Temperature-dependent composition of summertime PM in observations and model predictions across the Eastern U.S.

Throughout the U.S., summertime fine particulate matter (PM) exhibits a strong temperature (T) dependence. Reducing the PM enhancement with T could reduce the public health burden of PM now and in a warmer future. Atmospheric models are a critical tool for probing the processes and components driving observed behaviors. In this work, we describe how observed and modeled aerosol abundance and composition varies with T in the present-day Eastern U.S. with specific attention to the two major PM components: sulfate (SO ) and organic carbon (OC). Observations in the Eastern U.S. show an average measured summertime PM-T sensitivity of 0.67 μg/m/K, with CMAQ v5.4 regional model predictions closely matching this value. Observed SO and OC also increase with T; however, the model has component-specific discrepancies with observations. Specifically, the model underestimates SO concentrations and their increase with T while overestimating OC concentrations and their increase with T. Here, we explore a series of model interventions aimed at correcting these deviations. We conclude that the PM-T relationship is driven by inorganic and organic systems that are highly coupled, and it is possible to design model interventions to simultaneously address biases in PM component concentrations as well as their response to T.