Abstract : 3N.5
Interaction between the atmosphere and mountain forest: Local scale assessment of energy and water fluxes

Julia Stoyanova, Christo Georgiev
National Institute of Meteorology and Hydrology

The strength of interaction among soil, forest, and atmosphere is of decisive importance in formation of microclimate at mountain environment. A site-scale model ‘Forest_SVAT_Bg’ has been developed for using as an appropriate tool for evaluation of relevant forested-land-atmosphere biophysical feedbacks. This is a simple one-dimensional (vertical) Soil–Vegetation–Atmosphere Transfer scheme for evaluation of mechanisms that drive the energy and water cycle coupling and shape the ecosystem interface with the atmosphere on a local scale.

The paper presents a case study of modelling the soil-vegetation-atmosphere continuum dynamics on short-term time scale and small space scales appropriate for a single homogeneous patch in scare studied mountain environment of the Balkans (24°41΄; 41°40΄).

The forest_SVAT_Bg model is used for accounting the key parameter that controls the portioning of energy and water fluxes at vegetated land surface, which is the actual evapotranspiration AET and the soil water balance of the surface layer (0-30 cm), deep horizon (0-80 cm) and root zone depth. Soil moisture simulations are validated by in situ measurements and confirm a good model performance (R2 between 0.62 and 0.74). The seasonal forest-atmosphere dynamic coupling is evaluated and the main microclimate modulators (net radiation Rn and its portioning into latent LE -, sensible H-, and soil heat S) at ‘average’ and extreme site environment (relatively ‘dry’/‘wet’) are derived.

Gradients in surface sensible and latent heating associated with different surface states or fluxes are identified. The growing season H/LE ratio averages to 0.46, being 0.71 at ‘relatively dry’ and 0.28 at ‘relatively wet’ conditions. These knowledge about covariances among the microclimate drivers as well as understanding the coupling between natural ecosystems and meteorological processes may be critically important for forecasting extreme events (e.g. flash-floods and droughts) at mountain environment. Modeling framework presents an bottom-up integration approach for geo-referenced land surface-atmosphere analysis that would provide necessary capabilities for scaling the processes related to soil-plant-atmosphere dynamics.