Application of a regional air quality model to study aspects of the characteristics of the TOMS/SBUV Tropospheric Ozone Residual (TOR)

Studies of episodes in the planetary boundary layer (PBL) using the Tropospheric Ozone Residual (TOR) that is calculated as the difference between the vertically-integrated stratospheric ozone using data from the Solar Backscatter Ultraviolet (SBUV) remote sensing system and the total ozone from the Total Ozone Mapping Spectrometer (TOMS), rely heavily on the notion that the enhanced levels of ozone in the PBL have a marked influence on the TOR values and its distribution. It has been shown in past studies that the enhanced ozone in the PBL during an episode could increase the value of the TOR by as much as 10 DU. However, it also has been shown that there is poor correspondence between the daily surface ozone concentration and the TOR and between daily values of the vertically-integrated ozone in the troposphere using ozonesonde data and the TOR. Best correspondence between surface ozone and the TOR and between daily values of the vertically-integrated ozone in the troposphere using ozonesonde data and the TOR was found in monthly, seasonal, and annual average data. The question remains is there a relationship between the TOR and the ozone in the lower troposphere and when is the ozone in the lower troposphere a significant contributor to the value and distribution of the TOR. In this study, we have attempted to develop some insight into what vertical levels in the troposphere provided the principal contribution to the distribution of the TOR. In particular, the study examined how the ozone distribution in the lower, middle or upper troposphere contributed to the TOR and its distribution. In order to accomplish the objective of this study, ozone data from simulations using the United States Environmental Protection Agency (EPA) Models-3 Community Multiscale Air Quality (CMAQ) model were combined with TOMS/SBUV TOR data for a case study in July 1988.