Influence of the Bermuda High on interannual variability of summertime ozone in the Houston–Galveston–Brazoria region

Yuxuan Wang,Lu Shen,Beixi Jia,Sing-Chun Wang,Yuanyu Xie,Mark Estes

doi:10.5194/acp-16-15265-2016

Abstract

Abstract. The Bermuda High (BH) quasi-permanent pressure system is the key large-scale circulation pattern influencing summertime weather over the eastern and southern US. Here we developed a multiple linear regression (MLR) model to characterize the effect of the BH on year-to-year changes in monthly-mean maximum daily 8 h average (MDA8) ozone in the Houston–Galveston–Brazoria (HGB) metropolitan region during June, July, and August (JJA). The BH indicators include the longitude of the BH western edge (BH-Lon) and the BH intensity index (BHI) defined as the pressure gradient along its western edge. Both BH-Lon and BHI are selected by MLR as significant predictors (p < 0.05) of the interannual (1990–2015) variability of the HGB-mean ozone throughout JJA, while local-scale meridional wind speed is selected as an additional predictor for August only. Local-scale temperature and zonal wind speed are not identified as important factors for any summer month. The best-fit MLR model can explain 61–72 % of the interannual variability of the HGB-mean summertime ozone over 1990–2015 and shows good performance in cross-validation (R2 higher than 0.48). The BH-Lon is the most important factor, which alone explains 38–48 % of such variability. The location and strength of the Bermuda High appears to control whether or not low-ozone maritime air from the Gulf of Mexico can enter southeastern Texas and affect air quality. This mechanism also applies to other coastal urban regions along the Gulf Coast (e.g., New Orleans, LA, Mobile, AL, and Pensacola, FL), suggesting that the BH circulation pattern can affect surface ozone variability through a large portion of the Gulf Coast.

Highlights

Surface ozone, as an important air pollutant, has significant adverse impacts on both public health and agriculture
We first examined whether this feature can be explained by near-surface temperature, which has been suggested as an important meteorological factor affecting surface ozone in many regions (Fu et al, 2015; Rasmussen et al, 2012; Camalier et al, 2007)
The Bermuda High (BH)-Lon has a higher correlation with the HGBmean meridional wind (V ; r = −0.4—0.7) but does not correlate with the zonal wind (U )

Summary

Introduction

As an important air pollutant, has significant adverse impacts on both public health and agriculture. Surface ozone is influenced by emissions of its precursors, and by meteorological conditions (e.g., Jacob and Winner, 2009). Largescale circulation patterns can lead to local meteorological conditions that are favorable for ozone episodes, such as high temperatures, low wind speeds, clear skies, and stagnation (Nielsen-Gammon et al, 2005a; Ngan and Byun, 2011; Pearce et al, 2011; Psilogloue et al, 2013; Pugliese et al, 2014). Surface ozone in the western US is affected by mid-latitude cyclones that transport Asian pollution eastward across the Pacific (Lin et al, 2012) and latespring stratospheric intrusions occurring more frequently following strong La Niña winters (Lin et al, 2015). In the Midwest and the northeastern US, polar jet frequency is a good

Results

Discussion

Conclusion