Simulation Of Surface Water And Heat Fluxes In The Upper Minjiang River Based On SiB2

The water and heat exchange between the surface and the atmosphere plays a key role in global weather and climate change,hydrology and ecosystem processes.It's important to accurate and quantitative modeling and monitoring regional land surface water/heat flux,which has great significant to improve the utilization of regional water and heat resources,restore regional ecology,improve the accuracy of weather forecasts,and rationally manage water resources.Land surface process models have significant advantages in continuous dynamic simulation of surface water and heat fluxes in regional scale.Amount them,the Si B2(Simple Biosphere Model 2)land surface model is one of the ideal land surface process models for modeling surface water/heat fluxes.Howener,its adaptability research in mountain environment is insufficient.As a view to this question,taking the upper Minjiang River as a research area,the thesis uses the Si B2 model to simulate surface water and heat fluxes at the regional scale.The main work and research results of the thesis are as follows:(1)Based on the Si B2 model definition of vegetation and soil types,simplified classification of land use data and soil data in the upper Minjiang River.And then,according to the spatial resolution of 1 ° × 1 °,the vegetation types and soil types that occupy the most area in each pixel are calculated,so as to construct a parameterization scheme of the Si B2 model that reduces the impact of spatial heterogeneity in the study area,and finally make the large-scale regional water and heat flux simulation has a good operational.Verification of ET estimated by the model in different time scales suggests that the Si B2 model is feasible in the research area.Correlation coefficients of simulated evapotranspiration and measured evapotranspiration on daily scale in February,May,August,and November were0.708,0.747,0.58,and 0.617,respectively.The relative error on the monthly scale is between 1.48% and 20.72%;the annual relative error is 6.99%.(2)Analysis of evapotranspiration of different vegetations in the upper Minjiang River shows that each vegetation has obvious characteristics of dailyvariation and obvious seasonality.The daily evapotranspiration is smaller in February and November,and the daily evapotranspiration is larger in May and August.On the monthly scale,the vegetation evapotranspiration in the upper Minjiang River has obvious seasonal changes with climate change.In the growing season,the evapotranspiration accounts for more than 58% of the total annual evapotranspiration,while the evapotranspiration accounts for less than 40% of the annual total in the non-growing season.(3)Analysis of continuous dynamic changes of regional hydrothermal characteristics in the upper Minjiang River in 2013.The results show that regional evapotranspiration is larger in spring and summer,with daily average evapotranspiration of 3.71 mm and 3.88 mm,followed by autumn,daily average evapotranspiration is 1.87 mm,and minimum in winter,daily average evapotranspiration is 1.01 mm.The high-value areas of spring evapotranspiration are mainly concentrated in low-altitude areas such as Dujiangyan,where crops are densely grown.The overall evapotranspiration in the study area is high in summer and autumn,and the high-value areas are mainly concentrated in the sub-watersheds such as Heishui,Zagunao,and Minjiang.Evapotranspiration in the study area is generally low in winter.Areas with high evapotranspiration are mainly concentrated in areas below 3000 m above sea level.(4)Regression analysis of evapotranspiration and environmental factors in the study area show that the evapotranspiration is significantly correlated with temperature and altitude on an annual scale,with correlation coefficients of 0.785 and0.733,respectively.And the correlation with precipitation was poor.On the monthly scale,evapotranspiration shows obvious seasonality with temperature and altitude,and the correlation coefficient with precipitation is higher in winter than in other seasons.The seasonal changes of monthly evapotranspiration are basically consistent with the trends of temperature and precipitation.All three peak in summer and then decline.Compared with the other five counties,the evapotranspiration in Dujiangyan has the lowest correlation with temperature and precipitation.