There is a new NRC post-doctoral research opportunity on the topic of convection initiation under my mentorship at the National Severe Storms Laboratory. If interested, please contact me and also visit the NRC web site.
Since 1989 I've collaborated with Prof. Roger Pielke, Sr. of the Colorado State University Department of Atmospheric Sciences on the topic of boundary layer-land surface interaction studies. Roger and I have focused our collaborative work on the theme of dryline modeling studies. Via my close collaboration with Roger, I've enjoyed access to the Colorado State University Regional Atmospheric Modeling System (CSU-RAMS), versions of which have been installed on NSSL workstations in support of this ongoing study. In academic and personal terms it has been a very positive experience for me to have the privilege of working closely with Roger and his graduate students over these past 9+ years! Out of our work have come several formal publications (see also the informal publications on our work from several conferences and meetings) on dryline and boundary layer-land surface modeling:
Ziegler, C., W. Martin, R. Pielke, and R. Walko, 1995: A modeling study of the dryline. J. Atmos. Sci., 52, 263-285.
Pielke, R., T. Lee, J. Copeland, J. Eastman, C. Ziegler, and C. Finley, 1997: Use of USGS-provided data to improve weather and climate simulations. Ecological Applications, 7, 3-19.
Shaw, B., R. Pielke, and C. Ziegler, 1997: A three-dimensional numerical simulation of a Great Plains dryline. Mon. Wea. Rev., 125, 1489-1506.
Ziegler, C., T. Lee, and R. Pielke, 1997: Convective initiation at the dryline: A modeling study. Mon. Wea. Rev., 125,1001-1026.
The latter study reports on multi- and nested-grid mesoscale simulations of the 15, 16, and 26 May 1991 dryline cases which were probed by the NOAA P-3 aircraft and mobile CLASS soundings during the COPS-91 experiment. The following movies (animated .GIFs) of these simulations illustrate results reported in that paper.
The 15 May 1991 simulation depicts deep convection along a dryline segment in the eastern Texas Panhandle region. An initial round of moderate convection is followed by explosive secondary development as a deep moisture surge reaches the growing convection along the dryline from the south. The moisture surge associates with deepening of the solenoidally driven secondary circulation along and east of the dryline.
The 16 May 1991 simulation depicts isolated deep convection along a dryline segment in northeastern Oklahoma just southwest of Tulsa. Note the initial development of moderate convection along large-aspect ratio rolls east of the advancing dryline. Explosive intensification of isolated deep convection occurs as the dryline advances from the west.
The 26 May 1991 simulation depicts isolated deep convection along a dryline segment in extreme northwestern Oklahoma just west of Woodward. As the dryline segment rotates into an orientation roughly normal to the moist low level flow ahead of the dryline, the following events occur: 1) the secondary circulation deepens; 2) moisture uplift is enhanced and shear simply sweeps moisture along the convergence band; 3) "rope" feeder cloud band develops along rotated dryline segment; 4) explosive deep convective development is forced at eastern end of cloud band due to forced lift of moist air along the length of the convergence band.
I've analyzed and reported on an observational study of the 24 May 1989 (COPS-89) dryline (Ziegler and Hane, MWR, 1993) and the multi-case dryline study during COPS-91 (Hane, Ziegler, and Bluestein, BAMS, 1993). A manuscript on "The initiation of moist convection at the dryline: Forecast issues from a case study perspective" interprets detailed mesoscale dryline and cloud observations from the 15 May 1991 (COPS-91), 7 June 1994 (VORTEX-94), and 6 May 1995 (VORTEX-95) cases (Ziegler and Rasmussen, WAF, 1998).
Since the conclusion of VORTEX in summer of 1995, I've been involved in discussions with Erik Rasmussen (NSSL/CIMMS) and Jerry Straka of the University of Oklahoma School of Meteorology (OU/SOM) and others, on the topic of convective initiation. To solve the difficult problem of forecasting convective initiation (made abundantly clear during our field exercises in VORTEX!), we've thought about how to conduct a possible "Thunderstorm Initiation Mobile Experiment" or TIMEx (see also the discussion of TIMEx elsewhere on my Home Page). Our plans to study boundaries and the storm initiation process have been contributed to the design of the convection initiation component of the International H2O Project (IHOP) to be conducted 13 May - 30 June 2002.
During IHOP we expect to collect the definitive data set on convection initiation that will: 1) illuminate how initiation is controlled by cumulus dynamics, boundary layer processes, and mesoscale environmental factors; 2) demonstrably improve nowcasts, short-range forecasts, and mesoscale NWP forecasts of the earliest stages of deep moist convection. As in COPS and VORTEX, our experimental design for IHOP is committed to the concept of mobile field sensor deployment to permit adaptive sampling providing needed resolution of significant mesoscale weather events.
