Co-occurrence of Extreme Heat and Pollution in the Southwest United States
Arjun Maganti, Zachary Espinosa
Affiliation: Basis Independent Silicon Valley
IJSCAR Vol. 2, Issue 1 (2025) · pp. 9–14
Abstract
In this research paper we examine the co-occurrence of extreme heat and humidity in the Southwest United States between 2003 and 2023. Using simple statistical regression analysis time series analysis and spatial compositing we demonstrate that humidity when coinciding with extreme heat tends to exacerbate air pollution. Specifically we find that humidity and heat have the largest impact of PM d <2.5um and carbon monoxide (CO) with a lesser impact on other pollutants. We hypothesize the hygroscopic nature of PM2.5 particles and the reactive CO molecules with NOx and VOC compounds lead to amplified reaction rates during extreme heat and humidity. Next we examine the meteorological conditions associated with the co-occurrence of extreme heat and humidity in Los Angeles and Sacramento. We demonstrate that heat waves in Los Angeles are associated with strong northwesterly winds originating in the Mojave Desert that are associated with anomalous warm atmospheric heat transport. This is also associated with decreased on-shore winds from the Pacific Ocean which typically have a cooling effect. Decreased onshore winds resultantly lead to an exacerbation of heat conditions. These findings can contribute to further prevention of possible wildfire events caused by extreme heat conditions and also lead to further protections against cases of extreme pollution in the southwestern United States.
Keywords: co-occurrence of extreme heat and pollution, climate change, Southwest United States, compound events, air pollution