The influence of atmospheric chemistry and climate on atmosphere-biosphere interactions

A modeling tool is developed to investigate the feedbacks between the terrestrial biosphere and the atmosphere, two major components of the Earth system. Changes in environmental variables such as solar radiation, temperature, and atmospheric water vapor can influence the water and energy balances at the land surface. These changes can, in turn, strongly impact vegetation processes, including transpiration, photosynthesis, and the emission of biogenic volatile organic compounds (VOCs). These processes are part of the complex mechanisms within the Earth system that can feedback upon each other and create unexpected responses.; A biogenic VOC emissions algorithm is developed for use within the modeling system. Biogenic VOC emissions, including isoprene, monoterpenes and ORVOCs, account for over half of the total amount of VOCs emitted in East Asia. Additionally, the emissions can be significantly affected by both land cover changes and rising CO₂ concentrations. Because of their importance in predicting ground-level ozone, these terrestrial biosphere-atmosphere feedbacks could have an important influence on air quality prediction and compliance.; As part of the coupled climate-land surface model development, a new land surface model, the Common Land Model (CLM0) is integrated into a regional climate model (RegCM2). For a yearlong simulation over East Asia, the RegCM2/CLM0 slightly improves the winter cold bias that is present in the former RegCM2 simulation and reproduces the seasonal cycle of climate in the region.; Three-dimensional fields of anthropogenic aerosols are added to the RegCM2/CLM0 to investigate biosphere-atmosphere feedbacks. The presence of aerosols reduces leaf temperatures crucial for photosynthesis and biogenic VOC emissions. In a five-day summertime simulation that includes the so-called direct effect of aerosols, there is a 5–8 degree reduction in leaf temperatures within the canopy. In the absence of aerosols, leaf temperatures are beyond the optimum leaf temperature, which slows the photosynthetic rate. The presence of aerosols reduces these temperatures below the optimum, leading to an increase in photosynthesis and transpiration. This result indicates a previously undiscovered mechanism between aerosols and the terrestrial biosphere, and this could have significant implications for future studies in aerosol-climate interactions and the terrestrial carbon balance.