Cloud phase identification of Arctic boundary-layer clouds from airborne spectral reflection measurements: test of three approaches

Ehrlich, André; Bierwirth, Eike; Wendisch, Manfred; Gayet, J.-F.; Mioche, Guillaume; Lampert, Astrid; Heintzenberg, Jost

doi:10.5194/acp-8-7493-2008

Cited by 72 publications

(82 citation statements)

References 46 publications

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“…Ten HALO research flights from Barbados are envisioned, each with a duration of 9 h bracketing two 4-h flights of the ATR-42 (with a refuelling in between). (Wirth et al 2009) SMART Up-and downward-looking spectral (300-2200 nm) radiance and irradiance measurements (Wendisch et al 2001;Ehrlich et al 2008) SpecMACS Downward-looking hyper-spectral (400-2500 nm) line imager Thermal imager Downward-looking (10.8 and 12 lm) two channel line imager (in development) Dropsondes AVAPs system with four-channel receiver supporting Vaisala RD94 Sondes (ten channel receiver in development)…”

Section: Aircraft Measurementsmentioning

confidence: 99%

EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation

et al. 2017

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Trade-wind cumuli constitute the cloud type with the highest frequency of occurrence on Earth, and it has been shown that their sensitivity to changing environmental conditions will critically influence the magnitude and pace of future global warming. Research over the last decade has pointed out the importance of the interplay between clouds, convection and circulation in controling this sensitivity. 123Surv Geophys (2017) 38:1529-1568 https://doi.org/10.1007/s10712-017-9428-0 cumuli at cloud base is very sensitive to changes in environmental conditions, while process models suggest the opposite. To understand and resolve this contradiction, we propose to organize a field campaign aimed at quantifying the physical properties of tradecumuli (e.g., cloud fraction and water content) as a function of the large-scale environment. Beyond a better understanding of clouds-circulation coupling processes, the campaign will provide a reference data set that may be used as a benchmark for advancing the modelling and the satellite remote sensing of clouds and circulation. It will also be an opportunity for complementary investigations such as evaluating model convective parameterizations or studying the role of ocean mesoscale eddies in air-sea interactions and convective organization.

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Section: Aircraft Measurementsmentioning

confidence: 99%

EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation

et al. 2017

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“…Cloud thermodynamic phase affects radiative forcing by modulating absorption of incoming solar radiation, particle evolution, and lifetime (Ehrlich et al, 2008;. Previous satellite observational studies have shown that clouds are shifting poleward in the northern and southern hemispheric extratropical storm tracks (Bender et al, 2012;Marvel et al, 2015;Norris et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Global spectroscopic survey of cloud thermodynamic phase at high spatial resolution, 2005–2015

et al. 2018

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Abstract. The distribution of ice, liquid, and mixed phase clouds is important for Earth's planetary radiation budget, impacting cloud optical properties, evolution, and solar reflectivity. Most remote orbital thermodynamic phase measurements observe kilometer scales and are insensitive to mixed phases. This under-constrains important processes with outsize radiative forcing impact, such as spatial partitioning in mixed phase clouds. To date, the fine spatial structure of cloud phase has not been measured at global scales. Imaging spectroscopy of reflected solar energy from 1.4 to 1.8 µm can address this gap: it directly measures ice and water absorption, a robust indicator of cloud top thermodynamic phase, with spatial resolution of tens to hundreds of meters. We report the first such global high spatial resolution survey based on data from 2005 to 2015 acquired by the Hyperion imaging spectrometer onboard NASA's Earth Observer 1 (EO-1) spacecraft. Seasonal and latitudinal distributions corroborate observations by the Atmospheric Infrared Sounder (AIRS). For extratropical cloud systems, just 25 % of variance observed at GCM grid scales of 100 km was related to irreducible measurement error, while 75 % was explained by spatial correlations possible at finer resolutions.

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“…During these missions, a suite of different active and passive remote sensing instruments was operated on board HALO, including passive solar radiance measurements by SMART Ehrlich et al, 2008) and the mini-DOAS (Hüneke, 2016). While SMART measured radiometrically calibrated radiance I N S in the nadir direction, the mini-DOAS instrument simultaneously measures in the nadir and varying sideward viewing directions in UV/VIS/IR wavelength ranges.…”

Section: Airborne Measurementsmentioning

confidence: 99%

“…The system is extensively described in Wendisch et al (2001) and Ehrlich et al (2008). In this paper the focus is on I N S measurements which are available for the four HALO missions introduced above.…”

Section: The Smart Instrumentmentioning

confidence: 99%

Potential of remote sensing of cirrus optical thickness by airborne spectral radiance measurements at different sideward viewing angles

et al. 2017

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Abstract. Spectral radiance measurements collected in nadir and sideward viewing directions by two airborne passive solar remote sensing instruments, the Spectral Modular Airborne Radiation measurement sysTem (SMART) and the Differential Optical Absorption Spectrometer (mini-DOAS), are used to compare the remote sensing results of cirrus optical thickness τ . The comparison is based on a sensitivity study using radiative transfer simulations (RTS) and on data obtained during three airborne field campaigns: the North Atlantic Rainfall VALidation (NARVAL) mission, the MidLatitude Cirrus Experiment (ML-CIRRUS) and the Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems (ACRIDICON) campaign. Radiative transfer simulations are used to quantify the sensitivity of measured upward radiance I with respect to τ , ice crystal effective radius r eff , viewing angle of the sensor θ V , spectral surface albedo α, and ice crystal shape. From the calculations it is concluded that sideward viewing measurements are generally better suited than radiance data from the nadir direction to retrieve τ of optically thin cirrus, especially at wavelengths larger than λ = 900 nm. Using sideward instead of nadir-directed spectral radiance measurements significantly improves the sensitivity and accuracy in retrieving τ , in particular for optically thin cirrus of τ ≤ 2.The comparison of retrievals of τ based on nadir and sideward viewing radiance measurements from SMART, mini-DOAS and independent estimates of τ from an additional active remote sensing instrument, the Water Vapor Lidar Experiment in Space (WALES), shows general agreement within the range of measurement uncertainties. For the selected example a mean τ of 0.54 ± 0.2 is derived from SMART, and 0.49 ± 0.2 by mini-DOAS nadir channels, while WALES obtained a mean value of τ = 0.32 ± 0.02 at 532 nm wavelength, respectively. The mean of τ derived from the sideward viewing mini-DOAS channels is 0.26 ± 0.2. For the few simultaneous measurements, the mini-DOAS sideward channel measurements systematically underestimate (−17.6 %) the nadir observations from SMART and mini-DOAS. The agreement between mini-DOAS sideward viewing channels and WALES is better, showing the advantage of using sideward viewing measurements for cloud remote sensing for τ ≤ 1. Therefore, we suggest sideward viewing measurements for retrievals of τ of thin cirrus because of the significantly enhanced capability of sideward viewing compared to nadir measurements.

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Cloud phase identification of Arctic boundary-layer clouds from airborne spectral reflection measurements: test of three approaches

Cited by 72 publications

References 46 publications

EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation

EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation

Global spectroscopic survey of cloud thermodynamic phase at high spatial resolution, 2005–2015

Potential of remote sensing of cirrus optical thickness by airborne spectral radiance measurements at different sideward viewing angles

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