2015—2020年中国土地利用变化遥感制图及时空特征分析

持续地开展国家尺度土地利用/覆盖变化遥感监测对于新时代国土空间规划和“美丽中国”蓝图绘制具有重要的科学价值。本文采用Landsat 8 OLI、GF-2等卫星遥感数据,融合遥感大数据云计算和专家知识辅助人机交互解译方法,研发了中国土地利用变化（2015—2020年）和2020年土地利用现状矢量数据（CLUD 2020）,建立了完整的30 a（20世纪80年代末—2020年）每隔5 a的30 m分辨率中国土地利用动态数据库。基于CLUD 2020数据,从全国和区域两个尺度揭示了2015—2020年中国土地利用变化的总体规律、区域分异和主要特征。研究表明：将遥感大数据云计算生成的30 m分辨率植被覆盖变化和地表类型变化检测信息融入到人机交互遥感解译方法,可有效地提高大范围土地利用变化遥感制图的效率和变化图斑辨识的准确性;精度评价表明,CLUD 2020一级类型制图的综合精度达95%。总体上,全国范围内国土空间开发强度与2010—2015年比较进入相对稳定状态。期间全国耕地面积仍保持减少态势,空间分异特征为耕地南减北增,东北松嫩平原及其与三江平原交界区大规模的旱地向水田转移,西北新疆南部开垦和北部退耕/撂荒并存;全国城乡建设用地持续增加,空间分异特征表现为由以往的沿海地区和超大、大城市集聚转向中西部地区的大中小城镇周边蔓延为主。全国范围的林草自然生态用地面积持续减少,但强度与2010—2015年比较有所下降;受气候变化的持续影响,青藏高原地区的河流湖泊等水域面积显著增加。以上土地利用变化格局与“十三五”期间国家高质量发展、生态文明建设宏观战略和气候变化的影响密切相关。     

近10年新疆积雪面积时空变化研究

区域尺度积雪信息的时空监测对确定雪灾的影响范围及灾情等级划分具有重要意义。本文利用近10年的MODIS积雪产品,按月最大面积的规则合成;分析了新疆积雪覆盖面积的时空变化特征,结果表明:时间上,新疆积雪面积有减少的趋势。空间上,近10年新疆积雪季节内永久性积雪覆盖区域主要分布在阿勒泰山脉、天山北麓及沿昆仑山脉西南部。其中天山及阿尔泰山之间的河谷及盆地的草原积雪面积波动主导了新疆整体积雪总面积的波动。     

Rainfall–runoff,flood inundation and sensitivity analysis of the 2014 Pakistan flood in the Jhelum and Chenab river basin

ABSTRACT

The major flood of 2014 in the two eastern, transboundary rivers, the Jhelum and Chenab in Punjab, Pakistan, was simulated using the two-dimensional rainfall–runoff model. The simulated hydrograph showed good agreement with the observed discharge at the model outlet and intervening barrages, with a Nash-Sutcliffe efficiency of 0.86 at the basin outlet. Further, simulated flood inundation extent showed good agreement with the MODIS imagery with a fit (%) of 0.87. For some affected areas that experienced short-duration flooding, local housing damage data confirmed the simulated results. Besides the rainfall–runoff and flood inundation modelling, parameter sensitivity analysis was undertaken to identify the influence of various river and floodplain parameters. The analysis showed that the river channel geometric parameters and the roughness coefficients exerted the primary influence over flood extent and peak flow.     

Maximum Sustainable Yield Estimates of Ladypees,Sillago sihama(Forsskl),Fishery in Pakistan Using the ASPIC and CEDA Packages

Using surplus production model packages of ASPIC(a stock-production model incorporating covariates) and CEDA(Catch effort data analysis),we analyzed the catch and effort data of Sillago sihama fishery in Pakistan.ASPIC estimates the pa-rameters of MSY(maximum sustainable yield),Fmsy(fishing mortality),q(catchability coefficient),K(carrying capacity or unexploited biomass) and B1/K(maximum sustainable yield over initial biomass).The estimated non-bootstrapped value of MSY based on logistic was 598 t and that based on the Fox model was 415 t,which showed that the Fox model estimation was more conservative than that with the logistic model.The R2 with the logistic model(0.702) is larger than that with the Fox model(0.541),which indicates a better fit.The coefficient of variation(cv) of the estimated MSY was about 0.3,except for a larger value 88.87 and a smaller value of 0.173.In contrast to the ASPIC results,the R2 with the Fox model(0.651-0.692) was larger than that with the Schaefer model(0.435-0.567),indicating a better fit.The key parameters of CEDA are:MSY,K,q,and r(intrinsic growth),and the three error assumptions in using the models are normal,log normal and gamma.Parameter estimates from the Schaefer and Pella-Tomlinson models were similar.The MSY estimations from the above two models were 398 t,549 t and 398 t for normal,log-normal and gamma error distributions,re-spectively.The MSY estimates from the Fox model were 381 t,366 t and 366 t for the above three error assumptions,respectively.The Fox model estimates were smaller than those for the Schaefer and the Pella-Tomlinson models.In the light of the MSY estimations of 415 t from ASPIC for the Fox model and 381 t from CEDA for the Fox model,MSY for S.sihama is about 400 t.As the catch in 2003 was 401 t,we would suggest the fishery should be kept at the current level.Production models used here depend on the assumption that CPUE(catch per unit effort) data used in the study can reliably quantify temporal variability in population abundance,hence the mod-eling results would be wrong if such an assumption is not met.Because the reliability of this CPUE data in indexing fish population abundance is unknown,we should be cautious with the interpretation and use of the derived population and management parameters.     

A unified presentation of the Voigt functions

In the present paper, we have given a generalization of a unified study of the Voigt functionsK(x, y) andL(x, y) obtained by Srivastava and Miller (1987; Vol. 135, pp. 111–118) which play an important role in several diverse fields of physics-such as astrophysical spectroscopy and the theory of neutron reactions. Explicit expressions for these functions are given in terms of relatively more familiar special functions of one and two variables; indeed, each of these representations will naturally lead to various other needed properties of the Voigt functions.     

A dynamic theory of hydrocarbon migration

This paper presents a new analysis of secondary migration of hydrocarbon that does not require capillary forces for trapping, but instead uses the method of characteristics and wave theory. The waves change speed and either reflect or refract (or partially reflect and partially refract) as they contact with layers of different flow capacities. Reflection of a certain wave from a boundary starts hydrocarbon accumulation below that boundary. The method is easy to use and conforms readily to graphical solution. For the sake of simplicity there is only two-phase flow. The application of this method gives new insights into the physics of migration and entrapment of oil. The method gives realistic times for oil accumulation and points to oil generation rate as the most sensitive variable. Oil and water densities, viscosities, and permeability are also important. We find that at the very small generation rates usually assumed the time required to develop a given column thickness is insensitive to the distance from the source rock. In general, the method also predicts a non-uniform saturation in the oil column caused by an interaction between buoyancy and viscous forces. Being based on the dynamic interactions of viscous and buoyancy forces, our theory is considerably at odds with hydrostatic approaches. We assume no capillary pressure, one-dimensional flow, and no regional groundwater flow, conditions which are not realized in actual migration. The theory should be viewed therefore as an end member of a more general theory; nevertheless, the largely graphical solutions give fundamental insights that are difficult to obtain by other techniques.     

Acute and chronic toxic effects of the carbamate pesticide Sevin on some haematological,biochemical and enzymatic parameters in the fresh water teleost fish Channa punctatus

The effects of exposure to LC₅₀ (10.5 mg/l) for 96 h and to a sublethal concentration (1.05 mg/l) of Sevin for 120 days have been observed on some haematological, biochemical and enzymatic parameters of Channa punctatus. The fish were hyperglycemic and hyperlactemic and the glycogen content of the liver and muscles decreased, but the lactic acid content of two tissues increased. The activity of hexokinase increased in the kidney, intestine, liver and muscles but decreased in the gills and brain. The activity of lactate dehydrogenase decreased in the kidney and intestine, and increased in the liver, muscles, brain and gills. The pyruvate dehydrogenase activity decreased in all the six tissues. Both the exposures produced a decrease in the succinate dehydrogenase activity of the liver. The enzyme activity decreased in the brain, gills and muscles after chronic exposure, whereas the kidney and intestine showed an elevation in enzyme activity.     

Simplified analysis method for multistorey base-isolated structures on viscoelastic halfspace

A simplified procedure for the analysis of single-storey base-isolated structures on a viscoelastic halfspace is extended to multistorey structures. Results of displacements and base shear obtained by this procedure compare favourably to exact results obtained by a computer program that has been developed.     

Development of a flood forecasting system using IFAS: a case study of scarcely gauged Jhelum and Chenab river basins

Development of a well-calibrated, distributed hydrological model for flood forecasting based on rainfall and snowmelt is quite challenging, especially when in situ data is limited or unavailable. This paper presents the study carried out to parameterise the Integrated Flood Analysis System (IFAS) model for the trans-boundary, scarcely gauged catchments of Jhelum and Chenab rivers in Pakistan. Rainfall-runoff analysis was performed with a two-layered tank configuration, integrating snowmelt and dam and barrage operation from the very upstream in India to Trimmu Barrage in Pakistan. A grid size of 5?×?5 km was considered. Global map topography, land cover and soil data was utilised. The model was tested considering different magnitudes of floods of the years 2014, 2015 and 2017. The results showed that the satellite rainfall product, i.e. Global Satellite Mapping of Precipitation (GSMaP-NRT), underestimated the rainfall volume, compared to the ground-gauged rainfall. The GSMaP-IF correction method showed poor performance owing to the lack of ground observatory rainfall data for correcting the trans-boundary part of the basin. The GSMaP-Type1 correction method showed good results, except for the confluence point where complex flow conditions were not properly reproduced by the model. In addition, the incorporation of dam and barrages in the model improved the simulated flow results. It is concluded that the satellite rainfall estimates must be corrected to improve the results. Snowmelt module estimated the snowmelt contribution as 3 to 7% and 4 to 23% of the average daily discharge during the monsoon season at Mangla Dam and Marala Barrage, respectively, during 2014 and 2015. This study assessed various correction methods and concluded that the model and methodology used in the study functioned well with suitable precipitation.     

Application of geographical information system for mapping/monitoring seismological hazards in Pakistan

This study attempts to use the geographic information system (GIS) technique to map and understand the tectonics and crustal structures of Pakistan. Maps of surficial tectonic features and seismological parameters including Moho depth, P_n velocity and P_g velocity are complied. Based on the seismological data-set of the country the earthquake hazard map of Pakistan is also presented by applying regression technique on seismological, geological and topographical parameters. A case study of 8 October 2005 earthquake is used to validate the hazard map. It is envisaged that the developed GIS database would help policy-makers and scientists in natural hazard evaluation, seismic risk assessment and understanding of earthquake occurrences in Pakistan.