2017 Ozone Season Summary

The 2017 ozone season had the second-fewest exceedance days in recorded history in the state of Maryland. There were 17 days when at least one monitor measured 8-hour average ozone greater than 70 parts per billion (ppb). Excluding the special purpose monitor on Hart-Miller Island in the Chesapeake Bay, there were only 12 exceedance days. The only year with fewer exceedance days than 2017 was 2014 when temperatures remained cooler than normal and transport patterns were mostly unfavorable for high ozone concentrations in Maryland.
 
Overall there were significantly fewer ozone exceedance days in 2017 with near typical summer conditions as compared to near-record heat in 2016. For the 2017 summer (June, July and August), Maryland was near average, just slightly cooler (0.6℉) than the 20th-century average. Along the I-95 corridor temperatures were a bit warmer, but nearly precisely average for the region.

2017 Ozone Exceedance Days in Maryland
(preliminary data)

Historically, Maryland ozone episodes have been regional and consistent. Essentially, yesterday's ozone would persist into the next day, resulting in another exceedance day. However, as background ozone concentrations (the ozone found in the free atmosphere) have faded, so too has the persistence of ozone across the region, and with it, multi-day ozone episodes are fewer, more sporadic and briefer. 

The Hart-Miller Island (HMI) monitoring project has continued to be a success story. 2017 was the first full ozone season measuring ozone and providing "ground truth" for air quality in the Chesapeake Bay. Similar to 2016, MDE found that generally, the air over the Bay does contain higher ozone concentrations than land sites but less than predicted by the air quality models. The HMI monitor was the highest reading ozone monitor in the state about 25% of all days it operated. Of the 17 exceedance days, HMI was the highest reading on 11 days. 


Hart Miller Island Monitoring Station with Jay Szymborski 
Hart-Miller Island (HMI) Ozone Monitoring Project














Detailed Quality of Air Summary Reports are published monthly and are available here. Reports for previous years Ozone Seasons are available here.