Laura Pan

General Information

ACD - TIIMES
Scientist III
UTLS

Contact Information:
PO Box 3000, Boulder, CO 80307-3000
Office: FL0-2160
Telephone: 303-497-1467
Email: liwen@ucar.edu
Home Page - Vita

Research Focus FY08:

Figure 1. Cross section along the High Resolution Dynamics Limb Sounder (HIRDLS) Field of View (FOV) track (shown on the NA map in next figure) on May 11, 2007.  The layer structure of the intrusion is consistently shown in the ozone cross section measured by HIRDLS (upper) and the PTLR cross section based on the GFS analyses (lower). The GFS analyses thermal tropopause (black dots), zonal wind (black contour), 350 and 400 K isentropes (black broken) and PV (2, 4, 6, and 8 pvu) contours are shown on the cross sections. Figure 2. Sandwiched stratosphere sampled by NCAR-NSF GV during START08 April 18, 2008. (a) The region of double tropopause over North America based on high resolution NCEP/GFS meteorological analyses. The colors represent the minimum potential temperature lapse rate (dq/dz (K/km)) between the two tropopauses. The red line marks the segment of the flight track shown in panel (b and c). (b)cross along the flight track with potential temperature lapse rate (color image), potential vorticity (purple contours), potential temperature (black contours) and the GV flight track (colored by the ozone values). (c) GV measurements during the segment including pressure altitude (gray), potential temperature (black), ozone (red) and carbon monoxide (blue).

Diagnosing transport from troposphere to stratosphere associated with the secondary tropopause, satellite data, meteorological field and aircraft observations

It has long been recognized that the temperature lapse rate based thermal tropopause definition produces breaks and multiple tropopauses in the extratropics. Recent analyses using global high resolution GPS data has shown that the area of double tropopause is much more extensive than previously realized. The trend of its occurrence in a changing climate is a question of research awaiting improved measurements with long enough of a record for this type of study. The transport of chemical species related to the double tropopause has been hinted by ozone measurements in the past (refs). Newly available satellite data from High Resolution Dynamics Limb Sounder (HIRDLS) on Aura demonstrated the connection between the occurrence of the secondary tropopause and the chemical transport from troposphere to stratosphere. Figure 1 shows an example of low ozone layer above the primary extratropical tropopause and below the secondary tropopause, which is an extension of the tropical tropopause. A similar structure is also found in the potential temperature lapse rate, derived from the NCEP/GFS meteorological analyses, for the same cross section. (Pan et al., submitted, 2008)

This observation of relationship between the chemical structure and the meteorological field made it possible for the development of a forecast tool for aircraft observations, which in turn allowed successful in situ observations of this intruding tropospheric layer during the Stratosphere Troposphere Analyses of Regional Transport (START08) experiment. Figure 2 shows an example measurement from the NCAR-NSF Gulfstream V aircraft research flight on April 18, 2008, including meteorological analyses and in situ measurements. As indicated by the figure, the flight successfully observed an extensive layer of intruding tropospheric like air between the two tropopauses. The large suite of chemical species measured will help characterizing the chemical impact of this type of event. The analyses of these new data will be the focus of next year.

Community Service FY08:

• Principal investigator and mission scientist of START08 campaign, April-June 2008
• Member: International Commission on Middle Atmosphere (ICMA), The International Association of Meteorology and Atmospheric Sciences (IAMAS), 2007-2011
• Convener, Special symposium on climate processes in the upper troposphere and stratosphere, IAMAS/IAPSO Assembly, Montreal, Canada, July 2009

Scientific Talks FY08:

• The Use of the AIRS ozone data in the Research of Upper troposphere and Lower Stratosphere (UTLS) chemistry and dynamics (Greenbelt, MD, October 2007)
• Dynamical variability of ozone and mixing near the extratropical tropopause from Atmospheric Infrared Sounder (AIRS) data (San Francisco, CA, December 2007)
• START08 Science Overview (Boulder, CO, January 2008)
• START08 experiment and Tropospheric Intrusion associated with the secondary tropopause (Boulder, CO, January 2008)
• Transport diagnostics in the extratropical UTLS (Boulder, CO, March 2008)
• START08 Highlights (Boulder, CO, June 2008)
• GV experience during START08 (Boulder, CO, August 2008)
• START08 experiment: Scientific Concept and initial results (Juelich, Germany, September 2008)

Publications FY08:

Kinnison, D. E., G. P. Brasseur, S. Walters, R. R. Garcia, D. R. Marsh, F. Sassi, V. L. Harvey, C. E. Randall, L. Emmons, J.-F. Lamarque, P. Hess, J. J. Orlando, X. X. Tie, W. Randel, L. L. Pan, A. Gettelman, C. Granier, T. Diehl, U. Niemeier, A. J. Simmons, 2007: Sensitivity of chemical tracers to meteorological parameters in the MOZART-3 chemical transport model. J. Geophys. Res., 112, D20302, doi: 10.1029/2006JD007879.

Grubisic, V., J.D. Doyle, J. Kuettner, S. Mobbs, R.B. Smith, C.D. Whiteman, R. Dirks, S. Czyzyk, S.A. Cohn, S. Vosper, M. Weissmann, S. Haimov, S.F.J. De Wekker, L.L. Pan, and F.K. Chow, 2008: The Terrain-Induced Rotor Experiment. Bull. Amer. Meteor. Soc., 89, 15131533.

Pan, L.L.,  W. J. Randel, J. C. Gille, W. D. Hall, B. Nardi, S. Massie, V. Yudin, R. Khosravi, P. Konopka, and D. Tarasick (2008), Tropospheric intrusions associated with the secondary tropopause, submitted to JGR, 2008.