Squall Lines: the impact of coastal stable
atmospheric marine layers
Mesoscale convective systems that develop upstream of a large water body (ocean, sea, large lake) and move toward the coastline respond to the stable marine atmospheric boundary layer (MABL), which can propagate tens of kilometers inland as a sea breeze. Storm response is sensitive to the buoyancy and depth of the MABL, as well as the time of collision in the storm's lifecycle. While the presence of a stable boundary layer can contribute to storm decay, it is not always a detriment to storm survival, and at times can contribute to enhanced storm intensity. The Lombardo Lab uses a combination of idealized numerical simulations, case study simulations, and observations to quantify the impact of the heterogeneous coastal environment on severe thunderstorms.
Squall Lines: the impact of coastal terrain
Globally, most regions impacted by coastal squall lines have topographic relief, such as plateaus and mountains, immediately upstream of the coast. As storms move over the variable terrain toward the coast, they respond to the resultant changes in environmental instability and vertical wind shear. Additionally, characteristics of a storm’s cold pool - a diabatically generated density current that spreads out along the ground initiating new convection and moving the storm forward - changes as it ascends and descends the sloping surfaces, impacting storm intensity and its ability to traverse obstacles. Through numerical process studies, we are quantifying and isolating the impact of topography and the coastal marine layer on coastal squall lines in globally representative environments.
Coastal Squall Lines and Climate Change
Coastal squall lines will respond to future changes in the environment, including instability, vertical wind shear, sea surface temperature and the associated marine atmospheric boundary layer. Global circulations models suggest a substantial increase in severe storm frequency along the eastern US coastline. This is especially problematic given the large population clustered along the coastline, which is projected to exponentially increase. The Lombardo lab is mechanistically quantifying storm-scale changes in future coastal squall line initiation, physical processes, and hazards. This work will either support or contradict GCM-projected changes in storm activity, and inform response preparations necessary to mitigate future loss in coastal zones.
Tropical Mesoscale Convective Systems
The Boreal Summer Intraseasonal Oscillation (BSISO) is a large convection and circulation anomaly which propagates eastward and northward across Maritime Continent and Western Pacific Ocean. The oscillation can produce regional precipitation and wind hazards, is associated with active and break cycles of the Asian monsoons, modulates tropical cyclones, and modifies the extra tropics through teleconnections, though the mechanisms controlling its propagation are poorly understood. As part of the Propagation of Intraseasonal Tropical Oscillations (PISTON) ONR DRI, the Lombardo lab is quantifying the impact of the heterogeneous Maritime Continent archipelago environment on tropical mesoscale convective systems which comprise the BSISO. http://onrpiston.colostate.edu
Image courtesy of the Japanese Meteorological Agency/CIRA RAMMB
Sea breezes are local, diurnal coastal circulations, that form in response to density gradients across the coastline. Correct predictions of sea breeze events are critical for utility companies who rely on accurate temperature forecasts, especially during heat waves, to adequately prepare for electricity load demands on the powergrid. The Lombardo lab uses mesoscale numerical models in conjunction with regional atmospheric and sea surface temperature observations to evaluate the ability of the models to accurately predict and represent the physical processes associated with sea breezes, as well as explore the sensitivity of these predictions to the numerical representation of local geography and sea surface temperature resolution.