Modeling And Application Of Meteorological Elements Profile In Forest Canopy

Carbon and water cycling in terrestrial ecosystem has become the core issue of global climate change scientific research. It was important to predict future climate change that carbon and water flux was simulated accurately in terrestrial ecosystem. Using the data of microclimate observed at temperate coniferous and broad-leaved mixed forest ecosystem over Changbai Mountain during 2003 to 2008, with April, July, October and January represented as spring, summer, autumn and winter, respectively, the vertical distribution patterns of them and their diurnal variations were analyzed on typical sunny days in four representative months, and the profile functions of air temperature and vapor pressure with observed height under the canopy top were constructed by method of using the top of canopy air temperature and water vapor pressure as normalized values. The results are as followed:(1)The diurnal variation of air temperature characterized by single peak curve obviously with the highest value at 15:00 and the lowest at dawn. The diurnal air temperature range decreased with higher height in all seasons and with the maximum diurnal air temperature range in autumn and minimum in winter. (2)In spring, autumn and winter, air temperature within forest increased as height ascended accompanied by obvious diurnal change pattern. The vertical gradient of air temperature was extremely large at times except noon, whereas the gradient was small and even showed the trend of air temperature decreasing as height ascended at noon. In summer, air temperature increased with observed height higher at any times. (3)The diurnal variations of the vapor pressure were different in four seasons. The vapor pressure showed diurnal patterns by single peak curve in spring, autumn and winter contract with that by double peak curve in summer. (4)The vertical distribution of vapor pressure at given time was seasonal divergence obviously, whereas at given season they had the similar vertical distribution at different times. The vertical gradient of vapor pressure was larger in summer than that in other seasons characterized by vapor pressure went down with observed height higher. (5) Establishing model of temperature profile:Th=a-TH-exp(b-(h-H)/H), The model had good simulation for diurnal variations at different observed heights(P<0.01), and the simulated results had obvious seasonal changes, good simulation in Spring and Winter and the error was less than 0.25℃, so RMSE was less than 0.46℃ increased in Summer and Autumn. (6)Comparison simulated values of canopy carbon flux that were using temperature profile model and observed data, respectively, the results showed their slope k≈1.00 and R2≥0.9988, The simulated Temperature could replace gradient observed data and be used to canopy simulation study of carbon and water flux. The basis was provided by research results for accurate simulation and promotion the model of canopy carbon and water flux.