Influence of the Asian Monsoon on the Couplings between Stomatal Conductance and Micrometeorological Variables of Forest Ecosystems in East Asia

Abstract:

The performance of land surface models deteriorates under extreme climate conditions (e.g., drought) because of fundamental changes in the system structure. The ecohydrologic system is complex system in which the relationships between the variables in the system change depending on time and system state. A monsoon introduces a profound alteration in process which may define a shift in the system state. Transpiration in the ecohydrologic system is an important point of contact between water, carbon, and energy exchange subsystems, and the stomatal conductance is one of the key factors which controls transpiration.

We utilized transfer entropy in a dynamical process network application to define changes in system state by observing changes in the couplings between this system’s carbon, water, and energy subsystems. We quantified the transfer entropy from the micrometeorological variables of a flux tower i.e., solar radiation, vapor pressure deficit, air temperature, and soil water content to the stomatal conductance for the five forest ecosystems in East Asia. The strength of this coupling increased significantly during and after the monsoon. Based on the result, we are modifying the parameterization of stomatal conductance to integrate the biological adaptation to the monsoon into the simulation of transpiration in a land surface model.

Acknowledgment. This research was supported by the Korea Meteorological Administration Research and Development Program under Grant CATER 2014-3030.