Implementation of a two-way interactive atmospheric and ecological model and its application to the central United States

A coupled Regional Atmospheric Modeling System (RAMS) and ecosystem (CENTUR Y) modeling system has been developed to study regional- scale two- way int eractions between the atmosphere and biosphere. Both atmospheric forcings a nd ecological parameters are prognostic variables in the linked system. The atmospheric and ecosystem models exchange information on a weekly time ste p. CENTURY receives as input air temperature, precipitation, radiation, win d speed, and relative humidity simulated by RAMS. From CENTURY- produced ou tputs, leaf area index, and vegetation transimissivity are computed and ret urned to RAMS. In this way, vegetation responses to weekly and seasonal atm ospheric changes are simulated and fed back to the atmospheric-land surface hydrology model. The coupled model was used to simulate the two- way biosphere and atmospher e feedbacks from 1 January to 31 December 1989, focusing on the central Uni ted States. Validation was performed for the atmospheric portion of the mod el by comparing with U. S. summary- of- the- day meteorological station obs ervational datasets, and for the ecological component by comparing with adv anced very high- resolution radiometer remote- sensing Normalized Differenc e Vegetation Index datasets. The results show that seasonal vegetation phen ological variation strongly influences regional climate patterns through it s control over land surface water and energy exchange. The coupled model ca ptures the key aspects of weekly, seasonal, and annual feedbacks between th e atmospheric and ecological systems. In addition, it has demonstrated its usefulness as a research tool for studying complex interactions between the atmosphere, biosphere, and hydrosphere.