Howard E. Motteler

An overview of the AIRS radiative transfer model

The two main elements of the Atmospheric Infrared Sounder radiative transfer algorithm (AIRS-RTA) are described in this paper: 1) the fast parameterization of the atmospheric transmittances that are used to perform the AIRS physical retrievals and 2) the spectroscopy used to generate the parameterized transmittances. We concentrate on those aspects of the spectroscopy that are especially relevant for temperature and water vapor retrievals. The AIRS-RTA is a hybrid model in that it parameterizes most gases on a fixed grid of pressures, while the water optical depths are parameterized on a fixed grid of water amounts. Water vapor, ozone, carbon monoxide, and methane profiles can be varied, in addition to the column abundance of carbon dioxide.

Comparison of neural networks and regression-based methods for temperature retrievals

Two methods for performing clear-air temperature retrievals from simulated radiances for the Atmospheric Infrared Sounder are investigated. Neural networks are compared with a well-known linear method in which regression is performed after a change of bases. With large channel sets, both methods can rapidly perform clear-air retrievals over a variety of climactic conditions with an overall RMS error of less than 1 K. The Jacobian of the neural network is compared with the Jacobian (the regression coefficients) of the linear method, revealing a more fine-scale variation than expected from the underlying physics, particularly for the neural net. Some pragmatic information concerning the application ofneural nets to retrieval problems is also included.

Validation of the AIRS Radiative Transfer Algorithm

This paper presents comparisons between observed AQUA-AIRS spectra and spectra computed from the European Center for Medium Range Forecasting (ECMWF) numerical weather prediction model fields.

Validation of the AIRS radiative transfer algorithm using ECMWF datafields

The Atmospheric Infrared Sounder (AIRS) was launched in early May 2002. This new high-spectral resolution sounder is the first of a new generation of temperature and humidity sounders for numerical weather prediction and climate change studies. In addition, AIRS should be able to detect several minor gases, including ozone, carbon monoxide, methane and carbon dioxide. This paper presents a preliminary comparison between observed AIRS spectra and spectra computed from the ECMWF (European Center for Medium Range Forecasting) model fields. A key component of this comparison is the selection of clear fields of view, which we limited to night views over ocean, allowing the use of the relatively well known sea surface emissivity.

On testing hierarchies for protocols

The authors consider a protocol specification represented as a fully specified Mealy automata, and the problem of testing an implementation for conformance to such a specification. No single sequence-based test can be completely reliable, if one allows for the possibility of an implementation with an unknown number of extra states. They define a hierarchy of test sequences, parameterized by the length of behaviors under test. For the reset method of conformance testing, they prove that the hierarchy has the property that any fault detected by test i is also detected by test i+1, and show that this sequence of tests converges to a reliable conformance test. For certain bridge sequence methods for constructing test sequences, this result does not always hold. In experiments with several specifications, they observe that given a small number of extra states in an implementation, the sequence of tests converge to a total fault coverage for small values of i, for both reset and bridge sequence methods. They also observe that the choice of characterizing sequence has less effect on fault coverage than the choice of behavior length or number of extra states in the implementation. >

Suomi NPP/JPSS Cross-track Infrared Sounder (CrIS): Calibration Validation With The Aircraft Based Scanning High-resolution Interferometer Sounder (S-HIS)

A summary of the Cross-track Infrared Sounder (CrIS) radiometric calibration validation assessment conducted using the aircraft based Scanning High-resolution Interferometer Sounder (S-HIS) during the SNPP 2013 calibration validation campaign is presented.

Undetected faults in protocol testing

We investigate ways in which UIO-based conformance testing can fail to catch faults, including single and multiple faults, faults with extra or missing states, and faults at both the test sequence and subsequence levels. Given a particular error and test method, the error is masked if it is not detected by the test method. Many forms of fault masking are possible, and all test methods we have considered exhibit some forms of masking. Faults captured at the test subsequence level may become masked at the sequence level, and vice versa. Fault masking has been used to argue relative merits of various testing methods. Because of the pervasiveness of masking, we cannot use masking alone to argue that one UIO-based test method is superior to another. Information about the density of masked faults among all faults is needed to evaluate a test method. >

Radiative transfer observations with AIRS

The Atmospheric Infrared Sounder (AIRS) was launched in early May 2002. The temperature and humidity fields retrieved from this new high-spectral resolution sounder will be used for numerical weather prediction and climate change studies. This paper presents a comparisons between observed AIRS spectra and spectra computed from profiles using the worldwide radiosonde network, as well as spectra computed from the ECMWF (European Center for Medium Range Weather Forecasts) model fields.

Wavelength division multiplexed (WDM) data-block switching for parallel computing and interconnects

We report a new generation switch, the data-block switch, which can greatly increase the capacity and reduce the complexity of the interconnect network of a parallel computing system. By using WDM techniques, parallel data can be multiplexed and transmitted through a single fiber. By using photonic switching techniques, we can switch a block of parallel data in one switch operation to any site desired. In this work, we demonstrate such an operation with our fabricated 1 X 2 semiconductor optical amplifier (SOA) switch. This integrated device is an active/passive Y- junction waveguide device with a passive waveguide region in the middle and 3 active waveguide regions at each end. The amplified spontaneous emission spectrum of the SOA shows that this broadband switch can easily cover a wavelength range of more than 64 ITU wavelength grids (100 GHz). The switch operation of multiple wavelengths and the switching speed of the device were studied. A switching time of around 400 ps was achieved.

Fast computation of monochromatic infrared atmospheric transmittances using compressed look-up tables

We have developed a new information-content based look-up table technique for the fast computation of near- monochromatic atmospheric transmittances in the infrared that is well suited for nadir viewing satellite and airplane observations. It allow a user to quickly compute near- monochromatic radiances using a very simple algorithm that is easily ported to many machine architectures. Radiative transfer based on look-up tables of monochromatic absorption coefficients could speed calculations, but they are impractical due to their large size and the need to interpolate long wavenumber vectors in temperature and pressure. We use a singular value decomposition to transform monochromatic look-up tables of absorption coefficients into a compressed representation that is almost 100 times smaller. Moreover, temperature and pressure interpolations can be performed in this compressed representation, resulting in significant savings in computation times and computer I/O. We start with the line-by-line computation of a set of tables of absorption coefficients for each relevant gas. Each 25 wavenumber table has 10,000 wavenumber points and 1,100 temperature/pressure layers. For water vapor we add an extra dimension to these tables that spans 5 water vapor profiles to provide variability in the self-broadening of water vapor spectral lines. On average we need 37 basis vectors for water, 12 for carbon dioxide, and 6 for each of the other required gases in order to reproduce the absorption coefficient tables to an accuracy equivalent to a nadir-viewing monochromatic brightness temperature error of 0.1K.