Air Quality during Heatwave Periods over Land and Water during the OWLETS-2 Campaign

The Ozone Water-Land Environmental Transition Study 2 (OWLETS-2) field campaign during the summer of 2018 was designed to characterize spatial and vertical distribution of pollutants in the upper west bank of the Chesapeake Bay, within the I-95 corridor of Washington, DC, and Baltimore, MD, region. During the intensive periods (June, 2018), two heatwaves had been observed, accompanied with high ozone concentration episodes reported by the Maryland Department of Environment (MDE). This study has two folded subjects. One is to present the results from the Howard University Beltsville Campus (HUBC) effort to characterize the evolution of thermodynamic parameters, aerosol, and trace gases mixing ratios within the Planetary Boundary Layer (PBL) during these heatwave periods. At HUBC campus, an array of upper air measurements monitors thermodynamic parameters (Micro-Wave Radiometer, Radiometrics, model 3000), and aerosols (Ceilometer, Luft, model Nimbus-15K) profiles. MDE has an air quality monitor station that collects trace gases (O₃, NOx, CO, and SO₂), and surface aerosols (PM 2.5, and PM10), and wind profile (RAPTOR DBS-BL/LAP-3000). During these heatwave periods, 12 ozonesondes (EnSci, model Z with Vaisala RS92 SGPD) were launched. At the end of each heatwave period, high ozone concentration (> 80ppb) were observed within the PBL, showing how the air quality has deteriorated for this region.

Also, four boat cruises were performed to monitor the in situ conditions at the surface of the Chesapeake Bay (see figure 1). The boat was instrumented with a suit of instruments to measure trace gases (O₃, SO₂, CO, NOx), meteorological data (pressure, temperature,, humidity, and wind), radiation data (solar radiances, irradiance, and water skin temperature), and aerosols (spectrometer, and aerosol backscatter profile). Early results show that the highest ozone levels (74 ppb) were detected on the second day of the second heatwave, on 6/30, with moderate SO2 and CO concentration levels (0.49ppb and 0.45 ppb, respectively). After 2 days, on 7/2, ozone concentrations did not exceed 70 ppb, with similar concentration levels of SO2 and CO (0.51 and 0.35 ppm respectively), and air temperature 2 to 3 ⁰C higher. On the other hand, aerosol total concentration increased from 6/29 to 7/2, from 59.7 to 159 #/cm3, respectively.

Figure1: Boat trajectory (yellow line) over the Chesapeake Bay during OWLETS 2 campaign on 7/2/2018.