Abstract : F.3
Comparison of stable boundary layer evolution in a small basin and over the surrounding plain

Maura Hahnenberger, C. David Whiteman, Sebastian W. Hoch
University of Utah

During October 2006 a major field campaign, the Meteor Crater Experiment (METCRAX), took place in the Arizona Meteor Crater about 65 km east of Flagstaff, AZ. One of the main goals of the experiment was to better understand the cold pool build up and break up in this small idealized basin during periods with weak external forcing. Measurements were taken of both the vertical structure inside the crater and over the surrounding flat plain during several Intensive Observational Periods (IOPs). The ambient conditions for these IOPs ranged from quiescent nights to nights with higher wind speeds and more turbulence.

A quantitative comparison of plain and basin boundary layer cooling rates and magnitudes has never previously been undertaken. Here, we will investigate IOPs with strong, moderate, and weak external forcing and will compare the inversion structures and strengths between the plain and basin. This information will help us understand the differences between inversion formation and development in small basins and adjacent flat plains and the temporal evolution of cooling rates. We find that there is enhanced cooling in the crater atmosphere leading to colder temperatures within the crater compared to temperatures at the same elevation over the surrounding plain. These differences in temperature structure vary with ambient wind speed. Higher wind speeds lead to more advection and mixing both in the crater and over the surrounding plain. The radiative and non-radiative energy budgets are evaluated to determine reasons for the timing and rates of cooling.