Microwave Properties of Frozen Precipitation around a North Atlantic Cyclone

Schols, J. L.; Weinman, J. A.; Alexander, G. David; Stewart, Ronald E.; Angus, L. J.; Lee, A. C. L.

doi:10.1175/1520-0450(1999)038<0029:mpofpa>2.0.co;2

Cited by 25 publications

(14 citation statements)

References 34 publications

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“…Effective medium mixing theories have been used by [5], [6], [18], and [19] to represent the dielectric constant of snow at frequencies below 90 GHz [20]. Using these models for the higher frequencies seemed to produce inappropriate electromagnetic characteristics.…”

Section: ) Snow Size Parameter Selectionmentioning

confidence: 99%

A physical model to determine snowfall over land by microwave radiometry

Skofronick-Jackson

Kim

Weinman

et al. 2004

IEEE Trans. Geosci. Remote Sensing

116

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Abstract-Falling snow is an important component of global precipitation in extratropical regions. This paper describes the methodology and results of physically based retrievals of snow falling over land surfaces. Because microwave brightness temperatures emitted by snow-covered surfaces are highly variable, precipitating snow above such surfaces is difficult to observe using window channels that occur at low frequencies ( 100 GHz). Furthermore, at frequencies 37 GHz, sensitivity to liquid hydrometeors is dominant. These problems are mitigated at high frequencies ( 100 GHz) where water vapor screens the surface emission, and sensitivity to frozen hydrometeors is significant. However, the scattering effect of snowfall in the atmosphere at those higher frequencies is also impacted by water vapor in the upper atmosphere. The theory of scattering by randomly oriented dry snow particles at high microwave frequencies appears to be better described by regarding snow as a concatenation of "equivalent" ice spheres rather than as a sphere with the effective dielectric constant of an air-ice mixture. An equivalent sphere snow scattering model was validated against high-frequency attenuation measurements. Satellite-based high-frequency observations from an Advanced Microwave Sounding Unit (AMSU-B) instrument during the March 5-6, 2001 New England blizzard were used to retrieve snowfall over land. Vertical distributions of snow, temperature, and relative humidity profiles were derived from the Mesoscale Model (MM5) cloud model. Those data were applied and modified in a radiative transfer model that derived brightness temperatures consistent with the AMSU-B observations. The retrieved snowfall distribution was validated with radar reflectivity measurements obtained from a ground-based radar network.

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Section: ) Snow Size Parameter Selectionmentioning

confidence: 99%

A physical model to determine snowfall over land by microwave radiometry

Skofronick-Jackson

Kim

Weinman

et al. 2004

IEEE Trans. Geosci. Remote Sensing

116

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“…Equation 4 is based on a similar expression developed by Magono and Nakamura (1965) (see also Schols et al 1999). In Eq.…”

Section: Model and Results For Convective Rainmentioning

confidence: 99%

TRMM Precipitation Radar and Microwave Imager Observations of Convective and Stratiform Rain over Land and their Theoretical Implications.

Prabhakara

Iacovazzi

Yoo

2002

Journal of the Meteorological Society of Japan

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Observations of brightness temperature, Tb, made over land regions by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) radiometer are analyzed with the help of nearly simultaneous measurements of the vertical profiles of reflectivity factor, Z, made by the Precipitation Radar (PR) onboard the TRMM satellite. Furthermore, this analysis is done separately over convective and stratiform rain regions. This examination reveals a clear relationship between TMI and PR data. Possible explanation for this relationship is explored with the help of radiative transfer calculations. With this approach, we demonstrate that the 85 GHz observations of TMI can be simulated crudely from the observations of Z. However, the 37 and 19 GHz observations are not as well simulated, possibly because of horizontal non-uniformity in the hydrometeor distribution in the broad footprints of these channels and contamination introduced by land-surface emissivity. On the other hand, from TMI and PR observations, we find that the brightness temperature difference (T19-T37) minimizes these sources of error. Our simulations of (T19-T37) over convective rain regions are in reasonable agreement with this finding. This investigation indicates that the TMI 85 GHz channel yields the best information about rain over tropical land, because it has minimal surface contamination, strong extinction, and a fine footprint. The brightness temperature difference (T19-T37) can supplement the information given by the 85 GHz channel.

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“…TBSCAT was developed and provided by P. W. Rosenkranz (personal communication) based on his radiative transfer algorithm [2], improvements on standard millimeter-wave atmospheric transmittance models [24], [25], and the complex permittivities for water and ice given by [26] and [27], respectively. To simulate brightness temperatures using TBSCAT, all hydrometeors were assumed to be spherical and homogeneous [28], [29] with size distributions that are inverse-exponential functions of diameter as given in (1), where F (λ) for each ice species was used in place of the density ρ. Because F (λ) is generally not dependent upon hydrometeor diameters below 200 GHz, F (λ) was made independent of altitude or size distribution functions.…”

Section: Tbscatmentioning

confidence: 99%

Comparison of AMSU Millimeter-Wave Satellite Observations, MM5/TBSCAT Predicted Radiances, and Electromagnetic Models for Hydrometeors

Surussavadee

Staelin

2006

IEEE Trans. Geosci. Remote Sensing

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This paper addresses the following: 1) millimeterwave scattering by icy hydrometeors and 2) the consistency between histograms of millimeter-wave atmospheric radiances observed by satellite instruments [Advanced Microwave Sounding Unit-A/B (AMSU-A/B)] and those predicted by a mesoscale numerical weather prediction (NWP) model (MM5) in combination with a two-stream radiative transfer model (TBSCAT). This observed consistency at 15-km resolution supports use of MM5/TBSCAT as a useful simulation tool for designing and assessing global millimeter-wave systems for remote sensing of precipitation and related parameters at 50-200 GHz. MM5 was initialized by National Center for Environmental Prediction NWP analyses on a 1 • grid approximately 5 h prior to each AMSU transit and employed the Goddard explicit cloud physics model. The scattering behavior of icy hydrometeors, including snow and graupel, was assumed to be that of spheres having an ice density F (λ) and the same average Mie scattering cross sections as computed using a discrete-dipole approximation implemented by DDSCAT for hexagonal plates and six-pointed rosettes, respectively, which have typical dimensional ratios observed aloft. No tuning beyond the stated assumptions was employed. The validity of these approximations was tested by varying F (λ) for snow and graupel so as to minimize discrepancies between AMSU and MM5/TBSCAT radiance histograms over 122 global storms. Differences between these two independent determinations of F (λ) were less than ∼0.1 for both snow and graupel. Histograms of radiances for AMSU and MM5/TBSCAT generally agree for 122 global storms and for subsets of convective, stratiform, snowy, and nonglaciated precipitation.

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Microwave Properties of Frozen Precipitation around a North Atlantic Cyclone

Cited by 25 publications

References 34 publications

A physical model to determine snowfall over land by microwave radiometry

A physical model to determine snowfall over land by microwave radiometry

TRMM Precipitation Radar and Microwave Imager Observations of Convective and Stratiform Rain over Land and their Theoretical Implications.

Comparison of AMSU Millimeter-Wave Satellite Observations, MM5/TBSCAT Predicted Radiances, and Electromagnetic Models for Hydrometeors

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