Interannual variability and trends of summertime PM2.5-based air quality in the Intermountain West

Summertime air quality is a growing public health concern in the populated region of Northern Utah. Whereas winter air pollution is highly linked with local atmospheric temperature inversions associated with upper atmospheric high-pressure and radiational cooling in valleys, the relationship between climate factors and the frequency of poor air quality during summer is still unknown. Analyzing the last 20 years of data, we demonstrated that summertime unhealthy days (as defined by PM2.5 air quality index level) in Northern Utah highly correlate with the number of dry-hot days, wildfire size, and an upper atmospheric ridge over the Northwestern United States. The persistent atmospheric ridge enhances lightning-caused fire burned areas in northwestern states and then transports the wildfire smoke toward Northern Utah. Similarly, climate model simulations confirm observational findings, such as an increasing trend of the upper atmospheric ridge and summertime dry days in the northwestern states. Such metrics developed in this study could be used to establish longer-term monitoring and seasonal forecasting for air quality and its compounding factors, which is currently limited to forecasting products for only several days.

Automated summary

This study examines the relationship between climate factors and summer air quality in Northern Utah. The analysis of 20 years of data reveals that the number of unhealthy days is strongly correlated with dry-hot days, wildfire size, and an upper atmospheric ridge over the Northwestern United States. Climate model simulations confirm these observations, suggesting a trend of increasing upper atmospheric ridge and dry days in the northwestern states.