Collaborative Research: Physical Drivers of Equivalent Temperature Variability

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This research project will quantify historical and projected future variability in equivalent temperature in the eastern United States. Equivalent temperature is a metric that considers the total energy content of near-surface air by accounting for both the dry (sensible heat) and moist (latent heat) components. It therefore aligns well with human heat stress, which increases when temperature and humidity are simultaneously elevated. Because equivalent temperature is sensitive to changes in both temperature and humidity, variations in equivalent temperature can reflect processing occurring across a range of scales from global to regional. The objective of this project is to diagnose and attribute historical changes in equivalent temperature to processes occurring at the regional scale (e.g. changes in humidity resulting from soil moisture anomalies), the synoptic scale (e.g. changes in temperature and humidity associated with changes in the atmospheric circulation), and the global scale (e.g. changes in temperature and humidity associated with changes in radiative forcing from greenhouse gases). The project will investigate these processes within coupled atmosphere ocean general circulation models and regional climate models in the context of developing 21st-century equivalent temperature projections.This project will address research needs identified in the National Climate Assessment process: to better understand atmospheric responses to atmospheric composition change and to improve understanding of atmospheric changes that may threaten human health and well-being. Equivalent temperature variability has not been previously considered in terms of multiple scales of influence. Attributing variations in equivalent temperature to the underlying processes across the spatial scales at which they act will allow exploration of mechanistic understanding of equivalent temperature tendencies in the historical record. Downscaling atmosphere ocean general circulation models using statistical and dynamical approaches with knowledge of the driving processes will allow the researchers to develop the best available projections of future equivalent temperature output and to contextualize those projections within a rigorous understanding of drivers of historical change. The results of the project will have broad implications for climate change adaptation and planning, because changes in equivalent temperature and its components may be critical for both human health and agriculture this century. Project results will be institutionally archived and made available to the research community. The project provides support for multiple graduate students at each institution, and thus contributes to development of the next generation of geographers and atmospheric scientists.