Understanding orographic effects on surface observations at Macquarie Island

Wang, Zhan; Belusic, Danijel; Huang, Yi; Siems, Steven T.; Manton, Michael J.. 2016 Understanding orographic effects on surface observations at Macquarie Island. Journal of Applied Meteorology and Climatology, 55 (11). 2377-2395.

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The meteorological observations on Macquarie Island have become of increasing value for efforts to understand the unique nature of atmospheric processes over the Southern Ocean. While the island is of modest elevation (peak altitude of 410 m), the orographic effects on observations on this island are still not clear. High-resolution numerical simulations [Weather Research and Forecasting (WRF) Model] with and without terrain have been used to identify orographic effects for four cases representing common synoptic patterns at Macquarie Island: a cold front, a warm front, postfrontal drizzle, and a midlatitude cyclone. Although the simulations cannot capture every possible feature of the precipitation, preliminary results show that clouds and precipitation can readily be perturbed by the island with the main enhancement of precipitation normally in the lee in accordance with the nondimensional mountain height being much less than 1. The weather station is located at the far north end of the island and is only in the lee to southerly and southwesterly winds, which are normally associated with drizzle. The station is on the upwind side for strong northwesterly winds, which are most common and can bring heavier frontal precipitation. Overall the orographic effect on the precipitation record is not found to be significant, except for the enhancement of drizzle found in southwesterly winds. Given the strong winds over the Southern Ocean and the shallow height of the island, the 3D nondimensional mountain height is smaller than 1 in 93.5% of the soundings. As a result, boundary layer flow commonly passes over the island, with the greatest impact in the lee.

Item Type: Publication - Article
Digital Object Identifier (DOI):
CEH Sections/Science Areas: Reynard
ISSN: 1558-8424
Additional Keywords: rainfall, atmosphere-land interaction, in situ atmospheric observations, numerical analysis, numerical modeling
NORA Subject Terms: Meteorology and Climatology
Date made live: 14 Dec 2016 15:04 +0 (UTC)

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