P. Chilson | Ronin Institute (original) (raw)
Papers by P. Chilson
Boundary-Layer Meteorology, 2015
Small-scale turbulent fluctuations of temperature are known to affect the propagation of both ele... more Small-scale turbulent fluctuations of temperature are known to affect the propagation of both electromagnetic and acoustic waves. Within the inertial-subrange scale, where the turbulence is locally homogeneous and isotropic, these temperature perturbations can be described, in a statistical sense, using the structure-function parameter for temperature, C 2 T. Here we investigate different methods of evaluating C 2 T , using data from a numerical large-eddy simulation together with atmospheric observations collected by an unmanned aerial system and a sodar. An example case using data from a late afternoon unmanned aerial system flight on April 24 2013 and corresponding large-eddy simulation data is presented and discussed.
Journal of Geophysical Research, 2003
We study a generalization of the original Einstein-Podolsky-Rosen thought experiment. It is essen... more We study a generalization of the original Einstein-Podolsky-Rosen thought experiment. It is essentially a delayed choice experiment applied to entangled particles. The basic idea is: given two observers sharing position-momentum entangled photons, one party chooses whether she measures position or momentum of her photons after the particles leave the source. The other party should infer her action by checking for the absence or presence of characteristic interference patterns after subjecting his particles to certain optical pre-processing. An occurance of apparent signaling is attributed to the difficulty in treating single photons simultaneously at a quantum mechanical and quantum electrodynamic level, as required by the experiment, and points to the need for a careful study of an aspect of the foundations of quantum mechanics and electrodynamics.
Annales Geophysicae, 2005
A novel phase calibration technique for use with the multiple-frequency Range IMaging (RIM) techn... more A novel phase calibration technique for use with the multiple-frequency Range IMaging (RIM) technique is introduced based on genetic algorithms. The method is used on data collected with the European Incoherent SCATter (EISCAT) VHF radar during a 2002 experiment with the goal of characterizing the vertical structure of Polar Mesosphere Summer Echoes (PMSE) over northern Norway. For typical Doppler measurements, the initial phases of the transmitter and receiver are not required to be the same. The EISCAT receiver systems exploit this fact, allowing a multistatic configuration. However, the RIM method relies on the small phase differences between closely spaced frequencies. As a result, the high-resolution images produced by the RIM method can be significantly degraded if not properly calibrated. Using an enhanced numerical radar simulator, in which data from multiple sampling volumes are simultaneously generated, the proposed calibration method is validated. Subsequently, the method is applied to preliminary data from the EISCAT radar, providing first results of RIM images of PMSE. Data using conventional analysis techniques, and confirmed by RIM, reveal an often-observed double-layer structure with higher stability in the lower layer. Moreover, vertical velocity oscillations exhibit a clear correlation with the apparent motion of the layers shown in the echo power plots.
Journal of Atmospheric and Oceanic Technology, 2008
The daytime atmospheric convective boundary layer (CBL) is characterized by strong turbulence tha... more The daytime atmospheric convective boundary layer (CBL) is characterized by strong turbulence that is primarily caused by buoyancy forced from the heated underlying surface. The present study considers a combination of a virtual radar and large eddy simulation (LES) techniques to characterize the CBL. Data representative of a daytime CBL with wind shear were generated by LES and used in the virtual boundary layer radar (BLR) with both vertical and multiple off-vertical beams and frequencies. To evaluate the virtual radar, a multiple radar experiment (MRE) was conducted using five virtual radars with common resolution volumes at two different altitudes. Three-dimensional wind fields were retrieved from the virtual radar data and compared with the LES output. It is shown that data produced from the virtual BLR are representative of what one expects to retrieve using a real BLR and the measured wind fields match those of the LES. Additionally, results from a frequency domain interferom...
Geophysical Research Letters, 1996
GEOPHYSICAL RESEARCH LETTERS, VOL. 23, NO. 20, PAGES 2745-2748, OCTOBER 1, 1996 A comparison of a... more GEOPHYSICAL RESEARCH LETTERS, VOL. 23, NO. 20, PAGES 2745-2748, OCTOBER 1, 1996 A comparison of ambipolar diffusion coefficients in meteor trains using VHF radar and UV lidar Phillip B. Chilson, Peter Czechowsky, and Gerhard Schmidt Max-Planck-Institut für ...
The ESRAD 52 MHz MST radar (67° 53 ' N, 21 ° 06 ' E) has observed thin layers of enhanced radar e... more The ESRAD 52 MHz MST radar (67° 53 ' N, 21 ° 06 ' E) has observed thin layers of enhanced radar echoes in the winter mesosphere during several recent solar proton events. The detection of these polar mesosphere winter echoes (PMWE) is generally found to correlates well with low values of λ (the ratio of negative ion density to electron density). However PMWE are found to persist for values of λ up to ~100. Present knowledge of the nature of neutral turbulence in the winter mesosphere suggests that such turbulence cannot generate electron density fluctuations with scale-sizes as short as the 3 m needed to produce radar echoes at 52 MHz. This is particularly true as λ increases to ~100. Joint observations from ESRAD and the EISCAT 224 MHz radar suggest that PMWE is also detectable at 67 cm scale-sizes, further increasing the difficulty in explaining the echoes by neutral turbulence. Joint observations from ESRAD and lidar are also inconsistent with the expected behaviour of turbulence. Together with results concerning the thickness, echo aspect-sensitivity and echo spectral-width of the PMWE, these observation leads to the conclusion that the layers cannot be explained by turbulence alone. A role for charged aerosols in creating PMWE is proposed. The presence of aerosols is supported by the lidar observations.
Advances in Polar …, 2002
Thin layers of enhanced radar echoes in the winter mesosphere have been observed by the ESRAD 52 ... more Thin layers of enhanced radar echoes in the winter mesosphere have been observed by the ESRAD 52 MHz MST radar (67° 53 ' N, 21 ° 06 ' E) during several recent solar proton events. These polar mesosphere winter echoes (PMWE) can occur at any time of day or night above 70 km altitude, whereas below this height they are seen only during daytime. An energy deposition / ion-chemical model is used to calculate electron and ion densities from the observed proton fluxes. It is found that PMWE occurrence correlates well with low values of λ (the ratio of negative ion density to electron density). There is a sharp cutoff in PMWE occurrence at λ ~ 10 2 , which is independent of electron density. No direct dependence of PMWE occurrence on electron density can be found within the range represented by the solar proton events, with PMWE being observed at all levels of electron density corresponding to values of λ < 10 2. Together with results concerning the thickness, echo aspect-sensitivity and echo spectral-width of the PMWE, this observation leads to the conclusion that the layers cannot be explained by turbulence alone. A role for charged aerosols in creating PMWE is proposed.
Values of turbulence kinetic energy (TKE) and TKE dissipation rate can be obtained from radar est... more Values of turbulence kinetic energy (TKE) and TKE dissipation rate can be obtained from radar estimates of velocity and Doppler spectral width. However, these estimates usually do not have sufficient temporal resolution and lead to filtered results that do not allow straightforward theoretical interpretation. A procedure is proposed for evaluation of velocity distribution properties from radar measurements using flow fields generated by means of numerical large eddy simulation (LES). The TKE estimates are obtained from LES ...
89th Annual Meeting of the AMS, Phoenix, AZ, Jan 11, 2009
The two techniques most often used to retrieve the three-dimensional wind (zonal, meridional, and... more The two techniques most often used to retrieve the three-dimensional wind (zonal, meridional, and vertical) from wind profiling radars are Doppler Beam Swinging (DBS) and Spaced Antenna (SA). These well-known techniques are based on the assumption of homogeneity across the region defined by the radar beam directions. However, this assumption is not always valid due to the presence of spatial inhomogeneities in the wind field and shear. The SA method incorporates only a vertical beam for transmission. The ...
STRUCTURE, 2007
The daytime atmospheric convective boundary layer (CBL) is characterized by strong turbulence tha... more The daytime atmospheric convective boundary layer (CBL) is characterized by strong turbulence that is primarily caused by buoyancy forced from the heated underlying surface. The present study considers a combination of radar and large eddy simulation (LES) techniques to characterize the CBL. Data representative of the daytime CBL with wind shear have been generated by LES, and used in the virtual boundary layer radar (BLR) with multiple vertical and off-vertical beams. A multiple radar experiment (MRE) was conducted ...
Journal of Applied Meteorology and Climatology, 2011
Sounding of nonprecipitating clouds with the 10-cm wavelength Weather Surveillance Radar-1988 Dop... more Sounding of nonprecipitating clouds with the 10-cm wavelength Weather Surveillance Radar-1988 Doppler (WSR-88D) is discussed. Readily available enhancements to signal processing and volume coverage patterns of the WSR-88D allow observations of a variety of clouds with reflectivities as low as −25 dBZ (at a range of 10 km). The high sensitivity of the WSR-88D, its wide velocity and unambiguous range intervals, and the absence of attenuation allow accurate measurements of the reflectivity factor, Doppler velocity, and spectrum width fields in clouds to ranges of about 50 km. Fields of polarimetric variables in clouds, observed with a research polarimetric WSR-88D, demonstrate an abundance of information and help to resolve Bragg and particulate scatter. The scanning, Doppler, and polarimetric capabilities of the WSR-88D allow real-time, three-dimensional mapping of cloud processes, such as transformations of hydrometeors between liquid and ice phases. The presence of ice particles is ...
Journal of Applied Meteorology and Climatology, 2011
Sounding of nonprecipitating clouds with the 10-cm wavelength Weather Surveillance Radar-1988 Dop... more Sounding of nonprecipitating clouds with the 10-cm wavelength Weather Surveillance Radar-1988 Doppler (WSR-88D) is discussed. Readily available enhancements to signal processing and volume coverage patterns of the WSR-88D allow observations of a variety of clouds with reflectivities as low as −25 dBZ (at a range of 10 km). The high sensitivity of the WSR-88D, its wide velocity and unambiguous range intervals, and the absence of attenuation allow accurate measurements of the reflectivity factor, Doppler velocity, and spectrum width fields in clouds to ranges of about 50 km. Fields of polarimetric variables in clouds, observed with a research polarimetric WSR-88D, demonstrate an abundance of information and help to resolve Bragg and particulate scatter. The scanning, Doppler, and polarimetric capabilities of the WSR-88D allow real-time, three-dimensional mapping of cloud processes, such as transformations of hydrometeors between liquid and ice phases. The presence of ice particles is ...
Abstract. The ESRAD 52-MHz and the EISCAT 224-MHz radars in northern Scandinavia observed thin la... more Abstract. The ESRAD 52-MHz and the EISCAT 224-MHz radars in northern Scandinavia observed thin layers of strongly enhanced radar echoes from the mesosphere (Polar Mesosphere Winter Echoes – PMWE) during a solar proton event in November 2004. Using the interferometric capabil-ities of ESRAD it was found that the scatterers responsible for PMWE show very high horizontal travel speeds, up to 500 ms−1 or more, and high aspect sensitivity, with echo ar-rival angles spread over as little as 0.3◦. ESRAD also de-tected, on some occasions, discrete scattering regions mov-ing across the field of view with periodicities of a few sec-onds. The very narrow, vertically directed beam of the more powerful EISCAT radar allowed measurements of the spec-tral widths of the radar echoes both inside the PMWE and from the background plasma above and below the PMWE. Spectral widths inside the PMWE were found to be indis-tinguishable from those from the background plasma. We propose that scatter from highly...
Boundary-Layer Meteorology, 2015
Small-scale turbulent fluctuations of temperature are known to affect the propagation of both ele... more Small-scale turbulent fluctuations of temperature are known to affect the propagation of both electromagnetic and acoustic waves. Within the inertial-subrange scale, where the turbulence is locally homogeneous and isotropic, these temperature perturbations can be described, in a statistical sense, using the structure-function parameter for temperature, C 2 T. Here we investigate different methods of evaluating C 2 T , using data from a numerical large-eddy simulation together with atmospheric observations collected by an unmanned aerial system and a sodar. An example case using data from a late afternoon unmanned aerial system flight on April 24 2013 and corresponding large-eddy simulation data is presented and discussed.
Journal of Geophysical Research, 2003
We study a generalization of the original Einstein-Podolsky-Rosen thought experiment. It is essen... more We study a generalization of the original Einstein-Podolsky-Rosen thought experiment. It is essentially a delayed choice experiment applied to entangled particles. The basic idea is: given two observers sharing position-momentum entangled photons, one party chooses whether she measures position or momentum of her photons after the particles leave the source. The other party should infer her action by checking for the absence or presence of characteristic interference patterns after subjecting his particles to certain optical pre-processing. An occurance of apparent signaling is attributed to the difficulty in treating single photons simultaneously at a quantum mechanical and quantum electrodynamic level, as required by the experiment, and points to the need for a careful study of an aspect of the foundations of quantum mechanics and electrodynamics.
Annales Geophysicae, 2005
A novel phase calibration technique for use with the multiple-frequency Range IMaging (RIM) techn... more A novel phase calibration technique for use with the multiple-frequency Range IMaging (RIM) technique is introduced based on genetic algorithms. The method is used on data collected with the European Incoherent SCATter (EISCAT) VHF radar during a 2002 experiment with the goal of characterizing the vertical structure of Polar Mesosphere Summer Echoes (PMSE) over northern Norway. For typical Doppler measurements, the initial phases of the transmitter and receiver are not required to be the same. The EISCAT receiver systems exploit this fact, allowing a multistatic configuration. However, the RIM method relies on the small phase differences between closely spaced frequencies. As a result, the high-resolution images produced by the RIM method can be significantly degraded if not properly calibrated. Using an enhanced numerical radar simulator, in which data from multiple sampling volumes are simultaneously generated, the proposed calibration method is validated. Subsequently, the method is applied to preliminary data from the EISCAT radar, providing first results of RIM images of PMSE. Data using conventional analysis techniques, and confirmed by RIM, reveal an often-observed double-layer structure with higher stability in the lower layer. Moreover, vertical velocity oscillations exhibit a clear correlation with the apparent motion of the layers shown in the echo power plots.
Journal of Atmospheric and Oceanic Technology, 2008
The daytime atmospheric convective boundary layer (CBL) is characterized by strong turbulence tha... more The daytime atmospheric convective boundary layer (CBL) is characterized by strong turbulence that is primarily caused by buoyancy forced from the heated underlying surface. The present study considers a combination of a virtual radar and large eddy simulation (LES) techniques to characterize the CBL. Data representative of a daytime CBL with wind shear were generated by LES and used in the virtual boundary layer radar (BLR) with both vertical and multiple off-vertical beams and frequencies. To evaluate the virtual radar, a multiple radar experiment (MRE) was conducted using five virtual radars with common resolution volumes at two different altitudes. Three-dimensional wind fields were retrieved from the virtual radar data and compared with the LES output. It is shown that data produced from the virtual BLR are representative of what one expects to retrieve using a real BLR and the measured wind fields match those of the LES. Additionally, results from a frequency domain interferom...
Geophysical Research Letters, 1996
GEOPHYSICAL RESEARCH LETTERS, VOL. 23, NO. 20, PAGES 2745-2748, OCTOBER 1, 1996 A comparison of a... more GEOPHYSICAL RESEARCH LETTERS, VOL. 23, NO. 20, PAGES 2745-2748, OCTOBER 1, 1996 A comparison of ambipolar diffusion coefficients in meteor trains using VHF radar and UV lidar Phillip B. Chilson, Peter Czechowsky, and Gerhard Schmidt Max-Planck-Institut für ...
The ESRAD 52 MHz MST radar (67° 53 ' N, 21 ° 06 ' E) has observed thin layers of enhanced radar e... more The ESRAD 52 MHz MST radar (67° 53 ' N, 21 ° 06 ' E) has observed thin layers of enhanced radar echoes in the winter mesosphere during several recent solar proton events. The detection of these polar mesosphere winter echoes (PMWE) is generally found to correlates well with low values of λ (the ratio of negative ion density to electron density). However PMWE are found to persist for values of λ up to ~100. Present knowledge of the nature of neutral turbulence in the winter mesosphere suggests that such turbulence cannot generate electron density fluctuations with scale-sizes as short as the 3 m needed to produce radar echoes at 52 MHz. This is particularly true as λ increases to ~100. Joint observations from ESRAD and the EISCAT 224 MHz radar suggest that PMWE is also detectable at 67 cm scale-sizes, further increasing the difficulty in explaining the echoes by neutral turbulence. Joint observations from ESRAD and lidar are also inconsistent with the expected behaviour of turbulence. Together with results concerning the thickness, echo aspect-sensitivity and echo spectral-width of the PMWE, these observation leads to the conclusion that the layers cannot be explained by turbulence alone. A role for charged aerosols in creating PMWE is proposed. The presence of aerosols is supported by the lidar observations.
Advances in Polar …, 2002
Thin layers of enhanced radar echoes in the winter mesosphere have been observed by the ESRAD 52 ... more Thin layers of enhanced radar echoes in the winter mesosphere have been observed by the ESRAD 52 MHz MST radar (67° 53 ' N, 21 ° 06 ' E) during several recent solar proton events. These polar mesosphere winter echoes (PMWE) can occur at any time of day or night above 70 km altitude, whereas below this height they are seen only during daytime. An energy deposition / ion-chemical model is used to calculate electron and ion densities from the observed proton fluxes. It is found that PMWE occurrence correlates well with low values of λ (the ratio of negative ion density to electron density). There is a sharp cutoff in PMWE occurrence at λ ~ 10 2 , which is independent of electron density. No direct dependence of PMWE occurrence on electron density can be found within the range represented by the solar proton events, with PMWE being observed at all levels of electron density corresponding to values of λ < 10 2. Together with results concerning the thickness, echo aspect-sensitivity and echo spectral-width of the PMWE, this observation leads to the conclusion that the layers cannot be explained by turbulence alone. A role for charged aerosols in creating PMWE is proposed.
Values of turbulence kinetic energy (TKE) and TKE dissipation rate can be obtained from radar est... more Values of turbulence kinetic energy (TKE) and TKE dissipation rate can be obtained from radar estimates of velocity and Doppler spectral width. However, these estimates usually do not have sufficient temporal resolution and lead to filtered results that do not allow straightforward theoretical interpretation. A procedure is proposed for evaluation of velocity distribution properties from radar measurements using flow fields generated by means of numerical large eddy simulation (LES). The TKE estimates are obtained from LES ...
89th Annual Meeting of the AMS, Phoenix, AZ, Jan 11, 2009
The two techniques most often used to retrieve the three-dimensional wind (zonal, meridional, and... more The two techniques most often used to retrieve the three-dimensional wind (zonal, meridional, and vertical) from wind profiling radars are Doppler Beam Swinging (DBS) and Spaced Antenna (SA). These well-known techniques are based on the assumption of homogeneity across the region defined by the radar beam directions. However, this assumption is not always valid due to the presence of spatial inhomogeneities in the wind field and shear. The SA method incorporates only a vertical beam for transmission. The ...
STRUCTURE, 2007
The daytime atmospheric convective boundary layer (CBL) is characterized by strong turbulence tha... more The daytime atmospheric convective boundary layer (CBL) is characterized by strong turbulence that is primarily caused by buoyancy forced from the heated underlying surface. The present study considers a combination of radar and large eddy simulation (LES) techniques to characterize the CBL. Data representative of the daytime CBL with wind shear have been generated by LES, and used in the virtual boundary layer radar (BLR) with multiple vertical and off-vertical beams. A multiple radar experiment (MRE) was conducted ...
Journal of Applied Meteorology and Climatology, 2011
Sounding of nonprecipitating clouds with the 10-cm wavelength Weather Surveillance Radar-1988 Dop... more Sounding of nonprecipitating clouds with the 10-cm wavelength Weather Surveillance Radar-1988 Doppler (WSR-88D) is discussed. Readily available enhancements to signal processing and volume coverage patterns of the WSR-88D allow observations of a variety of clouds with reflectivities as low as −25 dBZ (at a range of 10 km). The high sensitivity of the WSR-88D, its wide velocity and unambiguous range intervals, and the absence of attenuation allow accurate measurements of the reflectivity factor, Doppler velocity, and spectrum width fields in clouds to ranges of about 50 km. Fields of polarimetric variables in clouds, observed with a research polarimetric WSR-88D, demonstrate an abundance of information and help to resolve Bragg and particulate scatter. The scanning, Doppler, and polarimetric capabilities of the WSR-88D allow real-time, three-dimensional mapping of cloud processes, such as transformations of hydrometeors between liquid and ice phases. The presence of ice particles is ...
Journal of Applied Meteorology and Climatology, 2011
Sounding of nonprecipitating clouds with the 10-cm wavelength Weather Surveillance Radar-1988 Dop... more Sounding of nonprecipitating clouds with the 10-cm wavelength Weather Surveillance Radar-1988 Doppler (WSR-88D) is discussed. Readily available enhancements to signal processing and volume coverage patterns of the WSR-88D allow observations of a variety of clouds with reflectivities as low as −25 dBZ (at a range of 10 km). The high sensitivity of the WSR-88D, its wide velocity and unambiguous range intervals, and the absence of attenuation allow accurate measurements of the reflectivity factor, Doppler velocity, and spectrum width fields in clouds to ranges of about 50 km. Fields of polarimetric variables in clouds, observed with a research polarimetric WSR-88D, demonstrate an abundance of information and help to resolve Bragg and particulate scatter. The scanning, Doppler, and polarimetric capabilities of the WSR-88D allow real-time, three-dimensional mapping of cloud processes, such as transformations of hydrometeors between liquid and ice phases. The presence of ice particles is ...
Abstract. The ESRAD 52-MHz and the EISCAT 224-MHz radars in northern Scandinavia observed thin la... more Abstract. The ESRAD 52-MHz and the EISCAT 224-MHz radars in northern Scandinavia observed thin layers of strongly enhanced radar echoes from the mesosphere (Polar Mesosphere Winter Echoes – PMWE) during a solar proton event in November 2004. Using the interferometric capabil-ities of ESRAD it was found that the scatterers responsible for PMWE show very high horizontal travel speeds, up to 500 ms−1 or more, and high aspect sensitivity, with echo ar-rival angles spread over as little as 0.3◦. ESRAD also de-tected, on some occasions, discrete scattering regions mov-ing across the field of view with periodicities of a few sec-onds. The very narrow, vertically directed beam of the more powerful EISCAT radar allowed measurements of the spec-tral widths of the radar echoes both inside the PMWE and from the background plasma above and below the PMWE. Spectral widths inside the PMWE were found to be indis-tinguishable from those from the background plasma. We propose that scatter from highly...