General Characteristics of the Atmospheric Boundary Layer Over a Flaw Lead Polynya Region in Winter and Spring

Abstract

A time series of microwave radiometric profiles over Arctic Canada's Cape Bathurst (70 • N, 124.5 • W) flaw lead polynya region from 1 January to 30 June, 2008 was examined to determine the general characteristics of the atmospheric boundary layer in winter and spring. A surface based or elevated inversion was present on 97% of winter (JanuaryMarch) days, and on 77% of spring (April-June) days. The inversion was the deepest in the first week of March (≈1100 m), and the shallowest in June (≈250 m). The mean temperature and absolute humidity from the surface to the top of the inversion averaged 250.1 K (−23.1 • C), and 0.56 × 10 −3 kg m −3 in winter, and in spring averaged 267.5 K (−5.6 • C), and 2.77 × 10 −3 kg m −3 . The median winter atmospheric boundary-layer (ABL) potential temperature profile provided evidence of a shallow, weakly stable internal boundary layer (surface to 350 m) topped by an inversion (350-1,000 m). The median spring profile showed a shallow, near-neutral internal boundary layer (surface to 350 m) under an elevated inversion (600-800 m). The median ABL absolute humidity profiles were weakly positive in winter and negative in spring. Estimates of the convergence of sensible heat and water vapour from the surface that could have produced the turbulent internal boundary layers of the median profiles were 0.67 MJ m −2 and 13.1 × 10 −3 kg m −2 for the winter season, and 0.66 MJ m −2 and 33.4 × 10 −3 kg m −2 for the spring season. With fetches of 10-100 km, these accumulations may have resulted from a surface sensible heat flux of 15-185 W m −2 , plus a surface moisture flux of 0.001-0.013 mm h −1 (or a latent heat flux of 0.7-8.8 W m −2 ) in winter, and 0.003-0.033 mm h −1 (or a latent heat flux of 2-22 W m −2 ) in spring.

The impact of heterogeneous surface temperatures on the 2-m air temperature over the Arctic Ocean under clear skies in spring

“…Two different values are applied that are typical for the Arctic BL (Lüpkes et al, 2012b). The first one, 350 m, was, for example, measured over a flaw lead polynya in the Canadian Archipelago by Raddatz et al (2011). The second one, 100 m, is close to often observed values (reported e.g.…”

Advances in understanding and parameterization of small-scale physical processes in the marine Arctic climate system: a review

“…Raddatz et al (2011) found similar temperature inversion frequencies for a Canadian polynya region, whereas Tjernström and Graversen (2009) reported, based on SHEBA, that inversions, either surface-based or elevated, are practically always present in the central Arctic. The spatial distribution of temperature inversions is inhomogeneous and strongly controlled by the surface type, the prevailing large-scale circulation conditions and by coastal topography (Pavelsky et al, 2011;Wetzel and Brummer, 2011;Kilpeläinen et al, 2012).…”

“…Mixing in the stratified interior ocean is related to internal wave energy, which tends to be low under the Arctic Ocean ice cover (Levine et al, 1985). Microstructure measurements conducted during the IPY show that the Arctic Ocean is a quiescent environment with background mixing rates close to molecular levels (Rainville and Winsor, 2008;Fer, 2009). Efficient vertical mixing and upward oceanic heat fluxes occur, however, along the continental rise and over topographic features where the warm boundary current is guided (Sirevaag and Fer, 2009;Fer et al, 2010).…”

All-Sky Downwelling Longwave Radiation and Atmospheric-Column Water Vapour and Temperature over the Western Maritime Arctic

“…The hourly IPY-CFL MWR temperatures and water vapour profiles have been used to characterize and link the winter through early summer atmospheric boundary layer over Amundsen Gulf to the sea-ice cover (Raddatz, Asplin, Candlish, & Barber, 2011;. The addition of the late summer and fall profiles from ArcticNet2009 to the IPY-CFL time series created a composite year of hourly water vapour profiles which have been used to determine the annual cycle of monthly median precipitable water (PW), and the maximum monthly PW resulting from water vapour intrusions over the western maritime Arctic (Raddatz, Galley, Candlish, Asplin, & Barber, 2012).…”