CASE-STUDY MODELING OF TURBULENT AND MESOSCALE FLUXES OVER THE BOREASREGION

Results from aircraft and surface observations provided evidence for t he existence of mesoscale circulations over the Boreal Ecosystem-Atmos phere Study (BOREAS) domain. Using an integrated approach that include d the use of analytical modeling, numerical modeling, and data analysi s, we have found that there are substantial contributions to the total budgets of heat over the BOREAS domain generated by mesoscale circula tions. This effect is largest when the synoptic flow is relatively wea k, yet it is present under less favorable conditions, as shown by the case study presented here. While further analysis is warranted to docu ment this effect, the existence of mesoscale flow is not surprising, s ince it is related to the presence of landscape patches, including lak es, which are of a size on the order of the local Rossby radius and wh ich have spatial differences in maximum sensible heat flux of about 30 0 W m(-2). We have also analyzed the vertical temperature profile simu lated in our case study as well as high-resolution soundings and we ha ve found vertical profiles of temperature change above the boundary la yer height, which we attribute in part to mesoscale contributions. Our conclusion is that in regions with organized landscapes, such as BORE AS, even with relatively strong synoptic winds, dynamical scaling crit eria should be used to assess whether mesoscale effects should be para meterized or explicitly resolved in numerical models of the atmosphere .