A Sensitivity Analysis of WRF-Simulated Cold Air Damming Using Variable Parameterization Schema

Cold air damming (CAD) is a common phenomenon in Northern New England U.S.A. in which cold air persists to the south and east of the northern Appalachian Mountains during region-wide warm air advection. CAD often allows for wintry precipitation to persist for extended periods and can negatively impact transportation and local commerce in Northern New England, especially during the winter months. Numerical models are known to struggle with the evolution of CAD, particularly the erosion process and the portrayal of the vertical temperature profile and precipitation type. Numerical models often mix-out the cold air too soon, which can lead to the unanticipated continuation of hazardous wintry weather.

This National Science Foundation (NSF)-funded study utilizes the Weather Research and Forecasting Model (WRF-ARW) to investigate the sensitivity of variable microphysical and planetary boundary layer (PBL) schema to the WRF forecast of the evolution and vertical extent of CAD in Northern New England. For example, a simulation of CAD on 11 January 2014 using the Mellor-Yamada-Janjic (MYJ) PBL and WRF single-moment 3-class ice microphysics schema reveals a longer duration CAD than the Yonsei University (YSU) schema, which mixes out CAD too quickly. The simulation also provides excellent insight into the depth and maximum height of the cold pool. This research tests different combinations of schema and compares their differences from surface weather station observations over Northern New England. Further improvements to the WRF simulations are possible with the assimilation of the aforementioned observations and those from the Mount Washington Observatory (MWO) Auto Road Vertical Profile (ARVP).