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- Author or Editor: B. Stankov x
- Journal of Applied Meteorology and Climatology x
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Abstract
A near-real-time integrated temperature and water vapor sounding system has been designed and in operation since June 1993. It combines hourly data from the ground-based radio acoustic sounding system (RASS), a two-channel microwave radiometer, standard surface meteorological instruments, a lidar ceilometer, and the Aerodynamic Research Incorporated Communication, Addressing and Reporting System aboard commercial airlines with space-based data from the TIROS-N Operational Vertical Sounder (TOVS). The physical retrieval algorithm provided by the International TOVS Processing Package is used for combining the ground- and space-based temperature and humidity profiles. The first-guess profiles of temperature and humidity required by the physical retrieval algorithm arc obtained by using a statistical inversion technique and the ground-based remote sensors measurements.
Statistical error estimates are presented for the hourly. near-real-time, ground-, and space-based retrieved temperature and humidity profiles based on 119 soundings collected during a two-month-long experiment conducted at Platteville, Colorado, during February and March 1994. Radiosonde data collected by the Environmental Technology Laboratory and the Winter Icing and Storms Program in Platteville and the National Weather Service in Denver, Colorado, are used for comparison. The comparison showed excellent agreement between retrieved and radiosonde soundings. Retrieved temperature profiles show better performance than the retrieved humidity profiles because of the high vertical resolution of the RASS measurements. It is suggested that adding more information from the new individual remote sensors as they develop, through the technique used here, would lead to further profiling improvements.
Abstract
A near-real-time integrated temperature and water vapor sounding system has been designed and in operation since June 1993. It combines hourly data from the ground-based radio acoustic sounding system (RASS), a two-channel microwave radiometer, standard surface meteorological instruments, a lidar ceilometer, and the Aerodynamic Research Incorporated Communication, Addressing and Reporting System aboard commercial airlines with space-based data from the TIROS-N Operational Vertical Sounder (TOVS). The physical retrieval algorithm provided by the International TOVS Processing Package is used for combining the ground- and space-based temperature and humidity profiles. The first-guess profiles of temperature and humidity required by the physical retrieval algorithm arc obtained by using a statistical inversion technique and the ground-based remote sensors measurements.
Statistical error estimates are presented for the hourly. near-real-time, ground-, and space-based retrieved temperature and humidity profiles based on 119 soundings collected during a two-month-long experiment conducted at Platteville, Colorado, during February and March 1994. Radiosonde data collected by the Environmental Technology Laboratory and the Winter Icing and Storms Program in Platteville and the National Weather Service in Denver, Colorado, are used for comparison. The comparison showed excellent agreement between retrieved and radiosonde soundings. Retrieved temperature profiles show better performance than the retrieved humidity profiles because of the high vertical resolution of the RASS measurements. It is suggested that adding more information from the new individual remote sensors as they develop, through the technique used here, would lead to further profiling improvements.
Abstract
This study of a 5-yr continuous record of midtropospheric horizontal wind components from a radar wind profiler operating at Fleming, Colorado, shows a broad spectral peak centered around a period of 1 week and a minimum at about 4 months, in addition to the expected 1-yr peak. However, when the records are separated according to seasons, the pattern becomes more complicated, with several distinct peaks and clear differences between the summer and winter behavior emerging. In this paper the different spectral patterns observed are presented and the synoptic-scale features in the weather that could produce them are speculated on.
Abstract
This study of a 5-yr continuous record of midtropospheric horizontal wind components from a radar wind profiler operating at Fleming, Colorado, shows a broad spectral peak centered around a period of 1 week and a minimum at about 4 months, in addition to the expected 1-yr peak. However, when the records are separated according to seasons, the pattern becomes more complicated, with several distinct peaks and clear differences between the summer and winter behavior emerging. In this paper the different spectral patterns observed are presented and the synoptic-scale features in the weather that could produce them are speculated on.
Abstract
Methods by which attitude ranges of supercooled cloud liquid water in the atmosphere may be estimated are explored using measurements from a combination of ground-based remote sensors. The tests were conducted as part of the Winter Icing and Storms Project that took place in eastern Colorado during the winters of 1990, 1991, and 1993. The basic method augments microwave radiometer measurements of path-integrated liquid water with observations from additional remote sensors to establish height limits for the supercooled liquid. One variation uses a simple adiabatic parcel lifting model initiated at a cloud-base height determined from a ecilometer, temperature and pressure from a radio acoustic sounding system or rawinsonde, and combines these with the radiometers total liquid measurement to obtain an estimate of the liquid cloud-top height. Since it does not account for liquid loss by entrainment or ice-liquid interaction processes this method tends to underestimate the true liquid cloud top; for two cases examined in detail, 54% of icing pilot reports in the area were from above this estimated height. Some error is introduced due to differences in sampling locations and from horizontal variability in liquid water content. Vertical cloud boundaries from a Ka-band radar were also used in the study; these often indicated thicker clouds than the liquid-layer depths observed from research aircraft, possibly due to the ambiguity of the ice-liquid phase distinction.
Comparisons of liquid vertical profiles are presented, using normalized profile shapes based an uniform, adiabatic, and aircraft-derived composite assumptions. The adiabatic and climatological profile shapes generally agreed well with measurements from a research aircraft and were more realistic than the uniform profile. Suggestions for applications of these results toward a red-time aviation hazard identification system are presented.
Abstract
Methods by which attitude ranges of supercooled cloud liquid water in the atmosphere may be estimated are explored using measurements from a combination of ground-based remote sensors. The tests were conducted as part of the Winter Icing and Storms Project that took place in eastern Colorado during the winters of 1990, 1991, and 1993. The basic method augments microwave radiometer measurements of path-integrated liquid water with observations from additional remote sensors to establish height limits for the supercooled liquid. One variation uses a simple adiabatic parcel lifting model initiated at a cloud-base height determined from a ecilometer, temperature and pressure from a radio acoustic sounding system or rawinsonde, and combines these with the radiometers total liquid measurement to obtain an estimate of the liquid cloud-top height. Since it does not account for liquid loss by entrainment or ice-liquid interaction processes this method tends to underestimate the true liquid cloud top; for two cases examined in detail, 54% of icing pilot reports in the area were from above this estimated height. Some error is introduced due to differences in sampling locations and from horizontal variability in liquid water content. Vertical cloud boundaries from a Ka-band radar were also used in the study; these often indicated thicker clouds than the liquid-layer depths observed from research aircraft, possibly due to the ambiguity of the ice-liquid phase distinction.
Comparisons of liquid vertical profiles are presented, using normalized profile shapes based an uniform, adiabatic, and aircraft-derived composite assumptions. The adiabatic and climatological profile shapes generally agreed well with measurements from a research aircraft and were more realistic than the uniform profile. Suggestions for applications of these results toward a red-time aviation hazard identification system are presented.
Abstract
A radio acoustic sounding system (RASS), coupled with the NOAA/Wave Propagation Laboratory 915-MHz wind profiler, observed an arctic front and arctic air mass that passed over Denver, Colorado, between 1 and 5 February 1989. The RASS temperature measurements extended to approximately 1.5 km above ground level and were taken at 15-min intervals during the frontal passage and at 1-h intervals thereafter. During the frontal passage on 1 February, the RASS documented a temperature decrease of >15°C. The succeeding cold air (∼−20° to −40°C) over Denver never exceeded 1.3 km in depth. The frontal inversion at the top of the cold air mass was 300 m in depth and possessed large static stability [−∂θ/∂p ∼ 80 K (100 mb)−1] and vertical wind shear [∂V/∂p ∼ 30 m s−1 (100 mb)−1]. Temporal fluctuations (∼3 h) in the depth of the cold air were observed by the RASS between the operational 12-h rawinsonde observing periods. Simultaneous RASS and rawinsonde measurements showed good agreement with regard to key thermal features.
Abstract
A radio acoustic sounding system (RASS), coupled with the NOAA/Wave Propagation Laboratory 915-MHz wind profiler, observed an arctic front and arctic air mass that passed over Denver, Colorado, between 1 and 5 February 1989. The RASS temperature measurements extended to approximately 1.5 km above ground level and were taken at 15-min intervals during the frontal passage and at 1-h intervals thereafter. During the frontal passage on 1 February, the RASS documented a temperature decrease of >15°C. The succeeding cold air (∼−20° to −40°C) over Denver never exceeded 1.3 km in depth. The frontal inversion at the top of the cold air mass was 300 m in depth and possessed large static stability [−∂θ/∂p ∼ 80 K (100 mb)−1] and vertical wind shear [∂V/∂p ∼ 30 m s−1 (100 mb)−1]. Temporal fluctuations (∼3 h) in the depth of the cold air were observed by the RASS between the operational 12-h rawinsonde observing periods. Simultaneous RASS and rawinsonde measurements showed good agreement with regard to key thermal features.
Abstract
Remote soundings of precipitable water vapor from three systems are compared with each other and with ground truth from radiosondes. Ancillary data from a mesoscale network of surface observing stations and from wind-profiling radars are also used in the analysis. The three remote-sounding techniques are: (a) a reflectance technique using spectral data collected by the Airborne Visible-Infrared Imaging Spectrometer (AVIRIS); (b) an emission technique using Visible-Infrared Spin Scan Radiometer (VISSR) Atmospheric Sounder (VAS) data acquired from the National Oceanic and Atmospheric Administration's (NOAA) Geostationary Operational Environmental Satellite (GOES); and (c) a microwave technique using data from a limited network of three ground-based dual-channel microwave radiometers. The data were taken over the Front Range of eastern Colorado on 22–23 March 1990. The generally small differences between the three types of rernote-sounding measurements are consistent with the horizontal and temporal resolutions of the instruments. The microwave and optical reflectance measurements agreed to within 0. 1 cm; comparisons of the microwave data with radiosondes were also either that good or explainable. The largest differences between the VAS and the microwave radiometer at Elbert were between 0.4 and 0.5 cm and appear to he due to variable terrain within the satellite footprint.
Abstract
Remote soundings of precipitable water vapor from three systems are compared with each other and with ground truth from radiosondes. Ancillary data from a mesoscale network of surface observing stations and from wind-profiling radars are also used in the analysis. The three remote-sounding techniques are: (a) a reflectance technique using spectral data collected by the Airborne Visible-Infrared Imaging Spectrometer (AVIRIS); (b) an emission technique using Visible-Infrared Spin Scan Radiometer (VISSR) Atmospheric Sounder (VAS) data acquired from the National Oceanic and Atmospheric Administration's (NOAA) Geostationary Operational Environmental Satellite (GOES); and (c) a microwave technique using data from a limited network of three ground-based dual-channel microwave radiometers. The data were taken over the Front Range of eastern Colorado on 22–23 March 1990. The generally small differences between the three types of rernote-sounding measurements are consistent with the horizontal and temporal resolutions of the instruments. The microwave and optical reflectance measurements agreed to within 0. 1 cm; comparisons of the microwave data with radiosondes were also either that good or explainable. The largest differences between the VAS and the microwave radiometer at Elbert were between 0.4 and 0.5 cm and appear to he due to variable terrain within the satellite footprint.
Abstract
A numerical technique is described for synthesizing realistic atmospheric temperature and humidity profiles. The method uses an ensemble of radiosonde measurements collected at a site of interest. Erroneous profiles are removed by comparing their likelihood with prevailing meteorological conditions. The remaining profiles are decomposed using the method of empirical orthogonal functions. The corresponding eigenprofiles and the statistics of the expansion coefficients are used to numerically generate synthetic profiles that obey the same statistics (i.e., have the same mean, variability, and vertical correlation) as the initial dataset. The technique was applied to a set of approximately 1000 temperature and humidity soundings made in Denver, Colorado, during the winter months of 1991–95. This dataset was divided into four cloud classification categories and daytime and nighttime launches to better characterize typical profiles for the eight cases considered. It was found that 97% of the variance in the soundings could be accounted for by using only five eigenprofiles in the reconstructions. Ensembles of numerically generated profiles can be used to test the accuracy of various retrieval algorithms under controlled conditions not usually available in practice.
Abstract
A numerical technique is described for synthesizing realistic atmospheric temperature and humidity profiles. The method uses an ensemble of radiosonde measurements collected at a site of interest. Erroneous profiles are removed by comparing their likelihood with prevailing meteorological conditions. The remaining profiles are decomposed using the method of empirical orthogonal functions. The corresponding eigenprofiles and the statistics of the expansion coefficients are used to numerically generate synthetic profiles that obey the same statistics (i.e., have the same mean, variability, and vertical correlation) as the initial dataset. The technique was applied to a set of approximately 1000 temperature and humidity soundings made in Denver, Colorado, during the winter months of 1991–95. This dataset was divided into four cloud classification categories and daytime and nighttime launches to better characterize typical profiles for the eight cases considered. It was found that 97% of the variance in the soundings could be accounted for by using only five eigenprofiles in the reconstructions. Ensembles of numerically generated profiles can be used to test the accuracy of various retrieval algorithms under controlled conditions not usually available in practice.
