Search Results
You are looking at 1 - 10 of 23 items for :
- Author or Editor: W. L. Smith x
- Journal of Applied Meteorology and Climatology x
- Refine by Access: All Content x
Abstract
Abstract
Abstract
In this paper, the algorithm used for calculating the water vapor distribution from SIRS-B spectral radiances is given. Examples are presented illustrating the effects of errors in the water vapor absorption coefficients and the specified temperature profile on the retrieval of the water vapor profile. Comparisons of satellite-derived and radiosonde-observed water vapor profiles indicate that the errors of the SIRS-derived relative humidity in the middle troposphere (i.e., the 400–600 mb layer) are less than 20%. Relative humidity errors in the lower troposphere (600–1000 mb) are somewhat larger but still less than 30%.
Abstract
In this paper, the algorithm used for calculating the water vapor distribution from SIRS-B spectral radiances is given. Examples are presented illustrating the effects of errors in the water vapor absorption coefficients and the specified temperature profile on the retrieval of the water vapor profile. Comparisons of satellite-derived and radiosonde-observed water vapor profiles indicate that the errors of the SIRS-derived relative humidity in the middle troposphere (i.e., the 400–600 mb layer) are less than 20%. Relative humidity errors in the lower troposphere (600–1000 mb) are somewhat larger but still less than 30%.
Abstract
Cloud altitudes specified from the Infrared Temperature Profile Radiometer on the Nimbus 5 satellite are compared with simultaneous observations by radiosonde and ground-based ranging measurements conducted with the lidar system at CSIRO in Aspendale, Victoria, Australia, during September 1976. The results show that the cloud altitudes deduced by the CO2 channel absorption method are in general agreement with the lidar and radiosonde determinations, regardless of the cloud opacity and amount.
Abstract
Cloud altitudes specified from the Infrared Temperature Profile Radiometer on the Nimbus 5 satellite are compared with simultaneous observations by radiosonde and ground-based ranging measurements conducted with the lidar system at CSIRO in Aspendale, Victoria, Australia, during September 1976. The results show that the cloud altitudes deduced by the CO2 channel absorption method are in general agreement with the lidar and radiosonde determinations, regardless of the cloud opacity and amount.
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
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.
