TICFIRE: a far infrared payload to monitor the evolution of thin ice clouds

Blanchet, Jean‐Pierre; Royer, A.; Châteauneuf, François; Bouzid, Yacine; Blanchard, Yann; Hamel, Jean‐François; Lafontaine, Jean de; Gauthier, Pierre; O’Neill, Norman T.; Pancrati, Ovidiu; Garand, Louis

doi:10.1117/12.898577

Cited by 12 publications

(11 citation statements)

References 8 publications

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“…The Turner (2005) method was also employed at Eureka (Nunavut, Canada) to retrieve cloud optical depth and cloud microphysical parameters from AERI spectra acquired between (Cox et al, 2014. A proposed satellite-based instrument, with the goal of characterizing thin ice clouds in the Arctic using far and thermal infrared channels (Blanchet et al, 2011), was recently tested during an airborne campaign in the High Arctic (Libois et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry

et al. 2017

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Abstract. Multiband downwelling thermal measurements of zenith sky radiance, along with cloud boundary heights, were used in a retrieval algorithm to estimate cloud optical depth and effective particle diameter of thin ice clouds in the Canadian High Arctic. Ground-based thermal infrared (IR) radiances for 150 semitransparent ice clouds cases were acquired at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80 • N, 86 • W). We analyzed and quantified the sensitivity of downwelling thermal radiance to several cloud parameters including optical depth, effective particle diameter and shape, water vapor content, cloud geometric thickness and cloud base altitude. A lookup table retrieval method was used to successfully extract, through an optimal estimation method, cloud optical depth up to a maximum value of 2.6 and to separate thin ice clouds into two classes: (1) TIC1 clouds characterized by small crystals (effective particle diameter ≤ 30 µm), and (2) TIC2 clouds characterized by large ice crystals (effective particle diameter > 30 µm). The retrieval technique was validated using data from the Arctic High Spectral Resolution Lidar (AHSRL) and Millimeter Wave Cloud Radar (MMCR). Inversions were performed over three polar winters and results showed a significant correlation (R 2 = 0.95) for cloud optical depth retrievals and an overall accuracy of 83 % for the classification of TIC1 and TIC2 clouds. A partial validation relative to an algorithm based on high spectral resolution downwelling IR radiance measurements between 8 and 21 µm was also performed. It confirms the robustness of the optical depth retrieval and the fact that the broadband thermal radiometer retrieval was sensitive to small particle (TIC1) sizes.

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Section: Introductionmentioning

confidence: 99%

Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry

et al. 2017

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“…Radiometers essentially trade spectral resolution for radiometric resolution. This is the route chosen for the TICFIRE project (Thin Ice Clouds in the Far‐InfraRed Experiment) [ Blanchet et al , ; Libois et al , ], which consists of a filter wheel IR imager with channels spanning the whole IR range from 8 to 50 μm. This mission, currently under review at the Canadian Space Agency, will be dedicated to the observation of ice clouds in the polar regions and can be viewed as a FIR extension of MODIS.…”

Section: Introductionmentioning

confidence: 99%

Added value of far‐infrared radiometry for remote sensing of ice clouds

Libois

Blanchet

2017

JGR Atmospheres

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Several cloud retrieval algorithms based on satellite observations in the infrared have been developed in the last decades. However, these observations only cover the midinfrared (MIR, λ < 15 μm) part of the spectrum, and none are available in the far‐infrared (FIR, λ≥ 15 μm). Using the optimal estimation method, we show that adding a few FIR channels to existing spaceborne radiometers would significantly improve their ability to retrieve ice cloud radiative properties. For clouds encountered in the polar regions and the upper troposphere, where the atmosphere is sufficiently transparent in the FIR, using FIR channels would reduce by more than 50% the uncertainties on retrieved values of optical thickness, effective particle diameter, and cloud top altitude. Notably, this would extend the range of applicability of current retrieval methods to the polar regions and to clouds with large optical thickness, where MIR algorithms perform poorly. The high performance of solar reflection‐based algorithms would thus be reached in nighttime conditions. Since the sensitivity of ice cloud thermal emission to effective particle diameter is approximately 5 times larger in the FIR than in the MIR, using FIR observations is a promising venue for studying ice cloud microphysics and precipitation processes. This is highly relevant for cirrus clouds and convective towers. This is also essential to study precipitation in the driest regions of the atmosphere, where strong feedbacks are at play between clouds and water vapor. The deployment in the near future of a FIR spaceborne radiometer is technologically feasible and should be strongly supported.

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“…Like cirrus at midlatitudes (Cox et al, 2010;Maestri et al, 2014), ice clouds encountered in the Arctic significantly affect the atmosphere radiative budget in the FIR, especially because they can fill the whole troposphere (Grenier et al, 2009). In very dry conditions, they act as particularly efficient emitters that radiatively cool the atmosphere (Blanchet et al, 2011). Unlike the tropics, such ice cloud layers occur at any altitude, from the ground to the stratosphere (polar stratospheric clouds).…”

Section: Introductionmentioning

confidence: 99%

“…The FIR range includes the strongly absorbing pure rotation band of water vapour and coincides with a maximum in the water vapour continuum strength (Shine et al, 2012). As such, it is especially promising for remote sensing of water vapour in the coldest regions of the atmosphere, that is the upper troposphere and the stratosphere Shahabadi and Huang, 2014), and the polar regions in general Blanchet et al, 2011;Palchetti et al, 2015). The emission maximum of Planck's function shifts towards the FIR with decreasing temperature, so that increasingly more energy is emitted from this spectral region compared to the more widely used 6.7 µm vibrational-rotational band .…”

Section: Introductionmentioning

confidence: 99%

“…For this reason, most measurements taken with the Far-InfraRed Radiometer (FIRR; Libois et al, 2016) during the campaign consisted of vertical profiles of upwelling radiance from the surface up to about 6 km. The FIRR was developed as a technology demonstrator for the Thin Ice Clouds in Far-InfraRed Experiment (TICFIRE; Blanchet et al, 2011) satellite mission, the primary focus of which is on the water cycle in the Arctic, and ice clouds in particular. Like cirrus at midlatitudes (Cox et al, 2010;Maestri et al, 2014), ice clouds encountered in the Arctic significantly affect the atmosphere radiative budget in the FIR, especially because they can fill the whole troposphere (Grenier et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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Airborne observations of far-infrared upwelling radiance in the Arctic

Libois¹,

Ivanescu

Blanchet³

et al. 2016

Atmos. Chem. Phys.

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Abstract. The first airborne measurements of the FarInfraRed 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 vapour 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, 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 of obtaining 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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TICFIRE: a far infrared payload to monitor the evolution of thin ice clouds

Cited by 12 publications

References 8 publications

Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry

Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry

Added value of far‐infrared radiometry for remote sensing of ice clouds

Airborne observations of far-infrared upwelling radiance in the Arctic

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