Effects of Land Use on Energy Budget in the Semi-Arid Region of Inner Mongolia, China

The objectives of this paper are to mechanistically explain the variability of energy (Rn, L, G, Q, H, T) and water (ET, E, EF, Tr, LWSI, Wleaf, M) fluxes along a climatic and land use gradient using a network of in situ eddy flux towers and examine the spatial variability of Rn and G in contributing energy enclosure to better incorporate land surface characteristics in modeling regional water and energy balances. Energy balance closure for the study sites ranged from 0.75 to 0.89 (30-min scale), from 0.87 to 1.04 (daily scale), and from 0.91 to 1.10 (annual scale). The seasonal changes in Rn, LE, Hs and G of the four sites were similar, with very low values during the snow cover from December to February and increasing trend in the growing season. The energy enclosure had a daily average residual of 8-19 W m-2 with an ordinary least squares slope of 83-96%, and the largest residual of 50-70 W m-2 with replicates at large scales. This enclosure variation was larger due to G than to Rn. The uncertainty associated with Rn was 18 W m-2 (5% of Rn) at midday and 11 W m-2 (13%) for daily mean, while G was 60 W m-2 (13%) at midday and 27 W m-2 (35%) for daily mean. The maximum spatial variation integrating Rn and G contributing to energy enclosure was near 40 W m-2 (40%) on daily base. When linking the above ground measurements with MODIS, we assesed how land use change changes the energy budget of the region. The results allow us to partition the transpiration and evaporation from ET.