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Brian Medeiros, Clara Deser, Robert A. Tomas, and Jennifer E. Kay

1. Introduction Low-level temperature inversions are a noted feature of the Arctic winter climate ( Serreze et al. 1992 ; Zhang et al. 2011 ). The so-called Arctic inversion mediates the surface energy balance and contributes to amplifying the high-latitude surface temperature response to anthropogenic increases in greenhouse gas (GHG) concentrations ( Serreze and Barry 2005 ). The amplified warming over the Arctic Ocean and surrounding continents in recent years has been most pronounced in

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Rolf F. Hertenstein

present, widespread turbulence is almost always found in the lower levels to the lee of elevated terrain. The Lower Turbulent Zone LTZ; Lester and Fingerhut 1974 ) describes the turbulent layer downwind of elevated terrain, above the surface layer, and under an undulating stable layer (e.g., an inversion) comprising the waves themselves. Turbulence within the LTZ has also been referred to as rotor-zone turbulence ( WMO 1973 ). We note that the aviation community often uses the term “rotor” when

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Robert R. Gillies, Shih-Yu Wang, and Marty R. Booth

1. Introduction It is well known that winter inversions often result in poor air quality in certain regions of the Intermountain West. Here, distinct topographic conditions tend to maintain the pooling of stable, relatively cold air in valleys and mountain basins, resulting in persistent inversions ( Lockhart 1943 ; Wolyn and McKee 1989 ; Whiteman et al. 1999 , 2001 ; Billings et al. 2006 ). These inversions subsequently trap air pollutants and degrade the air quality over time ( Holzworth

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Warwick Grace and Graeme Tepper

1. Introduction Current Australian guidelines are that spraying should not be undertaken when hazardous inversions exist. Internationally, similar guidelines usually exclude the term “hazardous.” Since there are currently no known methods for spray applicators to determine whether a hazardous inversion exists as compared with a nonhazardous inversion and since surface inversions tend to occur on most nights in most places, adherence to this guidance precludes spraying crop protection products

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Joseph Egger and Klaus-Peter Hoinka

1. Introduction Many aspects of large-scale fluid dynamics can be understood within the framework of “potential vorticity (PV) thinking” ( Hoskins et al. 1985 , hereafter HMR ), where PV plays a central role as a materially conserved quantity in the absence of friction and heating. It is sufficient according to this concept to know the distribution of PV at a certain moment as well as balance and boundary conditions to derive most other variables by PV inversion (PVI) (e.g., Vallis 1996

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Yehui Zhang, Dian J. Seidel, Jean-Christophe Golaz, Clara Deser, and Robert A. Tomas

1. Introduction Surface-based inversions (SBIs), where atmospheric temperature increases with height from the surface, are a frequent feature of the atmospheric boundary layer in the Arctic and Antarctic. They are found in more than ~40% of nighttime radiosonde observations and more than ~20% of daytime observations at stations poleward of 60 degrees latitude and occur more often in winter than summer ( Seidel et al. 2010 ). Two mechanisms dominate the formation of low-level and surface

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Guangxia Cao, Thomas W. Giambelluca, Duane E. Stevens, and Thomas A. Schroeder

1. Introduction The inversion in the trade wind regime of the Tropics and subtropics is the result of the interaction between large-scale subsiding air from the upper troposphere and convection-driven rising air from lower levels (e.g., Malkus 1956 ; Augstein et al. 1973 ; Riehl 1979 ; Albrecht 1984 ). Albrecht presented a simple model of the thermodynamic structure of the planetary boundary layer (PBL) in the trade wind zone in which inversion height was shown to be influenced by “sea

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Tiina Nygård, Teresa Valkonen, and Timo Vihma

controlled by temperature and, therefore, humidity in the atmosphere typically decreases with height. Humidity inversions (i.e., layers where the specific humidity increases with height) are, however, common features in the lower troposphere in the polar areas ( Curry et al. 1996 ; Devasthale et al. 2011 ; Vihma et al. 2011a ). Factors that are known to contribute to humidity inversions can roughly be divided into two categories: 1) processes that are sources/sinks to the water vapor content of the

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William J. Randel and Fei Wu

1. Introduction The tropopause inversion layer (TIL) refers to a region of enhanced static stability above the extratropical tropopause, associated with a narrow-scale temperature inversion. The TIL was discovered in analysis of high-vertical-resolution radiosonde measurements by Birner et al. (2002) and Birner (2006) , using a tropopause-based vertical coordinate system. Because of substantial variability in the height of the extratropical tropopause (linked to synoptic-scale eddies), the

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Sebastian H. Mernild and Glen E. Liston

1. Introduction Air temperature inversions—increasing temperatures with elevation—are present throughout the Arctic, covering a wide range of spatial and temporal domains. While these inversions can exist over a wide range of landscapes, and be the result of numerous processes and interactions, the inversion climatology literature mostly focuses on studies of single valley or basin locations (e.g., Putnins 1970 ; Kahl 1990 ; Kahl et al. 1992 ; Serreze et al. 1992 ; Kadygrov et al. 1999

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