The foreign-continuum absorption of water vapour in the far-infrared (50–500 cm−1)

We present a new derivation of the foreign-broadened water vapour continuum in the far-infrared (far-IR) pure rotation band between 24 μm and 120 μm (85–420 cm −1 ) from field data collected in flight campaigns of the Continuum Absorption by Visible and IR radiation and Atmospheric Relevance (CAVIAR) project with Imperial College's Tropospheric Airborne Fourier Transform Spectrometer (TAFTS) far-IR spectro-radiometer instrument onboard the Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft; and compare this new derivation with those recently published in the literature in this spectral band. This new dataset validates the current Mlawer–Tobin-Clough–Kneizys–Davies (MT-CKD) 2.5 model parametrization above 300 cm −1 , but indicates the need to strengthen the parametrization below 300 cm −1 , by up to 50 per cent at 100 cm −1 . Data recorded at a number of flight altitudes have allowed measurements within a wide range of column water vapour environments, greatly increasing the sensitivity of this analysis to the continuum strength.

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Spectral composition of the water vapour self-continuum absorption within 2.7 and 6.25 µm bands

Journal of Quantitative Spectroscopy and Radiative Transfer ◽

10.1016/j.jqsrt.2019.02.024 ◽

2019 ◽

Vol 228 ◽

pp. 97-105 ◽

Cited By ~ 7

Author(s):

Igor V. Ptashnik ◽

Tatyana E. Klimeshina ◽

Alexander A. Solodov ◽

Andrey A. Vigasin

Keyword(s):

Water Vapour ◽

Spectral Composition ◽

Continuum Absorption

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Development and recent evaluation of the MT_CKD model of continuum absorption

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2011.0295 ◽

2012 ◽

Vol 370 (1968) ◽

pp. 2520-2556 ◽

Cited By ~ 202

Author(s):

Eli J. Mlawer ◽

Vivienne H. Payne ◽

Jean-Luc Moncet ◽

Jennifer S. Delamere ◽

Matthew J. Alvarado ◽

...

Keyword(s):

Water Vapour ◽

Line Shape ◽

Mathematical Formulation ◽

Field Measurements ◽

Continuum Absorption ◽

Semi Empirical ◽

Vapour Molecule ◽

Primary Agent ◽

The Continuum

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).

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Remote sounding of atmospheric temperature from satellites IV. The selective chopper radiometer for Nimbus 5

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1973.0085 ◽

1973 ◽

Vol 334 (1597) ◽

pp. 149-170 ◽

Cited By ~ 43

Keyword(s):

Water Vapour ◽

Near Infrared ◽

Far Infrared ◽

Atmospheric Temperature ◽

Horizontal Resolution ◽

Ice Clouds ◽

New Instrument ◽

Remote Sounding ◽

Complete Set ◽

High Clouds

An improved version of the selective chopper radiometer which has successfully flown for three years on the Nimbus 4 satellite has been built for the Nimbus 5 satellite which was launched in December 1972. The new instrument has 16 channels, eight of which observe emission from the 15 μm band of carbon dioxide for remote temperature sounding, two observe emission from water-vapour and ice clouds in the far infrared, one observes emission from low atmospheric water-vapour, three are in spectral regions where the atmosphere is substantially transparent, i.e. window regions, and two observe reflected sunlight from high clouds near to 2.7 μm in the near infrared. The horizontal resolution of the instrument is about 25 km and a complete set of measurements is made every 4 s. The design, construction and calibration of the instrument are described.

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Interpretation of the water vapour continuum absorption spectra in 0.94 and 1.13 micron bands taking into account the contribution from intermediate line wings

24th International Symposium on Atmospheric and Ocean Optics: Atmospheric Physics ◽

10.1117/12.2504190 ◽

2018 ◽

Author(s):

Anna Simonova ◽

Igor V. Ptashnik

Keyword(s):

Water Vapour ◽

Absorption Spectra ◽

Continuum Absorption

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FORUM Earth Explorer 9: Characteristics of Level 2 Products and Synergies with IASI-NG

Remote Sensing ◽

10.3390/rs12091496 ◽

2020 ◽

Vol 12 (9) ◽

pp. 1496

Author(s):

Marco Ridolfi ◽

Samuele Del Bianco ◽

Alessio Di Roma ◽

Elisa Castelli ◽

Claudio Belotti ◽

...

Keyword(s):

Water Vapour ◽

Far Infrared ◽

Spectral Emissivity ◽

Spectral Radiance ◽

Calibration Error ◽

Water Path ◽

Cloud Parameters ◽

Ice Water Path ◽

Ice Water ◽

Level 2

FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) has been approved to be the ninth Earth Explorer mission of the European Space Agency. The mission is scheduled for launch on a Polar satellite in the 2025–2026 time frame. The core FORUM instrument is a Fourier Transform Spectrometer measuring, with very high accuracy, the upwelling spectral radiance, from 100 to 1600 cm − 1 (from 100 to 6.25 microns in wavelength), thus covering the Far-Infrared (FIR), and a Mid-Infrared (MIR) portion of the spectrum emitted by the Earth. FORUM will fly in loose formation with the MetOp-SG-1A satellite, hosting the Infrared Atmospheric Sounding Interferometer – New Generation (IASI-NG). IASI-NG will measure only the MIR part of the upwelling atmospheric spectrum, from 645 to 2760 cm − 1 (from 15.5 to 3.62 microns in wavelength), thus, the matching FORUM measurements will supply the missing FIR complement. Together, the two missions will provide, for the first time, a spectrally resolved measurement of the full Earth emitted thermal spectrum. The calibrated spectral radiance will be, on its own, the main product of the FORUM mission, however, the radiances will also be processed up to Level 2, to determine the vertical profile of water vapour, surface spectral emissivity and cloud parameters in the case of cloudy atmospheres. In this paper we assess the performance of the FORUM Level 2 products based on clear-sky simulated retrievals and we study how the FORUM and IASI-NG matching measurements can be fused in a synergistic retrieval scheme, to provide improved Level 2 products. Considering only the measurement noise and the systematic calibration error components, we find the following figures for the synergistic FORUM and IASI-NG retrieval products. In the upper troposphere/lower stratosphere region, individual water vapour profiles can be retrieved with 1 km vertical sampling and an error ranging from 10% to 15%. In the range from 300 to 600 cm − 1 , surface spectral emissivity can be retrieved with an absolute error as small as 0.001 in dry Polar atmospheres. Ice cloud parameters such as ice water path and cloud top height can be retrieved with errors smaller than 10% and 1 km, respectively, for ice water path values ranging from 0.2 to 60 g/m 2 .

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Application of φ-IASI to IASI: retrieval products evaluation and radiative transfer consistency

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-8771-2009 ◽

2009 ◽

Vol 9 (22) ◽

pp. 8771-8783 ◽

Cited By ~ 30

Author(s):

G. Masiello ◽

C. Serio ◽

A. Carissimo ◽

G. Grieco ◽

M. Matricardi

Keyword(s):

Water Vapour ◽

Forward Model ◽

Continuum Absorption ◽

Weather Forecasts ◽

Time Profiles ◽

Spectral Residual ◽

Atmospheric Sounding ◽

Medium Range ◽

Temperature Water

Abstract. Retrieval products for temperature, water vapour and ozone have been obtained from spectral radiances measured by the Infrared Atmospheric Sounding Interferometer flying onboard the first European Meteorological Operational satellite. These products have been used to check the consistency of the forward model and its accuracy and the expected retrieval performance. The study has been carried out using a research-oriented forward-inverse methodology, called φ-IASI, that the authors have specifically developed for the new sounding interferometer. The performance of the forward-inversion strategy has been assessed by comparing the retrieved profiles to profiles of temperature, water vapour and ozone obtained by co-locating in space and time profiles from radiosonde observations and from the European Centre for Medium-Range Weather Forecasts analysis. Spectral residuals have also been computed and analyzed to assess the quality of the forward model. Two versions of the high-resolution transmission molecular absorption database have been used, which mostly differ for ozone absorption line parameters, line and continuum absorption of both CO2 and H2O molecules. Their performance has been assessed by inter-comparing the results, and a consistent improvement in the spectral residual has been found when using the most updated release.

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