Simulation Study Of Hydrothermal Transport In Yangling Agricultural Area Under The Background Of Global Climatic Change

With the intensive human activities, the increase of greenhouse gases is animportant reason for global warming, which changes the agriculture regionalcharacteristics and planting structure and has an effect on agricultural production.Researching the changes of meteorological elements and the energy and water cyclehas important significance to reveal the impact of climate change on agriculturalproduction. This paper researches the meteorological elements change and space-timepattern evolution trend of Yangling agricultural area by using the meteorologicalstatistical methods and the soil-vegetation-atmosphere coupled model. Meteorologicalstatistical methods include the unary linear regression method, the moving averagemethod and the abnormal degree analysis method. These methods are used todetermine the trend and rate of meteorological elements change, and the time andsignificative degree of the changes. The soil-vegetation-atmosphere coupled model isestablished in the basic equations of atmospheric motion, and adopts reasonableturbulent boundary layer parameterization schemes and land surface parameterizationschemes. The model has been used to study the interaction between land surfacephysical process and atmospheric boundary layer. In this paper, the meteorologicalstatistical analysis method is applied firstly, and the climate change and seasonalvariation characteristics of Yangling agricultural area during1955~2010have beenobtained. On this basis, changes of meteorological elements of winter wheat andsummer maize growth period have been studied. Then, the hydrothermal transport ofwinter wheat and summer maize growth period is simulated by using the improvedsoil-vegetation-atmosphere coupled model. It has been obtained the space-timepattern evolution trend of energy and water cycle in Yangling agricultural area. Finally, some sensitivity experiments have been conducted using the model, and theinfluences of albedo, soil water content and vegetation coverage have been researched.The major contributions and conclusions are as follows:1. Meteorological statistical analysis method is applied for climate changeresearch. The annual average temperature of study area presents a rising trend from1955to2010. Warming starts from the mid-1980s, especially since the1990s. Theaverage temperature of all seasons are on the rise. The annual precipitation presents adecreasing trend, because the decrease of precipitation in spring and autumn. Theannual sunshine duration presents a decreasing trend. Anomalies are mostly negativeafter1980. The sunshine duration decreases in all seasons.2. Variations of meteorologic elements and its impacts in winter wheat growthperiod have been analyzed. The warming trend of winter wheat growth period is verysignificant during1955~2010. The benefits of warming include helping the normalseedling emergence, increasing tillering number, ensuring safe wintering, andpromoting earing and spike differentiation. But serious high temperature can affectthe production. An increasing number of precipitations in wintering stage play animportant role on adding entropy and heat preservation. Precipitation increased inreturning green stage can add the number of tillers. The decreasing precipitation injointing-booting and earing-flowering stage can reduce production. Reduction ofsunshine duration forms weak seedlings easily, which hinders photosynthesis.3. Variations of meteorologic elements and its impacts in summer maize growthperiod have been analyzed. During1955~2010, warming in seedling and mature stageof summer maize conducive to the emergence and filling. The decreased temperatureof earing and flower stage can affect production. Increasing precipitation from sow tothe emergence promotes seedling growth. After seedling emergence, the decreasingprecipitation is not conducive to root development. Decreasing precipitation ofjointing stage hinders the panicle development and stem leaf growth. Increasingprecipitation from tasseling to filling stage can ensure high yield. It is not conduciveto the growth that sunshine duration reduces throughout the growing period, whichaffects the yield and quality of maize. 4. Hydrothermal transport has been simulated by using the improvedsoil-vegetation-atmosphere coupled model in crop growth period. With the increase ofvegetation coverage, the net radiation and latent heat flux increases, and the soil heatflux decreases in wheat growth period. The heat cycle manifested as sensible heat inearlier winter and wintering stage, but latent heat after returning green. In maizegrowth period, the net radiation decreases. The soil heat flux decreases with theincrease of vegetation coverage. The heat cycle manifested as latent heat throughoutthe maize growth period. When the settings of initial water content are the same, thesoil water content declines slowly with low vegetation coverage. The potentialtemperature profile of winter wheat and summer maize growth period has obviousseasonal characteristics. Specific humidity decreases with the increase of height inspace. Turbulent kinetic energy and turbulent exchange coefficient is significantlyreduced with increasing vegetation coverage.5. Some sensitivity experiments have been conducted using the improvedsoil-vegetation-atmosphere coupled model. When the albedo decreases, the surfacetemperature, net radiation and latent heat flux increase. Changes in the sensible heatflux, soil heat flux and soil moisture are not obvious. When the soil water contentdecreases, the surface temperature increases, and the net radiation and latent heat fluxdecrease. Changes in the sensible heat flux and soil heat flux are not obvious. Whenthe vegetation coverage increases, the surface temperature and soil heat flux decrease,and the net radiation, sensible heat flux and latent heat flux increase. In the afternoon,the decline of soil water content becomes smaller gradually.