Maurice Herman - Academia.edu (original) (raw)
Papers by Maurice Herman
International Journal of Remote Sensing, 1997
POLDER (POLarization and Directionality of the Earth&... more POLDER (POLarization and Directionality of the Earth's Reflectances) is a new instrument devoted to the global observation of the polarization and directionality of solar radiation reflected by the Earth surface-atmosphere system. This radiometer has been on board the Japanese ADEOS platform since August 1996. This paper describes the main algorithms of the POLDER "Earth radiation budget (ERB) & clouds "
A SAGE-2 validation program was performed using ground based lidars and balloon-borne polarimetri... more A SAGE-2 validation program was performed using ground based lidars and balloon-borne polarimetric and photographic experiments. Between the tropopause height and 23 km, good agreement is found between the SAGE-2 1.02 micron extinction profiles and the lidar profiles, using for the conversion of backscattering into extinction an aerosol model consistent with the SAGE-2 spectral extinction. The extinction profiles deduced from the limb photographs at 0.44 and 0.375 microns present a good agreement with the SAGE-2 profiles respectively at 0.453 and 0.385 microns. The size distribution retrieved from the near infrared polarimetric observations leads to a spectral variation of the extinction in good agreement with SAGE-2 data, in the same altitude range. Above 23 to 25 km, observations are scarce and the data of poorer quality because of the low aerosol content. The 1.02 micron extinction profiles seem to agree with the ruby lidar and the limb photographs profiles. But any conclusion co...
A photopolarimeter designed to measure the radiance and the polarization ratio at lambda equals 0... more A photopolarimeter designed to measure the radiance and the polarization ratio at lambda equals 0.85 microns and lambda equals 1.65 microns is set up on a gondola of a stratospheric balloon. By rotating the gondola, measurements of the diffuse solar light are obtained for a wide range of the scattering angles. An inversion scheme, based on the assumption of a log-normal size distribution, provides the relevant size parameters, the refractive index, and the slant optical thicknesses of the aerosols. Since 1983, this experiment was launched twice a year from Aire Sur Adour (S-E of France). The post-El Chichon atmospheric stratospheric aerosol proved to be quite stable in size and nature (hydratid sulfuric acid), but the abundance decreased by a factor of 10 between 1983 and 1987. The experiment was also launched to observe the stratosphere during the Arctic winter. Two flights, on January 28, 1988 and January 18, 1990, corresponded to an unperturbed atmosphere. But during a third flig...
A balloon borne polarimetric experiment, RADIBAL, was launched from Kiruna to observe the propert... more A balloon borne polarimetric experiment, RADIBAL, was launched from Kiruna to observe the properties of polar stratospheric cloud particles, from limb scannings of the radiance and of the polarization of the scattered sunlight. On February 4, 1990 during the CHEOPS 3 campaign, when the stratospheric temperature was about 190 K, a polar stratospheric cloud (PSC) was sampled. At the top of the PSC, an upper thin layer no more than 2 km thick, was shown to be composed of rather large, micron sized particles, as assessed from the forward scattering feature. Difficulties in retrieving the polarization from calculations for spherical particles suggest that they might be crystalline particles. Below this layer, the PSC consisted very probably of spherical particles. In this part of the cloud, the polarization features indicate that, from the lower to the upper levels, the size distribution of the particles narrowed, suggesting a preferential growth process on the smaller class of particles...
ESA journal
An attempt to develop a practical model of atmospheric effects between 0.35-4 microns in order to... more An attempt to develop a practical model of atmospheric effects between 0.35-4 microns in order to form a data base engineers can use in designing optical remote sensing instruments for spacecraft is reported. The total radiation received by an earth-viewing satellite is modeled as the spectrum received at the detector and the geometry of the angle of view. Formulas are developed for the incoming radiation at the earth surface, the atmospheric diffusion, and the reflection of solar radiation by the atmosphere, in addition to the total of all three factors. Atmospheric, sky, and diffuse luminance are quantified, along with the influence of the proportion of clear sky and the efficiency of the instrument signal. Application of the models to the OCM and OII instruments is shown to produce imagery with accuracy better than 5 percent.
Proceedings of the International Astronomical Union
The analysis of the sunlight scattered by Venus gives some insight into its clouds. The measureme... more The analysis of the sunlight scattered by Venus gives some insight into its clouds. The measurements of polarized light are probably more sensitive to the nature of their constituents, and some recent studies seem to be able to give a satisfactory interpretation of this part of the scattered light. But the polarized light concerns the upper part of the clouds, and it is interesting to compare these results with intensity measurements. The phase curves, for the integrated light, leave some indeterminations, so we have studied whether the intensity distribution on the Venus disk could give more accurate informations. A simple model of a homogeneous plane parallel cloud has been used, and the influence of various parameters has been tested (single scattering albedo, refractive index of particles and size distribution, optical depth of the cloud).
Journal of the Atmospheric Sciences
Observations by the television system on Mariner 10 of solar radiation reflected by Venus are ana... more Observations by the television system on Mariner 10 of solar radiation reflected by Venus are analyzed by means of comparisons with theoretical computations. It is found that the distribution of radiance across the planetary disc in blue and orange light cannot be explained by a single homogeneous cloud consistent with polarization measurements. Preliminary work has been done for analysis of the Mariner 10 data with a two-cloud model. It is anticipated that the data will allow the extraction of some knowledge of the variations of the optical thickness of the upper cloud, and of the reflectivities of both layers.
An analytical expression of the measured reflectance is established for the general case of a non... more An analytical expression of the measured reflectance is established for the general case of a nonlambertian and nonuniform ground. The signal is nearly linear in function of the intrinsic atmospheric reflectance, the actual target reflectance, and two average reflectances, angular and spatial; the relative importance of these contributions is discussed for various cases of turbidity. The method is applied in order to study the reduction of contrast for targets of various size including bidirectional properties. Particular attention is paid to the contribution of the target environment to the apparent reflectance of a lambertian ground. Another application concerns the ocean diffuse reflectance and a correction algorithm for such measurements is proposed; the possibility of remote sensing of chlorophyll content is discussed.
The optical phenomena produced by reflected infrared solar radiation are studied in order to form... more The optical phenomena produced by reflected infrared solar radiation are studied in order to formulate a model useful to satellite designers. The investigated problems include surface reflectance bands, gaseous absorption, and molecular and aerosol diffusion. A numerical model which represents the diffusion phenomena in a simple form and with high accuracy is presented, but the model's domain is restricted to weak concentrations of aerosols and it does not apply to clouds. Examples of satellite instrument corrections using the model are included.
Journal of the Atmospheric Sciences
A computer code was developed in terms of a three-layer model for the earth-atmosphere system, us... more A computer code was developed in terms of a three-layer model for the earth-atmosphere system, using a two-stream approximation for the troposphere and stratosphere. The analysis was limited to variable atmosphere loading by solar radiation over an unperturbed section of the atmosphere. The scattering atmosphere above a Lambertian ground layer was considered in order to derive the planar albedo and the spherical albedo. Attention was given to the influence of the aerosol optical thickness in the stratosphere, the single scattering albedo and asymmetry factor, and the sublayer albedo. Calculations were performed of the zonal albedo and the planetary radiation balance, taking into account a stratospheric aerosol layer containing H2SO4 droplets and volcanic ash. The resulting ground temperature disturbance was computed using a Budyko (1969) climate model. Local decreases in the albedo in the summer were observed in high latitudes, implying a heating effect of the aerosol. An accompanyi...
Antarctic journal of the United States / National Science Foundation
Proceedings of SPIE - The International Society for Optical Engineering
POLDER has been launched on the Japanese ADEOS platform in August 1996. Due to its multi-directio... more POLDER has been launched on the Japanese ADEOS platform in August 1996. Due to its multi-directional, multispectral and multi-polarization capabilities, this new radiometer gives useful information on the clouds and on their influence on the radiation in the shortwave range. The POLDER bidirectional observation capability provides the polarization signatures within a large range of scattering angles in three spectral bands centered on 443, 670 and 865 nm with a spatial resolution of 7km X 7km. These original features allow to obtain some information both on cloud thermodynamic phase and even on the cloud microphysic of particles. Cloud phase recognition is important for cloud studies. Ice crystals correspond to physical process and properties that differ from those of liquid water drops. The angular POLDER airborne observations, liquid cloud droplets exhibit the very specific polarization features of the rainbow for scattering angels near 140 degrees. Conversely, according to theore...
The POLDER instrument was launched onboard the ADEOS satellite in August 1996. It provided contin... more The POLDER instrument was launched onboard the ADEOS satellite in August 1996. It provided continuous measurements of the Earth Reflectances between November 96 and June 97 when the failure of the platform doomed all instruments onboard. Another similar instrument was launched in December 2002, although no measurements are available yet. POLDER has the original capability to measure the directional signature of the reflectance: A single Earth target is observed from up to 14 different directions as the satellite flies over. This signature, together with the spectral information, provides a strong constraint on the aerosol model to be inverted. Moreover, the POLDER radiometer measures the polarization state of the reflected light. This information provides yet another constraint for the aerosol model. Besides, over land surfaces, the polarized reflectance may be used to estimate the aerosol optical thickness. The presentation will discuss the original capabilities of POLDER, the inve...
Aircraft photopolarimetric observation of cloud and snow fields made by the POLDER (Polarization ... more Aircraft photopolarimetric observation of cloud and snow fields made by the POLDER (Polarization and Directionality of the Earth Reflectance) instrument during the EUCREX (European Cloud Radiation Experiment) and RACER (Research Antarctica Coastal Ecosystem Rates) campaigns are presented. Over clouds, the polarized component of the reflectance at the wavelength of 450 nm and scattering angles of 90 to 100 deg is sensitive to the molecular optical thickness between the cloud top and aircraft altitudes and, therefore, may be used for cloud altimetry. Liquid water clouds and snow exhibit similar spectral and bidirectional characteristics, but distinct polarization signatures. In the rainbow region (scattering angles of about 140 deg), water droplets strongly polarize incident sunlight while snow crystals do not, making it possible to distinguish the two types targets by scanning the angular polarization.
Simultaneous AERONET measurements and aerosol retrievals from PARASOL and MODIS/Terra are compare... more Simultaneous AERONET measurements and aerosol retrievals from PARASOL and MODIS/Terra are compared. Advantages of each instrument are described; for instance PARASOL can detect non-spherical particles within the coarse mode, which is not the case of MODIS. Simulations of MODIS (PARASOL respectively) measurements from PARASOL (MODIS) inverted aerosol models are also performed (cross- simulations). Directional and polarized informations from PARASOL with simultaneous MODIS spectral data can be combined to retrieve more accurately aerosol optical properties. Results from the joint inversion scheme are compared to AERONET data.
The paper shows the sensitivity of POLDER aerosol index to biomass burning and others anthropogen... more The paper shows the sensitivity of POLDER aerosol index to biomass burning and others anthropogenic aerosol particles. Discrimination between these two aerosol types is possible using complementary fires distribution information provided by ATSR-2. Semi-quantitative validation against suspended particles matter concentration is also presented.
IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477), 2003
... On the other hand, polarized radiance modeling in the 443 channel is not simple (multiple sca... more ... On the other hand, polarized radiance modeling in the 443 channel is not simple (multiple scattering) and depends on the altitude of ... funded by the Centre National d'Etudes Spatiales (CNES), the Centre National de la Recherche Scientifique (CNRS), the Conseil Général du ...
International Journal of Remote Sensing, 1997
POLDER (POLarization and Directionality of the Earth&... more POLDER (POLarization and Directionality of the Earth's Reflectances) is a new instrument devoted to the global observation of the polarization and directionality of solar radiation reflected by the Earth surface-atmosphere system. This radiometer has been on board the Japanese ADEOS platform since August 1996. This paper describes the main algorithms of the POLDER "Earth radiation budget (ERB) & clouds "
A SAGE-2 validation program was performed using ground based lidars and balloon-borne polarimetri... more A SAGE-2 validation program was performed using ground based lidars and balloon-borne polarimetric and photographic experiments. Between the tropopause height and 23 km, good agreement is found between the SAGE-2 1.02 micron extinction profiles and the lidar profiles, using for the conversion of backscattering into extinction an aerosol model consistent with the SAGE-2 spectral extinction. The extinction profiles deduced from the limb photographs at 0.44 and 0.375 microns present a good agreement with the SAGE-2 profiles respectively at 0.453 and 0.385 microns. The size distribution retrieved from the near infrared polarimetric observations leads to a spectral variation of the extinction in good agreement with SAGE-2 data, in the same altitude range. Above 23 to 25 km, observations are scarce and the data of poorer quality because of the low aerosol content. The 1.02 micron extinction profiles seem to agree with the ruby lidar and the limb photographs profiles. But any conclusion co...
A photopolarimeter designed to measure the radiance and the polarization ratio at lambda equals 0... more A photopolarimeter designed to measure the radiance and the polarization ratio at lambda equals 0.85 microns and lambda equals 1.65 microns is set up on a gondola of a stratospheric balloon. By rotating the gondola, measurements of the diffuse solar light are obtained for a wide range of the scattering angles. An inversion scheme, based on the assumption of a log-normal size distribution, provides the relevant size parameters, the refractive index, and the slant optical thicknesses of the aerosols. Since 1983, this experiment was launched twice a year from Aire Sur Adour (S-E of France). The post-El Chichon atmospheric stratospheric aerosol proved to be quite stable in size and nature (hydratid sulfuric acid), but the abundance decreased by a factor of 10 between 1983 and 1987. The experiment was also launched to observe the stratosphere during the Arctic winter. Two flights, on January 28, 1988 and January 18, 1990, corresponded to an unperturbed atmosphere. But during a third flig...
A balloon borne polarimetric experiment, RADIBAL, was launched from Kiruna to observe the propert... more A balloon borne polarimetric experiment, RADIBAL, was launched from Kiruna to observe the properties of polar stratospheric cloud particles, from limb scannings of the radiance and of the polarization of the scattered sunlight. On February 4, 1990 during the CHEOPS 3 campaign, when the stratospheric temperature was about 190 K, a polar stratospheric cloud (PSC) was sampled. At the top of the PSC, an upper thin layer no more than 2 km thick, was shown to be composed of rather large, micron sized particles, as assessed from the forward scattering feature. Difficulties in retrieving the polarization from calculations for spherical particles suggest that they might be crystalline particles. Below this layer, the PSC consisted very probably of spherical particles. In this part of the cloud, the polarization features indicate that, from the lower to the upper levels, the size distribution of the particles narrowed, suggesting a preferential growth process on the smaller class of particles...
ESA journal
An attempt to develop a practical model of atmospheric effects between 0.35-4 microns in order to... more An attempt to develop a practical model of atmospheric effects between 0.35-4 microns in order to form a data base engineers can use in designing optical remote sensing instruments for spacecraft is reported. The total radiation received by an earth-viewing satellite is modeled as the spectrum received at the detector and the geometry of the angle of view. Formulas are developed for the incoming radiation at the earth surface, the atmospheric diffusion, and the reflection of solar radiation by the atmosphere, in addition to the total of all three factors. Atmospheric, sky, and diffuse luminance are quantified, along with the influence of the proportion of clear sky and the efficiency of the instrument signal. Application of the models to the OCM and OII instruments is shown to produce imagery with accuracy better than 5 percent.
Proceedings of the International Astronomical Union
The analysis of the sunlight scattered by Venus gives some insight into its clouds. The measureme... more The analysis of the sunlight scattered by Venus gives some insight into its clouds. The measurements of polarized light are probably more sensitive to the nature of their constituents, and some recent studies seem to be able to give a satisfactory interpretation of this part of the scattered light. But the polarized light concerns the upper part of the clouds, and it is interesting to compare these results with intensity measurements. The phase curves, for the integrated light, leave some indeterminations, so we have studied whether the intensity distribution on the Venus disk could give more accurate informations. A simple model of a homogeneous plane parallel cloud has been used, and the influence of various parameters has been tested (single scattering albedo, refractive index of particles and size distribution, optical depth of the cloud).
Journal of the Atmospheric Sciences
Observations by the television system on Mariner 10 of solar radiation reflected by Venus are ana... more Observations by the television system on Mariner 10 of solar radiation reflected by Venus are analyzed by means of comparisons with theoretical computations. It is found that the distribution of radiance across the planetary disc in blue and orange light cannot be explained by a single homogeneous cloud consistent with polarization measurements. Preliminary work has been done for analysis of the Mariner 10 data with a two-cloud model. It is anticipated that the data will allow the extraction of some knowledge of the variations of the optical thickness of the upper cloud, and of the reflectivities of both layers.
An analytical expression of the measured reflectance is established for the general case of a non... more An analytical expression of the measured reflectance is established for the general case of a nonlambertian and nonuniform ground. The signal is nearly linear in function of the intrinsic atmospheric reflectance, the actual target reflectance, and two average reflectances, angular and spatial; the relative importance of these contributions is discussed for various cases of turbidity. The method is applied in order to study the reduction of contrast for targets of various size including bidirectional properties. Particular attention is paid to the contribution of the target environment to the apparent reflectance of a lambertian ground. Another application concerns the ocean diffuse reflectance and a correction algorithm for such measurements is proposed; the possibility of remote sensing of chlorophyll content is discussed.
The optical phenomena produced by reflected infrared solar radiation are studied in order to form... more The optical phenomena produced by reflected infrared solar radiation are studied in order to formulate a model useful to satellite designers. The investigated problems include surface reflectance bands, gaseous absorption, and molecular and aerosol diffusion. A numerical model which represents the diffusion phenomena in a simple form and with high accuracy is presented, but the model's domain is restricted to weak concentrations of aerosols and it does not apply to clouds. Examples of satellite instrument corrections using the model are included.
Journal of the Atmospheric Sciences
A computer code was developed in terms of a three-layer model for the earth-atmosphere system, us... more A computer code was developed in terms of a three-layer model for the earth-atmosphere system, using a two-stream approximation for the troposphere and stratosphere. The analysis was limited to variable atmosphere loading by solar radiation over an unperturbed section of the atmosphere. The scattering atmosphere above a Lambertian ground layer was considered in order to derive the planar albedo and the spherical albedo. Attention was given to the influence of the aerosol optical thickness in the stratosphere, the single scattering albedo and asymmetry factor, and the sublayer albedo. Calculations were performed of the zonal albedo and the planetary radiation balance, taking into account a stratospheric aerosol layer containing H2SO4 droplets and volcanic ash. The resulting ground temperature disturbance was computed using a Budyko (1969) climate model. Local decreases in the albedo in the summer were observed in high latitudes, implying a heating effect of the aerosol. An accompanyi...
Antarctic journal of the United States / National Science Foundation
Proceedings of SPIE - The International Society for Optical Engineering
POLDER has been launched on the Japanese ADEOS platform in August 1996. Due to its multi-directio... more POLDER has been launched on the Japanese ADEOS platform in August 1996. Due to its multi-directional, multispectral and multi-polarization capabilities, this new radiometer gives useful information on the clouds and on their influence on the radiation in the shortwave range. The POLDER bidirectional observation capability provides the polarization signatures within a large range of scattering angles in three spectral bands centered on 443, 670 and 865 nm with a spatial resolution of 7km X 7km. These original features allow to obtain some information both on cloud thermodynamic phase and even on the cloud microphysic of particles. Cloud phase recognition is important for cloud studies. Ice crystals correspond to physical process and properties that differ from those of liquid water drops. The angular POLDER airborne observations, liquid cloud droplets exhibit the very specific polarization features of the rainbow for scattering angels near 140 degrees. Conversely, according to theore...
The POLDER instrument was launched onboard the ADEOS satellite in August 1996. It provided contin... more The POLDER instrument was launched onboard the ADEOS satellite in August 1996. It provided continuous measurements of the Earth Reflectances between November 96 and June 97 when the failure of the platform doomed all instruments onboard. Another similar instrument was launched in December 2002, although no measurements are available yet. POLDER has the original capability to measure the directional signature of the reflectance: A single Earth target is observed from up to 14 different directions as the satellite flies over. This signature, together with the spectral information, provides a strong constraint on the aerosol model to be inverted. Moreover, the POLDER radiometer measures the polarization state of the reflected light. This information provides yet another constraint for the aerosol model. Besides, over land surfaces, the polarized reflectance may be used to estimate the aerosol optical thickness. The presentation will discuss the original capabilities of POLDER, the inve...
Aircraft photopolarimetric observation of cloud and snow fields made by the POLDER (Polarization ... more Aircraft photopolarimetric observation of cloud and snow fields made by the POLDER (Polarization and Directionality of the Earth Reflectance) instrument during the EUCREX (European Cloud Radiation Experiment) and RACER (Research Antarctica Coastal Ecosystem Rates) campaigns are presented. Over clouds, the polarized component of the reflectance at the wavelength of 450 nm and scattering angles of 90 to 100 deg is sensitive to the molecular optical thickness between the cloud top and aircraft altitudes and, therefore, may be used for cloud altimetry. Liquid water clouds and snow exhibit similar spectral and bidirectional characteristics, but distinct polarization signatures. In the rainbow region (scattering angles of about 140 deg), water droplets strongly polarize incident sunlight while snow crystals do not, making it possible to distinguish the two types targets by scanning the angular polarization.
Simultaneous AERONET measurements and aerosol retrievals from PARASOL and MODIS/Terra are compare... more Simultaneous AERONET measurements and aerosol retrievals from PARASOL and MODIS/Terra are compared. Advantages of each instrument are described; for instance PARASOL can detect non-spherical particles within the coarse mode, which is not the case of MODIS. Simulations of MODIS (PARASOL respectively) measurements from PARASOL (MODIS) inverted aerosol models are also performed (cross- simulations). Directional and polarized informations from PARASOL with simultaneous MODIS spectral data can be combined to retrieve more accurately aerosol optical properties. Results from the joint inversion scheme are compared to AERONET data.
The paper shows the sensitivity of POLDER aerosol index to biomass burning and others anthropogen... more The paper shows the sensitivity of POLDER aerosol index to biomass burning and others anthropogenic aerosol particles. Discrimination between these two aerosol types is possible using complementary fires distribution information provided by ATSR-2. Semi-quantitative validation against suspended particles matter concentration is also presented.
IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477), 2003
... On the other hand, polarized radiance modeling in the 443 channel is not simple (multiple sca... more ... On the other hand, polarized radiance modeling in the 443 channel is not simple (multiple scattering) and depends on the altitude of ... funded by the Centre National d'Etudes Spatiales (CNES), the Centre National de la Recherche Scientifique (CNRS), the Conseil Général du ...