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James S. Risbey, Didier P. Monselesan, Terence J. O’Kane, Carly R. Tozer, Michael J. Pook, and Peter T. Hayman

Issues/266magrn17/damaging_spring_frosts.pdf . Risbey , J. , T. O’Kane , D. Monselesan , C. Franzke , and I. Horenko , 2018 : On the dynamics of austral heat waves . J. Geophys. Res. Atmos. , 123 , 38 – 57 , https://doi.org/10.1002/2017JD027222 . 10.1002/2017JD027222 Schultz , D. , W. Bracken , and L. Bosart , 1998 : Planetary- and synoptic-scale signatures associated with Central American cold surges . Mon. Wea. Rev. , 126 , 5 – 27 , https://doi.org/10

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Haile Xue, Jian Li, Tingting Qian, and Hongping Gu

and Chen 2017 ; Udina et al. 2017 ). In addition, models require high resolution to resolve both the realistic topography and the associated small-scale atmospheric processes. The properties (amplitude and wavelength) of lee waves are considerably influenced by mountain parameters and planetary boundary layer (PBL) processes ( Pearce and White 1967 ; Jiang et al. 2006 ; Smith 2007 ; Wang et al. 2010 ; Li and Chen 2017 ). The PBL parameterization schemes in mesoscale numerical models are

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Chenjie Huang, Y-L. Lin, M. L. Kaplan, and J. J. Charney

subtropical jet stream resulting in strong upper-level convergence. Brotak and Reifsnyder (1977a) examined 52 major wildland fires (“major” fires being those that burned more than 5000 acres) in the eastern half of the United States and found that 75% of these fires occurred immediately behind or just ahead of surface cold fronts downstream from small-amplitude but intense 500-hPa short-wave troughs. It has been recognized that prevailing near-surface weather conditions or the atmospheric planetary

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Leonard M. Druyan and Timothy M. Hall

interval is 4 mm day-( Shading indicates a positive (southerly) component of the model level 2 (~890 rob) wind.gence contributes to wave development and is notmerely a passive consequence of deep convection.Figure 8 also implies that, west of the trough, advec~tion of drier air during August-September somewhatinhibits moist convection.7. Discussion Differences in the planetary circulation betweenJune-August 1987 and 1988 were part of the atmospheric response to opposite phases of a significant1108

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D. M. Leahey, M. C. Hansen, and M. B. Schroeder

only near the ground, but also withinthe capping inversion surmounting the convectivelyactive planetary boundary layer (PBL) (Hooke andJones 1986). A wide variety of dynamic phenomenaare causes of gravity wave excitation. These includewind shear, thunderstorm activity, and frontal passages(Finnigan et al. 1984; Stull 1976; Egger et al. 1993;Haase 1991 ). Mountain lee waves are also manifestations of gravity wave phenomena. They will tend tooccur in the upper atmosphere at discontinuities in

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Andre K. Pattantyus, Sen Chiao, and Stanley Czyzyk

Valley were investigated in this paper using the Weather Research and Forecasting Model. The results affirmed the model’s ability to recapture the transient nature of such events using high spatial resolution. It appears that the resonant-amplification wave theory as described by Clark and Peltier (1984) is most suitable to explain these downslope wind events. Planetary boundary layer schemes were evaluated to determine which most adequately represented the 15 April 2008 event. Model temperatures

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T. Cherubini, S. Businger, R. Lyman, and M. Chun

1. Introduction Atmospheric turbulence is a key challenge in ground-based astronomy because it dramatically impacts the angular resolution of a telescope. Small-scale temperature and moisture fluctuations in the atmosphere result in fluctuations of the refractive index. The wave front of radiation traveling through the atmosphere changes as it encounters inhomogeneities in the refractive index, degrading optical image quality. The intensity of the turbulent fluctuations of the atmospheric

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Joshua P. Hacker, Ian G. McKendry, and Roland B. Stull

). Jaffe et al. (1999) document anthropogenic pollutants from Asia reaching the Pacific Northwest, but this was the first documented case of mineral dust reaching North America from Asia (although there is ice-core evidence of Asian dust reaching Greenland in the past; Biscaye et al. 1997 ). This spectacular and unusual event raised questions about mechanisms of free-tropospheric–planetary boundary layer (FT–PBL) exchange that would permit mineral aerosol transported in the middle and lower

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Roland J. Boucher and Hans Ottersten

JOURNAL OF APPLIED METEOROLOGY VOLIJME~0 Doppler Radar Observation of Wind Structure in Snow ROLAND J. BOUCHER AND HANS OTTERSTEN1 Air Force Cambridge Research Laboratories, Bedford, Mass. (Manuscript received 30 July 1970, in revised form 16 December 1970) ABSTRACT Sinusoidal variations in the longitudinal speed of the wind in the planetary boundary layer are observedwith a C

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G. A. Herbert, W. A. Hass, and J. K. Angell

local weather conditions. This study shows a good correlation between depth of the surface mixed layerand the percentage of spiked signatures. The variability of the maximum overpressure also increases withincrease in low-level wind speed. Both these results suggest that turbulence in the planetary boundary layeris the main cause of spiked signatures and the associated large variation in maximum overpressure. Thereis some evidence that waves within an inversion contribute to overpressure variability

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