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A physical model to determine snowfall over land by microwave radiometry
- IEEE T. Geosci Remote Sens
, 2004
"... 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 tem-peratures emitted by snow-covered surfaces are highly ..."
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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 tem-peratures 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 signifi-cant. 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 obser-vations 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 observa-tions. The retrieved snowfall distribution was validated with radar reflectivity measurements obtained from a ground-based radar network. Index Terms—Electromagnetic scattering, estimation, mil-limeter-wave radiometry, remote sensing, satellite, snow. I.
Source of Acquisition NASA Goddard Spacc Flight Center Nonspherical and Spherical Characterization of Ice in Hurricane Erin for Wideband Passive Microwave Comparisons
"... In order to better understand the characteristics of frozen cloud particles in hurricane systems, computed brightness temperatures were compared with radiometric observations of Hurricane Erin (2001) from the NASA ER-2 aircraft. The focus was oil the frozen particle microphysics and the high frequen ..."
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In order to better understand the characteristics of frozen cloud particles in hurricane systems, computed brightness temperatures were compared with radiometric observations of Hurricane Erin (2001) from the NASA ER-2 aircraft. The focus was oil the frozen particle microphysics and the high frequencies (2 85 GHz) that are particularly sensitive to frozen particles. Frozen particles in hurricanes are an indicator of increasing hurricane intensity. In fact "hot towers " associated with increasing hurricane intensity are composed of frozen ice cloud particles. (They are called hot towers because their column of air is warmer than the surrounding air temperature, but above about 5-7 krn to the tops of the towers at 15- 19 krn, the cloud particles are frozen.) This work showed that indeed, one can model information about cloud ice particle characteristics and indicated that mon-spherical ice shapes, instead of spherical particles, provided the best match to the observations. Overall, this work shows that while non-spherical particles show promise, selecting and modeling a proper ice particle parameterization can be difficult and additional in situ measurements are needed to define and validate appropriate parameterizations. This work is important for developing Global Precipitation
Using Opaque Microwave Bands
, 2004
"... This thesis describes the use of opaque microwave bands for global estimation of precipitation rate. An algorithm was developed for estimating instantaneous precip-itation rate for the Advanced Microwave Sounding Unit (AMSU) on the NOAA-15, NOAA-16, and NOAA-17 satellites, and the Advanced Microwave ..."
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This thesis describes the use of opaque microwave bands for global estimation of precipitation rate. An algorithm was developed for estimating instantaneous precip-itation rate for the Advanced Microwave Sounding Unit (AMSU) on the NOAA-15, NOAA-16, and NOAA-17 satellites, and the Advanced Microwave Sounding Unit and Humidity Sounder for Brazil (AMSU/HSB) aboard the NASA Aqua satellite. The algorithm relies primarily on channels in the opaque 54-GHz oxygen and 183-GHz water vapor resonance bands. Many methods for estimating precipitation rate using surface-sensitive microwave window channels have been developed by others. The algorithm involves a set of signal processing components whose outputs are fed into a neural net to produce a rain rate estimate for each 15-km spot. The signal processing components utilize techniques such as principal component analysis for characterizing groups of channels, spatial filtering for cloud-clearing brightness tem-
CORRECTING FOR PRECIPITATION EFFECTS IN SATELLITE-BASED PASSIVE MICROWAVE TROPICAL CYCLONE INTENSITY ESTIMATES
, 2005
"... Public reporting burden for this collection of Information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments ..."
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Public reporting burden for this collection of Information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this
First demonstration of airborne SAR to-mography using multibaseline L-band data
"... Abstract-The radiative transfer equation in a planar-stratified atmosphere with multiple scattering is solved by numerically integrating an ensemble of trial functions which are constructed so as to satisfy the boundary conditions (downward-propagating radiances) at the top of the atmosphere. The b ..."
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Abstract-The radiative transfer equation in a planar-stratified atmosphere with multiple scattering is solved by numerically integrating an ensemble of trial functions which are constructed so as to satisfy the boundary conditions (downward-propagating radiances) at the top of the atmosphere. The boundary conditions at the surface (reflection or scattering) are imposed after integration through the atmosphere. Opaque atmospheres constitute a special case of the latter boundary condition. The algorithm is very efficient because it requires solution, only once, of a set of linear equations of rank equal to half the number of radiation streams.
CORRECTING FOR PRECIPITATION EFFECTS IN SATELLITE-BASED PASSIVE MICROWAVE TROPICAL CYCLONE INTENSITY ESTIMATES
, 2005
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Atmospheric Chemistry and Physics
, 2002
"... The potential of polarization measurements from space at mm and sub-mm wavelengths for determining cirrus cloud parameters ..."
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The potential of polarization measurements from space at mm and sub-mm wavelengths for determining cirrus cloud parameters
PASSIVE MICROWAVE OBSERVATIONS OF THE HISTORIC FEBRUARY 2010 SNOW STORMS IN THE BALTIMORE/WASHINGTON D.C. AREA
"... The unprecedented snowfall during early February 2010 in the Baltimore/Washington area provided a unique opportunity to map, monitor and measure snowfall, snow cover extent, snow water equivalent (SWE), and snow melt using a suite of remote sensing instruments. Because snow cover in the Middle Atlan ..."
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The unprecedented snowfall during early February 2010 in the Baltimore/Washington area provided a unique opportunity to map, monitor and measure snowfall, snow cover extent, snow water equivalent (SWE), and snow melt using a suite of remote sensing instruments. Because snow cover in the Middle Atlantic area is in most years patchy and a true multi-layered snow pack is rarely established, utilizing a remote sensing approach to observe snow parameters is more challenging than in regions where falling snow and snow packs are more reliable. The Advanced Microwave Scanning Radiometer (AMSR-E) and Scanning Microwave/Instrument (SSM/I) data were used to assess SWE and the onset of melt. For this investigation, the Advanced Microwave Sounding Unit-B (AMSU-B) images were employed to detect falling snow. Snowfall observations and retrievals show that indeed falling snow signatures can be seen in high frequency brightness temperatures. Detection of falling snow is performed operationally, while retrieving falling snow rates is a new area of scientific research and still requires additional investigation. However, it is encouraging that, in general, where falling snow is occurring, on the surface below, snow cover is present. Pixels that are mixed with water seriously compromise the efficacy of snow pack observing sensors operating in the microwave portion of the electromagnetic spectrum. The Chesapeake Bay and its wide mouthed, tidewater tributaries thus negatively impacts efforts to derive SWE and snowmelt. Furthermore, the average daytime maximum temperatures in this region are well above
TEMPERATURE PROFILING AT SOUTHERN LATITUDES BY DEPLOYING MICROWAVE RADIOMETER
"... Multifrequency Microwave Radiometer (MP3000A) from Radiometrics Corporation is deployed at different places of Southern latitude for the profiling of one of thermodynamic variables like Temperature. The radiative intensity down- welling from the atmosphere and is expressed in an equivalent brightnes ..."
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Multifrequency Microwave Radiometer (MP3000A) from Radiometrics Corporation is deployed at different places of Southern latitude for the profiling of one of thermodynamic variables like Temperature. The radiative intensity down- welling from the atmosphere and is expressed in an equivalent brightness temperature. The radiation is a nonlinear function of the required quantities and we linearise the expression around a suitably chosen first guess, such as a climatological mean. We describe changes in the brightness temperature around the first guess by means of a weighting function which expresses the sensitivity of to the variation of the humidity or the temperature around their initial values. The variation of brightness temperature with height occurs at 51 – 53 GHz is observed but on the other hand the constancy of brightness temperature with height at 56 – 57 GHz is noticeable. This suggests that the measurement of temperature at a certain place by a ground based radiometer may provide good result by exploiting the 56 – 57 GHz band. In this band we have used four frequencies for the purpose. But to extend our study we have also made an attempt to retrieve the temperature profiles in 51 – 53 GHz band. The retrieval process starts with the calculations of and for two sub-ensembles of radiometric observations separately. Here and. The measured brightness temperatures at eight specified channel frequencies at Fortaleza, Brazil on 11th April,
