Figure 8. NOAA Hazard Management System (HMS) and Smoke Product
analysis of smoke (a) 21 Aug 2013 and (b) 30 Aug 2013. Below, three-day
backward FLEXPART-WRF trajectories corresponding to each episode is
provided (c) 21 Aug 2013 and (d) 30 Aug 2013. Additional trajectories
are placed in the data archive at
https://tropo.gsfc.nasa.gov/seacions/.
4.5.1. 17-21 August 2013: Evidence of biomass burning advected by a
cutoff low
The meteorological map provided in Figure 6a-c indicates biomass burning
transported by a cut-off low originating on 17 August 2013 00:00 UTC at
500 hPa over central Missouri. In this case the cut-off low was created
by a closed upper-level low pressure system that was cut off from a
westerly current (14 August 06:30 UTC) and it began moving
independently. The cut-off low remained nearly stationary until 19
August 00:00 UTC, at which time the trough filled in and moved eastward.
Due to the nature of the quasi-stationary system, the westerly flow of
air propagated the western fire plumes over the central U.S. and
southeast U.S. Figure 7a and 7c present a cross section and plane view
of the resulting low. Due to the low pressure system the trajectory
analysis indicated that smoke flowed from various fire locations to the
St. Louis area (see Figure 8). Figure 9a-c depicts the vertical ozone
and meteorological profiles representative of this time period (21
August). Refer to Figure 2 for corresponding ozonesonde curtain plots.