Articles | Volume 16, issue 23
Research article
09 Dec 2016
Research article |  | 09 Dec 2016

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

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

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.

Short summary
This paper provides empirical evidence that the year-to-year variability of summertime ozone over Houston is linked to the Bermuda High (BH) large-scale circulation patterns. It identifies two BH indices that can explain up to 70 % of the interannual variability of summertime ozone in Houston and illustrates the mechanism underlying the BH and ozone linkage. Such a mechanism is tested for applicability to other coastal urban regions along the US Gulf Coast.
Final-revised paper