During the month of March, 1981 the Sunset and Platteville Radar and Platteville Radar were opera... more During the month of March, 1981 the Sunset and Platteville Radar and Platteville Radar were operated primarily with vertical antenna beams. These radars are both VHF ST (Stratosphere-Troposphere) radars. The separation between them was 63 km, the Sunset site located in the foothills of the Rocky Mountains and the Platteville site was in the plains, just east of the mountains. Both radars were operated continuously for about three weeks with a time resolution of a few minutes. Both made measurements in the 4 to 20 km altitude interval with an altitude sampling of 1.2 km. The purpose is to compare the estimation of the altitude of the tropopause by these two radars with the altitude of the tropopause derived from standard NWS rawinsondes.
ABSTRACT Sensitive Doppler radars have recently been developed that can routinely observe wind in... more ABSTRACT Sensitive Doppler radars have recently been developed that can routinely observe wind in the free atmosphere up to stratospheric heights. One of these, the 40 MHz Sunset radar, was used to observe the three-dimensional wind field associated with a polar front jet stream near Boulder on 15-16 April 1976. The south wind, which was the strongest component (of the wind), was sampled about once a minute for over 14 h over altitudes ranging from 5 to 13 km MSL at 1 km intervals. The temporal variability of the south wind at each height is presented along with the average variability for all heights over the 14 h period. The average variability closely follows a 1/3 power law at least out to 4 h lag time. Since the 1/3 power law is consistent with inertial range turbulence theory, and since turbulence cannot possibly be three-dimensionally isotropic on these scales, it is suggested that the observations might be interpreted as evidence for a two-dimensional, 5/3 inertial range.
Abstract A statistical analysis of vertical air motion has been performed for data taken in the 3... more Abstract A statistical analysis of vertical air motion has been performed for data taken in the 3-20 km altitude range by the Poker Flat MST radar during the period September 1979-January 1982. The variability of vertical velocities is analyzed as a function of season, time of day and synoptic weather conditions. The overall frequency distribution of vertical velocities can be approximated by the sum of two normal distributions: one with variance about 10 times larger than the other. The variability of vertical velocity at all levels is found to correlate most closely with horizontal wind speed at 700 mb on a day-to-day basis. The total variance is larger in summer than in winter at all hours of the day and especially during the afternoon hours. A statistically significant diurnal variation of vertical motions is found during summer with amplitude in the midtroposphere near 2 cm s−1. Interpreting the vertical wind variability as a manifestation of vertically propagating waves, we compare the intensity her...
Vertical velocity power spectra obtained from Poker Flat, Alaska; Platteville, Colorado; Rhone De... more Vertical velocity power spectra obtained from Poker Flat, Alaska; Platteville, Colorado; Rhone Delta, France; and Ponape, East Caroline Islands using 50-MHz clear-air radars with vertical beams are given. The spectra were obtained by analyzing the quietest periods from the one-minute-resolution time series for each site. The lengths of available vertical records ranged from as long as 6 months at Poker Flat to about 1 month at Platteville. The quiet-time vertical velocity spectra are shown. Spectral period ranging from 2 minutes to 4 hours is shown on the abscissa and power spectral density is given on the ordinate. The Brunt-Vaisala (B-V) periods (determined from nearby sounding balloons) are indicated. All spectra (except the one from Platteville) exhibit a peak at periods slightly longer than the B-V period, are flat at longer periods, and fall rapidly at periods less than the B-V period. This behavior is expected for a spectrum of internal waves and is very similar to what is ob...
Vertical profiles of refractivity turbulence structure constant C2n (which is proportional to the... more Vertical profiles of refractivity turbulence structure constant C2n (which is proportional to the radar volume reflectivity) from about 5 to 15 km are measured by the Sunset Radar every 50 seconds. The method of determining such profiles from the radar Doppler spectra is described. The C2n profiles for about an hour are averaged to form (C2n(radar)). The profiles of (C2n(radar)) are quite variable: on the average they decrease by about two orders of magnitude from about 5 to 15 km, and they often change by one order of magnitude from day to day at a given height. A theoretical model is developed that enables the calculation of C2n from routine rawinsonde profiles of wind, temperature, and humidity. This model is based on the assumption that the fluctuations of refractivity that scatter the radio waves are in equilibrium with homogeneous, isotropic, steady‐state turbulence in the inertial subrange. An essential and new feature of this model is an estimate of the mean fraction of the ...
Results from a statistical analysis of backscattered signal power measurements at 4–18 km by the ... more Results from a statistical analysis of backscattered signal power measurements at 4–18 km by the clear‐air Doppler radars (MST radars, or wind profilers ) in the Colorado Profiler Network and at Poker Flat, Alaska, show a systematic diurnal variation during the summer months. These diurnal variations have a high level of statistical significance. In the midtroposphere the diurnal range is near 7 dB with largest values in the afternoon, probably associated with the enhanced turbulence and moisture levels due to afternoon convection. In the stratosphere the diurnal range is about 5 dB over Colorado, with smallest values in the afternoon. The stratospheric cycle is interpreted as a response to modulation of the amplitude of gravity waves propagating upward from the troposphere. The diurnal cycle at all heights becomes indistinct during the winter months.
This paper presents an analysis of a gravity wave event near the tropopause as seen by the vertic... more This paper presents an analysis of a gravity wave event near the tropopause as seen by the vertically looking antenna of the Poker Flat, Alaska, MST radar. The observations are presented as time series of vertical velocity, signal power and spectral width. These parameters are found to oscillate in a systematic fashion that illustrates the effect of gravity waves on the specular echoes. This is seen most clearly by examining the changing appearance of the Doppler spectrum with the phase of the gravity wave. The principal result is that specular echoes are observed only at certain phases of the wave. Examination of a large sample of data shows that more generally the occurrence of gravity waves tends to destroy specularity. The decrease in the magnitude of specular echoes can be parameterized by the width of their Doppler spectra.
Serial reflectivity measurements from paired instruments are examined during two field campaigns ... more Serial reflectivity measurements from paired instruments are examined during two field campaigns in order to determine the measurement errors of the instruments. The instruments studied are two collocated Joss-Waldvogel disdrometers (JWD) at Wallops Island, VA and two collocated profilers deployed at Ji-Parana, Brazil during TRMM LBA. Differencing the measured reflectivity from the instrument pairs eliminates most of the temporal variability of reflectivity making it possible to isolate instrument precision. The measured reflectivity differences from the paired disdrometers have a Gaussian-like distribution and an rms difference of 2.1 dBZ for individual minute samples . The time series of differences are not autocorrelated so that the standard error of the mean refectivity is found to be less than 0.1 dBZ for a 12-hour rain event. The measured reflectivity differences from the paired profilers also have a Gaussian-like distribution and an rms difference of 0.4 dBZ. The standard err...
Results from spectral analysis of ozone, wind, and temperature measurements collected during the ... more Results from spectral analysis of ozone, wind, and temperature measurements collected during the Global Atmospheric Sampling Program (GASP) are presented. These data were taken with instruments placed aboard B747 airliners in routine commercial service. About 90 percent of these data fall in the altitude range 9–13 km and about 75 percent are from latitudes 30 to 60 degrees North. The variance power spectra span the wavelength range from about 100–104 km for wind and temperature and 10–2400 km for ozone. Variation with latitude and season and between the troposphere and stratosphere are presented. Results are interpreted in the framework of geostrophic turbulence theory at long wavelengths, and quasi-two-dimensional turbulence and internal gravity waves at wavelengths below about 300–500 km. Numerical examples are used to illustrate that the spectrum of ozone variations is consistent with a spectrum of vertical displacements acting on a background vertical gradient of ozone.
During the month of March, 1981 the Sunset and Platteville Radar and Platteville Radar were opera... more During the month of March, 1981 the Sunset and Platteville Radar and Platteville Radar were operated primarily with vertical antenna beams. These radars are both VHF ST (Stratosphere-Troposphere) radars. The separation between them was 63 km, the Sunset site located in the foothills of the Rocky Mountains and the Platteville site was in the plains, just east of the mountains. Both radars were operated continuously for about three weeks with a time resolution of a few minutes. Both made measurements in the 4 to 20 km altitude interval with an altitude sampling of 1.2 km. The purpose is to compare the estimation of the altitude of the tropopause by these two radars with the altitude of the tropopause derived from standard NWS rawinsondes.
ABSTRACT Sensitive Doppler radars have recently been developed that can routinely observe wind in... more ABSTRACT Sensitive Doppler radars have recently been developed that can routinely observe wind in the free atmosphere up to stratospheric heights. One of these, the 40 MHz Sunset radar, was used to observe the three-dimensional wind field associated with a polar front jet stream near Boulder on 15-16 April 1976. The south wind, which was the strongest component (of the wind), was sampled about once a minute for over 14 h over altitudes ranging from 5 to 13 km MSL at 1 km intervals. The temporal variability of the south wind at each height is presented along with the average variability for all heights over the 14 h period. The average variability closely follows a 1/3 power law at least out to 4 h lag time. Since the 1/3 power law is consistent with inertial range turbulence theory, and since turbulence cannot possibly be three-dimensionally isotropic on these scales, it is suggested that the observations might be interpreted as evidence for a two-dimensional, 5/3 inertial range.
Abstract A statistical analysis of vertical air motion has been performed for data taken in the 3... more Abstract A statistical analysis of vertical air motion has been performed for data taken in the 3-20 km altitude range by the Poker Flat MST radar during the period September 1979-January 1982. The variability of vertical velocities is analyzed as a function of season, time of day and synoptic weather conditions. The overall frequency distribution of vertical velocities can be approximated by the sum of two normal distributions: one with variance about 10 times larger than the other. The variability of vertical velocity at all levels is found to correlate most closely with horizontal wind speed at 700 mb on a day-to-day basis. The total variance is larger in summer than in winter at all hours of the day and especially during the afternoon hours. A statistically significant diurnal variation of vertical motions is found during summer with amplitude in the midtroposphere near 2 cm s−1. Interpreting the vertical wind variability as a manifestation of vertically propagating waves, we compare the intensity her...
Vertical velocity power spectra obtained from Poker Flat, Alaska; Platteville, Colorado; Rhone De... more Vertical velocity power spectra obtained from Poker Flat, Alaska; Platteville, Colorado; Rhone Delta, France; and Ponape, East Caroline Islands using 50-MHz clear-air radars with vertical beams are given. The spectra were obtained by analyzing the quietest periods from the one-minute-resolution time series for each site. The lengths of available vertical records ranged from as long as 6 months at Poker Flat to about 1 month at Platteville. The quiet-time vertical velocity spectra are shown. Spectral period ranging from 2 minutes to 4 hours is shown on the abscissa and power spectral density is given on the ordinate. The Brunt-Vaisala (B-V) periods (determined from nearby sounding balloons) are indicated. All spectra (except the one from Platteville) exhibit a peak at periods slightly longer than the B-V period, are flat at longer periods, and fall rapidly at periods less than the B-V period. This behavior is expected for a spectrum of internal waves and is very similar to what is ob...
Vertical profiles of refractivity turbulence structure constant C2n (which is proportional to the... more Vertical profiles of refractivity turbulence structure constant C2n (which is proportional to the radar volume reflectivity) from about 5 to 15 km are measured by the Sunset Radar every 50 seconds. The method of determining such profiles from the radar Doppler spectra is described. The C2n profiles for about an hour are averaged to form (C2n(radar)). The profiles of (C2n(radar)) are quite variable: on the average they decrease by about two orders of magnitude from about 5 to 15 km, and they often change by one order of magnitude from day to day at a given height. A theoretical model is developed that enables the calculation of C2n from routine rawinsonde profiles of wind, temperature, and humidity. This model is based on the assumption that the fluctuations of refractivity that scatter the radio waves are in equilibrium with homogeneous, isotropic, steady‐state turbulence in the inertial subrange. An essential and new feature of this model is an estimate of the mean fraction of the ...
Results from a statistical analysis of backscattered signal power measurements at 4–18 km by the ... more Results from a statistical analysis of backscattered signal power measurements at 4–18 km by the clear‐air Doppler radars (MST radars, or wind profilers ) in the Colorado Profiler Network and at Poker Flat, Alaska, show a systematic diurnal variation during the summer months. These diurnal variations have a high level of statistical significance. In the midtroposphere the diurnal range is near 7 dB with largest values in the afternoon, probably associated with the enhanced turbulence and moisture levels due to afternoon convection. In the stratosphere the diurnal range is about 5 dB over Colorado, with smallest values in the afternoon. The stratospheric cycle is interpreted as a response to modulation of the amplitude of gravity waves propagating upward from the troposphere. The diurnal cycle at all heights becomes indistinct during the winter months.
This paper presents an analysis of a gravity wave event near the tropopause as seen by the vertic... more This paper presents an analysis of a gravity wave event near the tropopause as seen by the vertically looking antenna of the Poker Flat, Alaska, MST radar. The observations are presented as time series of vertical velocity, signal power and spectral width. These parameters are found to oscillate in a systematic fashion that illustrates the effect of gravity waves on the specular echoes. This is seen most clearly by examining the changing appearance of the Doppler spectrum with the phase of the gravity wave. The principal result is that specular echoes are observed only at certain phases of the wave. Examination of a large sample of data shows that more generally the occurrence of gravity waves tends to destroy specularity. The decrease in the magnitude of specular echoes can be parameterized by the width of their Doppler spectra.
Serial reflectivity measurements from paired instruments are examined during two field campaigns ... more Serial reflectivity measurements from paired instruments are examined during two field campaigns in order to determine the measurement errors of the instruments. The instruments studied are two collocated Joss-Waldvogel disdrometers (JWD) at Wallops Island, VA and two collocated profilers deployed at Ji-Parana, Brazil during TRMM LBA. Differencing the measured reflectivity from the instrument pairs eliminates most of the temporal variability of reflectivity making it possible to isolate instrument precision. The measured reflectivity differences from the paired disdrometers have a Gaussian-like distribution and an rms difference of 2.1 dBZ for individual minute samples . The time series of differences are not autocorrelated so that the standard error of the mean refectivity is found to be less than 0.1 dBZ for a 12-hour rain event. The measured reflectivity differences from the paired profilers also have a Gaussian-like distribution and an rms difference of 0.4 dBZ. The standard err...
Results from spectral analysis of ozone, wind, and temperature measurements collected during the ... more Results from spectral analysis of ozone, wind, and temperature measurements collected during the Global Atmospheric Sampling Program (GASP) are presented. These data were taken with instruments placed aboard B747 airliners in routine commercial service. About 90 percent of these data fall in the altitude range 9–13 km and about 75 percent are from latitudes 30 to 60 degrees North. The variance power spectra span the wavelength range from about 100–104 km for wind and temperature and 10–2400 km for ozone. Variation with latitude and season and between the troposphere and stratosphere are presented. Results are interpreted in the framework of geostrophic turbulence theory at long wavelengths, and quasi-two-dimensional turbulence and internal gravity waves at wavelengths below about 300–500 km. Numerical examples are used to illustrate that the spectrum of ozone variations is consistent with a spectrum of vertical displacements acting on a background vertical gradient of ozone.
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Papers by Kenneth S Gage