Previously the authors have developed a 1-D computer code, BLMARC (ReVelle, Nilsson and Kulmala, 1997) which has been utilized as a research tool for the International Arctic Ocean Expedition,1996 (AOE-96, which is supported by the Swedish Polar Secretariot). The model has a very high vertical resolution as well as the necessary fundamental physics including M-O similarity theory of the surface layer, turbulence-first order closure in the Ekman layer (with second order closure constraints), Solar and thermal radiation fluxes, the force-restore methd is applied at the lower boundary and there is also an evaluation of the surface energy budget, etc. It also includes fundamental flow chemistry with the analysis of 67 chemical compounds including the photochemistry of Sulfur, Ozone and of many organic compounds and also models aerosol physics including condensation and coagulation, gravitational and diffusive dry deposition, binary homogeneous nucleation of water and of sulfuric acid, etc. The model also allows a feedback between the thermal radiation field and low-level Stratus clouds and with the CCN produced through the growth of aerosol particles. The model uses a fourth order R-K numerical approach to reliably integrate the linear momentum conservation equations forward in time.
In this work we have applied the model to observing station 9604 of the AOE-96 expedition. This station can be contrasted to the previous station, 9603, which had low-level jets present, but no bursting effects, i.,e., no intermittent breakdowns of the turbulent boundary layer occured. It has been found recently that the drifting of a surface high pressure ridge during this station and its associated geostrophic wind speed and direction changes are critical to our detailed understanding of the behavior of the observed bursting. In this work we will also examine the role of the interaction between the leads, the pack ice and the lowest 2 km of the atmosphere on time scales from a few minutes to about 1-2 days. For example, one of the key parameters of the ice field was found to be its aerodynamic roughness and also its surface albedo. This breakdown phenomena is apparently quite common in the Polar regions as well as in middle latitudes over land (ReVelle, 1993, ReVelle and Coulter, 1995). Over the high Arctic Ocean it occurs during periods of highly stable atmospheric conditions in the summer period of perpetual daytime.
References:
ReVelle, D.O., 1993, Chaos and Bursting in the Planetary Boundary Layer, J. Applied Meteorology, Vol. 32, 1169-1180.
ReVelle, D.O. and R. L. Coulter, 1995, Paper 17.1, Bursting in the Near-surface Boundary Layer: Comparisons between Realistic Models and Observations, Preprint Volume of the 11th AMS Symposium on Boundary Layers and Turbulence, Charlotte, NC, 560-563.
ReVelle, D.O., E.D. Nilsson and M. Kulmala, P6.6, Modeling of the Arctic Boundary Layer: Comparisons with Measurements from the Arctic Ocean Expedition 1996, Preprints of the 12th AMS Symposium on Boundary Layers and Turbulence, Vancouver, B.C., Canada, 148-149