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Abstract
A CO2 cloud tracking technique to determine simultaneous heights and velocities of cloud motion winds is presented. Using animated CO2 channel imagery from VAS, multi-level cloud situations are separated into high, middle and low level cloud motion wind vectors by the CO2 slicing method. The VAS CO2 channel radiometric values are used in the CO2 absorption method to assign quantitative heights to the cloud vectors; cloud top pressures are determined from the ratio of the deviations in cloud produced radiances and the corresponding clear air values for three CO2 channels in a radiative transfer equation formulation. Two case studies are presented that show CO2 cloud-motion wind vectors to be in good agreement with radiosonde wind observations and CO2 cloud heights to be within a 50 mb rms deviation of radiosonde, bispectral and stereo height determinations.
Abstract
A CO2 cloud tracking technique to determine simultaneous heights and velocities of cloud motion winds is presented. Using animated CO2 channel imagery from VAS, multi-level cloud situations are separated into high, middle and low level cloud motion wind vectors by the CO2 slicing method. The VAS CO2 channel radiometric values are used in the CO2 absorption method to assign quantitative heights to the cloud vectors; cloud top pressures are determined from the ratio of the deviations in cloud produced radiances and the corresponding clear air values for three CO2 channels in a radiative transfer equation formulation. Two case studies are presented that show CO2 cloud-motion wind vectors to be in good agreement with radiosonde wind observations and CO2 cloud heights to be within a 50 mb rms deviation of radiosonde, bispectral and stereo height determinations.
Abstract
A seven-channel Multi-spectral Scanning Radiometer (MSR) was flown aboard the NASA Convair-990 aircraft during the GARP Atlantic Tropical Experiment (GATE) from June–September, 1974. The radiometer measures the total shortwave (0.2–5 μm) and longwave (5–50 μm) components of radiation and the radiation in specific absorption band and window regions that modulate the total radiation flux. Measurements of the angular distribution of radiation, including the upward and downward components, were obtained. The principal scientific objective of the MSR experiment was to obtain the atmospheric absorption data required for precise computations of radiative heating profiles from atmospheric state parameters. The method used to construct the infrared radiation heating computational model based on in situ GATE MSR observations is described. Radiative heating profiles computed with this model for both cloudy and cloudless atmospheres were compared with direct observations by flux radiometers and with profiles computed with the Rodgers and Walshaw model. The results indicate that the empirically based computational model should provide tropospheric radiative heating profiles sufficiently accurate for diagnostic and prognostic applications of GATE data.
Abstract
A seven-channel Multi-spectral Scanning Radiometer (MSR) was flown aboard the NASA Convair-990 aircraft during the GARP Atlantic Tropical Experiment (GATE) from June–September, 1974. The radiometer measures the total shortwave (0.2–5 μm) and longwave (5–50 μm) components of radiation and the radiation in specific absorption band and window regions that modulate the total radiation flux. Measurements of the angular distribution of radiation, including the upward and downward components, were obtained. The principal scientific objective of the MSR experiment was to obtain the atmospheric absorption data required for precise computations of radiative heating profiles from atmospheric state parameters. The method used to construct the infrared radiation heating computational model based on in situ GATE MSR observations is described. Radiative heating profiles computed with this model for both cloudy and cloudless atmospheres were compared with direct observations by flux radiometers and with profiles computed with the Rodgers and Walshaw model. The results indicate that the empirically based computational model should provide tropospheric radiative heating profiles sufficiently accurate for diagnostic and prognostic applications of GATE data.
Abstract
Pressure, density, temperature and wind measurements in the upper stratosphere and in the mesosphere resulted from a total of 53 rocket-grenade soundings conducted during the period 1960–1965. Most of the soundings were performed over North America (Wallops Island, 38N and Churchill, 59N) but some results were also obtained over the tropical Atlantic (Ascension Island, 8S) and over Northern Europe (Kronogard, 66N). Soundings were carried out simultaneously at these sites and were coordinated with soundings measing similar parameters over other areas of the globe.
Seasonal and latitudinal variations in the structure and circulation of this region of the atmosphere were derived from the results. Stratosphere temperatures vary with season and latitude in accordance with solar heating rates and with established circulation models. Temperatures above 65 km are substantially warmer in winter than in summer. Average seasonal temperature differences are about 40K at 80 km. They are very pronounced at midlatitudes (Wallops Island) and become even more extreme at high latitudes where in summer mesopause temperatures as low as 140K were observed. Maximum stratopause temperatures were observed during late winter-early summer. At Wallops Island these maxima of about 280K coincided with the period of transition from winter to summer circulation. Temperature profiles for all seasons at all sites intersect between 60 and 65 km at a temperature range of 230 to 240K.
The strong westerly flow in winter shows two pronounced cores, one persistent throughout the winter just above the stratopause, the other somewhat weaker and less persistent near 75 km. Deviations from the zonal flow indicate the existence of meteorological circulation cells on a synoptic scale with the average meridional flaw at Churchill strongly from the north during both summer and winter and at Wallops Island somewhat weaker from the south during the winter.
Abstract
Pressure, density, temperature and wind measurements in the upper stratosphere and in the mesosphere resulted from a total of 53 rocket-grenade soundings conducted during the period 1960–1965. Most of the soundings were performed over North America (Wallops Island, 38N and Churchill, 59N) but some results were also obtained over the tropical Atlantic (Ascension Island, 8S) and over Northern Europe (Kronogard, 66N). Soundings were carried out simultaneously at these sites and were coordinated with soundings measing similar parameters over other areas of the globe.
Seasonal and latitudinal variations in the structure and circulation of this region of the atmosphere were derived from the results. Stratosphere temperatures vary with season and latitude in accordance with solar heating rates and with established circulation models. Temperatures above 65 km are substantially warmer in winter than in summer. Average seasonal temperature differences are about 40K at 80 km. They are very pronounced at midlatitudes (Wallops Island) and become even more extreme at high latitudes where in summer mesopause temperatures as low as 140K were observed. Maximum stratopause temperatures were observed during late winter-early summer. At Wallops Island these maxima of about 280K coincided with the period of transition from winter to summer circulation. Temperature profiles for all seasons at all sites intersect between 60 and 65 km at a temperature range of 230 to 240K.
The strong westerly flow in winter shows two pronounced cores, one persistent throughout the winter just above the stratopause, the other somewhat weaker and less persistent near 75 km. Deviations from the zonal flow indicate the existence of meteorological circulation cells on a synoptic scale with the average meridional flaw at Churchill strongly from the north during both summer and winter and at Wallops Island somewhat weaker from the south during the winter.
Abstract
A least squares regression method is formulated for obtaining global temperature and geopotential height profiles from satellite radiation measurements, particularly those obtained by the Sate1lite Infra-Red Spectrometer (SIRS) aboard the Nimbus 3 satellite launched Apr. 14, 1969. Regression equations relating temperature and geopotential height to spectral radiance observations are derived. A method accounting for the influence of clouds, mountains, and hot terrain on the solutions is described. Results obtained from Nimbus 3 radiance data are presented.
The procedure described herein has been successfully applied to Nimbus 3 SIRS observations on a real-time basis. The temperature and geopotential heights obtained are being used operationally by the National Meteorological Center in their objective constant pressure analyses. Numerous meteorological results are given to demonstrate the usefulness of this new sounding tool.
Abstract
A least squares regression method is formulated for obtaining global temperature and geopotential height profiles from satellite radiation measurements, particularly those obtained by the Sate1lite Infra-Red Spectrometer (SIRS) aboard the Nimbus 3 satellite launched Apr. 14, 1969. Regression equations relating temperature and geopotential height to spectral radiance observations are derived. A method accounting for the influence of clouds, mountains, and hot terrain on the solutions is described. Results obtained from Nimbus 3 radiance data are presented.
The procedure described herein has been successfully applied to Nimbus 3 SIRS observations on a real-time basis. The temperature and geopotential heights obtained are being used operationally by the National Meteorological Center in their objective constant pressure analyses. Numerous meteorological results are given to demonstrate the usefulness of this new sounding tool.
Abstract
Evidence for the radiometric determination of air–water interface temperature gradients is presented. Inherent radiometric characteristics in the water molecule cause variations in the absorption coefficient that allow radiation at near-infrared frequencies (2000–5000 wavenumbers, 2.0–5.0 μm) to carry information about subsurface water temperatures. This radiation leaving the surface is predominantly sensitive to water temperature in the layer between the surface and the “effective optical depth” (inverse of the absorption coefficient). Where atmospheric transmittance is high and/or the instrument is near the liquid, the radiance variations with frequency record temperature variations with depth. To measure the small radiance variations with frequency, an instrument must be radiometrically stable in suitable frequency bands with low instrument noise.
A simulation of this technique's use for airborne beat flux measurement indicated feasibility from low altitudes at night. Laboratory experiments produced radiometric signals that strongly indicated that the thermal structures in an air–water interface can be studied in detail. Corrected for variations of emissivity and reflectivity with frequency, the water spectra showed multiple correlations with those gradients inferred from bulk temperature measurements that assumed conductive heat loss. The use of high spectral resolution increased the vertical resolution of the interface thermal structures. Although high spectral resolution is not required for a field application, problems of system noise, atmospheric absorption, and solar reflection are more tractable with its use.
This technique may be useful in laboratory studies of thermal structures relevant to heat and gas flow that reside in the air–water interface.
Abstract
Evidence for the radiometric determination of air–water interface temperature gradients is presented. Inherent radiometric characteristics in the water molecule cause variations in the absorption coefficient that allow radiation at near-infrared frequencies (2000–5000 wavenumbers, 2.0–5.0 μm) to carry information about subsurface water temperatures. This radiation leaving the surface is predominantly sensitive to water temperature in the layer between the surface and the “effective optical depth” (inverse of the absorption coefficient). Where atmospheric transmittance is high and/or the instrument is near the liquid, the radiance variations with frequency record temperature variations with depth. To measure the small radiance variations with frequency, an instrument must be radiometrically stable in suitable frequency bands with low instrument noise.
A simulation of this technique's use for airborne beat flux measurement indicated feasibility from low altitudes at night. Laboratory experiments produced radiometric signals that strongly indicated that the thermal structures in an air–water interface can be studied in detail. Corrected for variations of emissivity and reflectivity with frequency, the water spectra showed multiple correlations with those gradients inferred from bulk temperature measurements that assumed conductive heat loss. The use of high spectral resolution increased the vertical resolution of the interface thermal structures. Although high spectral resolution is not required for a field application, problems of system noise, atmospheric absorption, and solar reflection are more tractable with its use.
This technique may be useful in laboratory studies of thermal structures relevant to heat and gas flow that reside in the air–water interface.
Abstract
A key advantage of the National Weather Radar Testbed Phased Array Radar (PAR) is the capability to adaptively scan storms at higher temporal resolution than is possible with the Weather Surveillance Radar-1988 Doppler (WSR-88D): 1 min or less versus 4.1 min, respectively. High temporal resolution volumetric radar data are a necessity for rapid identification and confirmation of weather phenomena that can develop within minutes. The purpose of this paper is to demonstrate the PAR’s ability to collect rapid-scan volumetric data that provide more detailed depictions of quickly evolving storm structures than the WSR-88D. Scientific advantages of higher temporal resolution PAR data are examined for three convective storms that occurred during the spring and summer of 2006, including a reintensifying supercell, a microburst, and a hailstorm. The analysis of the reintensifying supercell (58-s updates) illustrates the capability to diagnose the detailed evolution of developing and/or intensifying areas of 1) low-altitude divergence and rotation and 2) rotation through the depth of the storm. The fuller sampling of the microburst’s storm life cycle (34-s updates) depicts precursors to the strong surface outflow that are essentially indiscernible in the WSR-88D data. Furthermore, the 34-s scans provide a more precise sampling of peak outflow. The more frequent sampling of the hailstorm (26-s updates) illustrates the opportunity to analyze storm structures indicative of rapid intensification, the development of hail aloft, and the onset of the downdraft near the surface.
Abstract
A key advantage of the National Weather Radar Testbed Phased Array Radar (PAR) is the capability to adaptively scan storms at higher temporal resolution than is possible with the Weather Surveillance Radar-1988 Doppler (WSR-88D): 1 min or less versus 4.1 min, respectively. High temporal resolution volumetric radar data are a necessity for rapid identification and confirmation of weather phenomena that can develop within minutes. The purpose of this paper is to demonstrate the PAR’s ability to collect rapid-scan volumetric data that provide more detailed depictions of quickly evolving storm structures than the WSR-88D. Scientific advantages of higher temporal resolution PAR data are examined for three convective storms that occurred during the spring and summer of 2006, including a reintensifying supercell, a microburst, and a hailstorm. The analysis of the reintensifying supercell (58-s updates) illustrates the capability to diagnose the detailed evolution of developing and/or intensifying areas of 1) low-altitude divergence and rotation and 2) rotation through the depth of the storm. The fuller sampling of the microburst’s storm life cycle (34-s updates) depicts precursors to the strong surface outflow that are essentially indiscernible in the WSR-88D data. Furthermore, the 34-s scans provide a more precise sampling of peak outflow. The more frequent sampling of the hailstorm (26-s updates) illustrates the opportunity to analyze storm structures indicative of rapid intensification, the development of hail aloft, and the onset of the downdraft near the surface.
Abstract
The method of real-time retrieval of atmospheric temperature profiles from Nimbus IV Satellite Infrared Spectrometer observations currently used in dynamical weather analysis-forecast operation is described. Each vertical temperature profile is determined by its deviation from a “guess” profile. The deviation is expressed as a linear combination of differences between the measured radiances and those computed from the guess profile. The coefficients are estimated, by matrix inversion, from the weighting functions (i.e., derivatives of atmospheric transmittance functions), which are regularized by the ratio of the expected variance of the measurement errors to the expected variance of the errors in the guess profile. The deviations are iterated until the variance of the radiance residuals is less than the expected variance of the measurement errors.
For weather analysis-forecast operation the dynamical forecast is used as the first guess; therefore, the calculated profiles should differ from the forecast profiles only when the measurable error in the forecast exceeds the instrumental noise level. The retrieved profiles are those which deviate least from the forecast in order to satisfy all the radiance observations. This property is well suited to dynamical forecasting in that it does not tend to produce erroneous atmospheric waves.
Abstract
The method of real-time retrieval of atmospheric temperature profiles from Nimbus IV Satellite Infrared Spectrometer observations currently used in dynamical weather analysis-forecast operation is described. Each vertical temperature profile is determined by its deviation from a “guess” profile. The deviation is expressed as a linear combination of differences between the measured radiances and those computed from the guess profile. The coefficients are estimated, by matrix inversion, from the weighting functions (i.e., derivatives of atmospheric transmittance functions), which are regularized by the ratio of the expected variance of the measurement errors to the expected variance of the errors in the guess profile. The deviations are iterated until the variance of the radiance residuals is less than the expected variance of the measurement errors.
For weather analysis-forecast operation the dynamical forecast is used as the first guess; therefore, the calculated profiles should differ from the forecast profiles only when the measurable error in the forecast exceeds the instrumental noise level. The retrieved profiles are those which deviate least from the forecast in order to satisfy all the radiance observations. This property is well suited to dynamical forecasting in that it does not tend to produce erroneous atmospheric waves.
Abstract
The daytime and nighttirne distribution of the ozone density in the atmosphere has been determined from ground-based measurements of the emission spectra of the strong 40,4 = 41,3 rotational line of ozone at 101.737 GHz (λ = 2.9 mm), using a least-squares parameter estimation technique. The inversion procedure is described, and a linearized model is used to obtain approximate error bounds on the ozone parameter estimates.
Abstract
The daytime and nighttirne distribution of the ozone density in the atmosphere has been determined from ground-based measurements of the emission spectra of the strong 40,4 = 41,3 rotational line of ozone at 101.737 GHz (λ = 2.9 mm), using a least-squares parameter estimation technique. The inversion procedure is described, and a linearized model is used to obtain approximate error bounds on the ozone parameter estimates.
Abstract
Climatological upper wind records have been found to be inadequate for certain statistical analyses such as the computation of interlevel correlation coefficients, time series analysis and persistence analysis. This article presents a comparison of upper wind data as observed and made available for climatological purposes with that of upper wind records that have been made serially complete. During the winter months at Kennedy Space Center the mean wind speed, as derived from the serially completed wind records, can be as much as 10 meters per second greater than the mean wind speed derived from the observed wind data.
Abstract
Climatological upper wind records have been found to be inadequate for certain statistical analyses such as the computation of interlevel correlation coefficients, time series analysis and persistence analysis. This article presents a comparison of upper wind data as observed and made available for climatological purposes with that of upper wind records that have been made serially complete. During the winter months at Kennedy Space Center the mean wind speed, as derived from the serially completed wind records, can be as much as 10 meters per second greater than the mean wind speed derived from the observed wind data.
Abstract
When fitting a raindrop size distribution using a gamma model from data collected by a disdrometer, some consideration needs to be given to the small drops that fail to be recorded (typical disdrometer minimum size thresholds being in the 0.3–0.5-mm range). To this end, a gamma estimation procedure using maximum likelihood estimation has recently been published. The current work adds another procedure that accounts for the left-truncation problem in the data; in particular, an L-moments procedure is developed. These two estimation procedures, along with a traditional method-of-moments procedure that also accounts for data truncation, are then compared via simulation of volume samples from known gamma drop size distributions. For the range of gamma distributions considered, the maximum likelihood and L-moments procedures—which perform comparably—are found to outperform the procedure of method-of-moments. As these three procedures do not yield simple estimates in closed form, salient details of the R statistical code used in the simulations are included.
Abstract
When fitting a raindrop size distribution using a gamma model from data collected by a disdrometer, some consideration needs to be given to the small drops that fail to be recorded (typical disdrometer minimum size thresholds being in the 0.3–0.5-mm range). To this end, a gamma estimation procedure using maximum likelihood estimation has recently been published. The current work adds another procedure that accounts for the left-truncation problem in the data; in particular, an L-moments procedure is developed. These two estimation procedures, along with a traditional method-of-moments procedure that also accounts for data truncation, are then compared via simulation of volume samples from known gamma drop size distributions. For the range of gamma distributions considered, the maximum likelihood and L-moments procedures—which perform comparably—are found to outperform the procedure of method-of-moments. As these three procedures do not yield simple estimates in closed form, salient details of the R statistical code used in the simulations are included.
