Page 1. ■Hi Thermal Microwave Radiation: Applications for Remote Sensing Edited by C Matzler Page... more Page 1. ■Hi Thermal Microwave Radiation: Applications for Remote Sensing Edited by C Matzler Page 2. IET ELECTROMAGNETIC WAVES SERIES 52 Series Editors: Professor PJB Clarricoats Professor EV Jull Thermal Microwave Radiation: Applications for Remote Sensing ...
EarthCARE space-borne radar will be the first radar in space with Doppler capability, enabling me... more EarthCARE space-borne radar will be the first radar in space with Doppler capability, enabling measurements of vertical motions of hydrometeors. The vertical velocity is very useful in classifying precipitating systems (convective systems versus stratiform, rain versus snow). Global distribution of hydrometeor vertical velocity is important in estimation of latent heat fluxes and in study of energy transportation in the atmosphere. A renewed interest in space-borne Doppler radars has recently sprouted as a response to the imminent launch (2015) of the W-band cloud profiling radar within the ESA/JAXA EarthCARE mission. Given the many caveats involved with high frequency space-borne Doppler radars (Doppler fading due to the fast satellite movement, small Nyquist velocity folding, non uniform beam filling issues, contamination by multiple scattering, antenna mispointing) a particularly challenging scenario for retrieving mean Doppler velocities is represented by convective clouds. In this work we will couple DOMUS, a Monte Carlo-based DOppler MUltiple Scattering radar simulator capable of accounting for non uniform beam filling (NUBF) conditions and multiple scattering enhancements, with high resolution WRF (Weather Research and Forecasting) mesoscale prediction model runs to study the potential of high frequency Doppler radars in retrieving vertical hydrometeor motions in atmosphere.
The 94 GHz EarthCARE radar (expected to be launched within three years) will be the first radar i... more The 94 GHz EarthCARE radar (expected to be launched within three years) will be the first radar in space with Doppler capabilities. The retrieval of hydrometeor fall speeds and air motions from the radar signal will be extremely challenging due to a variety of complications. In EarthCARE configuration (height=395 km, beam-width=0.08°, PRF around 6000 Hz) the following caveats have to be accounted for: a) the high satellite speed matched to the finite antenna beam-width produces consistent Doppler fading (σDoppler ≈ 3.25 m/s); b) Nyquist Doppler interval ( 4.5 m/s) can introduce relevant folding; c) non uniform beam filling conditions may cause biases in the mean Doppler velocity estimates; d) multiple scattering widens the Doppler spectrum and de-correlate the signal from the real mean velocity. A forward Doppler radar simulator capable of accounting both for non uniform beam filling conditions and multiple scattering enhancements has been coupled to an instrument simulator in order to reproduce the signal at the antenna port. In this paper the EarthCARE radar simulator has been applied to a variety of scenarios (convective rain, drizzle, cirrus sedimentation). The performance of different standard Doppler moment estimators is discussed for the three different situations. In convective scenarios it will be utterly tough to extract useful velocity information from EarthCARE observations.
Egu General Assembly Conference Abstracts, Apr 1, 2009
Multiple scattering strongly affects the CloudSat Profiling Radar reflectivity when the satellite... more Multiple scattering strongly affects the CloudSat Profiling Radar reflectivity when the satellite is over-passing moderate and heavy precipitation systems. Following a criterion developed by the authors in the past (Battaglia et al., 2008) and based on the freezing level altitude (FLA) and on the path integrated attenuation (PIA), oceanic CloudSat reflectivities profiles affected by multiple scattering are identified and further analysed. Profiles are clustered according to PIA, FLA, position and value of the profile maximum reflectivity, jump of the reflectivity from pixels close to the surface to the surface pixel. This last variable represents a rough estimate of the multiple-scattering strength, i.e. of the reflectivity enhancement produced by higher-than-one scattering orders in proximity to the surface. The slopes of the reflectivity profiles (which results from the combined effect of vertical variability, attenuation and multiple scattering) are then computed at different altitudes above the surface and their variability is discussed in relationships to the profile characteristic variables. Results from one full year of CloudSat data are discussed and compared with numerical simulation outputs based on Cloud Resolving Model (Battaglia and Simmer 2008). This study has strong relevance for attenuation-based retrievals of rainfall from high frequency space-borne radars (Matrosov et al., 2008). Battaglia, A., J. Haynes, T. L'Ecuyer, and C. Simmer, Identifying multiple-scattering-affected profiles in CloudSat observations over the Oceans, J. Geoph. Res., 113, D00A17, doi:101029/2008JD009960 Battaglia, A., and C. Simmer, How does multiple scattering affect the spaceborne W-band radar measurements at ranges close to and crossing the surface-range?, IEEE Tran. Geo. Rem. Sens., , Vol. 46, No. 6,1644-1651, 2008 Matrosov, S., Battaglia, A., Rodriguez, P. Effects of multiple scattering on attenuation-based retrievals of stratiform rainfall from CloudSat, J. Atm. Oc. Tech., , 25(12), 2199-2208, 2008
Although snow is the predominant type of precipitation in the sub-polar and polar latitudes, not ... more Although snow is the predominant type of precipitation in the sub-polar and polar latitudes, not many reliable remote-sensing methods of determining the vertical distributions of micro-physical snowfall parameters (i.e. snow mass density, snow crystal size and type) today exist. These parameters - together with temperature, humidity and turbulence - govern processes such as riming and aggregation, which in turn determine the ground-based snowfall rate. However, these parameters are highly variable in space and time and thus their measurement - and subsequent modeling - is a difficult task. The "Towards an Optimal estimation based Snow Characterization Algorithm" (DFG-TOSCA) project addresses these points in combining the unique information contained from a suite of ground-based sensors: microwave radiometers (22 - 150 GHz), 24 and 35 GHz radar, lidar, and in-situ measurement methods. During the winter of 2008/2009, such instruments were deployed at the Environmental Research Station Schneefernerhaus (UFS at 2650 m MSL) at the Zugspitze Mountain in Germany for deriving microphysical properties of falling snow. In the high altitude region of the UFS station snow events occur much more frequently than in lower regions and the low water vapor amounts account for clearer scattering signals from ice hydrometeors. We will present results of an extended case study where measured TBs at 90 and 150 GHz were found to be significantly enhanced during snowfall due to scattering of surface radiation at snow crystals and that this enhancement is clearly correlated with the radar derived snow water path. Radiative transfer (RT) simulations highlight the strong influence of the vertical distribution of cloud liquid water (liquid water path LWP<0.1 kgm-2) on the TB which in extreme cases can fully obscure the snow scattering signal. Simulation experiments for this specific case, using typical variations in snow amount, particle shape and snow particle size distribution revealed the equal importance of these contributors to the TB variations. Further, we show a statistical analysis of the whole TOSCA period which highlights the very frequent presence of super-cooled water within snow clouds and their importance to radiative transfer in the microwave spectral region. Finally we present results of RT studies that illustrate the benefit of combining passive and active microwave systems to disentangle the influences of different snow shape, SSD and SWP. The identification of potentially valuable ground-based instrument synergies for the retrieval of snowfall parameters from the surface will also be of importance for the development of new space-borne observational techniques.
With the launch of the Global Precipitation Mission core satellite expected for 2013, NASA is pla... more With the launch of the Global Precipitation Mission core satellite expected for 2013, NASA is planning and pursuing an intense ground validation program with campaigns all over the world (Brazil 2010, Finland 2010, Oklahoma 2011, Canada winter campaign 2011-2012) focused on physical validation of microwave-based rainfall algorithms. The ADvanced MIcrowave RAdiometer for Rain Identification (ADMIRARI) exploits its multi-frequency (10.7-21.0-36.5 GHz) polarimetric (H and V channel) capabilities to partition simultaneously rain and cloud water, thereby addressing an open key issue for improving precipitation estimates. This potentiality has already been extensively demonstrated during the field campaigns COPS over Southern Germany and EUCAARI in the Netherlands. During CHUVA (Cloud processes of tHe main precipitation systems in Brazil: A contribUtion to cloud resolVing modeling and to the GlobAl Precipitation Measurement ) ADMIRARI measures together with numerous ancillary instruments co-located at Alcântara observatory in Northern Brazil (e.g. microwave radiometer profiler, polarimetric X-band radar, disdrometers, micro rain radar, lidar, etc.). These measurements are intended to study warm rain convective systems and to create and validate a 3-D cloud processes database for such precipitation regimes. The operational ADMIRARI retrievals will contribute to the GPM effort in the following areas: 1) Identification of the microphysical cloud properties at the onset of precipitation in warm rain processes; 2) Improved understanding of bright band effects in radiative transfer models for microwave radiometry; 3) Characterization of the microphysical and electromagnetic/radiative properties of ice and mixed-phase precipitating clouds; 4) Partitioning of total liquid water content into cloud and precipitation (rain or snow) water equivalents for different climatological regimes including the validation of cloud resolving and weather forecast models to this respect. Until now, climatological rain/cloud partitioning statistics represent the major outcome of ADMIRARI measurements and will be presented for different climatological regimes. Moreover, ADMIRARI measurements from the CHUVA campaign and preliminary results regarding the observed cloud/rain partition will be shown, and a first assessment on the retrieval performance for an atmospheric regime not yet observed by ADMIRARI. We hope that these first results will lead to feedback from the GPM international community in order to improve and re-arrange the observational strategies in future GPM/GV field campaign where ADMIRARI is scheduled to take part.
Page 1. ■Hi Thermal Microwave Radiation: Applications for Remote Sensing Edited by C Matzler Page... more Page 1. ■Hi Thermal Microwave Radiation: Applications for Remote Sensing Edited by C Matzler Page 2. IET ELECTROMAGNETIC WAVES SERIES 52 Series Editors: Professor PJB Clarricoats Professor EV Jull Thermal Microwave Radiation: Applications for Remote Sensing ...
EarthCARE space-borne radar will be the first radar in space with Doppler capability, enabling me... more EarthCARE space-borne radar will be the first radar in space with Doppler capability, enabling measurements of vertical motions of hydrometeors. The vertical velocity is very useful in classifying precipitating systems (convective systems versus stratiform, rain versus snow). Global distribution of hydrometeor vertical velocity is important in estimation of latent heat fluxes and in study of energy transportation in the atmosphere. A renewed interest in space-borne Doppler radars has recently sprouted as a response to the imminent launch (2015) of the W-band cloud profiling radar within the ESA/JAXA EarthCARE mission. Given the many caveats involved with high frequency space-borne Doppler radars (Doppler fading due to the fast satellite movement, small Nyquist velocity folding, non uniform beam filling issues, contamination by multiple scattering, antenna mispointing) a particularly challenging scenario for retrieving mean Doppler velocities is represented by convective clouds. In this work we will couple DOMUS, a Monte Carlo-based DOppler MUltiple Scattering radar simulator capable of accounting for non uniform beam filling (NUBF) conditions and multiple scattering enhancements, with high resolution WRF (Weather Research and Forecasting) mesoscale prediction model runs to study the potential of high frequency Doppler radars in retrieving vertical hydrometeor motions in atmosphere.
The 94 GHz EarthCARE radar (expected to be launched within three years) will be the first radar i... more The 94 GHz EarthCARE radar (expected to be launched within three years) will be the first radar in space with Doppler capabilities. The retrieval of hydrometeor fall speeds and air motions from the radar signal will be extremely challenging due to a variety of complications. In EarthCARE configuration (height=395 km, beam-width=0.08°, PRF around 6000 Hz) the following caveats have to be accounted for: a) the high satellite speed matched to the finite antenna beam-width produces consistent Doppler fading (σDoppler ≈ 3.25 m/s); b) Nyquist Doppler interval ( 4.5 m/s) can introduce relevant folding; c) non uniform beam filling conditions may cause biases in the mean Doppler velocity estimates; d) multiple scattering widens the Doppler spectrum and de-correlate the signal from the real mean velocity. A forward Doppler radar simulator capable of accounting both for non uniform beam filling conditions and multiple scattering enhancements has been coupled to an instrument simulator in order to reproduce the signal at the antenna port. In this paper the EarthCARE radar simulator has been applied to a variety of scenarios (convective rain, drizzle, cirrus sedimentation). The performance of different standard Doppler moment estimators is discussed for the three different situations. In convective scenarios it will be utterly tough to extract useful velocity information from EarthCARE observations.
Egu General Assembly Conference Abstracts, Apr 1, 2009
Multiple scattering strongly affects the CloudSat Profiling Radar reflectivity when the satellite... more Multiple scattering strongly affects the CloudSat Profiling Radar reflectivity when the satellite is over-passing moderate and heavy precipitation systems. Following a criterion developed by the authors in the past (Battaglia et al., 2008) and based on the freezing level altitude (FLA) and on the path integrated attenuation (PIA), oceanic CloudSat reflectivities profiles affected by multiple scattering are identified and further analysed. Profiles are clustered according to PIA, FLA, position and value of the profile maximum reflectivity, jump of the reflectivity from pixels close to the surface to the surface pixel. This last variable represents a rough estimate of the multiple-scattering strength, i.e. of the reflectivity enhancement produced by higher-than-one scattering orders in proximity to the surface. The slopes of the reflectivity profiles (which results from the combined effect of vertical variability, attenuation and multiple scattering) are then computed at different altitudes above the surface and their variability is discussed in relationships to the profile characteristic variables. Results from one full year of CloudSat data are discussed and compared with numerical simulation outputs based on Cloud Resolving Model (Battaglia and Simmer 2008). This study has strong relevance for attenuation-based retrievals of rainfall from high frequency space-borne radars (Matrosov et al., 2008). Battaglia, A., J. Haynes, T. L'Ecuyer, and C. Simmer, Identifying multiple-scattering-affected profiles in CloudSat observations over the Oceans, J. Geoph. Res., 113, D00A17, doi:101029/2008JD009960 Battaglia, A., and C. Simmer, How does multiple scattering affect the spaceborne W-band radar measurements at ranges close to and crossing the surface-range?, IEEE Tran. Geo. Rem. Sens., , Vol. 46, No. 6,1644-1651, 2008 Matrosov, S., Battaglia, A., Rodriguez, P. Effects of multiple scattering on attenuation-based retrievals of stratiform rainfall from CloudSat, J. Atm. Oc. Tech., , 25(12), 2199-2208, 2008
Although snow is the predominant type of precipitation in the sub-polar and polar latitudes, not ... more Although snow is the predominant type of precipitation in the sub-polar and polar latitudes, not many reliable remote-sensing methods of determining the vertical distributions of micro-physical snowfall parameters (i.e. snow mass density, snow crystal size and type) today exist. These parameters - together with temperature, humidity and turbulence - govern processes such as riming and aggregation, which in turn determine the ground-based snowfall rate. However, these parameters are highly variable in space and time and thus their measurement - and subsequent modeling - is a difficult task. The "Towards an Optimal estimation based Snow Characterization Algorithm" (DFG-TOSCA) project addresses these points in combining the unique information contained from a suite of ground-based sensors: microwave radiometers (22 - 150 GHz), 24 and 35 GHz radar, lidar, and in-situ measurement methods. During the winter of 2008/2009, such instruments were deployed at the Environmental Research Station Schneefernerhaus (UFS at 2650 m MSL) at the Zugspitze Mountain in Germany for deriving microphysical properties of falling snow. In the high altitude region of the UFS station snow events occur much more frequently than in lower regions and the low water vapor amounts account for clearer scattering signals from ice hydrometeors. We will present results of an extended case study where measured TBs at 90 and 150 GHz were found to be significantly enhanced during snowfall due to scattering of surface radiation at snow crystals and that this enhancement is clearly correlated with the radar derived snow water path. Radiative transfer (RT) simulations highlight the strong influence of the vertical distribution of cloud liquid water (liquid water path LWP<0.1 kgm-2) on the TB which in extreme cases can fully obscure the snow scattering signal. Simulation experiments for this specific case, using typical variations in snow amount, particle shape and snow particle size distribution revealed the equal importance of these contributors to the TB variations. Further, we show a statistical analysis of the whole TOSCA period which highlights the very frequent presence of super-cooled water within snow clouds and their importance to radiative transfer in the microwave spectral region. Finally we present results of RT studies that illustrate the benefit of combining passive and active microwave systems to disentangle the influences of different snow shape, SSD and SWP. The identification of potentially valuable ground-based instrument synergies for the retrieval of snowfall parameters from the surface will also be of importance for the development of new space-borne observational techniques.
With the launch of the Global Precipitation Mission core satellite expected for 2013, NASA is pla... more With the launch of the Global Precipitation Mission core satellite expected for 2013, NASA is planning and pursuing an intense ground validation program with campaigns all over the world (Brazil 2010, Finland 2010, Oklahoma 2011, Canada winter campaign 2011-2012) focused on physical validation of microwave-based rainfall algorithms. The ADvanced MIcrowave RAdiometer for Rain Identification (ADMIRARI) exploits its multi-frequency (10.7-21.0-36.5 GHz) polarimetric (H and V channel) capabilities to partition simultaneously rain and cloud water, thereby addressing an open key issue for improving precipitation estimates. This potentiality has already been extensively demonstrated during the field campaigns COPS over Southern Germany and EUCAARI in the Netherlands. During CHUVA (Cloud processes of tHe main precipitation systems in Brazil: A contribUtion to cloud resolVing modeling and to the GlobAl Precipitation Measurement ) ADMIRARI measures together with numerous ancillary instruments co-located at Alcântara observatory in Northern Brazil (e.g. microwave radiometer profiler, polarimetric X-band radar, disdrometers, micro rain radar, lidar, etc.). These measurements are intended to study warm rain convective systems and to create and validate a 3-D cloud processes database for such precipitation regimes. The operational ADMIRARI retrievals will contribute to the GPM effort in the following areas: 1) Identification of the microphysical cloud properties at the onset of precipitation in warm rain processes; 2) Improved understanding of bright band effects in radiative transfer models for microwave radiometry; 3) Characterization of the microphysical and electromagnetic/radiative properties of ice and mixed-phase precipitating clouds; 4) Partitioning of total liquid water content into cloud and precipitation (rain or snow) water equivalents for different climatological regimes including the validation of cloud resolving and weather forecast models to this respect. Until now, climatological rain/cloud partitioning statistics represent the major outcome of ADMIRARI measurements and will be presented for different climatological regimes. Moreover, ADMIRARI measurements from the CHUVA campaign and preliminary results regarding the observed cloud/rain partition will be shown, and a first assessment on the retrieval performance for an atmospheric regime not yet observed by ADMIRARI. We hope that these first results will lead to feedback from the GPM international community in order to improve and re-arrange the observational strategies in future GPM/GV field campaign where ADMIRARI is scheduled to take part.
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Papers by Alessandro Battaglia