

Land use/cover (LULC) and climate change are two main factors affecting watershed hydrology. In this paper, individual and combined impacts of LULC and climate change on hydrologic processes were analysed applying the model Soil and Water Assessment Tool in a coastal Alabama watershed in USA. Temporally and spatially downscaled Global Circulation Model outputs predict a slight increase in precipitation in the study area, which is also projected to experience substantial urban growth in the future. Changes in flow frequency and volume in the 2030s (2016–2040) compared to a baseline period (1984–2008) at daily, monthly and annual time scales were explored. A redistribution of daily streamflow is projected when either climate or LULC change was considered. High flows are predicted to increase, while low flows are expected to decrease. Combined change effect results in a more noticeable and uneven distribution of daily streamflow. Monthly average streamflow and surface runoff are projected to increase in spring and winter, but especially in fall. LULC change does not have a significant effect on monthly average streamflow, but the change affects partitioning of streamflow, causing higher surface runoff and lower baseflow. The combined effect leads to a dramatic increase in monthly average streamflow with a stronger increasing trend in surface runoff and decreasing trend in baseflow. Copyright © 2013 John Wiley & Sons, Ltd.     

1959-2003年中国天山积雪的变化

Mcteorological data at 17 weather stations in the Tianshan Mountains from 1959 to 2003 were analyzed to explore the variations in temperature and snow cover.The abrupt change test for snow depth was performed using Mann-Kendall statistic.The spatial distribution of maximum snow depth was calculated by employing GIDS interpolation and DEM data.The results show that mean temperature in winter had a rising trend at a rate of 0.44℃/10a.The minimum temperature in winter increased more evidently at a rate of 0.79℃/10a.The maximum snow depth has obviously deepened at a rate of 1.15 cm/10 a in the past 45 years,and it was about 16% higher than the average during 1991-2003.The Mann-Kendall statistic test of snow depth indicates that the abrupt change occurred in 1976.The maximum increment for snow cover depth occurred in Zhaoshu(Kunes)(39.3%)and Nilka(39.7%)in the west Tiansban Mountains.In contrast,the snow cover depth reduced by 17% in Barkol in the east Tianshan Mountains.There was a primary change periodicity of about 2.8 years in snow cover.In addition,snow cover days with a depth more than 10 cm increased distinctly,however,there was no obvious advance or delay in snow beginning and ending dates.     

土地覆盖对岩溶地下河碳汇的影响——以广西打狗河流域为例

以广西打狗河为例,对比分析河流东、西两岸地下河的土地覆盖差异及其对岩溶碳汇的影响。打狗河东岸林地占56.13%,耕地占15.15%;而西岸林地、耕地分别只占20.8%、12.95%。但西岸的裸岩和荒地比例大,分别占29.57%和25.95%,而东岸分别占14.19%和10.98%。植被和土壤覆盖差异导致了东、西两岸碳循环的地球化学指标有明显的差异,东岸地下河水的HCO3-、Ca2+、PCO2(平均分别是233.71mg/L、85.5mg/L、909.46Pa)明显高于西岸(分别为177.26mg/L、64.65mg/L、257.37Pa),而东岸的SIC、pH值(分别为0.12和7.40)又低于西岸(分别是0.38和7.85)。因此,东岸有更强的岩溶动力条件,东岸地下河的平均碳汇强度比西岸高14%,其中,东岸下桥地下河的碳汇强度是西岸旦峒地下河的3.7倍。东西岸地下河水的δ13CDIC、TOC资料也进一步证明了土地覆盖条件对地下河岩溶碳汇具有重要的影响。