Study of polar thin ice clouds and aerosols seen by CloudSat and CALIPSO during midwinter 2007

Grenier, Patrick; Blanchet, Jean‐Pierre; Muñoz‐Alpizar, Rodrigo

doi:10.1029/2008jd010927

Cited by 53 publications

(77 citation statements)

References 47 publications

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“…The D eff ranges employed to define TIC1/TIC2 particles, for the averaging carried out in the creation of Fig. 2c, were, as in Grenier et al (2009), roughly based on their nondetectability to detectability threshold in radar backscatter returns.…”

Section: Sensitivity Of Thermal Infrared Radiometry To Thin Ice Cloudsmentioning

confidence: 99%

“…Thin ice cloud classification was carried out by Grenier et al (2009) using the active techniques of lidar and radar: CALIPSO and CloudSat data were employed to discriminate between TIC1 and TIC2 ice clouds using the CloudSat smallparticle sensitivity minimum of approximately 30-40 µm. In this study, we seek to demonstrate that TIC1 and TIC2 discrimination can be determined using zenith-looking IR radiance measurements acquired at the Eureka observatory in the Canadian High Arctic.…”

Section: Classification and Parameterization Of Thin Ice Cloudsmentioning

confidence: 99%

“…Inasmuch as ice particle size is difficult to retrieve from IR radiometry, the D eff component of our retrievals will be focused on a simple discrimination of large and small crystal sizes. This approach was motivated by previously published research that indicated such a discrimination would play a key role in characterizing an important aerosol-cloud interaction process in polar winter, namely precipitative cooling (see, for example, Blanchet and Girard, 1994;Grenier et al, 2009). An important aspect in this paper is that our COD and D eff retrievals will be validated using independent lidar and radar retrievals.…”

Section: Introductionmentioning

confidence: 99%

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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: Sensitivity Of Thermal Infrared Radiometry To Thin Ice Cloudsmentioning

confidence: 99%

Section: Classification and Parameterization Of Thin Ice Cloudsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…TIC-2A are topped by a substantial layer of very small (radar-unseen) ice crystals (TIC-1). In contrast, TIC-2B are not overlaided by TIC-1 (Grenier et al, 2009;Grenier and Blanchet, 2010). In this paper, TIC-1 and TIC-2A are not differentiated and therefore will be identified as TIC-1/2A.…”

Section: Introductionmentioning

confidence: 99%

“…The joint detection characteristics of both CloudSat radar and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar recently reveal the existence of two types of ice clouds (TICs) in the Arctic during the polar night and early spring (Grenier et al, 2009;Grenier and Blanchet, 2010). The type refers to the number of active instruments detecting the cloud; ice clouds of type 1 (TIC-1) are only seen by the lidar whereas ice clouds of type 2 (TIC-2) are seen by both the lidar and the radar.…”

Section: Introductionmentioning

confidence: 99%

On the relationship between Arctic ice clouds and polluted air masses over the North Slope of Alaska in April 2008

et al. 2014

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Abstract. Recently, two types of ice clouds (TICs) properties have been characterized using the Indirect and SemiDirect Aerosol Campaign (ISDAC) airborne measurements (Alaska, April 2008). TIC-2B were characterized by fewer (< 10 L −1 ) and larger (> 110 µm) ice crystals, and a larger ice supersaturation (> 15 %) compared to TIC-1/2A. It has been hypothesized that emissions of SO 2 may reduce the ice nucleating properties of ice nuclei (IN) through acidification, resulting in a smaller concentration of larger ice crystals and leading to precipitation (e.g., cloud regime TIC-2B). Here, the origin of air masses forming the ISDAC TIC-1/2A (1 April 2008) and TIC-2B (15 April 2008) is investigated using trajectory tools and satellite data. Results show that the synoptic conditions favor air masses transport from three potential SO 2 emission sources into Alaska: eastern China and Siberia where anthropogenic and biomass burning emissions, respectively, are produced, and the volcanic region of the Kamchatka/Aleutians. Weather conditions allow the accumulation of pollutants from eastern China and Siberia over Alaska, most probably with the contribution of acidic volcanic aerosol during the TIC-2B period. Observation Monitoring Instrument (OMI) satellite observations reveal that SO 2 concentrations in air masses forming the TIC-2B were larger than in air masses forming the TIC-1/2A. Airborne measurements show high acidity near the TIC-2B flight where humidity was low. These results support the hypothesis that acidic coating on IN could be at the origin of the formation of TIC-2B.

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Polar clouds and radiation in satellite observations, reanalyses, and climate models

Lenaerts

Tricht

Lhermitte

et al. 2017

Geophysical Research Letters

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Clouds play a pivotal role in the surface energy budget of the polar regions. Here we use two largely independent data sets of cloud and surface downwelling radiation observations derived by satellite remote sensing (2007–2010) to evaluate simulated clouds and radiation over both polar ice sheets and oceans in state‐of‐the‐art atmospheric reanalyses (ERA‐Interim and Modern Era Retrospective‐Analysis for Research and Applications‐2) and the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate model ensemble. First, we show that, compared to Clouds and the Earth's Radiant Energy System‐Energy Balanced and Filled, CloudSat‐CALIPSO better represents cloud liquid and ice water path over high latitudes, owing to its recent explicit determination of cloud phase that will be part of its new R05 release. The reanalyses and climate models disagree widely on the amount of cloud liquid and ice in the polar regions. Compared to the observations, we find significant but inconsistent biases in the model simulations of cloud liquid and ice water, as well as in the downwelling radiation components. The CMIP5 models display a wide range of cloud characteristics of the polar regions, especially with regard to cloud liquid water, limiting the representativeness of the multimodel mean. A few CMIP5 models (CNRM, GISS, GFDL, and IPSL_CM5b) clearly outperform the others, which enhances credibility in their projected future cloud and radiation changes over high latitudes. Given the rapid changes in polar regions and global feedbacks involved, future climate model developments should target improved representation of polar clouds. To that end, remote sensing observations are crucial, in spite of large remaining observational uncertainties, which is evidenced by the substantial differences between the two data sets.

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Study of polar thin ice clouds and aerosols seen by CloudSat and CALIPSO during midwinter 2007

Cited by 53 publications

References 47 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

On the relationship between Arctic ice clouds and polluted air masses over the North Slope of Alaska in April 2008

Polar clouds and radiation in satellite observations, reanalyses, and climate models

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