Evaluating Drought Responses of Surface Ozone Precursor Proxies:
Variations with Land Cover Type, Precipitation, and Temperature
Abstract
Prior work suggests drought exacerbates U.S. air quality by increasing
surface ozone concentrations. We analyze 2005-2015 tropospheric column
concentrations of two trace gases that serve as proxies for surface
ozone precursors retrieved from the OMI/Aura satellite: nitrogen dioxide
(ΩNO2; NOx proxy) and formaldehyde (ΩHCHO; VOC proxy). We find 3.5% and
7.7% summer drought enhancements for ΩNO2 and ΩHCHO, respectively,
corroborating signals previously extracted from ground-level
observations. When we subset by land cover type (using MCD12Q1) and
isolate the influences of precipitation and temperature on drought, we
find the strongest ΩHCHO drought enhancement (10%) in the woody
savannas of the Southeast US. This increase likely reflects biogenic VOC
emissions and occurs independently with both high temperature and low
precipitation. The strongest ΩNO2 drought enhancement (6.0%) occurs
over Midwest US croplands and grasslands, which we infer to reflect the
sensitivity of soil NOx emissions to temperature.