Microphysical Processes Within Winter Orographic Cloud and Precipitation Systems

Stoelinga, Mark T.; Stewart, Ronald E.; Thompson, Gregory; Thériault, Julie M.

doi:10.1007/978-94-007-4098-3_7

Cited by 39 publications

(46 citation statements)

References 193 publications

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“…The shear‐induced mechanical turbulence potentially enhanced vertical air motions in the 3000–4000 m layer. Updrafts potentially raised moist air up to water saturation promoting precipitation formation [ Houze , ; Stoelinga et al , ] and could be an explanation for the area‐wide increase in Z H at this time of day and the joint occurrence of high Z H and low Z DR values at those elevations (Figure ). As the strength of the wind shear increased during the investigated time period, the Z H signal also increased (Figures and ), indicating enhanced precipitation formation above the entire Davos region.…”

Section: Discussionmentioning

confidence: 99%

“…Considering the small width of the barrier Schiahorn (approximately 3 km), the advective time scale is much shorter than the conversion of condensates to precipitation and particle fallout. A local orographic cloud at this scale would be thus incapable of producing precipitation by itself [ Stoelinga et al , ]. A possible explanation for the coinciding small‐scale spatial pattern of low Z DR and high Z H signals and the enhanced efficiency for precipitation production at a small area (Figures c and d) is that the orographically induced ascent of the airflow at low elevation produced a different condensation regime leading to low‐level orographic cloud formation above the Schiahorn region.…”

Section: Discussionmentioning

confidence: 99%

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Orographic effects on snow deposition patterns in mountainous terrain

Mott¹,

et al. 2014

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Orographic lifting of air masses and other topographically modified flows induce cloud and precipitation formation at larger scales and preferential deposition of precipitation at smaller scales. In this study, we examine orographic effects on small-scale snowfall patterns in Alpine terrain. A polarimetric X-band radar was deployed in the area of Davos (Switzerland) to determine the spatial variability of precipitation. In order to relate measured precipitation fields to flow dynamics, we model flow fields with the atmospheric prediction model "Advanced Regional Prediction System. " Additionally, we compare radar reflectivity fields with snow accumulation at the surface as modeled by Alpine3D. We investigate the small-scale precipitation dynamics for one heavy snowfall event in March 2011 at a high resolution of 75 m. The analysis of the vertical and horizontal distribution of radar reflectivity at horizontal polarization and differential reflectivity shows polarimetric signatures of orographic snowfall enhancement near the summit region. Increasing radar reflectivity at horizontal polarization over the windward slopes toward the crest and downwind decreasing reflectivity over the leeward slopes is observed. The temporal variation of the location of maximum concentration of snow particles is partly attributed to the effect of preferential deposition of snowfall: For situations with strong horizontal winds, the concentration maximum is shifted from the ridge crest toward the leeward slopes. Qualitatively, we discuss the relative role of cloud microphysics such as the seeder-feeder mechanism versus atmospheric particle transport in generating the observed snow deposition at the ground.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Orographic effects on snow deposition patterns in mountainous terrain

Mott¹,

et al. 2014

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“…The dynamical and microphysical processes that affect the distribution and intensity of orographic precipitation vary with the dynamics and thermodynamics of the incipient airflow, the size and shape of the terrain, and the time scales controlling the growth and fallout of precipitation particles [see Roe (2005), Smith (2006), Houze (2012), Colle et al (2013), and Stoelinga et al (2013) for recent reviews]. Over the western United States, many orographic storms evolve through stable, transitional (frequently with frontal characteristics), and unstable stages (e.g., Hobbs 1975;Marwitz 1980;Cooper and Saunders 1980;Long et al 1990;Sassen et al 1990;Medina et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Finescale Orographic Precipitation Variability and Gap-Filling Radar Potential in Little Cottonwood Canyon, Utah

Campbell

Steenburgh

2014

Weather and Forecasting

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Finescale variations in orographic precipitation pose a major challenge for weather prediction, winter road maintenance, and avalanche forecasting and mitigation in mountainous regions. In this investigation, groundbased X-band radar observations collected during intensive observing period 6 (IOP6) of the Storm Chasing Utah Style Study (SCHUSS) are used to provide an example of these variations during a winter storm in the Wasatch Mountains of northern Utah. Emphasis is placed on precipitation features in and around Little Cottonwood Canyon (LCC), which cuts orthogonally eastward into the central Wasatch Mountains. Precipitation during the weakly stratified prefrontal storm stage featured a wavelike barrier-scale reflectivity maximum over the Wasatch Crest and upper LCC that extended weakly westward along the transverse ridges flanking LCC. This precipitation pattern appeared to reflect a veering wind profile, with southwesterly flow over the transverse ridges but cross-barrier westerly flow farther aloft. Sublimation within dry subcloud air further diminished low-level radar reflectivities over lower LCC. In contrast, the cold-frontal stage was associated with stronger reflectivities over lower LCC and the adjoining north-to northwest-facing canyon wall, consistent with shallow, northwesterly upslope flow. These results highlight the finescale precipitation variations that can occur during winter storms in complex terrain and demonstrate the potential for improved analysis and forecasting of precipitation in LCC using a gap-filling radar.

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“…However this assumption may not be accurate, especially for wintertime precipitation and in an orographic context. Indeed, according to several studies the melting layer may dip downwards with a few hundred metres in the proximity of terrain (for example Stoelinga et al (2013)), and melting layer thickness has been related to snowflake density and the presence of rimed particles above the melting layer (Wolfensberger et al, 2016). Several studies have reported on the melting layer variability at seasonal and large spatial (for example Harris et al (2000); Rudolph and Friedrich (2013)) and temporal scales.…”

mentioning

confidence: 99%

“…It is common practice to compensate for the lack of direct visibility with the radar by extrapolating the measurements collected at higher elevations to the ground level, using a vertical profile of reflectivity (VPR) to correct for the vertical change in the radar reflectivity measurement (Germann and Joss, 2002). This vertical change in reflectivity is related to changes in size, phase and fallspeed of hydrometeors, which is in turn dependent on both microphysical processes and the vertical profiles of temperature and humidity (Stoelinga et al, 2013).The melting layer (ML) is a typical feature in radar observations of the vertical structure of stratiform precipitation which designates the transition region from solid to liquid precipitation. It has a well-known signature in the (polarimetric) radar variables with a notable increase in the horizontal reflectivity factor (ZH) as well as a reduction of the copolar correlation coefficient (Rhohv) (Battan, 1973;Brandes and Ikeda, 2004).…”

mentioning

confidence: 99%