我国江淮流域近40年异常初终霜冻的分析   总被引：5，自引：1，他引：5       下载免费PDF全文

陈乾金  夏洪星 《应用气象学报》1995,6(1):50-55

该文用地面最低温度资料，以≤0℃作为霜冻指标，定量地确定出现异常霜冻的判别标准，研究了近40年初终霜冻异常的气候特征。结果表明:初终霜冻的异常明显存在地区差异。其变化周期以2～3年和准12年最普遍。其偏离均值大致有两种波型:反向变化和同向变化。前者在淮河流域较突出，后者在长江流域较普遍。当其出现反向变化趋势，且二者偏离均值达最大时，该时期为初霜冻异常偏早(偏晚)，终霜冻异常偏晚(偏早)的活跃期。同样，当初、终霜冻出现同向变化时，初、终霜冻异常活路期亦呈现同向变化。  相似文献   

Large-scale interannual variation of the summer monsoon over India and its empirical prediction     

Nityanand Singh 《Journal of Earth System Science》1995,104(1):1-36

Large-scale interannual variability of the northern summer southwest monsoon over India is studied by examining its variation in the dry area during the period 1871–1984. On the mean summer monsoon rainfall (June to September total) chart the 800 mm isohyet divides the country into two nearly equal halves, named as dry area (monsoon rainfall less than 800 mm) and wet area (monsoon rainfall greater than 800 mm). The dry area/wet area shows large variations from one year to another, and is considered as an index for assessing the large-scale performance of the Indian summer monsoon. Statistical and fluctuation characteristics of the summer monsoon dry area (SMDA) are reported. To identify possible causes of variation in the Indian summer monsoon, the correlation between the summer monsoon dry area and eleven regional/global circulation parameters is examined. The northern hemisphere surface air temperature, zonal/hemispheric/global surface air and upper air temperatures, Southern Oscillation, Quasi-biennial oscillation of the equatorial lower stratosphere, April 500-mb ridge along 75°E over India, the Indian surface air temperature and the Bombay sea level pressure showed significant correlation. A new predictor parameter that is preceding year mean monsoon rainfall of a few selected stations over India has been suggested in the present study. The stations have been selected by applying the objective technique ‘selecting a subset of few gauges whose mean monsoon rainfall of the preceding year has shown the highest correlation coefficient (CC) with the SMDA’. Bankura (Gangetic West Bengal), Cuddalore (Tamil Nadu) and Anupgarh (West Rajasthan) entered the selection showing a CC of 0.724. Using a dependent sample of 1951–1980 a predictive model (multiple CC = 0.745) has also been developed for the SMDA with preceding year mean monsoon rainfall of the three selected stations and the sea level pressure tendency at Darwin from Jan–Feb to Mar–May as independent parameters.  相似文献   

温江站有无降水日的边界层特征对比分析     

卢萍 《沙漠与绿洲气象(新疆气象)》2020,14(1):80-88

本文基于2016年6月21日~7月31日温江站边界层塔和加密探空观测获取的资料，对比分析了该站有雨日和无雨日的边界层大气特征，得到以下结论：1、温江站7月的降水量较多，降水时段以凌晨2:00~6:00居多，呈现典型的“夜雨”特征。2、边界层内大气各个气象要素场在有无降水日具有非常明显的差异，探空观测的低层大气表现为：无雨日白天边界层呈现典型的混合边界层特征。有雨日边界层大气温度总是小于无雨日，在极大值出现的午后时段二者的差值最大。有雨日近地层大气比湿在8:00、14:00和20:00三个时次都明显高于无有雨日，比湿日变化幅度低于无雨日。温江站边界层低层大气的风速总体较小，有雨日的风速明显大于无雨日。3、边界层塔观测显示：有雨日太阳短波辐射以及各个地表通量的极大值仅为无雨日的2/3左右。白天，有雨日的温度低于无雨日，日变化幅度比无雨日低3oC左右；夜间二者都呈现显著的逆温现象。有雨日白天比湿高于无雨日，夜间则低于无雨日，有无雨日比湿日变化幅度比无雨日少2g/kg；白天，有雨日风速日变幅也略小于无雨日，除了午后时段有雨日在凌晨2:00时还出现另外一个风速极大值点；有雨日的气压值总是略高于无雨日，白天的气压差值比夜间大。白天，有雨日各个地面观测量的极值出现时间总是略晚于无雨日1h左右。  相似文献   

Increasing the detail of European land use/cover data by combining heterogeneous data sets     

Konštantín Rosina  Filipe Batista e Silva  Pilar Vizcaino  Mario Marín Herrera  Sérgio Freire  Marcello Schiavina 《International Journal of Digital Earth》2020,13(5):602-626

ABSTRACT

Data on land use and land cover (LULC) are a vital input for policy-relevant research, such as modelling of the human population, socioeconomic activities, transportation, environment, and their interactions. In Europe, CORINE Land Cover has been the only data set covering the entire continent consistently, but with rather limited spatial detail. Other data sets have provided much better detail, but either have covered only a fraction of Europe (e.g. Urban Atlas) or have been thematically restricted (e.g. Copernicus High Resolution Layers). In this study, we processed and combined diverse LULC data to create a harmonised, ready-to-use map covering 41 countries. By doing so, we increased the spatial detail (from 25 to one hectare) and the thematic detail (by seven additional LULC classes) compared to the CORINE Land Cover. Importantly, we decomposed the class ‘Industrial and commercial units’ into ‘Production facilities’, ‘Commercial/service facilities’ and ‘Public facilities’ using machine learning to exploit a large database of points of interest. The overall accuracy of this thematic breakdown was 74%, despite the confusion between the production and commercial land uses, often attributable to noisy training data or mixed land uses. Lessons learnt from this exercise are discussed, and further research direction is proposed.  相似文献   

Assessing global Sentinel-2 coverage dynamics and data availability for operational Earth observation (EO) applications using the EO-Compass     

Martin Sudmanns  Dirk Tiede  Hannah Augustin  Stefan Lang 《International Journal of Digital Earth》2020,13(7):768-784

ABSTRACT

Sentinel-2 scenes are increasingly being used in operational Earth observation (EO) applications at regional, continental and global scales, in near-real time applications, and with multi-temporal approaches. On a broader scale, they are therefore one of the most important facilitators of the Digital Earth. However, the data quality and availability are not spatially and temporally homogeneous due to effects related to cloudiness, the position on the Earth or the acquisition plan. The spatio-temporal inhomogeneity of the underlying data may therefore affect any big remote sensing analysis and is important to consider. This study presents an assessment of the metadata for all accessible Sentinel-2 Level-1C scenes acquired in 2017, enabling the spatio-temporal coverage and availability to be quantified, including scene availability and cloudiness. Spatial exploratory analysis of the global, multi-temporal metadata also reveals that higher acquisition frequencies do not necessarily yield more cloud-free scenes and exposes metadata quality issues, e.g. systematically incorrect cloud cover estimation in high, non-vegetated altitudes. The continuously updated datasets and analysis results are accessible as a Web application called EO-Compass. It contributes to a better understanding and selection of Sentinel-2 scenes, and improves the planning and interpretation of remote sensing analyses.  相似文献   

Monitoring interannual dynamics of desertification in Minqin County,China, using dense Landsat time series     

Xiaolin Zhu  Kwok Huen Leung  Wing Sze Li  Lek Kin Cheung 《International Journal of Digital Earth》2020,13(8):886-898

ABSTRACT

Minqin County in northwestern China is highly affected by desertification. Campaigns have been initiated in recent decades to combat desertification in Minqin. To assess the effectiveness of these campaigns, this study used a dense Landsat time series from 1987 to 2017 to investigate the interannual dynamics of vegetation coverage and greenness over the past 31 years. First, this study applied an advanced technology to reconstruct a high-quality Landsat annual time series. Specifically, one image in the vegetation-peak season was selected as the base image in each year, and then problematic pixels were interpolated by the neighborhood similar pixel interpolator using ancillary images in the same year. Second, the land cover map and the enhanced vegetation index (EVI) were derived from all reconstructed images. Third, the change of vegetation coverage and EVI values over the 31 years were analyzed. The results show that the total vegetation coverage and greenness increased during the 31 years. Linking this change trend to other factors suggests that vegetation in Minqin County is highly affected by agriculture and groundwater supply rather than by climate. To mitigate desertification in a sustainable way, agriculture should be well managed to avoid overconsumption of natural resources such as underground water.  相似文献   

Testing the robustness of the physically-based ECOMAG model with respect to changing conditions     

A. Gelfan  Yu Motovilov  I. Krylenko  V. Moreido  E. Zakharova 《水文科学杂志》2020,65(Z1):1266-1285

Abstract

The robustness of the physically-based, semi-distributed hydrological model ECOMAG with respect to changing (climatic or land-use) conditions was evaluated for two basins, considered within the modelling workshop held in the frame of the 2013 IAHS conference in Göteborg, Sweden. The first basin, the Garonne River basin, France, is characterized mostly by changes in climatic conditions, while the second, Obyån Creek, Sweden, was exposed to drastic land cover change due to deforestation. Tests were conducted to evaluate the model’s ability to simulate with acceptable accuracy the changing hydrological regime of each basin and to retain, in the process, relatively stable values of the parameters. Acceptable performance of the ECOMAG model was obtained under the different combinations of the calibration/evaluation periods, including, importantly, the periods of hydrological regime changes in both basins.  相似文献   

北半球雪盖与我国夏季降水的相关分析   总被引：5，自引：0，他引：5  

王光宇  曾群柱 《冰川冻土》1994,16(2):181-184

本用１９６７－１９８３年北半球卫星雪盖资料，对北半球北美、欧亚和青藏高原三个区域雪盖与我国东部地区夏季降水进行了相关分析。分析表明，三个区域夏季雪盖与夏季降水，以欧亚雪盖与降水的相关性最好，与青茂高原的雪盖相关性最小；北美冬、夏季雪盖与降水相关分布有着某种相反的分布，而青藏高原冬、夏季积雪与降水相关分布却有着某种相似的分布。  相似文献   

中国天山艾肯达坂透风式下导风防雪工程     

王中隆 《山地学报》1994,(4)

据艾肯达坂风雪流形成条件，提出了贴地气层分离是公路吹雪堆积的机理，通过对密闭式下导风能量转换和流场结构的剖析，创造了透风式下导风防雪工程。其实施后，改变了公路因冬半年严重雪阻而不能通车的状况，经济效益和社会效益俱佳；  相似文献   

钱塘江护堤抛石铺盖的探地雷达试验   总被引：1，自引：0，他引：1  

邓世坤  王惠濂 《地球科学》1993,18(3):345-351

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