Characterization and Parametrization of Reynolds Stress and Turbulent Heat Flux in the Stably-Stratified Lower Arctic Troposphere Using Aircraft Measurements

Abstract

Aircraft measurements are used to characterize properties of clear-air turbulence in the lower Arctic troposphere. For typical vertical resolutions in general circulation models, there is evidence for both downgradient and countergradient vertical turbulent transport of momentum and heat in the mostly statically stable conditions within both the boundary layer and the free troposphere. Countergradient transport is enhanced in the free troposphere compared to the boundary layer. Three parametrizations are suggested to formulate the turbulent heat flux and are evaluated using the observations. The parametrization that accounts for the anisotropic nature of turbulence and buoyancy flux predicts both observed downgradient and countergradient transport of heat more accurately than those that do not. The inverse turbulent Prandtl number is found to only weakly decrease with increasing gradient Richardson number in a statistically significant way, but with large scatter in the data. The suggested parametrizations can potentially improve the performance of regional and global atmospheric models.

Particulate trimethylamine in the summertime Canadian high Arctic lower troposphere

“…3 (100 m) justifies the range of the mean BL height. The mean BL height within its range can be confirmed by results from an extensive study on BL height, mixing and stability during the NETCARE 2014 campaign (Aliabadi et al, 2016a). The capping temperature inversion above 390 m, inferred from values of e , represents a transport barrier for air masses between the BL and the free troposphere (FT).…”

Evidence for marine biogenic influence on summertime Arctic aerosol

“…Temperature profiles indicated a surface-based temperature inversion of ∼5 ∘ C up to an altitude of 300-400 m ( Figure S6). Aliabadi et al [2016] made similar observations using Polar6 observations and radiosondes to estimate a boundary layer height of 275 ± 164 m. We will refer to the portion of the lower troposphere with a positive vertical gradient in temperature profile as the boundary layer. The median boundary layer wind speed was 4.0 m s −1 compared to 5.1 m s −1 aloft ( Figure S8).…”

Boundary layer and free-tropospheric dimethyl sulfide in the Arctic spring and summer

“…DMS(g) vertical profiles are sensitive to the boundary layer height. For the July 2014 campaign, Aliabadi et al (2016b) reported an average boundary layer height of 275 ± 164 m. They showed that the profiles of the potential temperature exhibited a positive vertical gradient throughout the aircraft campaign (their Fig. 4).…”

“…In July 2014, both the measurements and simulation show a strong decrease in DMS(g) mixing ratios with altitude in the lowest 300 m. Aliabadi et al (2016a, b) estimated the boundary layer height as 275 ± 164 m, using data from radiosondes launched at Resolute Bay and the Amundsen icebreaker, during the 2014 campaign. Aliabadi et al (2016b) indicated that the magnitude of turbulent fluxes of momentum, heat and the associated diffusion coefficients are significantly reduced above the boundary layer height during the 2014 campaign. Thus, we find the strongest vertical gradient between the boundary layer and above.…”

“…More details of the instrument and corresponding aircraft measurements were recently published in other studies from the same campaign (e.g. Aliabadi et al, 2016b;Willis et al, 2016).…”