Research On Dynamic Change And Relationship Between Land Use/Cover And Evapotranspiration In Beijing-Tianjin-Hebei Rengion

This research obtained NDVI time-series of different land cover by Hants filter,combine with DEM data,ISODATA,NDWI(Normalized Differential Water Index),MNDWI(Modified Normalized Difference WaterIndex),NDSI(Normalized Difference Snow Index),using CART decision tree to investigate the land cover classification of Beijing-Tianjin-Hebei Region.Based on the remote sensing technique using MODIS and meteorological data,and bringing DEM data to establish a simple and practical model which is capable of depicting the main feature of the process of surface fluxes in Beijing-Tianjin-Hebei Region.This paper regards the Beijing-Tianjin-Hebei Region as a case and analyses the spatial-temporal distribution of LUCC and land surface evapotranspiration from 2001 to 2016,as follows:1)This paper divides the area of Beijing Tianjin Hebei into 7 types of land: one year,two mature farmland,one year cropping farmland,plain forest land,mountain forest land and shrub,grassland,vegetable and non Vegetation Land surface.The overall classification accuracy is more than 90% and the Kappa coefficient is more than 0.84.The results show that the classification results have higher accuracy.2)Taking into account of DEM,algorithm for solar radiation which includes direct solar radiation,diffuse sky radiation and reflection radiation from surrounding terrain was improved considering egional altitude,slope,aspect and the shelter of the topography around,and the sky view factor.It was proved that the correlation between the simulated solar radiation flux and the measured data is above 0.85.3)The instantaneous evapotranspiration was extended to daily,monthly and yearly evapotranspiration with EF and ETrF.The result showed plain aera and mountain aera had more evapotranspiration,Bashang plateau area had low evapotranspiration.For the inter-annual changes,the seasonal difference of evapotranspiration was obvious,highest in summer,followed by the spring and autumn,and lowest in winter.Monthly evapotranspiration in July(average was about 80mm)was higher than other months,monthly evapotranspiration in December(average was less 40mm)was the lowest.4)LUCC control the distribution of evapotranspiration in Beijng-Tianjin-Hebei Region.It is preasently obvious difference.Evapotranspiration volume average of land cover types.As following the change rule: bi-annual planting>vegetable field>forest land>single corp a year planting>grassland.The vegetation coverage also affects thedistribution of evapotranspiration in the Beijing-Tianjin-Hebei Region.Plain area and mountain aera had high vegetation coverage,Bashang plateau had low vegetation coverage,the evapotranspiration of the Beijing-Tianjin-Hebei Region large area mainly distributed in plain area and mountain aera.