Dynamical and Chemical Influences on PEM-Tropics Ozone Profiles

Abstract

Our investigation will determine the interplay of chemical and dynamical influences on ozone profiles in the PEM-Tropics B sampling region. Emphasis will be on answering the following questions: (a) what dynamical processes and chemical sources/sinks are responsible for ozone distributions in the PEM-Tropics region and for fine layers in ozone profiles seen on ozonesondes and in ozone aircraft profile data? (b) To the extent that convectively active regions are sampled on PEM-Tropics, can we explain ozone and other constituent profiles in these areas? Answers will be given using PEM-Tropics trace gas data in combination with satellite imagery and models used in analysis of previous aircraft missions: TRACE-A, TOTE/VOTE, STERAO-A and SONEX. Imagery includes: air-mass-classified total ozone and tropical tropospheric ozone (TTO) maps derived from TOMS, enhanced images composited from geostationary satellite data, and TOMS-derived (and potentially MODIS) aerosol products. Models include the GSFC point chemical and trajectory models for processes occurring in parcels

sampled and several versions of the Goddard cloud-resolving model. Imagery and air mass origins will be of high value to the PEM-Tropics B team as a whole. Accordingly, a minimum set of products that will be provided to the PEM Tropics-B archive within the protocol period is: (a) air-mass classified TOMS total ozone; (b) TTO maps by the modified-residual method; (c) satellite cloud and water vapor imagery for February-April 1999. Back trajectories from PEM-Tropics B ozonesondes and DC-8 and P-3B flight tracks will be archived as images and as data files. Specialized trajectory-based maps showing stratospheric-tropospheric mixing (in terms of reverse-domain-fill (RDF) potential vorticity) and convective influences in the PEM-Tropics B sampling region will also be archived as images.

I. BACKGROUND & SCOPE OF GSFC/AMES/UMD PEM-TROPICS B THEORY INVESTIGATION

The PEM-Tropics NRA (MTPE-97-13) lists as a major objective (B) "to evaluate the chemical and dynamical factors controlling ozone, OH, and aerosol levels over this [tropical Pacific] remote region." Sub-elements to which this proposal is directed are:

(2) "...investigate the factors responsible for large-scale low concentrations of tropospheric ozone over the equatorial Pacific;"

(3) "Study the role of the ITCZ and SPCZ as barriers to atmospheric transport between the northern and
southern hemispheres and within the South Pacific."

(4) "Investigate the scavenging of gases/aerosols associated with deep convection..."

Our investigation addresses (2) and (3) using a climatological approach, with ozone data from satellite and balloon sondes collected prior to and during PEM-Tropics-B, related satellite imagery and trajectory-based model analysis for interpretation. These data will provide a regional picture which integrates the aircraft and sonde data to be collected during the 1999 deployment. Collecting a pre PEM-Tropics B deployment climatology and comparison with PEM-Tropics A data will provide insight into transport barriers and the degree to which seasonally varying factors affect ozone, especially the low tropospheric ozone expected in early 1999. The primary dynamical influences on tropospheric ozone during the PEM-Tropics-B period are expected to derive from deep convection. Evaluation of these effects in sondes, satellite-derived tropospheric ozone and aircraft data will be made with cloud imagery, trajectories and cloud-resolving models. The role of scavenging as stated in PEM-Tropics B sub-element (4) will be assessed in the latter modeling work.

The approach and techniques used in our research follow on our previous analysis of tropical ozone data in TRACE-A [Thompson et al., 1996a,b; 1997; Pickering et al., 1996a,b; Kim et al., 1996]. In those studies, trajectories, photochemical and cloud modeling were used to explain ozonesondes, TOMS-derived tropospheric ozone, and DC-8 ozone and other constituent data. The basic science questions of TRACE-A were answered by a unique combination of trajectories, photochemical modeling, convective modeling with tracers, and a new high-density ozone satellite product. In the current investigation, the techniques used in TRACE-A will be augmented by imagery and analysis tools developed during two more recent DC-8 campaigns: the 1995-96 TOTE/VOTE mission that included the tropical Pacific and the 1997 SONEX mission in the North Atlantic.

Deliverables will consist of images and model output, viewable on a homepage, and transmitted to the PEM-Tropics B data archive within 6 months from the end of the field mission.

The next section summarizes our model products. An important feature of our investigation is its connection to ongoing NASA projects, which enables cost-sharing and greater science benefit. Resources for PEM-Tropics are augmented by people, hardware and software in other GSFC/Ames/U. Md projects: STRAT, TOTE/VOTE, POLARIS, SONEX and STERAO-A. Production of TOMS tropospheric ozone maps and absorbing aerosols is covered under ACMAP and TOMS funding. Real-time maps from Earth-Probe TOMS for daily tropical tropospheric ozone (TTO)

appear on http://metosrv2.umd.edu/~tropo. The newly funded SHADOZ will provide tropical ozonesonde data from PEM-T and other sites in a uniform format for larger community use, as these data become public.

II. DELIVERABLE MODEL PRODUCTS FOR PEM-TROPICS B SCIENCE TEAM FROM GSFC/AMES/UMD

Model Products deriving from this study will be available as images on a homepage maintained at GSFC or Ames with UMD links. These will be posted in a timely manner to maximize value to the PEM-Tropics Science Team. Images and selected model output will be put in the PEM-Tropics-B data archive within 6 months from end of deployment. The minimum set of our products is as follows:

Acronyms

ACMAP = Atmospheric Chemistry Modeling and Analysis Program

GEOS-DAO-ASM = Goddard Earth Observing System Data Assimilation System, Version 1

GTE = Global Tropospheric Experiment

ISCCP = International Satellite Cloud Climatology Project

ITCZ = InterTropical Convergence Zone

MPV = Modified Potential Vorticity

MTPE = Mission to Planet Earth

NCEP = National Centers for Environmental Prediction

PEM-Tropics = Pacific Exploratory Mission - Tropics (A=9/96; B=2/99)

PV = Potential Vorticity

RDF = Reverse-Domain Filling

SAFARI = Southern African Fire Atmospheric Research Initiative (1992)

SASS = Subsonic Assessment

SHADOZ = Southern Hemisphere Additional Ozonesondes

SONEX = SASS Ozone and Nitrogen Experiment

SPCZ = South Pacific Convergence Zone

SPRI = Space Physics Research Institute

STERAO = Stratosphere-Troposphere Experiments - Radiation, Aerosols, Ozone

STRAT = Stratospheric Tracers of Atmospheric Transport

SWISS = Satellite Weather Information for Stratospheric Science

TOMS = Total Ozone Mapping Spectrometer

TOTE/VOTE = Tropical Ozone Transport Experiment/Vortex Ozone Transport

Experiment (1995-96)

TRACE-A = Transport and Atmospheric Chemistry near the Equator- Atlantic (1992)

TRMM = Tropical Rainfall Measurement Mission

TTO = Tropical Tropospheric Ozone (Column amount)

UT = Upper Troposphere; UT/LS = UT/Lower Stratosphere

REFERENCES

Hudson, R. D., and A. M. Thompson, Tropical tropospheric ozone (TTO) maps from TOMS by the Modified-Residual method, J. Geophys. Res., in press, 1998.

Kim, J-H., R. D. Hudson and A. M. Thompson, A new method of deriving time-averaged tropospheric column ozone over the tropics using total ozone mapping spectrometer (TOMS) radiances: Intercomparison and analysis using TRACE-A data, J. Geophys. Res., 101, 24317-24330, 1996.

Pickering, K. E., et al., Convective transport of biomass burning emissions over Brazil during TRACE-A, J. Geophys. Res., 101, 23,993-24,012, 1996a.

Pickering, K. E., et al., TRACE-A trajectory intercomparison: 1. Effects of different input analyses, J. Geophys. Res., 101, 23,909-23,925, 1996b.

Thompson A. M., R. D. Diab, G. E. Bodeker, M. Zunckel G. J. R. Coetzee, C. B. Archer, D. P. McNamara, K. E. Pickering, J. B. Combrink, J.Fishman, and D. Nganga, Ozone over southern Africa during SAFARI-92/TRACE-A, J. Geophys. Res., 101, 23,793-23,807, 1996a.

Thompson, A. M., K. E. Pickering, D. P. McNamara, M. R. Schoeberl, R.D. Hudson, J. H. Kim, E. V. Browell, V. W. J. H. Kirchhoff, and D.Nganga, Where did tropospheric ozone over southern Africa and the tropical Atlantic come from in October 1992? Insights from TOMS, GTE/TRACE-A and SAFARI-92, J. Geophys. Res., 101, 24251-24278,1996b.

Thompson, A. M., W.-K. Tao, K. E. Pickering, J. R. Scala, and J. Simpson, Tropical deep convection and ozone formation, Bull. Amer.Met. Soc., 78, 1043-1054, 1997.