A Statistical and Physical Description of Hydrometeor Distributions in Colorado Snowstorms Using a Video Disdrometer

Brandes, Edward A.; Ikeda, Kyoko; Zhang, Guifu; Schönhuber, Michael; Rasmussen, Roy

doi:10.1175/jam2489.1

Cited by 212 publications

(225 citation statements)

References 46 publications

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“…3 shows probability distributions for maximum dimension D max , equivalent radius r eq , aspect ratio α, orientation θ, complexity χ and fall speed V . Median values with lower and upper quartiles for these quantities (Barthazy and Schefold, 2006;Brandes et al, 2007Brandes et al, , 2008Gunn, 1967;Heymsfield and Westbrook, 2010;Magono and Nakamura, 1965;Mitchell et al, 1990;Yuter et al, 2006;Zawadzki et al, 2010). The hydrometeors that were observed tended to have low complexity, with a clear preference for a near unity aspect ratio, suggesting a dominance of riming.…”

Section: Measurementsmentioning

confidence: 89%

Fall speed measurement and high-resolution multi-angle photography of hydrometeors in free fall

et al. 2012

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Abstract. We describe here a new instrument for imaging hydrometeors in free fall. The Multi-Angle Snowflake Camera (MASC) captures high-resolution photographs of hydrometeors from three angles while simultaneously measuring their fall speed. Based on the stereoscopic photographs captured over the two months of continuous measurements obtained at a high altitude location within the Wasatch Front in Utah, we derive statistics for fall speed, hydrometeor size, shape, orientation and aspect ratio. From a selection of the photographed hydrometeors, an illustration is provided for how the instrument might be used for making improved microwave scattering calculations. Complex, aggregated snowflake shapes appear to be more strongly forward scattering, at the expense of reduced back-scatter, than heavily rimed graupel particles of similar size.

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Section: Measurementsmentioning

confidence: 89%

Fall speed measurement and high-resolution multi-angle photography of hydrometeors in free fall

et al. 2012

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“…However, the disdrometer measures the size of the cross-sectional area instead of the maximum dimension of non-spherical particles. Assuming that the ice crystals fall randomly oriented through the sensitive volume (Brandes et al, 2007), Lempio et al (2007) found from theoretical experiments using a ray tracing model (Macke et al, 1998) that the products of the terminal velocity and the equivalent liquid water content, as a function of the cross-sectional area, for different types of snow crystals are of the same order of magnitude. That allows one common parameterization to be used for all kinds of crystals; for practical reasons, lump graupel was chosen.…”

Section: Shipboard Odm 470 Optical Disdrometer Measurementsmentioning

confidence: 99%

HOAPS and ERA-Interim precipitation over the sea: validation against shipboard in situ measurements

et al. 2016

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Abstract. The satellite-derived HOAPS (Hamburg OceanAtmosphere Parameters and Fluxes from Satellite Data) and ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis data sets have been validated against in situ precipitation measurements from ship rain gauges and optical disdrometers over the open ocean by applying a statistical analysis for binary estimates. For this purpose collocated pairs of data were merged within a certain temporal and spatial threshold into single events, according to the satellites' overpass, the observation and the ERAInterim times. HOAPS detects the frequency of precipitation well, while ERA-Interim strongly overestimates it, especially in the tropics and subtropics. Although precipitation rates are difficult to compare because along-track point measurements are collocated with areal estimates and the number of available data are limited, we find that HOAPS underestimates precipitation rates, while ERA-Interim's Atlantic-wide average precipitation rate is close to measurements. However, when regionally averaged over latitudinal belts, deviations between the observed mean precipitation rates and ERAInterim exist. The most obvious ERA-Interim feature is an overestimation of precipitation in the area of the intertropical convergence zone and the southern subtropics over the Atlantic Ocean. For a limited number of snow measurements by optical disdrometers, it can be concluded that both HOAPS and ERA-Interim are suitable for detecting the occurrence of solid precipitation.

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“…Specifically, disdrometer observations of particle size distributions (PSDs) in concert with observations of radar reflectivity or accumulated snow mass have been used to estimate snow bulk and microphysical properties. Brandes et al (2007) used 2-D video disdrometer and snow accumulation observations to estimate snow bulk densities. Huang et al (2010) also used 2-D video disdrometer observations, along with C-band radar reflectivities, to estimate the parameters of snow particle massdimension relations.…”

Section: N B Wood Et Al: Characterization Of Disdrometer Uncertainmentioning

confidence: 99%

Characterization of video disdrometer uncertainties and impacts on estimates of snowfall rate and radar reflectivity

et al. 2013

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Abstract. Estimates of snow microphysical properties obtained by analyzing collections of individual particles are often limited to short timescales and coarse time resolution. Retrievals using disdrometer observations coincident with bulk measurements such as radar reflectivity and snowfall amounts may overcome these limitations; however, retrieval techniques using such observations require uncertainty estimates not only for the bulk measurements themselves, but also for the simulated measurements modeled from the disdrometer observations. Disdrometer uncertainties arise due to sampling and analytic errors and to the discrete, potentially truncated form of the reported size distributions. Imaging disdrometers such as the Snowflake Video Imager and 2-D Video Disdrometer provide remarkably detailed representations of snow particles, but view limited projections of their three-dimensional shapes. Particle sizes determined by such instruments underestimate the true dimensions of the particles in a way that depends, in the mean, on particle shape, also contributing to uncertainties. An uncertainty model that accounts for these uncertainties is developed and used to establish their contributions to simulated radar reflectivity and snowfall rate. Viewing geometry effects are characterized by a parameter, φ, that relates disdrometer-observed particle size to the true maximum dimension of the particle. Values and uncertainties for φ are estimated using idealized ellipsoidal snow particles. The model is applied to observations from seven snow events from the Canadian CloudSat/CALIPSO Validation Project (C3VP), a mid-latitude cold-season cloud and precipitation field experiment. Typical total uncertainties are 4 dB for reflectivity and 40-60 % for snowfall rate, are highly correlated, and are substantial compared to expected uncertainties for radar and precipitation gauge observations. The dominant sources of errors are viewing geometry effects and the discrete, truncated form of the size distributions. While modeled Ze-S relationships are strongly affected by assumptions about snow particle mass properties, such relationships are only modestly sensitive to φ owing to partially compensating effects on both the reflectivity and snowfall rate.

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A Statistical and Physical Description of Hydrometeor Distributions in Colorado Snowstorms Using a Video Disdrometer

Cited by 212 publications

References 46 publications

Fall speed measurement and high-resolution multi-angle photography of hydrometeors in free fall

Fall speed measurement and high-resolution multi-angle photography of hydrometeors in free fall

HOAPS and ERA-Interim precipitation over the sea: validation against shipboard in situ measurements

Characterization of video disdrometer uncertainties and impacts on estimates of snowfall rate and radar reflectivity

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