The Temporal and Spatial Variation of Tropospheric Ozone Distribution and the Corresponding Weather in the Bay Area during CABOTS

This study is aiming to investigate the temporal and spatial variation of tropospheric ozone over the coast of northern California using ozonesonde data from Bodega Bay (BBY) and Half Moon Bay (HMB) during the California Baseline Ozone Transport Study (CABOTS) in the summer of 2016. Additionally, Trinidad head (THD) weekly ozonesondes are also utilized to evaluate the temporal and spatial variation along the coast. The goal is to quantify the exchange of lower and upper tropospheric ozone via large scale subsidence in association with synoptic conditions. The MERRA2 reanalysis data, OMI satellite datasets, and model simulations (e.g., WRF-Chem and RAQMS) are employed to evaluate the vertical distribution of ozone and the linkage between synoptic conditions and ozone profile characteristics. More than five cases are selected from last summer’s BBY launch according to the profile characteristics and synoptic conditions at the time. Preliminary results for the case from May 30 to June 2 show the evolution of ozone distribution due to the synoptic effects: the high ozone layer became thicker in the mid-troposphere during the four days while the ridge was building up over the Pacific Ocean, the southwest of California coast and the subsidence was becoming stronger. THD which is over 400 km apart from BBY, shows obvious different ozone vertical distribution from BBY especially the upper level troposphere. With extremely dry air layer, the main source of the BBY upper tropospheric ozone is from stratospheric intrusion. On the other hand, the higher ozone and more moisture upper layer of THD are more likely from horizontal transportation due to the strong wind. It is anticipated that the quantitative results will advance our ability to better monitor upper tropospheric ozone distribution in the Bay Area.