Subtropical‐polar jet interactions in Southern Plains dust storms

Abstract

The origin of two separate Southern High Plains dust storms, which occurred over a 2 day period in February 2007, is traced to an interaction between the subtropical jet (STJ) and the polar jet (PJ). A large‐scale thermal wind imbalance resulting from the confluence of these two jets led to a series of mesoscale circulations that ultimately produced the dust storms. Understanding the connectivity between the dust storms with differing geometries is central to the present investigation. The study rests on the interpretation of analyses from upper air and surface observations complemented by imagery from satellites, the 32 km gridded data set from the North American Regional Reanalysis, and a fine‐resolution (6 km grid) simulation from the Weather Research and Forecasting model. Principal assertions from the present study are (1) scale interaction is fundamental to the creation of an environment conducive to dust storm development, (2) low to middle tropospheric mass adjustment is the primary response to a large‐scale imbalance, (3) the mesoscale mass adjustment is associated with circulations about a highly accelerative jet streak resulting from the merger of the PJ and STJ, (4) the structure of the jet streak resulting from this merger governs the evolution of the geometry of the dust plumes, with plumes that initially had a straight‐line orientation developing a semicircular geometry, and (5) it is concluded that improvements in dust storm prediction will depend on an augmentation to the upper air network in concert with a flow‐dependent data assimilation strategy.

From Tropospheric Folding to Khamsin and Foehn Winds: How Atmospheric Dynamics Advanced a Record-Breaking Dust Episode in Crete

“…level PV-θ anomaly, baroclinic trough propagation, lower troposphere baroclinicity) is responsible for the formation and intensification of East Mediterranean cyclones and for the generation of dust storms [64][65][66][67].…”

The Role of Jet Adjustment Processes in Subtropical Dust Storms

“…This is consistent with Lewis et al (). A thermal wind imbalance accompanies this process and is caused by the confluence of the polar and subtropical jets, which produces a series of mesoscale circulations during dust storm genesis in many locations including the Southern Plains of the U.S. (Kaplan et al, ). These studies (Kaplan et al, , , ; Lewis et al, ) largely agree on the atmospheric processes for the generation of dust storms in the U.S., that is, the role of tropospheric jets, and a deep PBL with strong turbulence.…”

From Tropospheric Folding to Khamsin and Foehn Winds: How Atmospheric Dynamics Advanced a Record-Breaking Dust Episode in Crete

“…Moreover, as seen at the 850 hPa map (Figure 3b), a strong baroclinic zone extends from about 20°N, 12°E inside Sahara Desert up to the west coastline of Greece with a horizontal West-East temperature gradient of more than 15 °C between 15°-20° E. This combination of atmospheric dynamics (i.e. tropospheric folding, upper level imbalance, baroclinic trough propagation, lower troposphere baroclinicity) is responsible for the formation and intensification of East Mediterranean cyclones and also for the generation of dust storms (Kaplan et al, 2013;Kouroutzoglou et al, 2015;Pytharoulis 2017).…”