Reinhard Beer

Tropospheric emission spectrometer for the Earth Observing System's Aura satellite.

The Tropospheric Emission Spectrometer (TES) is an imaging infrared Fourier-transform spectrometer scheduled to be launched into polar Sun-synchronous orbit aboard the Earth Observing System’s Aura satellite in June 2003. The primary objective of the TES is to make global three-dimensional measurements of tropospheric ozone and of the physical–chemical factors that control its formation, destruction, and distribution. Such an ambitious goal requires a highly sophisticated cryogenic instrument operating over a wide frequency range, which, in turn, demands state-of-the-art infrared detector arrays. In addition, the measurements require an instrument that can operate in both nadir and limb-sounding modes with a precision pointing system. The way in which these mission objectives flow down to the specific science and measurement requirements and in turn are implemented in the flight hardware are described. A brief overview of the data analysis approach is provided.

TES on the aura mission: scientific objectives, measurements, and analysis overview

The Tropospheric Emission Spectrometer (TES) is a high-resolution infrared imaging Fourier transform spectrometer specifically aimed at determining the chemical state of the Earths lower atmosphere (the troposphere). In particular, TES produces vertical profiles 0-32 km of important pollutant and greenhouse gases such as carbon monoxide, ozone, methane, and water vapor on a global scale every other day.

Comparisons of Tropospheric Emission Spectrometer (TES) ozone profiles to ozonesondes: Methods and initial results

[1]xa0The Tropospheric Emission Spectrometer (TES) on the Earth Observing System (EOS)-Aura spacecraft measures global profiles of atmospheric ozone with vertical resolution of 6–7 km in the troposphere for the nadir view. For a first validation of TES ozone measurements we have compared TES-retrieved ozone profiles to ozonesondes from fall, 2004. In some cases the ozonesonde data are from dedicated launches timed to match the Aura overpass, while other comparisons are performed with routine data available from the Southern Hemisphere Additional Ozonesonde (SHADOZ) archive and World Ozone and Ultraviolet Data Center (WOUDC) data archives. We account for TES measurement sensitivity and vertical resolution by applying the TES-averaging kernel and constraint to the ozonesonde data before differencing the profiles. Overall, for V001 data, TES ozone profiles are systematically higher than sondes in the upper troposphere but compare well in the lower troposphere, with respect to estimated errors. These comparisons show that TES is able to detect relative variations in the coarse vertical structure of tropospheric ozone.

Observed vertical distribution of tropospheric ozone during the Asian summertime monsoon

[1]xa0We characterize the horizontal and vertical distribution of tropospheric ozone measured by the Tropospheric Emission Spectrometer (TES) over North Africa, the Middle East, and Asia. Studies have shown that the summertime circulation associated with the Asian monsoon significantly influences the spatial distribution of ozone and its precursors. However, there have been limited observations of the distribution of tropospheric ozone over this region. Over the Middle East, TES observations reveal abundances of ozone between 60 and 100 ppbv, with amounts over 80 ppbv typically occurring between 300 and 450 hPa, whereas over India, enhanced ozone abundances are near 300 hPa. Over central Asia, observed ozone amounts are 150–200 ppbv at altitudes near 300 hPa. These enhanced ozone abundances are observed in June and July, corresponding to the onset of the Asian monsoon, and begin to dissipate in August. Intercomparison of the TES data with ozone climatologies derived from the Measurements of Ozone and Water Vapor by in-Service Airbus Aircraft program show that the TES ozone is biased high by about 15% between 300 and 750 hPa, consistent with prior validation studies. Comparison of the assimilation of TES data into the GEOS-Chem model with assimilation of data from the Microwave Limb Sounder (MLS) and the Ozone Monitoring Instrument (OMI) into the Goddard Earth Observing System (GEOS-4) model shows consistency in the distribution of ozone. For example, at 7–8 km across North Africa, the Middle East, and Asia the bias between GEOS-Chem and the assimilated OMI and MLS fields was reduced from 6.8 to 1.4 ppbv following assimilation of the TES data.

Implementation of cloud retrievals for Tropospheric Emission Spectrometer (TES) atmospheric retrievals: part 1. Description and characterization of errors on trace gas retrievals

terms of a set of frequency-dependent nonscattering optical depths and a cloud height. These cloud parameters are retrieved jointly with surface temperature, emissivity, atmospheric temperature, and trace gases such as ozone from spectral data. We demonstrate the application of this approach using data from the Tropospheric Emission Spectrometer (TES) and test data simulated with a scattering radiative transfer model. We show the value of this approach in that it results in accurate estimates of errors for trace gas retrievals, and the retrieved values improve over the initial guess for a wide range of cloud conditions. Comparisons are made between TES retrievals of ozone, temperature, and water to model fields from the Global Modeling and Assimilation Office (GMAO), temperature retrievals from the Atmospheric Infrared Sounder (AIRS), tropospheric ozone columns from the Goddard Earth Observing System (GEOS) GEOS-Chem, and ozone retrievals from the Total Ozone Mapping Spectrometer (TOMS). In each of these cases, this cloud retrieval approach does not introduce observable biases into TES retrievals.

First satellite observations of lower tropospheric ammonia and methanol

[1]xa0The Tropospheric Emission Spectrometer (TES) on the EOS Aura satellite makes global measurements of infrared radiances which are used to derive profiles of species such as O3, CO, H2O, HDO and CH4 as routine standard products. In addition, TES has a variety of special modes that provide denser spatial mapping over a limited geographical area. A continuous-coverage mode (called “transect”, about 460 km long) has now been used to detect additional molecules indicative of regional air pollution. On 10 July 2007 at about 05:37 UTC (13:24 LMST) TES conducted such a transect observation over the Beijing area in northeast China. Examination of the residual spectral radiances following the retrieval of the TES standard products revealed surprisingly strong features attributable to enhanced concentrations of ammonia (NH3) and methanol (CH3OH), well above the normal background levels. This is the first time that these molecules have been detected in space-based nadir viewing measurements that penetrate into the lower atmosphere.

Ozone-CO correlations determined by the TES satellite instrument in continental outflow regions

0.4– 1.0 mol mol � 1 and consistent with ICARTT data. The GEOS-Chem model reproduces the O3-CO enhancement ratios observed in continental outflow, but model correlations are stronger and more extensive. We show that the discrepancy can be explained by spectral measurement errors in the TES data. These errors will decrease in future data releases, which should enable TES to provide better information on O3-CO correlations. Citation: Zhang, L., et al. (2006), Ozone-CO correlations determined by the TES satellite instrument in continental outflow regions, Geophys. Res. Lett., 33, L18804, doi:10.1029/2006GL026399.

Nadir measurements of carbon monoxide distributions by the Tropospheric Emission Spectrometer instrument onboard the Aura Spacecraft: Overview of analysis approach and examples of initial results

[1]xa0We provide an overview of the nadir measurements of carbon monoxide (CO) obtained thus far by the Tropospheric Emission Spectrometer (TES). The instrument is a high resolution array Fourier transform spectrometer designed to measure infrared spectral radiances from low Earth orbit. It is one of four instruments successfully launched onboard the Aura platform into a sun synchronous orbit at an altitude of 705 km on July 15, 2004 from Vandenberg Air Force Base, California. Nadir spectra are recorded at 0.06-cm−1 spectral resolution with a nadir footprint of 5 × 8 km. We describe the TES retrieval approach for the analysis of the nadir measurements, report averaging kernels for typical tropical and polar ocean locations, characterize random and systematic errors for those locations, and describe instrument performance changes in the CO spectral region as a function of time. Sample maps of retrieved CO for the middle and upper troposphere from global surveys during December 2005 and April 2006 highlight the potential of the results for measurement and tracking of global pollution and determining air quality from space.

Tropospheric vertical distribution of tropical Atlantic ozone observed by TES during the northern African biomass burning season

[1]xa0We present vertical distributions of ozone from the Tropospheric Emission Spectrometer (TES) over the tropical Atlantic Ocean during January 2005. Between 10N and 20S, TES ozone retrievals have Degrees of Freedom for signal (DOF) around 0.7–0.8 each for tropospheric altitudes above and below 500 hPa. As a result, TES is able to capture for the first time from space a distribution characterized by two maxima: one in the lower troposphere north of the ITCZ and one in the middle and upper troposphere south of the ITCZ. We focus our analysis on the north tropical Atlantic Ocean, where most of previous satellite observations showed discrepancies with in-situ ozone observations and models. Trajectory analyses and a sensitivity study using the GEOS-Chem model confirm the influence of northern Africa biomass burning on the elevated ozone mixing ratios observed by TES over this region.

Wavefronts and construction tolerances for a cat's-eye retroreflector.

A retroreflector (a device that reflects an incident beam of light through exactly 180 degrees ) constructed from a primary concave mirror and a small secondary mirror near its paraxial focus, the so-called cats-eye retroreflector, has been investigated. Ray-tracing of systems with both spherical and parabolic primaries suggests that the latter are considerably superior to the former and comparable to a cube-corner retroreflector. The investigation has also enabled mechanical tolerances for the construction of a cats-eye retroreflector to be deduced. The predicted tolerances may be much easier to attain than those for a cube-corner retroreflector.