Stratosphere‐to‐troposphere transport revealed by ground‐based lidar and ozonesonde at a midlatitude site

Abstract

[1] This paper presents ozone structures measured by a ground-based ozone lidar and ozonesonde at Huntsville, Alabama, on 27-29 April 2010 originating from a stratosphere-to-troposphere transport event associated with a cutoff cyclone and tropopause fold. In this case, the tropopause reached 6 km and the stratospheric intrusion resulted in a 2-km thick elevated ozone layer with values between 70 and 85 ppbv descending from the $306-K to 298-K isentropic surface at a rate of $5 km day À1 . The potential temperature was provided by a collocated microwave profiling radiometer. We examine the corresponding meteorological fields and potential vorticity (PV) structures derived from the analysis data from the North American Mesoscale model. The 2-PVU (PV unit) surface, defined as the dynamic tropopause, is able to capture the variations of the ozone tropopause estimated from the ozonesonde and lidar measurements. The estimated ozone/PV ratio, from the measured ozone and model derived PV, for the mixing layer between the troposphere and stratosphere is $41 ppbv/PVU with an uncertainty of $33%. Within two days, the estimated mass of ozone irreversibly transported from the stratospheric into the troposphere is between 0.07 Tg (0.9 Â 10 33 molecules) and 0.11 Tg (1.3 Â 10 33 molecules) with an estimated uncertainty of 59%. Tropospheric ozone exhibited enormous variability due to the complicated mixing processes. Low ozone and large variability were observed in the mid-troposphere after the stratospheric intrusion due to the westerly advection including the transition from a cyclonic system to an anticyclonic system. This study using high temporal and vertical-resolution measurements suggests that, in this case, stratospheric air quickly lost its stratospheric characteristics once it is irreversibly mixed down into the troposphere.Citation: Kuang, S., M. J. Newchurch, J. Burris, L. Wang, K. Knupp, and G. Huang (2012), Stratosphere-to-troposphere transport revealed by ground-based lidar and ozonesonde at a midlatitude site,

Evaluating Summer-Time Ozone Enhancement Events in the Southeast United States

“…To calculate stratospheric O 3 mixing ratios we multiple GEOS-5 potential vorticity unit (PVU, 1 PVU = 10 6 K m 2 kg −1 s −1 ) values by an O 3 :PV ratio of 41 nmol mol −1 /PVU. This value was chosen as it was derived from a study using TOLNet observations and model simulations to calculate O 3 :PV ratios associated with stratospheric transport at the location of the UAH TOLNet lidar site [18]. This value falls within the range of O 3 :PV ratios of 30-45 nmol mol −1 /PVU reported for stratospheric O 3 in past studies (e.g., [43][44][45][46]).…”

“…The first method is based upon the numerous recent studies that have used O 3 :PV ratios as a tracer for stratospheric air and O 3 (e.g., [18,[43][44][45][46]). To calculate stratospheric O 3 mixing ratios we multiple GEOS-5 potential vorticity unit (PVU, 1 PVU = 10 6 K m 2 kg −1 s −1 ) values by an O 3 :PV ratio of 41 nmol mol −1 /PVU.…”

“…The accuracy of the system has been discussed in previous studies and Lidar measurement precision is estimated to be ±10% in the lower troposphere and ±20% in the upper troposphere [15,16]. Data from the UAH TOLNet lidar system is publically available [14] and has been used to examine atmospheric chemistry relevant topics such as air pollution transport, nocturnal O 3 enhancements, stratosphere-troposphere exchange, boundary layer pollution entrainment, wildfire impacts on O 3 , and lightning NO x generated O 3 (e.g., [17][18][19]). During this study we evaluated all UAH TOLNet observations for the month of June 2013 to identify anomalous O 3 lamina (see Section 3.1).…”

How stratospheric are deep stratospheric intrusions?

“…In groundbased lidar time series (e.g. Langford et al, 1996;Eisele et al, 1999;Trickl et al, 2003Trickl et al, , 2010Zanis et al, 2003;Kuang et al, 2012) the O 3 mixing ratio in stratospheric intrusions drops from typically 100 to 150 ppb in the middle and upper troposphere to roughly half the value or less at (e.g.) 3000 m, sometimes within just half a day.…”

TOLNET – A Tropospheric Ozone Lidar Profiling Network for Satellite Continuity and Process Studies

“…Ozone can be generated throughout the troposphere as a secondary product of industrial or mobile emissions and it can also be transported from the stratosphere [1]. Upper-air observations are particularly important because the ozone produced aloft and transported over appreciable distances can significantly affect surface air quality.…”