Soundings and Satellite Ozone Combine to Reveal Mechanisms for the Intraseasonal Variability of Tropospheric O$_3$ during the Indian Winter Monsoon (INDOEX Period)

HR: 1340h
AN: A33D-0108 [Abstracts]
TI: Soundings and Satellite Ozone Combine to Reveal Mechanisms for the Intraseasonal Variability of Tropospheric O$_3$ during the Indian Winter Monsoon (INDOEX Period)
AU: * Guan, H
EM: guan@clio.arc.nasa.gov
AF: BAER Institute, MS 245-5 Ames Research Center, Moffett Field, CA 94035 United States
AU: * Guan, H
EM: guan@clio.arc.nasa.gov
AF: NASA Ames Research Center, MS 245-5, Moffett Field, CA 94035 United States
AU: Chatfield, R B
EM: guan@clio.arc.nasa.gov
AF: NASA Ames Research Center, MS 245-5, Moffett Field, CA 94035 United States
AU: Thompson, A M
EM: thompson@gator1.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Code 916, Greenbelt, MD 20771 United States
AU: Smit, H J
EM: h.smit@fz-juelich.de
AF: Forschungszentrum J〕ich, CG-II: Troposphв, Juelich, CO D-52425 Germany
AB: The tropospheric ozone (O$_3$) column over the Northern Hemisphere Indian Ocean displays complex temporal and spatial variability. We describe daily northern-winter variations over the northern Indian Ocean for the INDOEX period. In this period, a rich dataset of soundings allows us to disentangle this rich spatial and temporal variability in terms of underlying process. Total tropospheric ozone, TTO, satellite data [Hudson and Thompson, 1998] provides geographic descriptions for the whole region, and is validated in our study. Vital information about vertical distribution comes from ozonesondes aboard the Research Vessel Ronald H. Brown, moving 15$^\circ$S to 15$^\circ$N, and from special sondes launched at Kaashidhoo in the Maldives (5$^\circ$N). Analysis shows that (a) elevated low-level O$_3$over the northern Indian Ocean mainly originated from the Indian subcontinent with a maximum contribution from high emission areas, generally the northern industrial-agricultural around the Ganges Plain. Convective activity just south of Sri Lanka significantly affects pollutant outflow from the Northern Indian Subcontinent. (b) The middle tropospheric O$_3$ maximum observed over the Northern Indian Ocean alternates from different sources, sometimes changing rapidly. (c) Mixing in of stratospheric air introduced along the subtropical jet apparently often raised tropospheric O$_3$ at the beginning of March by $\sim$40--50 ppbv, especially poleward of ~10$^\circ$N. (d) Convective lofting of Asian pollutants could also add about 20--50 ppbv to middle troposphere at 5--10$^\circ$N, alternating with stratospheric influence. The soundings show that one influence producing high ozone can be replaced by another within a few hours. Similarly, TTO maps also suggest that features with different origins can merge. The southern (pollutant) buildup seen in TTO has long-range effects, traveling towards across Africa. Our broadest point is that the variance of tropical tropospheric ozone is only poorly captured by seasonal averages or those based on global circulation indicators like warm/cold-phase ENSO.
UR: http://geo.arc.nasa.gov/sgg/chatfield/recentRes.html
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting