Origin and Frequency of Near-Surface Statically Stable Layers and Elevated Weak-Static Stability Layers during the Ontario Winter Lake-Effect Systems (OWLeS) Project

Near-surface statically stable layers and elevated weak-static stability layers are known to have significant influences on the growth and intensity of lake-effect storm systems. However, their origins and frequency, especially near the eastern Great Lakes, are generally not known. 

 

The Ontario Winter Lake-effect Systems (OWLeS) field project was conducted during December 2013 and January 2014 in the vicinity of Lake Ontario.  Link to https://www.eol.ucar.edu/field_projects/owles for background information and associated websites.  As part of the field project, approximately 300 successful high vertical-resolution rawinsonde launches were conducted at various locations on various project days by five participating organizations:  Hobart and William Smith Colleges, The University of Illinois, The State University of New York at Oswego, Millersville University, and The University of Utah.  In addition, the OWLeS field project benefited from 1200 UTC, 0000 UTC, and occasional 1800 UTC rawinsonde launches at the National Weather Service (NWS) Weather Forecast Office in Buffalo, NY. High-resolution data are also available from other regional NWS sites.

 

Upon preliminary investigation of the corresponding data, it was found that at times, lake-effect systems occurred in the presence of layers of upwind near-surface static stability (e.g., see Fig. 1) and elevated layers of weak-static stability (e.g., see Fig. 2).  In the former case, the stable layer formed within the plume of lake-modified air from Lake Michigan, potentially influencing lake-effect processes over Lake Ontario. In the latter case, lake-effect snow persisted far downstream from Lake Erie towards the south shore of Lake Ontario.

 

The present research will document the frequency of occurrence of such cases from the rawinsonde data described above, and employ the Hybrid Single Particle Lagrangian Integrated Trajectory Model in an attempt to trace the origins of those stability layers.  In addition, atmospheric fields from the Weather Research and Forecasting model, initialized using a regional ensemble data assimilation system, will be used to create cross section analyses in order to reveal both types of stability layers and their origins. Finally, the presence of both types of stability layers will be correlated with specific modes of lake-effect systems.

 

 

Fig. 1. Data from the KDTX rawinsonde launch at 1200 UTC on 7 January 2014. Note the surface - 970 hPa layer of stable static stability.

 

 

Fig. 2.  Data from a State University of New York at Oswego rawinsonde launch at 2013 UTC on 6 January 2014 from Sodus Point, NY.  Note the 780 - 700 hPa layer of weak static stability.