GC102-0014
Observations of sea breeze frontal impacts on NYC metro-area O3-distributions

Tuesday, 15 December 2020
Poster
Zongshan Han1, Jorge Gonzalez2, Hongnian Liu3, Yonghua Wu4, David Melecio-Vazquez2, Brian C McDonald5,6, Harold Gamarro7 and Robert D Bornstein8, (1)Nanjing University, Nanjing, China, (2)CUNY City College of New York, Mechanical Engineering, New York, NY, United States, (3)Nanjing University, School of Atmospheric Sciences, Nanjing, China, (4)The City College of New York, New York, NY, United States, (5)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (6)Chemical Sciences Laboratory, NOAA Earth System Research Laboratories, Boulder, CO, United States, (7)CUNY City College of New York, New York, United States, (8)Meteorology, San Francisco, CA, United States
Abstract:
Ozone pollution is a significant air quality challenge for large coastal cities such as NYC metropolitan area, whose concentrations are affected by sea breeze frontal (SBF) passages. The high O3 episode (> 100 ppb) that impacted NYC and inland New Jersey (NJ) on 2 July 2018 was investigated during the Long Island Sound Tropospheric Ozone Study (LISTOS) field campaign. During 1210 to 1230 EST, a sharp aerosol concentration decrease was observed by the City College of New York (CCNY) ceilometer.

The approach of two upper level regional high-pressure systems (Hs) into the NYC area produced low regional daytime Planetary Boundary Layer (PBL)-heights, high temperatures and sunshine on the episode day. The two SBFs observed over NYC and Connecticut, respectively, seemed to merge over NJ at 1500 EST. The NYC front was initially located concurrently with the surface O3 peak, but the SBF moved ahead of the peak as it moved inland over NJ. The upper level mid-afternoon O3 peak at 12 EST east of NYC at Flax Pond, Long Island (LI) was a remnant of earlier residual-layer transported from NYC, while a surface Central LI from 0900 to 1200 EST resulted from recirculation within the SBF.

The CCNY PBL time section ceilometer profiles showed that the SBF passed CCNY just after 1100 EST, consistent with its surface position as determined from analysis of a network of wind velocity observations. The passage first advected clean marine PBL air into City which resulted in a sharp V-shaped temporary (30 min) decrease in aerosol backscattering, followed by a return to pre-frontal peak values. Strong downdrafts behind its inland moving “gravity current head” brought upper level clean air downward to the surface at 1210 to 1230 EST. The resulting second decrease in backscattering resulted in near constant values, albeit at a higher plateau than existed before the front first passed CCNY. This SBF modulated urban air quality episode thus seems to be a unique well documented 40D event that merits further research efforts, e.g., uWRF-Chem simulations.

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