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Chahine, M. T.

Publications and source records attributed to Chahine, M. T..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Remote sensing and climate parameters

The fundamental problem in deriving weather and climate procedures from satellite data lies in the proper selection of sets of sounding frequencies, and in the derivation of accurate algorithms that are capable of uncoupling the effects of these variables to retrieve the true value of each unknown parameter separately. This uncoupling is presently based on the relaxation principle of Chahine (1968, 1970), which allows each parameter to be retrieved analytically without a priori assumptions as to the properties of the other unknowns in the field of view. Attention is given to work conducted with the High Resolution IR Sounder and the Microwave Sounding Unit instruments carried by the NOAA Weather Satellite.

Chahine, M. T.↗
NASA NTRS1982

The GLAS physical inversion method for analysis of HIRS2/MSU sounding data

Goddard Laboratory for Atmospheric Sciences has developed a method to derive atmospheric temperature profiles, sea or land surface temperatures, sea ice extent and snow cover, and cloud heights and fractional cloud, from HIRS2/MSU radiance data. Chapter 1 describes the physics used in the radiative transfer calculations and demonstrates the accuracy of the calculations. Chapter 2 describes the rapid transmittance algorithm used and demonstrates its accuracy. Chapter 3 describes the theory and application of the techniques used to analyze the satellite data. Chapter 4 shows results obtained for January 1979.

Susskind, J.↗
NASA NTRS1982

Remote sensing of cloud parameters

Day and night mapping of the global distributions of the horizontal cloud covers and the corresponding cloud-top pressure levels are derived from the same set of infrared radiance data used to retrieve clear-column temperature profiles. General formulation of the problem is presented with illustrations for the simple case of a single layer of non-reflecting clouds. Experimental verification is obtained using 15 micron data measured by the NOAA-VTPR infrared sounder. After correcting for water vapor emission, the results show that the effective cloud cover derived from 15 micron data is less than that obtained from visible data.

Chahine, M. T.↗
NASA NTRS1982

Infrared remote sensing of the vertical and horizontal distribution of clouds

An algorithm has been developed to derive the horizontal and vertical distribution of clouds from the same set of infrared radiance data used to retrieve atmospheric temperature profiles. The method leads to the determination of the vertical atmospheric temperature structure and the cloud distribution simultaneously, providing information on heat sources and sinks, storage rates and transport phenomena in the atmosphere. Experimental verification of this algorithm was obtained using the 15-micron data measured by the NOAA-VTPR temperature sounder. After correcting for water vapor emission, the results show that the cloud cover derived from 15-micron data is less than that obtained from visible data.

Chahine, M. T.↗
NASA NTRS1982

Determination of the horizontal and vertical distribution of clouds from infrared satellite sounding data

A numerical algorithm, based on a physical inversion of the radiative transfer equation, is developed to retrieve the global distribution of the horizontal cloud cover, the cloud-top pressure levels and their temperature. The algorithm makes use of infrared and microwave temperature sounding data to derive the clear-column vertical temperature profiles and then uses the same infrared sounding data to obtain the corresponding cloud parameters. Experimental verification of this method is carried out using data from the High resolution Infrared Sounder (HIRS) and the Microwave Sounding Unit (MSU) operating on the NOAA weather satellite system.

Chahine, M. T.↗
NASA NTRS1981

Remote sensing of sea surface temperature in the 3.7 micron CO2 band

The main sources of error in remote sensing of sea surface temperature are discussed. The interfering effects of reflected solar radiation, reflected thermal flux, clouds and haze and atmospheric attenuation are examined. The components of measured sea surface radiances, such as clear column radiance, surface emission, atmospheric emission, reflected thermal downward flux, and reflection of solar flux, are analytically presented. The use of the 3.7 micron region window to obtain the radiance to four percent accuracy is discussed. The advantages to be obtained by the use of narrow bandpass channels are assessed.

Chahine, M. T.↗
NASA NTRS1981

Passive optical and infrared meteorology

Applications of passive visible and infrared techniques to the study of meteorological parameters are presented. For the remote sensing of temperature and humidity profiles, infrared sounder improvements have proceeded with the narrow band-pass channels approach, and the partially scanned interferogram approach. Current and planned infrared and microwave sea-surface temperature sounders have an expected accuracy of approximately 2 K, and this can be improved by using three super window channels from the 3.7 micron window region, with narrow band passes away from principal water vapor absorption lines. Cloud data remote sensing is currently performed from satellites, and these visible and infrared images have been used to track weather patterns. In addition, a passive infrared correlation-spectroscopy technique has been proposed for wind measurements. Finally, these techniques have also been applied to monitor such parameters as the Solar Constant, aerosols, and minor gas constituents.

Chahine, M. T.↗
NASA NTRS1980

Structure and meteorology of the middle atmosphere of Venus Infrared remote sensing from the Pioneer orbiter

The results of the Pioneer Venus orbiter radiometric temperature-sounding experiment are presented with examples of each of the primary data products. The measured temperature field is used to model the dynamics of the middle atmosphere from 60 to 140 km, and the thermal and solar fluxes are used to calculate the planetary radiation budget. The data for the diurnal variation of temperature at a given height show fairly small amplitudes up to an altitude of about 95 km, above which the day to night contrast increases rapidly with height. At the equator the dependence of temperature in the stratosphere on solar longitude is dominated by a wave number 2 solar tide with an amplitude of about 10 K. The equator to pole gradients are larger than expected, and the stratosphere is typically 15 to 20 K warmer at the pole than at the equator. The most significant discovery concerning the cloud morphology is a dipole structure consisting of two clearings in the cloud at locations straddling the pole and rotating around it every 2.7 days.

Taylor, F. W.↗
NASA NTRS1980

Infrared remote sensing of sea surface temperature

The surface temperature TS of the ocean and solid earth can be derived from the radiance data measured in the 3.7 micron transparent region between 2700 and 2500 per cm as well as from the 11 micron water vapor continuum between 960 and 775 per cm. The effects on the accuracy of the recovered values of TS of surface emissivity, reflection of solar radiation and variations in the concentration of water vapor in the atmosphere are different in the two bands. In this paper, the accuracy of the surface temperature derived from each of these two transparent spectral regions is discussed. The possibility of determining the difference between the air temperature at the surface and the true skin surface temperature is also considered.

Chahine, M. T.↗
NASA NTRS1979

Remote sensing of cloud distribution

Day and night mapping of the global distribution of the horizontal cloud-cover and the corresponding cloud-top pressure levels can be derived from the same infrared data used to derive clear column temperature profiles. Applications to the 15 micrometer VTPR data are given. Extension of this approach for the determination of the radiative transfer properties of clouds is presented and the possibility of using such information to infer cloud types is discussed.

Chahine, M. T.↗
NASA NTRS1979

Derivation of clear-column temperature profiles with high vertical resolution and accuracy

It is noted that the optimum tradeoff between accuracy and resolution for current sounders leads to an rms accuracy of 2.5 K and a vertical resolution of about 5 km, while current numerical weather prediction models require temperature profiles with an accuracy of 1-1.5 K and a vertical resolution of about 2 km in the troposphere. The present paper shows that improvements in both the vertical resolution and accuracy require improvements in the informational content of the sounding systems and cannot be achieved by numerical means alone. Results are presented from a sounding system with narrow band channels to illustrate the improvements which can be achieved with future sounders. Finally, the results of several numerical simulations are discussed which show that clear column temperature profiles can be derived in the presence of clouds with an rms accuracy of 1.5 K and vertical resolution of 2 km in the troposphere.

Chahine, M. T.↗
NASA NTRS1977

Remote sounding of cloudy atmospheres. II - Multiple cloud formations

The dual frequency-range principle developed in Part I (Chahine, 1974) for infrared remote sounding of atmospheric temperature profiles in the presence of a single cloud layer is extended here to the case of multiple cloud formations. The approach requires no a priori knowledge of the spectral properties of the clouds or the number of cloud layers in the fields of view. The method of solution requires measurements over adjacent fields of view and leads to the determination of the clear-column atmospheric temperature profiles with the same degree of accuracy and vertical resolution permitted under cloudless conditions. Numerical verifications are carried out to illustrate the stability and accuracy of the method using simulated radiance data, from the 4.3 and 15 micron CO2 bands in the terrestrial atmosphere, in the presence of up to three cloud layers in the fields of view.

Chahine, M. T.↗
NASA NTRS1977

Remote sounding of cloudy atmospheres. III - Experimental verifications

The cloud-filtering technique developed in Parts I and II of this study is experimentally verified in this paper. The verification is based on radiance data measured in the 4.3 and 15 micron CO2 bands using a multidetector sounder mounted on an aircraft. The results presented here show that, from the aircraft height of 7.6 km and in the presence of multiple cloud formations, it is possible to recover simultaneously: (1) the clear-column atmospheric temperature profile with an rms error of 1 K with respect to radiosondes, (2) the land and sea surface temperature at all sun zenith angles. The accuracy of the recovered sea-surface temperature is 0.5-1 K with respect to measured bucket temperatures, (3) the humidity profile (water vapor mixing ratio) with a precision of 10%, (4) the fractional covers and heights of up to three cloud formations, and (5) the types of clouds, i.e., whether convective or nonconvective.

Chahine, M. T.↗
NASA NTRS1977

Spectral band passes for a high precision satellite sounder

Atmospheric temperature soundings with significantly improved vertical resolution can be obtained from carefully chosen narrow band-pass measurements in the 4.3-micron band of CO2 by taking advantage of the variation of the absorption coefficients, and thereby the weighting functions, with pressure and temperature. A set of channels has been found in the 4.2-micron region that is capable of yielding about 2-km vertical resolution in the troposphere. The concept of a complete system is presented for obtaining high resolution retrievals of temperature and water vapor distribution, as well as surface and cloud top temperatures, even in the presence of broken clouds.

Kaplan, L. D.↗
NASA NTRS1976

Infrared multidetector spectrometer for remote sensing of temperature profiles in the presence of clouds

An infrared multidetector spectrometer with channels in the 4.3-micron and 15-micron CO2 bands for the remote sensing of temperature profiles in the presence of clouds is described. Results obtained from aircraft flights in July 1975 over ocean sites under various conditions of cloudiness demonstrate the capability of the dual frequency technique to recover surface temperatures to an accuracy of + or - 0.5 K in the presence of up to 90% cloud cover.

Aumann, H. H.↗
NASA NTRS1975

An analytical transformation for remote sensing of clear-column atmospheric temperature profiles

An exact analytical transformation is presented for the remote sensing of atmospheric temperature profiles in the presence of clouds. The transformation permits direct retrieval of clear-column temperature profiles without the need to predetermine the corresponding clear-column radiances. A numerical illustration is given for simulated observations in the 15 micron CO2 band in the terrestrial atmosphere. The resulting method is numerically very fast and is especially suitable for handling the massive amount of data needed for numerical weather prediction.

Chahine, M. T.↗