J. Moncet

ABSTRACT Modeled land surface microwave emissivity compared to satellite‐based estimateOver snow‐free vegetated areas, the emissivities agree reasonably wellFurther evaluation is provided by direct comparison with satellite observationsModeled land surface microwave emissivity compared to satellite‐based estimateOver snow‐free vegetated areas, the emissivities agree reasonably wellFurther evaluation is provided by direct comparison with satellite observations

ABSTRACT Accurate knowledge of local surface emissivity is required for lower troposphere microwave remote sensing over land and for land surface parameter retrievals. Ideally, for a stand-alone microwave system (i.e., without an external source of surface temperature), a priori emissivity accuracies of 0.01 or less are needed to minimize the impact of cloud liquid water on temperature and water vapor retrievals and to improve surface temperature retrievals to 2 K or better. We are developing a system for land surface microwave emissivity retrieval and using it to derive emissivities in the AMSR-E channels over a full year. The system now incorporates both AMSR-E and SSM/I brightness temperatures and MODIS-derived land surface temperature (LST) products. We have examined the temporal variability of retrieved local surface emissivities and describe approaches developed to identify and minimize sources of error in the retrieval. The emissivity retrieval system is a precursor for a dynamic emissivity database to be fully implemented for NPOESS CMIS with coincident VIIRS LST observations available up to six times per day.

ABSTRACT Coding schemes suitable for progressive transmission of still pictures in NTSC composite format are studied. Transform coding methods based on the discrete cosine transform (DCT) and the WalshHadamard transform (WHT) are used. The transform coefficients are segmented into groups having similar properties. Variable blocklength to variable length codes are used to encode the quantized coefficients for each of the groups. Progressive transmission is achieved by sending the coefficients belonging to particular groups in successive passes over the image. Results are presented for coding the NTSC signal sampled at four times the color subcarrier frequency with an orthogonal structure, and at twice the subcarrier frequency with a hexagonal structure.

This report has described the results of a study undertaken at AER to identify and implement a state of the art nonlinear retrieval approach to characterize line of sight variability of atmospheric thermal and constituent environments. This path characterization capability was designed to interface with the existing Geophysics Laboratory (GL) line-by-line radiance/transmittance code, FASCODE. Accomplishments of the study include: (a) a review of the relevant literature concerning potential path characterization retrieval algorithms, selection of a physical least squares (PLS) nonlinear retrieval approach for implementation based on criteria including flexibility within the context of FASCODE and a certain degree of robustness in application; (b) development of a stand alone, preprocessing screening procedure to identify potential channels for path characterization based on user requirements; (c) formulation and implementation of the path characterization retrieval algorithm includin...

The large volume of existing and planned infrared observations of Mars have prompted the development of a new martian radiative transfer model that could be used in the retrievals of atmospheric and surface properties. The model is based on the Optimal Spectral Sampling (OSS) method [1]. The method is a fast and accurate monochromatic technique applicable to a wide range of remote sensing platforms (from microwave to UV) and was originally developed for the real-time processing of infrared and microwave data acquired by instruments aboard the satellites forming part of the next-generation global weather satellite system NPOESS (National Polarorbiting Operational Satellite System) [2]. As part of our on-going research related to the radiative properties of the martian polar caps, we have begun the development of a martian OSS model with the goal of using it to perform self-consistent atmospheric corrections necessary to retrieve caps emissivity from the Thermal Emission Spectrometer ...

We have developed the Integrated Algorithm Testbed (IATB) to address the development and validation needs of current and future remote sensing platforms. The core of the IATB is the Optimal Spectral Sampling (OSS) radiative transfer model. OSS is a robust approach to radiative transfer modeling which addresses the need for algorithm speed, accuracy, and flexibility. The OSS technique allows for the rapid calculation of radiance for any class of multispectral, hyperspectral, or ultraspectral sensors at any spectral resolution operating in any region from microwave through UV wavelengths by selecting and appropriately weighting the monochromatic points that contribute over the sensor bandwidth. This allows for the calculation to be performed at a small number of spectral points while retaining the advantages of a monochromatic calculation such as exact treatment of multiple scattering and/or polarization. The OSS method is well suited for remote sensing applications which require extr...

ABSTRACT Monthly-average estimates of latent heat flux have been derived from a combination of satellite-derived microwave emissivities, day-night differences in land surface temperature (from microwave AMSR-E), downward solar and infrared fluxes from ISCCP cloud analysis, and MODIS visible and near-infrared surface reflectances. The estimates, produced with a neural network, were compared with data from the Noah land surface model, as produced for GLDAS-2, and with two alternative estimates derived from different datasets and methods. Areas with extensive, persistent, substantial discrepancies between the satellite and land surface model fluxes have been analyzed with the aid of data from flux towers. The sources of discrepancies were found to include problems with the model surface roughness length and turbulent exchange coefficients for mid-latitude cropland areas in summer, inaccuracies in the precipitation data that were used as forcing for the land surface model, and model underestimation of transpiration in some forests during dry periods. At the tower sites analyzed, agreement with tower data was generally closer for our satellite-derived fluxes than for the land surface model fluxes, in terms of monthly averages.

ABSTRACT The Support of Environmental Requirements for Cloud Analysis and Archives (SERCAA) program is a two phase basic research program to develop techniques for analysis of multi-source multi-spectral satellite sensor data for the purpose of estimating cloud fractional amount, location, height, and type. In the first phase, cloud analysis algorithms were developed for each imaging sensor. A major innovation was an analysis integration approach to combine the separate algorithm results from the temporally, spatially, and spectrally inconsistent sources into a single logically consistent analysis. In the second phase, work includes algorithms for retrieval and estimation of the cloud physical and optical properties such as phase, drop size distribution, optical thickness, and emissivity. Also under investigation are cloud environment parameters including vertical profiles of temperature and moisture available from sounding sensors.

Code-excited linear prediction (CELP) is examined for the coding of speech signals. The methodology is developed to allow for a joint optimization of waveform selection, waveform scaling, and pitch filter determination. Methods to accommodate high-pitch speakers (pitch lag smaller than the analysis frame size) are given. The requirements for coding the synthesis parameters into a bit stream at 4.8 kb/s are discussed. The coder has been tested at channel error rates of 0.001, with only minor degradations in the resulting speech. An adaptive postfilter has been added to achieve a small increase in perceived speech quality

Land surface models (LSMs) are essential components of general circulation models for representing exchanges of heat, water, and trace gases between the atmosphere and the surface/biosphere system. Current LSMs have substantial uncertainties and discrepancies among them. Thermal infrared and microwave satellite data can provide information very useful for analyzing LSM performance, complementing information from visible and near-infrared data. For example,

The Optimal Spectral Sampling (OSS) method is a rapid and accurate technique for the numerical modeling of narrow-band transmittances in media with non-homogeneous thermodynamic properties containing a mixture of absorbing gases with variable concentrations. The method has been initially designed for the modeling of radiances measured by satellite or aircraft-borne sensors in the infrared and microwave and is particularly well suited for remote sensing applications and for the assimilation of satellite observations in numerical weather prediction (NWP) models. Both applications require fast and accurate models to produce radiances and Jacobians used for the real time inversion of the satellite observations. In this paper we provide a brief description of the method and discuss its accuracy and computational performance in the context of its application to retrieval of atmospheric parameters from sounding and imaging sensor (e.g. AIRS and MODIS) observations. Both clear and cloudy co...

Water vapour continuum absorption is an important contributor to the Earth's radiative cooling and energy balance. Here, we describe the development and status of the MT_CKD (MlawerTobinCloughKneizysDavies) water vapour continuum absorption model. The perspective adopted in developing the MT_CKD model has been to constrain the model so that it is consistent with quality analyses of spectral atmospheric and laboratory measurements of the foreign and self continuum. For field measurements, only cases for which the characterization of the atmospheric state has been highly scrutinized have been used. Continuum coefficients in spectral regions that have not been subject to compelling analyses are determined by a mathematical formulation of the spectral shape associated with each water vapour monomer line. This formulation, which is based on continuum values in spectral regions in which the coefficients are well constrained by measurements, is applied consistently to all water vapour monomer lines from the microwave to the visible. The results are summed-up (separately for the foreign and self) to obtain continuum coefficients from 0 to 20 000 cm(-1). For each water vapour line, the MT_CKD line shape formulation consists of two components: exponentially decaying far wings of the line plus a contribution from a water vapour molecule undergoing a weak interaction with a second molecule. In the MT_CKD model, the first component is the primary agent for the continuum between water vapour bands, while the second component is responsible for the majority of the continuum within water vapour bands. The MT_CKD model should be regarded as a semi-empirical model with strong constraints provided by the known physics. Keeping the MT_CKD continuum consistent with current observational studies necessitates periodic updates to the water vapour continuum coefficients. In addition to providing details on the MT_CKD line shape formulation, we describe the most recent update to the model, MT_CKD_2.5, which is based on an analysis of satellite- and ground-based observations from 2385 to 2600 cm(-1) (approx. 4 μm).

ABSTRACT A fast and numerically accurate model for monochromatic transfer in scattering atmospheres has been developed to extend the capabilities of the existing LBLRTM line-by-line model to the treatment of clouds and aerosols. The algorithm is based on the adding-doubling method and is specifically designed to perform radiance calculations in both the thermal and the solar regimes using any specified number of computational streams. The efficient implementation of the adding-doubling scheme makes it possible to use the multiple-scattering algorithm in retrieval applications, an essential requirement for the intended use of the algorithm in atmospheric validation studies. The algorithm is applied to observations of water clouds from the ground-based high spectral resolution atmospheric emitted radiance interferometer (AERI) made during the daytime. Retrieval of cloud mode radius, cloud liquid water, and effective cloud fraction is required to model the AERI radiance measurements in the 520-1500cm-1 band and in the 1800-3020cm-1 band which contains significant scattered solar energy. An initial assessment is made of the spectral information content of the AERI measurements for water cloud properties and of the quality of the spectral fits obtainable with those three parameters in the two spectral bands.

We have commenced the development of efficient and accurate radiative transfer models for scattering and gaseous absorption in a spherical atmosphere, through a combination of the Gauss-Seidel Spherical Radiative Transfer (GSSRTM) and the Optimal Spectral Sampling (OSS) models. The combined models will be made available to the research community for use in validation, retrievals, and data assimilation from limb-sounding instruments, particularly the Mars Climate Sounder and future instruments for Mars and other planets. This work is very timely, as new instrument concepts will emerge from the ongoing NRC Decadal Survey. The traditional way of training an OSS model (e.g., for a down-looking configuration in the thermal regime) is directly in radiances. Radiance training allows for taking into account variations across wide spectral bands (e.g., the Planck function, cloud/aerosol optical properties, surface properties) in the OSS node selection and weights calculation. However, the GS...

ABSTRACT A brightness temperature is defined as a linear function of the Planck radiance, with the linear coefficients optimized to minimize the difference between the brightness temperature and the physical temperatures of atmospheric and terrestrial emitters. Radiative transfer (RT) calculations can be accelerated by formulating the integration in terms of this brightness temperature while producing output in terms of radiance or brightness temperature. Approximation errors are < 0.012 K for RT model applications up to 400 GHz, for any upward, downward, or limb-view geometry, which is about an order of magnitude smaller than for the common brightness temperature derived from a second-order expansion of the Planck function. When products of an RT model that uses this optimized Planck approximation are compared with measurements and the measured radiance is high (equivalent brightness temperature is >170 K), it can be advantageous to apply a complementary approximation to the measurements to benefit from error compensation between the model and the measurements. Alternatively, error compensation can be obtained if the calibration and RT equations use consistent brightness temperature approximations.

Abstract: This report summarizes four years of the Phillips Laboratory and AER, Inc.'s efforts in the calibration of the DMSP SSM/T-2 millimeter wave moisture sounder. Thirteen underflights of the T-2 were made by the NASA ER-2 research aircraft which carried the ...