A Simple Reclassification Method for Correcting Uncertainty in Land Use/Land Cover Data Sets Used with Land Surface Models

With increasing computational resources, environmental models are run at finer grid spacing to resolve the land surface characteristics. The land use/land cover (LULC) data sets input into land surface models are used to assign various default parameters from a look-up tables. The objective of this study is to assess the potential uncertainty in the LULC data and to present a reclassification method for improving the accuracy of LULC data sets. The study focuses on the Southern Great Plains and specifically the Walnut River Watershed in southeastern Kansas, USA. The uncertainty analysis is conducted using two data sets: The National Land Cover Dataset 1992 (NLCD 92) and the Gap Analysis Program (GAP) data set, and a reclassification logic tree. A comparison of these data sets showed that they do not agree for approximately 27% of the watershed. Moreover, an accuracy assessment of these two data sets indicated that neither had an overall accuracy as high as 80%. Using the relationships between land-surface characteristics and LULC, a reclassification of the watershed was conducted using a logical model. This model iteratively reclassified the uncertain pixels according to their surface characteristics. The model utilized normalized difference vegetation index (NDVI) measurements during April and July 2003, elevation, and slope. The reclassification yielded a revised LULC dataset that was substantially improved. The overall accuracy of the revised data set was nearly 93%. The study results suggest: (i) as models adopt finer grid spacings, the uncertainty in the LULC data will become significant; (ii) assimilating NDVI into the land-surface models can reduce the uncertainty due to LULC assignment; (iii) the standard LULC data sets must be used with caution when the focus is on local scale; and (iv) reclassification is a valuable means of improving the accuracy of LULC data sets prior to applying them to local issues or phenomena.     

流域土地利用/覆被变化的水文效应及洪水响应

干旱与洪涝灾害已成为全球关心的重大问题.土地利用/覆被变化影响雨水的截留、下渗、蒸发等水文要素及其产汇流过程,并进而影响流域出口断面的流量过程,加大流域洪涝灾害发生的频率和强度.深入研究土地利用/覆被变化对洪涝灾害的影响,对于社会经济可持续发展具重要意义.通过分析和总结已进行的有关流域土地利用/覆被变化的水文效应及洪水响应研究工作进展,讨论了其研究内容、方法及现有工作的不足之处.     

Land transformation and pond sediment information

Five years of observations on sedimentation rates in two ponds located near transformed land areas in the Kobe district of central Japan have shown the relationship between sedimentation and development during land transformation. One of the ponds observed has artificial land transformation in its drainage area (KR), whereas the other does not (KN). The sedimentation rate in the pond without artificial land transformation is roughly proportional to the rainfall intensity, whereas in the pond with land transformation it is related to change in the transformed area as well as the rainfall intensity. The relative sedimentation rate (sedimentation rate divided by the catchment area and rainfall intensity) is also related to loss on ignition and grain density; large relative sedimentation rates correspond to low loss on ignition and high grain density, suggesting that these factors are very sensitive to land transformation. Changes in catchment factors, which indicate the topographical and hydrological conditions in the catchment area, are inversely proportional to change in the ratio of the reclaimed to the natural area; this is indicative of change in the erodibility of the surface material in the catchment area. © 1997 John Wiley & Sons, Ltd.     

Land uplift due to subsurface fluid injection

The subsurface injection of fluid (water, gas, vapour) occurs worldwide for a variety of purposes, e.g. to enhance oil production (EOR), store gas in depleted gas/oil fields, recharge overdrafted aquifer systems (ASR), and mitigate anthropogenic land subsidence. Irrespective of the injection target, some areas have experienced an observed land uplift ranging from a few millimetres to tens of centimetres over a time period of a few months to several years depending on the quantity and spatial distribution of the fluid used, pore pressure increase, geological setting (depth, thickness, and area extent), and hydro-geomechanical properties of the injected formation. The present paper reviews the fundamental geomechanical processes that govern land upheaval due to fluid injection in the subsurface and presents a survey of some interesting examples of anthropogenic uplift measured in the past by the traditional levelling technique and in recent times with the aid of satellite technology. The examples addressed include Long Beach, Santa Clara Valley, and Santa Ana basin, California; Las Vegas Valley, Nevada; Cold Lake and other similar sites, Canada; Tokyo and Osaka, Japan; Taipei, Taiwan; Krechba, Algeria; Upper Palatinate, Germany; Chioggia and Ravenna, Italy.     

沙漠陆面过程参数化与模拟

沙漠地区植被稀疏、干旱少雨,其陆面物理过程具有与全球其它地区显著不同的特点.本文利用巴丹吉林沙漠观测资料,分析和计算了地表反照率、比辐射率、粗糙度和土壤热容量、热传导系数等关键陆面过程参数,建立了适合于沙漠地区的陆面过程模式DLSM (Desert Land Surface Model),并与NOAH陆面过程模式的模拟结果和观测资料进行了比较.结果表明:巴丹吉林沙漠地表反照率为0.273,比辐射率为0.950,地表粗糙度为1.55×10^-3 m,土壤热容量和热扩散系数分别为1.08×10⁶ J·m^-3·K^-1和3.34×10^-7 m²·s.辐射传输、感热输送和土壤热传导过程是影响沙漠地区地表能量平衡的主要物理过程.通过对这三种过程的准确模拟检验,DLSM能够较准确地模拟巴丹吉林沙漠地气能量交换特征;短波辐射、长波辐射和感热通量的模拟结果与观测值间的标准差分别为7.98,6.14,33.9 W·m^-2,与NOAH陆面过程模式的7.98,7.72,46.6 W·m^-2的结果接近.地表反照率是沙漠地区最重要的陆面过程参数,地表反照率增大5%,向上短波辐射通量随之增加5%,感热通量则减小2.8%.本文研究结果对丰富陆面过程参数化方案,改进全球陆面过程模式、气候模式具有参考意义.     

Monitoring Urban Land Use by Earth Observation

This paper discuses the use of high resolution spaceborne Earth observation data in studies of the urban environment. Adopting a rigorous, mathematical approach, it introduces the Spatial Re-classification Kernel (SPARK) algorithm; this is appliedto a suburban area in the south-east of London. It also introduces a region-based, structural pattern recognition approach to the same problem through which urban land use might be inferred from an analysis of the morphological properties and structural relations of discrete land cover regions identified in fine spatial resolution images.     

Comparative Evaluation of Infiltration Models under Different Land Covers

Water Resources - Quantification of infiltration characteristics of soil is a complex problem because of its variability, selection of suitable infiltration model, and determination of infiltration...     

Initialisation of Land Surface Variables for Numerical Weather Prediction

Land surface processes and their initialisation are of crucial importance for Numerical Weather Prediction (NWP). Current land data assimilation systems used to initialise NWP models include snow depth analysis, soil moisture analysis, soil temperature and snow temperature analysis. This paper gives a review of different approaches used in NWP to initialise land surface variables. It discusses the observation availability and quality, and it addresses the combined use of conventional observations and satellite data. Based on results from the European Centre for Medium-Range Weather Forecasts (ECMWF), results from different soil moisture and snow depth data assimilation schemes are shown. Both surface fields and low-level atmospheric variables are highly sensitive to the soil moisture and snow initialisation methods. Recent developments of ECMWF in soil moisture and snow data assimilation improved surface and atmospheric forecast performance.     

晋陕豫交界区地震活动性分析

分析了晋陕豫交界区临汾、渭南地区的地震活动性,认为自1800年以来,运城地区地震活动明显增强,且有向韩城扩散的趋势     

昆明市地面沉降发展过程及其特征

利用1979－1998年昆明市地面沉降监测资料分析昆明市南部地区，即二环南路以南地区大面积地面沉降。该地区形成两个明显的漏斗形沉降区，一个是以小板桥为中心的沉降区，其中在朱家村、巫家坝机场、广卫村、小喜村、六甲、官渡等地较为明显，在沉降中心（小板桥）沉降量达227．5mm(1985-1998年），平均下沉速率在17mm/a左右，最大达30.00mm/a；另一个沉降中心在海埂以北的河尾村、渔户村一逞地区，没降中心的沉降量达100．4mm(1993-1997年），下沉速度达到25．1mm/a。对昆明市地面沉降现象与古滇池松软的湖相沉积、局部地区的地下水资源长期超采以及该地区强震活动的因果关系进行了初步探讨。     

Identifying Synergy Between Remedial Strategies and Land Reuse

"Today the environmental professional teams with the developer to use remedial technologies and approaches that complement planned land use and, conversely, use land in a fashion that accommodates environmental site conditions."     

Impact of Land Use on Ground-Water Quality in Southern Delawarea

A ground-water quality monitoring study was conducted in Kent and Sussex Counties, Delaware. In the coastal region of Sussex County, 210 wells were sampled 12 times each. In noncoastal Sussex and Kent Counties, 272 wells were sampled once each season over a period of one year. Over 99 percent of the wells were in the water-table aquifer. In coastal Sussex County, 32% of the wells had average nitrate concentrations above the EPA drinking-water standard of 10 mg/1 N. In noncoastal Sussex County and Kent County, 21% and 8% of the wells respectively, had nitrate concentrations above 10 mg/1. The highest nitrate concentrations occurred in areas with intensive broiler production or intensive crop production with excessively-drained soils. Nitrate concentrations in forest areas were <1.5 mg/1. Poultry manure, septic tanks and fertilizers all contributed to the high nitrate concentrations. Poultry manure was one of the major causes of nitrate contamination in four out of the five top prioritized ground-water problem areas. Bacteria contamination was low in all sampling areas. Lead, cadmium and chromium were far below drinking-water standards in all but a few wells.     

东南沿海活动地块的初步划分

东南沿海地区无论过去还是现在都是华南中强地震多发区，西文度菌 从地质、地球物理和地球化学相结合的角度，并根据地震学、海洋地质学及深部构造物理资料，对东南沿海活动地块作一个初步划分，并对其地震活动性作了初步分析，得出了地块内部比较统一的地震活动图像。     

Sedimentary Enzyme Kinetics of Land/Water Ecotones with Reed Domination

Land/water ecotones, the transitional boundary zone between terrestrial and aquatic ecosystems, can effectively trap and assimilate nutrients from external sources. The changes of nutrient cycling will cause a response in enzyme activity. In this paper, the enzyme kinetics of land/water ecotones in a shallow eutrophic wetland in China, dominated by a reed (Phragmites australis) community, are studied. The results indicate that land/water ecotones exhibit a strong filtration function and nutrient factor is an important feature affecting the distribution of enzymes in the transect of the littoral zone. The obvious spatial differences of enzyme activities and nutrients are present in the transect of the reed beds. The land area is the hot zone, where significant changes in enzyme activity occur. T‐test results show that the landward spot, 1 m away from the water‐land interface, is quite different from other spots, and the 1 m spot is the hot spot where great biochemical change happens. The principal component analysis of the environmental variables shows that nutrient factors have an important affect on enzyme distribution in the transect of the littoral zone. The nutrient factor explains about 54% of the observed variance. In particular, TOC (total organic carbon) correlates with the other five factors (TN; total nitrogen, TP; total phosphorus, phosphatase, β‐glucosidase, and urease) with correlative coefficients of 0.932, 0.595, 0.488, 0.433, and –0.468, respectively. The results indicate that TOC is a very important factor in Baiyangdian wetlands.     

国内外地面沉降现状与研究

系统地介绍了国内外地面沉降的现状、引起沉降的原因、地面沉降的机理和地面沉降灾害预测与监测。特别针对上海地区随着大规模的城市建设产生的由工程环境效应引起的地面沉降及其监测与研究做了阐述。     

Empirical and Numerical Modeling of T-phase Propagation from Ocean to Land

—?T-phase propagation from ocean onto land is investigated by comparing data from hydrophones in the water column with data from the same events recorded on island and coastal seismometers. Several events located on Hawaii and the emerging seamount Loihi generated very large amplitude T phases that were recorded at both the preliminary IMS hydrophone station at Point Sur and land-based stations along the northern California coast. We use data from seismic stations operated by U. C. Berkeley along the coast of California, and from the PG&;E coastal California seismic network, to estimate the T-phase transfer functions. The transfer function and predicted signal from the Loihi events are modeled with a composite technique, using normal mode-based numerical propagation codes to calculate the hydroacoustic pressure field and an elastic finite difference code to calculate the seismic propagation to la nd-based stations. The modal code is used to calculate the acoustic pressure and particle velocity fields in the ocean off the California coast, which is used as input to the finite difference code TRES to model propagation onto land. We find both empirically and in the calculations that T phases observed near the conversion point consist primarily of surface waves, although the T phases propagate as P waves after the surface waves attenuate. Surface wave conversion occurs farther offshore and over a longer region than body wave conversion, which has the effect that surface waves may arrive at coastal stations before body waves. We also look at the nature of T phases after conversion from ocean to land by examining far inland T phases. We find that T phases propagate primarily as P waves once they are well inland from the coast, and can be observed in some cases hundreds of kilometers inland. T-phase conversion at tenuates higher frequencies, however we find that high frequency energy from underwater explosion sources can still be observed at T-phase stations.     

The Influence of Clay Zones on Land Subsidence from Groundwater Pumping

The objective of this article is to analyze the influence of clay zones on subsidence from groundwater pumping. Finite element analyses were conducted on a sand‐only aquifer and a sand aquifer with two clay zones located at different distances from the well face. A model that accounts for recoverable and nonrecoverable strains was used to simulate the sand and clay. This model couples the groundwater flow with the stress‐deformation response of the aquifer materials. Each aquifer was pumped from a single well for a period of 6 months, and then the groundwater level was lowered gradually to an elevation below the elevation of the clay zones and kept there for 10 years. The groundwater level was then raised gradually back to the original elevation over a period of 10 years. The results of the analyses show that the ground surface subsidence profile is strongly influenced by the presence of the clays zones. The ground surface sags where these clay zones are present resulting in a wavy ground surface profile. Subsidence continued when pumping is stopped, albeit at a much slower rate than during pumping, and when the groundwater level is below the elevation of the clay zones. Clay zones further away from the well face lag the subsidence of clay zones nearer the well face because of lower changes in hydrostatic head. Sags in ground surface subsidence profile from groundwater pumping are indicators of the presence of low hydraulic conductive geological materials.     

Upper Mantle Anisotropy in Victoria Land (Antarctica)

—During the Austral Summers 1993–94 and 1994–95, we operated two temporary seismic arrays in the Victoria Land region, Antarctica. The first was located around the Mt. Melbourne volcano, near Terra Nova Bay, and the second southward, along the ACRUP1 Geotraverse. The aim of these experiments was to provide additional constraints on the Moho geometry and on lithosphere-astheno sphere structure in this zone. For this reason, a number of techniques were applied to recorded teleseismic data. In this paper we describe the results of the analysis on SKS- and S-wave splitting, which show the presence of seismic anisotropy. Computed fast polarization directions range, on average, between 131° and 166°, and delay times are on the order of 1 s. We presume that anisotropy is mainly located in the upper mantle, although we cannot detect, at present, if a contribution from the crust does exist. The fast polarization direction we determine is quite parallel to the opening of the Ross Sea, an active rift system, but also to the Absolute Plate Motion direction. Therefore, we assume that the identified anisotropy may be induced by the extension, activated by plate motion and is still related to it.