Optimal Configuration of a Far‐Infrared Radiometer to Study the Arctic Winter Atmosphere

Abstract. A far infrared radiometer (FIRR) dedicated to measure radiation emitted by clear and cloudy atmospheres was developed as a breadboard for the Thin Ice Clouds in Far InfraRed Experiment (TICFIRE) satellite project. The FIRR detector is an array of 80×60 uncooled microbolometers coated with gold black to enhance the absorptivity and responsivity. A ﬁlter wheel is used to select atmospheric radiation in 9 spectral bands ranging from 8 to 50 µm. Calibrated radiances are obtained using two well-calibrated blackbodies. Images are acquired at a frame rate of 120 Hz, and temporally averaged to reduce electronic noise. A complete measurements sequence takes about 120 seconds. With a ﬁeld-of view of 6°, the FIRR is not intended to be an imager. Hence spatial average is computed over 193 illuminated pixels to increase the signal-to-noise ratio and consequently the detector resolution. This results in an improvement by a factor of 5 compared to individual pixel measurements. Another threefold increase in resolution is obtained using 193 non-illuminated pixels to remove correlated electronic noise, leading an overall resolution of approximately 0.015 W m–2 sr–1. Laboratory measurements performed on well known targets suggest an absolute accuracy close to 0.02 W m–2 sr–1, which ensures to retrieve atmospheric radiance with an accuracy better than 1%. Preliminary in situ experiments performed from the ground in winter and in summer on clear and cloudy atmospheres are compared to radiative transfer simulations. They point out the FIRR ability to detect clouds and changes in relative humidity of a few percent in various atmospheric conditions, paving the way for the development of new algorithms dedicated to ice cloud characterization and water vapor retrieval.

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A microbolometer-based far infrared radiometer to study thin ice clouds in the Arctic

Atmospheric Measurement Techniques ◽

10.5194/amt-9-1817-2016 ◽

2016 ◽

Vol 9 (4) ◽

pp. 1817-1832 ◽

Cited By ~ 9

Author(s):

Quentin Libois ◽

Christian Proulx ◽

Liviu Ivanescu ◽

Laurence Coursol ◽

Ludovick S. Pelletier ◽

...

Keyword(s):

Far Infrared ◽

Frame Rate ◽

The Arctic ◽

Spatial Average ◽

Electronic Noise ◽

Atmospheric Conditions ◽

Ice Clouds ◽

Detector Resolution ◽

In Situ Experiments ◽

Infrared Radiometer

Abstract. A far infrared radiometer (FIRR) dedicated to measuring radiation emitted by clear and cloudy atmospheres was developed in the framework of the Thin Ice Clouds in Far InfraRed Experiment (TICFIRE) technology demonstration satellite project. The FIRR detector is an array of 80 × 60 uncooled microbolometers coated with gold black to enhance the absorptivity and responsivity. A filter wheel is used to select atmospheric radiation in nine spectral bands ranging from 8 to 50 µm. Calibrated radiances are obtained using two well-calibrated blackbodies. Images are acquired at a frame rate of 120 Hz, and temporally averaged to reduce electronic noise. A complete measurement sequence takes about 120 s. With a field of view of 6°, the FIRR is not intended to be an imager. Hence spatial average is computed over 193 illuminated pixels to increase the signal-to-noise ratio and consequently the detector resolution. This results in an improvement by a factor of 5 compared to individual pixel measurements. Another threefold increase in resolution is obtained using 193 non-illuminated pixels to remove correlated electronic noise, leading an overall resolution of approximately 0.015 W m−2 sr−1. Laboratory measurements performed on well-known targets suggest an absolute accuracy close to 0.02 W m−2 sr−1, which ensures atmospheric radiance is retrieved with an accuracy better than 1 %. Preliminary in situ experiments performed from the ground in winter and in summer on clear and cloudy atmospheres are compared to radiative transfer simulations. They point out the FIRR ability to detect clouds and changes in relative humidity of a few percent in various atmospheric conditions, paving the way for the development of new algorithms dedicated to ice cloud characterization and water vapor retrieval.

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Far-infrared radiometer to map OH in the middle atmosphere

10.2514/6.1985-3007 ◽

1985 ◽

Author(s):

I. NOLT ◽

J. RADOSTITZ ◽

K.V. CHANCE ◽

W. TRAUB ◽

P. ADE

Keyword(s):

Middle Atmosphere ◽

Far Infrared ◽

Infrared Radiometer

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A well-written description of a novel far-infrared radiometer, but some questions remain

10.5194/amt-2015-379-rc2 ◽

2016 ◽

Author(s):

Anonymous

Keyword(s):

Far Infrared ◽

Written Description ◽

Infrared Radiometer

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Airborne observations of far-infrared upwelling radiance in the Arctic

10.5194/acp-2016-724 ◽

2016 ◽

Cited By ~ 1

Author(s):

Quentin Libois ◽

Liviu Ivanescu ◽

Jean-Pierre Blanchet ◽

Hannes Schulz ◽

Heiko Bozem ◽

...

Keyword(s):

Strong Dependence ◽

Temperature Stability ◽

Far Infrared ◽

Temperature Inversion ◽

Specific Humidity ◽

The Arctic ◽

Ice Clouds ◽

Airborne Measurements ◽

Cloud Properties ◽

Arctic Atmosphere

Abstract. The first airborne measurements of the Far-InfraRed Radiometer (FIRR) were performed in April 2015 during the panarctic NETCARE campaign. Vertical profiles of spectral upwelling radiance in the range 8–50 μm were measured in clear and cloudy conditions from the surface up to 6 km. The clear-sky profiles highlight the strong dependence of radiative fluxes to the temperature inversion typical of the Arctic. Measurements acquired for total column water vapor from 1.5 to 10.5 mm also underline the sensitivity of the far-infrared greenhouse effect to specific humidity. The cloudy cases show that optically thin ice clouds increase the cooling rate of the atmosphere by a factor up to three, making them important pieces of the Arctic energy balance. One such cloud exhibited a very complex spatial structure, characterized by large horizontal heterogeneities at the kilometre-scale. This emphasizes the difficulty to obtain representative cloud observations with airborne measurements, but also points out how challenging it is to model polar clouds radiative effects. These radiance measurements were successfully compared to simulations, suggesting that state-of-the-art radiative transfer models are suited to study the cold and dry Arctic atmosphere. Although FIRR in situ performances compare well to its laboratory performances, complementary simulations show that upgrading the FIRR radiometric resolution would greatly increase its sensitivity to atmospheric and cloud properties. Improved instrument temperature stability in flight and expected technological progress should help meet this objective. The campaign overall highlights the potential for airborne far-infrared radiometry and constitutes a relevant reference for future similar studies dedicated to the Arctic, and for the development of spaceborne instruments.

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The fog/low stratus clouds in the Arctic: detection with multispectral satellite imagery

10.5194/egusphere-egu2020-10867 ◽

2020 ◽

Author(s):

Daria Tatsii ◽

Natalia Fedoseeva

Keyword(s):

Satellite Imagery ◽

Complex Structure ◽

Far Infrared ◽

The Arctic ◽

Underlying Surface ◽

Polar Regions ◽

Stratus Clouds ◽

Spectral Bands ◽

Multispectral Satellite Imagery ◽

Important Challenge

&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; The safe operation of aviation and shipping, particularly in areas of insufficient coverage of automatic meteorological stations in the Arctic requires accurate interpretation of satellite images. Operational detection of fog and low stratus clouds and recognizing of them on the background of snow and ice cover and cloudiness of the upper layer is very important challenge.&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; &#160;The verified images obtained by Aqua and Terra satellites with a scanning radiometer MODIS, which operates in 36 spectral bands, with wavelengths from 0.4 &#181;m to 14.4 &#181;m, were collected.&#160; With the Beam VISAT 5.0 software, which was designed to work with satellite data in raster format, thematic digital techniques of satellite multispectral information, based on difference in the values of the integral brightness of the images, both in optical and far-infrared ranges of the spectrum, have been developed. &#160;These techniques, models of additive color synthesis, improve the quality of interpretation of fogs and low stratus clouds in terms of the complex structure of cloudiness and underlying surface in polar regions. Developed RGB combinations, which are based on the selected MODIS bands are:<ol><li>RGB (1.6 &#181;m; 0.8 &#181;m; 0.6 &#181;m)</li> <li>RGB (0.8 &#181;m; 3.9-8.7 &#181;m; 10.8 &#181;m)</li> <li>RGB (0.8 &#181;m; 1.6 &#181;m; 3.9-8.7 &#181;m)</li> <li>RGB ((0-12)-(0-11) &#181;m, (0-11)-(0-3.8) &#181;m, (0-11) &#181;m)</li> </ol>&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; Analysis of the obtained images has shown that the developed models of color synthesis help to distinguish the fog/low stratus clouds under different conditions of cloudiness and underlying surface accurately.Key words: remote sensing, satellite imagery, additive color synthesis, fog, low stratus clouds, polar regions

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Superfluid-Helium-Cooled Rocket-Borne Far-Infrared Radiometer

Applied Optics ◽

10.1364/ao.10.001043 ◽

1971 ◽

Vol 10 (5) ◽

pp. 1043 ◽

Cited By ~ 6

Author(s):

A. G. Blair ◽

F. Edeskuty ◽

R. D. Hiebert ◽

D. M. Jones ◽

J. P. Shipley ◽

...

Keyword(s):

Superfluid Helium ◽

Far Infrared ◽

Infrared Radiometer

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Simultaneous retrieval of water vapour and temperature profiles and cirrus clouds properties from measurements of far infrared spectral radiance over the Antarctic Plateau

10.5194/amt-2016-181 ◽

2016 ◽

Author(s):

Gianluca Di Natale ◽

Luca Palchetti ◽

Giovanni Bianchini ◽

Massimo Del Guasta

Keyword(s):

Radiative Transfer ◽

Water Vapour ◽

Far Infrared ◽

Cirrus Clouds ◽

The Arctic ◽

Spectral Radiance ◽

Temperature Profiles ◽

Ice Clouds ◽

Antarctic Plateau ◽

Ice Water

Abstract. The possibility to discriminate the contribution of the atmosphere and ice clouds by using spectral infrared measurements is a fundamental step to quantify the cloud effect in the climate models. The simultaneous retrieval of clouds and atmospheric parameters allows to take into account the possible correlations between the variables. In this paper we describe the development of a routine able to perform the simultaneous retrieval and its application to the analysis of the spectral measurements acquired by the REFIR-PAD (Radiation Explorer Far Infrared – Prototype for Applications and Development) spectroradiometer, operative from Antarctic Plateau since 2012. This routine is able to operate the retrieval with reduced computing time comparable with the REFIR-PAD data acquisition time. The analysis allowed to retrieve the water vapour and temperature profiles and the clouds optical and micro-physical properties, such as the generalised effective diameter (Dge) and the ice water path (IWP), by exploiting the spectral band between 230–980 cm−1. To simulate the radiative transfer, the LBLRTM (Line By Line Radiative Transfer Model) was integrated with a specific code based on the delta-Eddington two-stream approximation, and further the cirrus clouds single scattering properties were derived from a database for hexagonal column habits. In order to identify the ice clouds a back-scattering and depolarisation lidar was available on the site and allowed to infer the position and the cloud thickness used in the simulations. A climatology of the vertical profiles of water vapour and temperature, was performed by using the daily radiosounding available at the base and it was used to build the a priori and initial guess profiles used in the fitting routine. An optimal estimation method with a Levenberg-Marquardt approach was applied to perform the retrieval. The comparison of results with radiosoundings demonstrates that the retrieved atmospheric state is not disturbed by the clouds presence. Finally, the retrieved clouds parameters were compared with the statistical correlation between the cloud temperature (Tc) and the optical depth measured in Antarctica at Dumond D'Urville and the effective diameters with the ice water content (IWC) obtained in the Arctic region finding a general agreement.

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