The Study Of Flux Footprint Intypical Subtropical Monsoon Man-planted Forest

The eddy covariance technique is a micrometeorological method to directly measure the exchanges of carbon, water and energy between the vegetation and atmosphere. The spatial resolution of meteorological observation of fluxes can expand from tens of meters to kilometers. The eddy covariance method is most accurate when the contributing area of the fluxes is topographically flat, and vegetation extends uniformly within the footprint area. Currently there are more than100eddy covariance flux observation sites in China. Most of them are established in non-ideal conditions such as forest, undulating surface, patchy canopy area. Therefore, it is important to accurately interpret the ecological representativeness of flux data by evaluation of the spatial representativeness of its footprint in China.To be able to compare the results of three analytical footprint models (FSAM, KM, H) and obtain the actual footprint of QYZ, we analyzed the turbulence flux data which is got from the open-path eddy covariance technique at23m and39m. The main results are as follows:1) Measure height affected the difference of footprint area between KM model (H model) and FSAM model. Roughness affected the difference of the peak of cross-integrated footprint between KM model (H model) and FSAM model. While atmospheric stability affected both differences of footprint area and the peak of cross-integrated footprint.2) The main reason for the differences of three models is that H-model is more empirical than FSAM-model and KM-model which are theoretical. The variance of the way of parametric for FSAM-model and KM-model leads to different results.3) The90%flux footprint of QYZ of23m:a is from10m to40m, e is from780m to1480m, d is from190m to310m, footprint area is from0.23km2to0.7km2, the peak of cross-integrated footprint is from7×10-4to5.9×10-3m-1, the peak locatiom of cross-integrated footprint is from60to150m. while for39m, a is from40m to120m, e is from1560m to3720m, d is from320m to620m, footprint area is from0.8km2to3.5km2, the peak of cross-integrated footprint is from2×10-4to2.7×10-3m-1, the peak locatiom of cross-integrated footprint is from140to580m.4) The90%flux footprint climatology of QYZ of23m is0.51—0.80km2in spring,0.50—>0.78km2in summer,0.32—0.53km2in autumn and0.41—0.65km2in winter; while The90%flux footprint climatology of QYZ of39m is2.34—3.41km2in spring,2.21—>3.10km2in summer,1.68—>2.43km2in autumn and1.79—2.83km2.