HR: 09:15h
AN: A51G-06    [Abstracts]
TI: The Daytime Mixed Layer Observed by Radiosonde, Profiler, and Lidar during MILAGRO
AU: * Shaw, W J
EM: will.shaw@pnl.gov
AF: Pacific Northwest National Laboratory, PO Box 999, MS K9-30, Richland, WA 99352, United States
AU: Pekour, M S
EM: mikhail.pekour@pnl.gov
AF: Pacific Northwest National Laboratory, PO Box 999, MS K9-30, Richland, WA 99352, United States
AU: Coulter, R L
EM: rl_coulter@anl.gov
AF: Argonne National Laboratory, 9700 South Cass Ave., Argonne, IL 60439, United States
AU: Martin, T J
EM: tjmartin@anl.gov
AF: Argonne National Laboratory, 9700 South Cass Ave., Argonne, IL 60439, United States
AU: Walters, J
EM: jwalters@southernco.com
AF: University of Alabama in Huntsville, Atmospheric Science Department University of Alabama in Huntsville 320 Sparkman Drive, NSSTC, Huntsville, AL 35806, United States
AB: During the 2006 MILAGRO field campaign centered in the Mexico City area, scientists from Pacific Northwest National Laboratory (PNNL), Argonne National Laboratory (ANL), and the University of Alabama in Huntsville (UAH) operated a variety of atmospheric profiling systems. The systems were located at the Mexican Petroleum Institute (IMP) in central Mexico City, at Tecámac University on the northeastern edge of the Mexico City urban area, and at Rancho la Bisnaga, a privately owned ranch. These sites are referred to as T0, T1, and T2 to reflect the idea of sequential arrival times of air parcels at each site under common transport conditions. T2 was approximately 50 km north of T1. Similar 915 MHz wind profiling radars were operated at all three sites. ANL additionally operated a sodar, a 523-nm micropulse lidar, and a radiosonde system at T1. At T2, PNNL additionally operated a radiosonde system. On aircraft sampling days, five radiosondes were launched at T1 during the daytime, and three were launched at T2. The collocation of profiling systems afforded an opportunity to compare the three primary methods of measuring the depth of deep mixing layers in the Mexico City environment. In this paper we will describe the methods of extracting mixing layer depth from each system as well as the results of the comparison. The results highlight the general agreement among the various methods, but also the ambiguity that results from multiple inversions for radiosondes and from elevated layers with significant particulate matter for lidars. We conclude that the wind profiler is the system of choice for identifying mixing layer depth from the MILAGRO campaign. In addition to the instrument comparison, we also have completed a description of the temporal variability of the mixing layer during the campaign as well as spatial variations among the three sites. We have interpreted our results in the contexts of the widely reported Norte events, of the days with and without occurrences of deep convection, and of wind profiler measurements of mixing layer depth from the IMADA-AVER campaign in 1997. Our findings include the results that turbulent mixing began at the surface 67.5 ± 15 min following sunrise, that daily mixed layer growth was nearly identical in the mean and in its variability between the IMADA-AVER and the MILAGRO campaigns, that conditions that produced deep convection did not systematically change morning boundary layer growth, and that Norte events did not seem to strongly perturb mixed layer behavior on the Central Mexican Plateau. Because of its relevance for aerosol particle size distributions, we will also describe the vertical structure of humidity relative to mixing layer depth.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0394 Instruments and techniques
DE: 3307 Boundary layer processes
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting