Terrain-Vegetation-Atmosphere Interactions during the North American Monsoon

Abstract:

Terrestrial surface processes and vegetation conditions are anticipated to play important roles in atmospheric phenomena over a range of temporal scales varying from the diurnal cycle up to intra-seasonal variability. In the North American Monsoon system, a strong vegetation response to summer precipitation in the form of regional ecosystem greening over mountainous terrain had long been recognized. Yet, until the North American Monsoon Experiment (NAME) in 2004 and its subsequent investigations, few details on terrain-vegetation-atmosphere interactions had been studied. This talk discusses advances in understanding the coupling of vegetation and hydrologic processes in mountainous landscapes and its implications for atmospheric feedbacks during the North American Monsoon. First, regional vegetation dynamics are quantified using long-term remote sensing observations, then linked to inter-annual precipitation variability, and subsequently used to enhance the intra-seasonal predictability of evapotranspiration. Second, seasonal vegetation dynamics are used to drive a spatially-explicit land surface model applied at two eddy-covariance sites and a medium-sized watershed to identify their impact on soil moisture, total evapotranspiration and its partitioning into soil evaporation and plant-mediated losses to the atmosphere. Third, vegetation dynamics are shown to alter land surface temperature across mountainous landscapes, thus potentially influencing mountain-valley circulations and mesoscale convective systems. Based on the evidence presented, some possible avenues of future research are outlined to quantify the relative importance terrain-vegetation-atmosphere interactions on the North American Monsoon system.