Search

Multisource rainfall products can be used to overcome the absence of gauged precipitation data for hydrological applications. This study aims to evaluate rainfall estimates from the Chinese S-band weather radar (CINRAD-SA), operational raingauges, multiple satellites (CMORPH, ERA-Interim, GPM, TRMM-3B42RT) and the merged satellite–gauge rainfall products, CMORPH-GC, as inputs to a calibrated probability distribution model (PDM) on the Qinhuai River Basin in Nanjing, China. The Qinhuai is a middle-sized catchment with an area of 799 km2. All sources used in this study are capable of recording rainfall at high spatial and temporal resolution (3 h). The discrepancies between satellite and radar data are analysed by statistical comparison with raingauge data. The streamflow simulation results from three flood events suggest that rainfall estimates using CMORPH-GC, TRMM-3B42RT and S-band radar are more accurate than those using the other rainfall sources. These findings indicate the potential to use satellite and radar data as alternatives to raingauge data in hydrological applications for ungauged or poorly gauged basins. [ABSTRACT FROM AUTHOR]

Oil spills cause damage in ocean environment. It is important to identify the oil spills for further treatment. We propose an oil spill detection method based on X-band marine radar image using texture analysis. In this method, first, received radar image was denoised by erasing co-channel interference and small speckles. Then, texture analysis was used to indicate the location of oil spills. In the texture analysis, we proposed a texture index calculated by four texture features of grey level co-occurrence matrix (GLCM). The texture index in oil spill area is higher than it in other place, which can be used for extracting oil spill area roughly. In the end, precise extraction of an oil spill was carried out by an adaptive thresholding algorithm on the area selected by the proposed texture index. According to the X-band marine radar images sampled in the oil spill accident on Xingang Port of Dalian, China, an oil spill detected by the proposed texture analysis method is comparable to visual interpretation. [ABSTRACT FROM AUTHOR]

In this study, we applied the edge-detection method of oil-spill monitoring to extract oil-spill features observed by the ENVISAT Advanced Synthetic Aperture Radar (ASAR) images over the coastal waters of Hong Kong and vicinity in northern South China Sea. Two examples in 2007 and 2008 over the coastal waters of the study area show that oil spills can be successfully detected by ASAR images at wind speeds around 4∼ 6 m/s independent of wind direction. The study also shows that it could be helpful for evaluating the potential impacts of oil spills on the coastal environment in Hong Kong and vicinity. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) from agricultural land is the most common form of water consumption in the North China Plain. Based on in situ measurements by an eddy covariance (EC) system, the present study tested the surface energy balance system (SEBS) model for estimating surface energy fluxes from a wheat/maize rotation cropland. Applicability of the SEBS model using Moderate Resolution Imaging Spectroradiometer (MODIS) land products to estimate ET was further validated. The model proved to be appropriate to measure heat flux during the wheat-growing season, but underestimated the sensible heat flux during the maize-growing season. Although the SEBS model performed better during the wheat-growing season, the relative error of the latent heat flux was within 20% in both wheat- and maize-growing seasons. Results showed that the SEBS model using remote sensing data could provide a reasonable estimate of the surface energy fluxes from an irrigated cropland in the North China Plain. [ABSTRACT FROM AUTHOR]

Radar satellite imagery was valuable in supporting extensive rescue operations after the Wenchuan Earthquake on 12 May 2008 due to its ability to operate independently of weather conditions, day and night. However, it is a challenging task to identify damaged or destroyed buildings using synthetic aperture radar (SAR) data. The standard procedure for identifying damaged buildings is to use change detection by comparing post-seismic to pre-seismic images, but almost no archived high-resolution SAR images were available of the rather remote area damaged by the Wenchuan Earthquake. Building-damage assessment using only post-event SAR images was therefore necessary to assess the areas of damage. In this paper, theoretical assumptions about the appearance of collapsed buildings in high-resolution SAR images were drawn and verified with visual feature interpretations of real SAR images from the area. [ABSTRACT FROM AUTHOR]

Precise global/regional land cover mapping is of fundamental importance in studies of land surface processes and modelling. Quantitative assessments of the map quality and classification accuracy for existing land cover maps will help to improve accuracy in future land cover mapping. We compare and evaluate four land cover datasets over China. The datasets include the Version 2 global land cover dataset of IGBP, MODIS land cover map 2001, a global land cover map produced by the University of Maryland, and the land cover map produced by the global land cover for the year 2000 (GLC 2000) project coordinated by the Global Vegetation Monitoring Unit of the European Commission Joint Research Centre. The four maps used different classification systems, which made the comparison difficult. So we first aggregated these maps by reclassifying them using a unified legend system. A large-scale, i.e. 1:100 000 land cover map of China was used as the reference data to validate the four maps. The results show that the GLC2000 land cover map represents the highest accuracy. However, it has obvious local labelling errors and a zero labelling accuracy for the wetland type. The MODIS land cover map ranks second for type area consistency and third for sub-fraction overall accuracy compared with reference data, which may be affected by the local labelling error. The IGBP land cover map has good labelling accuracy, although it has a local labelling error and third consistency for type area. The labelling accuracy and type area consistency for the reference data of UMd land cover map is low. We conclude that the accuracies of all the datasets cannot meet the requirements of land surface modelling. For the reference data, i.e. the 1:100 000 land cover map, the classification system needs to be transferred to a well recognized one that has been used commonly in land surface modelling. In addition, we propose an information fusion strategy to produce a more accurate land cover map of China whose classification system should be compatible with the well-accepted classification system used in land surface modelling. [ABSTRACT FROM AUTHOR]

The application of spaceborne imaging radar data to archaeological survey in arid regions was investigated at a study area in the Gobi Desert of southern Mongolia. A repertoire of computer enhancement regimens specific to archaeological applications was applied to RADARSAT imagery of the study area to reduce noise, detect lineaments, or otherwise enhance the data. The imagery was then georectified and integrated into a large area mosaic, creating detailed multi-layered image-maps that were used to direct ground exploration. During two field seasons with the Joint Mongolian-Russian-American Archaeological Expedition (JMRAAE) in 1997 and 1998, precise latitude/longitude information was obtained with Global Positioning Satellite (GPS) devices, establishing Ground Control Points with which to further georectify the image-maps. Both navigation and archaeological site selection were enhanced by hydrologic and topographic information in these satellite image-maps. The JMRAAE field team successfully located Palaeolithic cultural artifacts showing little or no surface expression, most often in association with ancient watercourses. The team was able to navigate accurately through the extreme desert terrain using the image-maps and GPS in this otherwise only minimally mapped area, thereby facilitating detailed archaeological reconnaissance and surrey. [ABSTRACT FROM AUTHOR]