A climatology of wintertime low-level jets in Nares Strait

Abstract

Intense, southward low-level winds are common in Nares Strait, between Ellesmere Island and northern Greenland. The steep topography along Nares Strait leads to channelling effects, resulting in an along-strait flow. This research study presents a 30-year climatology of the flow regime from simulations of the COSMO-CLM climate model. The simulations are available for the winter periods (November–April) 1987/88 to 2016/17, and thus, cover a period long enough to give robust long-term characteristics of Nares Strait. The horizontal resolution of 15 km is high enough to represent the complex terrain and the meteorological conditions realistically. The 30-year climatology shows that LLJs associated with gap flows are a climatological feature of Nares Strait. The maximum of the mean 10-m wind speed is around 12 m s-1 and is located at the southern exit of Smith Sound. The wind speed is strongly related to the pressure gradient. Single events reach wind speeds of 40 m s-1 in the daily mean. The LLJs are associated with gap flows within the narrowest parts of the strait under stably stratified conditions, with the main LLJ occurring at 100–250 m height. With increasing mountain Froude number, the LLJ wind speed and height increase. The frequency of strong wind events (>20 m s-1 in the daily mean) for the 10 m wind shows a strong interannual variability with an average of 15 events per winter. Channelled winds have a strong impact on the formation of the North Water polynya.

A Model-Based Climatology of Low-Level Jets in the Weddell Sea Region of the Antarctic

“…The COSMO-CLM (CCLM) model is a non-hydrostatic regional climate model used by a large climate research community. CCLM has been applied for several studies of the ABL in the polar regions [27,[31][32][33][34][35]. For the present paper, CCLM is used with a horizontal resolution of 15 km for the Weddell Sea region of the Antarctic (Figure 1) with the setup as described in [31].…”

A Three-Year Climatology of the Wind Field Structure at Cape Baranova (Severnaya Zemlya, Siberia) from SODAR Observations and High-Resolution Regional Climate Model Simulations during YOPP

“…The pressure differences were 6-8 hPa for the strongest cases of channeled flow with 10 m wind speeds of more than 20 m/s. For the Smith Sound of Nares Strait, [17] found pressure differences of more than 20 hPa along the strait associated with 10 m wind speeds of more than 25 m/s. The main part of the pressure differences was visible between the entrance and exit region of Smith Sound, while the wind maximum was located downstream of the gap.…”

“…Ref. [17] compared the CCLM simulations for 1987-2017 with meteorological stations in the area of Nares Strait. They found wind speed biases in the range of −1.5 to 0.9 m/s and temperature biases in the range of 0.5 to −5.7 • C for the winter, which resulted from the fact that the observations were taken at stations close to the coast and the observations were influenced by local effects.…”

“…For the grid points Sn and Ss, strong winds at 100 m were dominated by the channeling effect. Channeled flows are ageostrophic and driven by the pressure gradient along the channel [13,17]. Therefore we looked at the pressure difference between the grid points Ss and Sn and related this difference to the flow component along the strait and at both points.…”

“…They found the most extreme winds near Greenland and showed a 95%-tile of more than 20 m/s for Smith Sound. A more detailed climatology of LLJs in Nares Strait for winters 1987-2016 was shown by [17]. They also used the CCLM with 15 km resolution and found a mean 10 m wind speed of around 12 m/s at the southern exit of Smith Sound.…”