On the Dynamics of Hawaiian Cloud Bands: Comparison of Model Results with Observations and Island Climatology

Rasmussen, Roy; Smolarkiewicz, Piotr K.; Warner, J.

doi:10.1175/1520-0469(1989)046<1589:otdohc>2.0.co;2

Cited by 60 publications

(48 citation statements)

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“…1). Under stable conditions a weak reversed downslope flow can be produced (e.g., Smolarkiewicz et al 1988;Rasmussen et al 1989;Mo et al 2012), which may initiate a secondary surface cold front to enhance the orographic precipitation aloft. Because of the presence of the melting layer near the surface, the precipitation aloft would undergo phase changes and alter the environmental temperature.…”

Section: Discussionsupporting

confidence: 92%

A Case Study of Processes Impacting Precipitation Phase and Intensity during the Vancouver 2010 Winter Olympics

Thériault

Rasmussen

Smith

et al. 2012

Weather and Forecasting

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Accurate forecasting of precipitation phase and intensity was critical information for many of the Olympic venue managers during the Vancouver 2010 Olympic and Paralympic Winter Games. Precipitation forecasting was complicated because of the complex terrain and warm coastal weather conditions in the Whistler area of British Columbia, Canada. The goal of this study is to analyze the processes impacting precipitation phase and intensity during a winter weather storm associated with rain and snow over complex terrain. The storm occurred during the second day of the Olympics when the downhill ski event was scheduled. At 0000 UTC 14 February, 2 h after the onset of precipitation, a rapid cooling was observed at the surface instrumentation sites. Precipitation was reported for 8 h, which coincided with the creation of a nearly 08C isothermal layer, as well as a shift of the valley flow from up valley to down valley. Widespread snow was reported on Whistler Mountain with periods of rain at the mountain base despite the expectation derived from synoptic-scale models (15-km grid spacing) that the strong warm advection would maintain temperatures above freezing. Various model predictions are compared with observations, and the processes influencing the temperature, wind, and precipitation types are discussed. Overall, this case study provided a well-observed scenario of winter storms associated with rain and snow over complex terrain.

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Section: Discussionsupporting

confidence: 92%

A Case Study of Processes Impacting Precipitation Phase and Intensity during the Vancouver 2010 Winter Olympics

Thériault

Rasmussen

Smith

et al. 2012

Weather and Forecasting

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“…The variety of phenomena induced by the atmospheric flow past single isolated islands has been documented by numerous specific studies using satellite and aerial observations, as well as numerical techniques. For instance, field campaigns based on data collected during the 1985 Joint Hawaii Warm Rain Project and the 1990 Hawaiian Rainband Project (Austin et al, 1996;Rasmussen et al, 1989;Smolarkievicz et al, 1988) show that gravity waves, rainbands and deep convection may form as result of the trade-wind flow impinging on a tropical island. Besides, when wind flows around an island, a wind wake develops on the lee side.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulations of local circulations and pollution transport over Reunion Island

et al. 2011

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Abstract.A series of high-resolution (1 km) numerical simulations with a limited-area numerical model has been performed over Reunion Island. In the dynamical context of a regular maritime flow perturbed by a major topographic obstacle such as Reunion Island, the objectives are to identify the main atmospheric circulations at local-scale over the island and to improve the understanding of local-scale transport and dispersion of pollutants emitted from local sources. To investigate the effects of topography and land surface heating on low-level flows over the island, simulations representative of austral winter were performed in idealized conditions keeping the radiative forcing plus a background eastsouth-easterly synoptic flux of varying strengths, typical of the prevailing trade-wind conditions.The numerical experiments show mainly that flow splitting of the trade-wind occurs around the island, with enhanced winds blowing along the coast lines parallel to the synoptic flux, due to the lateral constriction of the flow by the island and resulting Venturi effect. Blocking occurs on the island side facing the trade-wind. The north-western area on the leeside is screened from the trade-wind by high mountains, and this enables the development of diurnal thermallyinduced circulations, combining downslope and land-breeze at night, and upslope and sea breeze at daytime. Flow splitting is modulated by radiative convergence toward the island at daytime, and divergence from the island at night. Stronger winds than the large-scale trade-wind occur along the coast at daytime (Venturi effect), whereas at night, the trade-wind flow is pushed few kilometres offshore by divergence of cooled air from the land.At night, the trade-wind flow is pushed few kilometres offshore by divergence of cooled air from the land.Correspondence to: D. Lesouëf (dorothee.lesouef@univ-reunion.fr) Consequently, a number of processes of pollution transport and dispersion have been identified. Vortices in the wake of the island were found to cause counterflow circulation and trapping of polluted air masses near the north-western coast. These air masses may in turn be sucked by anabatic wind systems during daytime (upslope and sea breezes) in the cirques and up to the summits of the island, and especially to Piton Maïdo (2200 m) where a new observatory of the Indian Ocean background atmosphere is being built. A "cap effect" above the mountains downstream from the volcano (to the south-east of the island), and especially above Piton Maïdo, might occur in case of development of inland and upslope breezes on the west coast. In this case, air pumped from lower layers may protect the observatory from the volcanic plume forced to pass over a "cap" of low-level air clean of volcanic emissions.

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“…The lateral boundary condition was cyclic and the mountain shape was also simplified. Since then, Clark and Farley's nesting model has been successfully used for various simulations such as a foehn event in the Alps (Hoinka and Clark, 1991), ideal experiments of the flow around an isolated mountain 1989, 1990, numerical experiments of orographic rain (Rasmussen et al, 1989;etc. ), and so on, while the lateral boundary conditions for the outer-most model were still artificial.…”

Section: Meteorologicalmentioning

confidence: 99%

A Numerical Study of the Local Downslope Wind “Yamaji-kaze” in Japan

Saitō¹

1994

Journal of the Meteorological Society of Japan

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A three-dimensional non-hydrostatic inelastic model using a radiative-nesting lateral boundary condition is presented, and is applied to the simulation of the Yamaji-kaze on 27 September 1991. A 2.5 km-resolution version of the model, which is double-nested with the operational hydrostatic model (Japan Spectral Model; JSM) of the Japan Meteorological Agency (JMA), successfully simulates the downslope wind and the associated internal hydraulic jump in the lee of the Shikoku Mountains.The non-hydrostatic anelastic model, which was used in a previous study (Saito, 1993), is modified so that it can express the time-changing environmental information through the lateral boundary condition. Variational calculus is used in order to obtain a three-dimensional mass-consistent initial wind field which satisfies the anelastic continuity equation and the upper and lower boundary conditions. The Orlanski-type radiation condition is employed for the lateral boundary condition of the inner model, using interpolated grid point values of the outer model as the external reference value. The validity of the nesting procedure is shown by a comparison with the non-hydrostatic linear analytic solution over a three-dimensional mountain.The Yamaji-kaze of the 27 September 1991 windstorm caused by Typhoon 9119 is presented, and realistic simulations are conducted using the 10km and 2.5km resolution non-hydrostatic models which are nested with JSM. The 10km-resolution model reproduces well the time change of the synoptic field by the approach of T9119, but does not simulate a conspicuous downslope wind. On the other hand, the 2.5km-resolution model reproduces well the downslope wind and the associated Yamaji-kaze front (internal hydraulic jump in the lee of the Shikoku Mountains). The characteristics of the model-reproduced wind field and the response of the jump to the magnitude of the environmental wind are generally consistent with the conceptual models of the Yamaji-kaze which have been proposed in previous studies (Saito and Ikawa, 1991a;Saito, 1993).Sensitivity experiments show that both the ground temperature and ground roughness affect the intensity of the downslope wind. In case of the Yamaji-kaze, not only the orographic characteristics of the Shikoku Mountains, which were emphasized in previous studies, but also the presence of the Hiuchi-nada (southern part of the Inland Sea in the lee of the Shikoku Mountains) contributes to intensifying the surface wind in the coastal plain through the difference in roughness between sea and land.

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On the Dynamics of Hawaiian Cloud Bands: Comparison of Model Results with Observations and Island Climatology

Cited by 60 publications

References 0 publications

A Case Study of Processes Impacting Precipitation Phase and Intensity during the Vancouver 2010 Winter Olympics

A Case Study of Processes Impacting Precipitation Phase and Intensity during the Vancouver 2010 Winter Olympics

Numerical simulations of local circulations and pollution transport over Reunion Island

A Numerical Study of the Local Downslope Wind “Yamaji-kaze” in Japan

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On the Dynamics of Hawaiian Cloud Bands: Comparison of Model Results with Observations and Island Climatology

Cited by 60 publications

References 0 publications

A Case Study of Processes Impacting Precipitation Phase and Intensity during the Vancouver 2010 Winter Olympics

A Case Study of Processes Impacting Precipitation Phase and Intensity during the Vancouver 2010 Winter Olympics

Numerical simulations of local circulations and pollution transport over Reunion Island

A Numerical Study of the Local Downslope Wind &ldquo;Yamaji-kaze&rdquo; in Japan

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A Numerical Study of the Local Downslope Wind “Yamaji-kaze” in Japan