Atmospheric tools

Earth Observation monitoring of atmospheric composition requires a diverse range of research tools to extract the maximum amount of information from the measurements.

Retrievals of atmospheric composition from these satellite observations crucially rely on our ability to accurately simulate the atmospheric spectra measured by these instruments. The principal tool used to simulate these observations is an atmospheric radiative transfer model, so-called because it solves the fundamental equation of radiative transfer through the atmosphere. These models require high quality spectroscopic data for all molecules absorbing and emitting in the atmosphere. In fact,

it is the distinctive spectral signature of a molecule that indicates its presence in the atmosphere, and can be used to quantify its abundance. The retrieval process itself essentially compares calculated with observed spectra to improve upon our prior knowledge of the atmospheric state vector (vertical distribution of temperature, pressure, molecular species, etc.) by minimising the residuals between observation and calculation.

Atmospheric Spectroscopy

CCl4 cross sections

26 PT sets over the spectral range 700–860 cm-1 (208–296 K and 7.5-760 Torr).

Contact: Jeremy Harrison (University of Leicester)

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HCFC-22 cross sections

30 PT sets over the spectral range 730–1380 cm-1 (191–295 K and 7.5 –762 Torr).

Contact: Jeremy Harrison (University of Leicester)

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CFC-12 cross sections

32 PT sets over the spectral range 800-1270 cm-1 (190-294 K and 7.5-761 Torr).

Contact: Jeremy Harrison (University of Leicester)

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HFC-134a cross sections

27 PT sets over the spectral range 750-1600 cm-1 (191-296 K and 22-761 Torr).

Contact: Jeremy Harrison (University of Leicester)

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HFC-23 cross sections

27 PT sets over the spectral range 950-1500 cm-1 (188-294 K and 23-762 Torr).

Contact: Jeremy Harrison (University of Leicester)

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Methanol cross sections

12 PT sets over the spectral range 2600-3250 cm-1 (204-296 K and 51-761 Torr).

Contact: Jeremy Harrison (University of Leicester)

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Methanol cross sections

12 PT sets over the spectral range 877-1167 cm-1 (204-295 K and 50-761 Torr).

Contact: Jeremy Harrison (University of Leicester)

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Acetonitrile cross sections

12 PT sets over the spectral range 880-1700 cm-1 (203-297 K and 50-760 Torr).

Contact: Jeremy Harrison (University of Leicester)

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Acetone cross sections

12 PT sets over the spectral range 2615-3300 cm-1 (195-296 K and 49-759 Torr).

Contact: Jeremy Harrison (University of Leicester)

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Acetone cross sections

19 PT sets over the spectral range 830-1950 cm-1 (194-298 K and 50-700 Torr).

Contact: Jeremy Harrison (University of Leicester)

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HITRAN

The most widely used spectroscopic database for atmospheric remote sensing is HITRAN (HIgh-resolution TRANsmission). The spectroscopic line parameters, based on the Voigt lineshape profile, can be obtained from the HITRAN website. The Total Internal Partition Function (TIPS) program, distributed with the database, is required for the temperature dependence of the line intensities. HITRAN also contains a number of absorption cross-section datasets for larger molecules, whose spectra consist of an abundance of densely packed lines. NERC/NCEO-funded absorption cross-section datasets can be downloaded from this website.

Contact: Jeremy Harrison (University of Leicester)

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Propane Cross Sections

12 PT sets over the spectral range 2540-3300 cm-1 (195-296 K and 40-763 Torr).

Contact: Jeremy Harrison (University of Leicester)

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Ethane Cross Sections

14 PT sets over the spectral range 2545-3315 cm-1 (194-297 K and 49-763 Torr).

Contact: Jeremy Harrison (University of Leicester)

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Atmospheric Modelling Tools

TOMCAT/SLIMCAT

A 3D off-line chemical transport model that uses winds and temperatures from meteorological analyses (e.g. from the UK Met Office or ECMWF) to specify the atmospheric transport and temperatures and calculates the abundances of chemical species in the troposphere and stratosphere.

NCEO contact: Martyn Chipperfield (University of Leeds).

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GEOS-Chem

A global 3D chemical transport model for atmospheric composition driven by meteorological input from the Goddard Earth Observing System (GEOS) of the NASA Global Modeling and Assimilation Office.

NCEO contact: Paul Palmer (University of Edinburgh).

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ESA PyOSSE - Package for Observation System Simulation Experiments

Observation System Simulation Experiments (OSSE) are a cost-effective numerical approach to realistically describe space-borne measurements and to evaluate their impact on current knowledge as part of preparing a science case for a particular space-borne mission; in our example experiment we quantify the impact of atmospheric measurements of a trace gas on improving our current prior understanding of surface fluxes (emission minus uptake) of that gas.

Contact: Liang Feng (University of Edinburgh)

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Atmospheric Radiative Transfer Models

Reference Forward Model (RFM)

The RFM is a line-by-line radiative transfer model. RFM maintenance and development is currently supported by NCEO. Extensive online documentation can be found on the Reference Forward Model website. Download the source code here.

Contact: Anu Dudhia (University of Oxford)

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RTTOV

RTTOV is a very fast radiative transfer model for nadir-viewing applications. The source code can be obtained from the dedicated RTTOV website.

Contact: Richard Siddans (Science and Technology Facilities Council)

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