Multi-site tropospheric ozone measurements across the North Tropical Atlantic during the summer of 2010

Evidence of a LNOX influence on middle/upper troposphere ozone‐mixing ratios at Dakar, Senegal during Northern Hemisphere summer season

“…Jenkins et al (2013a) show that the highest tropospheric column ozone is found at Dakar, Senegal during August/September 2010 relative to Cape Verde and downstream at Barbados and linked it to LNO X and continental outflow. Further, Jenkins et al (2013a) show higher ozone concentrations before the trough passage of African easterly waves (AEWs) (Burpee, 1972), where convection is concentrated, relative to post-trough conditions. Martin et al (2007) used a top-down satellite approach and the GEOS-Chem chemical transport model (GCTM) for estimating the impacts of LNO X on HNO 3 mixing ratios, column NO 2 and O 3 .…”

“…There are 20 pre‐monsoon/early monsoon measurements [June (9)/July (11)] and 20 mature/decaying monsoon measurements [August (11)/September (8)/October (1)]. Similar to Jenkins et al () we use the National Centers for Environmental Prediction (NCEP)/Global Reanalysis data (Kalnay et al , ) and the Worldwide Lightning Location Network (WWLLN) (Virts et al , ) data to characterize the wind flow at 400 hPa and to identify lightning locations during the period of June through September 2010. WWLLN detects primarily cloud to ground lightning (CG) and has a detection efficiency of less than 10% over continental areas (Rudlosky and Shea, ) but does capture lightning activity associated with AEWs (Price et al , ) in West Africa.…”

“…At Sao Vicente, Cape Verde (16.84°N, 24.87°W), some 500 km downstream of the African continent, Jenkins et al () show that while there is variability in the LT related to the Saharan air layer (SAL), the highest ozone‐mixing ratios are consistently found above this layer in the MT/UT which they attribute to LNO X from aged continental air transported from West Africa. Jenkins et al () show that the highest tropospheric column ozone is found at Dakar, Senegal during August/September 2010 relative to Cape Verde and downstream at Barbados and linked it to LNO X and continental outflow. Further, Jenkins et al () show higher ozone concentrations before the trough passage of African easterly waves (AEWs) (Burpee, ), where convection is concentrated, relative to post‐trough conditions.…”

“…Jenkins et al () show that the highest tropospheric column ozone is found at Dakar, Senegal during August/September 2010 relative to Cape Verde and downstream at Barbados and linked it to LNO X and continental outflow. Further, Jenkins et al () show higher ozone concentrations before the trough passage of African easterly waves (AEWs) (Burpee, ), where convection is concentrated, relative to post‐trough conditions.…”

“…An increasing number of in situ measurements during the Northern Hemisphere summer suggest that lightning is responsible for elevated MT/UT ozone concentrations downstream of West Africa (Jenkins et al, 2008;Nalli et al, 2011;Jenkins et al, 2012;Jenkins et al, 2013a). In situ measurements over the Equatorial Tropical Atlantic at 23 • W, and the Tropical North Atlantic during June, July, August and September (JJAS) show elevated O 3 mixing ratios above 500 hPa (Jenkins et al, 2008;Jenkins et al, 2013a).…”