Articles | Volume 9, issue 9
https://doi.org/10.5194/amt-9-4279-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/amt-9-4279-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Research article
| 
05 Sep 2016
Research article |
| 05 Sep 2016
Sky camera geometric calibration using solar observations
Bryan Urquhart
Department of Mechanical and Aerospace Engineering, University of California, San Diego, USA
Ben Kurtz
Department of Mechanical and Aerospace Engineering, University of California, San Diego, USA
Department of Mechanical and Aerospace Engineering, University of California, San Diego, USA
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B. Urquhart, B. Kurtz, E. Dahlin, M. Ghonima, J. E. Shields, and J. Kleissl
Atmos. Meas. Tech., 8, 875–890, https://doi.org/10.5194/amt-8-875-2015, https://doi.org/10.5194/amt-8-875-2015, 2015
Felipe A. Mejia, Ben Kurtz, Keenan Murray, Laura M. Hinkelman, Manajit Sengupta, Yu Xie, and Jan Kleissl
Atmos. Meas. Tech., 9, 4151–4165, https://doi.org/10.5194/amt-9-4151-2016, https://doi.org/10.5194/amt-9-4151-2016, 2016
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A method for retrieving cloud optical depth using a sky imager is presented. The method is applied to images taken at the Atmospheric Radiation Measurement site and validated against measurements from a microwave radiometer (MWR), output from the Min method for overcast skies, and τc retrieved by Beer's law from direct normal irradiance (DNI) measurements.
B. Urquhart, B. Kurtz, E. Dahlin, M. Ghonima, J. E. Shields, and J. Kleissl
Atmos. Meas. Tech., 8, 875–890, https://doi.org/10.5194/amt-8-875-2015, https://doi.org/10.5194/amt-8-875-2015, 2015
S.-H. Hong, J. M. H. Hendrickx, J. Kleissl, R. G. Allen, W. G. M. Bastiaanssen, R. L. Scott, and A. L. Steinwand
Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hessd-11-13479-2014, https://doi.org/10.5194/hessd-11-13479-2014, 2014
Manuscript not accepted for further review
V. Fung, J. L. Bosch, S. W. Roberts, and J. Kleissl
Atmos. Meas. Tech., 7, 1693–1700, https://doi.org/10.5194/amt-7-1693-2014, https://doi.org/10.5194/amt-7-1693-2014, 2014
Related subject area
Subject: Clouds | Technique: Remote Sensing | Topic: Instruments and Platforms
The first microwave and submillimetre closure study using particle models of oriented ice hydrometeors to simulate polarimetric measurements of ice clouds
Polarization upgrade of specMACS: calibration and characterization of the 2D RGB polarization-resolving cameras
Detection of small drizzle droplets in a large cloud chamber using ultrahigh-resolution radar
W-band S–Z relationships for rimed snow particles: observational evidence from combined airborne and ground-based observations
The generation of EarthCARE L1 test data sets using atmospheric model data sets
The EarthCARE mission – science and system overview
Processing reflectivity and Doppler velocity from EarthCARE's cloud-profiling radar: the C-FMR, C-CD and C-APC products
3D cloud envelope and cloud development velocity from simulated CLOUD (C3IEL) stereo images
Passive ground-based remote sensing of radiation fog
Locations for the best lidar view of mid-level and high clouds
VELOX – a new thermal infrared imager for airborne remote sensing of cloud and surface properties
Above-aircraft cirrus cloud and aerosol optical depth from hyperspectral irradiances measured by a total-diffuse radiometer
Impact of second-trip echoes for space-borne high-pulse-repetition-frequency nadir-looking W-band cloud radars
Spaceborne differential absorption radar water vapor retrieval capabilities in tropical and subtropical boundary layer cloud regimes
Multifrequency radar observations of clouds and precipitation including the G-band
Can machine learning correct microwave humidity radiances for the influence of clouds?
McRALI: a Monte Carlo high-spectral-resolution lidar and Doppler radar simulator for three-dimensional cloudy atmosphere remote sensing
Cirrus cloud shape detection by tomographic extinction retrievals from infrared limb emission sounder measurements
Absolute calibration method for frequency-modulated continuous wave (FMCW) cloud radars based on corner reflectors
Evaluation of the reflectivity calibration of W-band radars based on observations in rain
A technical description of the Balloon Lidar Experiment (BOLIDE)
Application of the shipborne remote sensing supersite OCEANET for profiling of Arctic aerosols and clouds during Polarstern cruise PS106
Mind the gap – Part 2: Improving quantitative estimates of cloud and rain water path in oceanic warm rain using spaceborne radars
Ice crystal characterization in cirrus clouds II: radiometric characterization of HaloCam for the quantitative analysis of halo displays
Mind the gap – Part 1: Accurately locating warm marine boundary layer clouds and precipitation using spaceborne radars
Free-fall experiments of volcanic ash particles using a 2-D video disdrometer
Microwave Radar/radiometer for Arctic Clouds (MiRAC): first insights from the ACLOUD campaign
A robust automated technique for operational calibration of ceilometers using the integrated backscatter from totally attenuating liquid clouds
Evaluation of differential absorption radars in the 183 GHz band for profiling water vapour in ice clouds
Use of polarimetric radar measurements to constrain simulated convective cell evolution: a pilot study with Lagrangian tracking
Improvement of airborne retrievals of cloud droplet number concentration of trade wind cumulus using a synergetic approach
Halo ratio from ground-based all-sky imaging
Aircraft-based stereographic reconstruction of 3-D cloud geometry
Polarization lidar: an extended three-signal calibration approach
The NCAS mobile dual-polarisation Doppler X-band weather radar (NXPol)
Initial report on polar mesospheric cloud observations by Himawari-8
Combining cloud radar and radar wind profiler for a value added estimate of vertical air motion and particle terminal velocity within clouds
A simple biota removal algorithm for 35 GHz cloud radar measurements
Improved cloud-phase determination of low-level liquid and mixed-phase clouds by enhanced polarimetric lidar
All-sky photogrammetry techniques to georeference a cloud field
Depolarization calibration and measurements using the CANDAC Rayleigh–Mie–Raman lidar at Eureka, Canada
Ice crystal characterization in cirrus clouds: a sun-tracking camera system and automated detection algorithm for halo displays
ISMAR: an airborne submillimetre radiometer
Application of oxygen A-band equivalent width to disambiguate downwelling radiances for cloud optical depth measurement
Toward autonomous surface-based infrared remote sensing of polar clouds: cloud-height retrievals
How big is an OMI pixel?
Differential absorption radar techniques: water vapor retrievals
Design and characterization of specMACS, a multipurpose hyperspectral cloud and sky imager
A microbolometer-based far infrared radiometer to study thin ice clouds in the Arctic
Uncertainties in cloud phase and optical thickness retrievals from the Earth Polychromatic Imaging Camera (EPIC)
Karina McCusker, Anthony J. Baran, Chris Westbrook, Stuart Fox, Patrick Eriksson, Richard Cotton, Julien Delanoë, and Florian Ewald
Atmos. Meas. Tech., 17, 3533–3552, https://doi.org/10.5194/amt-17-3533-2024, https://doi.org/10.5194/amt-17-3533-2024, 2024
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Polarised radiative transfer simulations are performed using an atmospheric model based on in situ measurements. These are compared to large polarisation measurements to explore whether such measurements can provide information on cloud ice, e.g. particle shape and orientation. We find that using oriented particle models with shapes based on imagery generally allows for accurate simulations. However, results are sensitive to shape assumptions such as the choice of single crystals or aggregates.
Anna Weber, Tobias Kölling, Veronika Pörtge, Andreas Baumgartner, Clemens Rammeloo, Tobias Zinner, and Bernhard Mayer
Atmos. Meas. Tech., 17, 1419–1439, https://doi.org/10.5194/amt-17-1419-2024, https://doi.org/10.5194/amt-17-1419-2024, 2024
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In this work, we introduce the 2D RGB polarization-resolving cameras of the airborne hyperspectral and polarized imaging system specMACS. A full characterization and calibration of the cameras including a geometric calibration as well as a radiometric characterization is provided, allowing for the computation of absolute calibrated, georeferenced Stokes vectors rotated into the scattering plane. We validate the calibration by comparing sunglint measurements to radiative transfer simulations.
Zeen Zhu, Fan Yang, Pavlos Kollias, Raymond A. Shaw, Alex B. Kostinski, Steve Krueger, Katia Lamer, Nithin Allwayin, and Mariko Oue
Atmos. Meas. Tech., 17, 1133–1143, https://doi.org/10.5194/amt-17-1133-2024, https://doi.org/10.5194/amt-17-1133-2024, 2024
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In this article, we demonstrate the feasibility of applying advanced radar technology to detect liquid droplets generated in the cloud chamber. Specifically, we show that using radar with centimeter-scale resolution, single drizzle drops with a diameter larger than 40 µm can be detected. This study demonstrates the applicability of remote sensing instruments in laboratory experiments and suggests new applications of ultrahigh-resolution radar for atmospheric sensing.
Shelby Fuller, Samuel A. Marlow, Samuel Haimov, Matthew Burkhart, Kevin Shaffer, Austin Morgan, and Jefferson R. Snider
Atmos. Meas. Tech., 16, 6123–6142, https://doi.org/10.5194/amt-16-6123-2023, https://doi.org/10.5194/amt-16-6123-2023, 2023
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Snowfall rate and radar reflectivity measurements were analyzed. We confirmed that the relationship between snowfall rate and reflectivity is dependent on snow particle type. It is likely that the measured snowfall was produced by solid (ice) particles colliding with liquid cloud droplets, forming rimed snow particles. This analysis is expected to improve snowfall rate estimation based on measurements made using W-band radars.
David P. Donovan, Pavlos Kollias, Almudena Velázquez Blázquez, and Gerd-Jan van Zadelhoff
Atmos. Meas. Tech., 16, 5327–5356, https://doi.org/10.5194/amt-16-5327-2023, https://doi.org/10.5194/amt-16-5327-2023, 2023
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The Earth Cloud, Aerosol and Radiation Explorer mission (EarthCARE) is a multi-instrument cloud–aerosol–radiation-oriented satellite for climate and weather applications. For this satellite mission to be successful, the development and implementation of new techniques for turning the measured raw signals into useful data is required. This paper describes how atmospheric model data were used as the basis for creating realistic high-resolution simulated data sets to facilitate this process.
Tobias Wehr, Takuji Kubota, Georgios Tzeremes, Kotska Wallace, Hirotaka Nakatsuka, Yuichi Ohno, Rob Koopman, Stephanie Rusli, Maki Kikuchi, Michael Eisinger, Toshiyuki Tanaka, Masatoshi Taga, Patrick Deghaye, Eichi Tomita, and Dirk Bernaerts
Atmos. Meas. Tech., 16, 3581–3608, https://doi.org/10.5194/amt-16-3581-2023, https://doi.org/10.5194/amt-16-3581-2023, 2023
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The EarthCARE satellite is due for launch in 2024. It includes four scientific instruments to measure global vertical profiles of aerosols, clouds and precipitation properties together with radiative fluxes and derived heating rates. The mission's scientific requirements, the satellite and the ground segment are described. In particular, the four scientific instruments and their performance are described at the level of detail required by mission data users.
Pavlos Kollias, Bernat Puidgomènech Treserras, Alessandro Battaglia, Paloma C. Borque, and Aleksandra Tatarevic
Atmos. Meas. Tech., 16, 1901–1914, https://doi.org/10.5194/amt-16-1901-2023, https://doi.org/10.5194/amt-16-1901-2023, 2023
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The Earth Clouds, Aerosols and Radiation (EarthCARE) satellite mission developed by the European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) features the first spaceborne 94 GHz Doppler cloud-profiling radar (CPR) with Doppler capability. Here, we describe the post-processing algorithms that apply quality control and corrections to CPR measurements and derive key geophysical variables such as hydrometeor locations and best estimates of particle sedimentation fall velocities.
Paolo Dandini, Céline Cornet, Renaud Binet, Laetitia Fenouil, Vadim Holodovsky, Yoav Y. Schechner, Didier Ricard, and Daniel Rosenfeld
Atmos. Meas. Tech., 15, 6221–6242, https://doi.org/10.5194/amt-15-6221-2022, https://doi.org/10.5194/amt-15-6221-2022, 2022
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3D cloud envelope and development velocity are retrieved from realistic simulations of multi-view
CLOUD (C3IEL) images. Cloud development velocity is derived by finding matching features
between acquisitions separated by 20 s. The tie points are then mapped from image to space via 3D
reconstruction of the cloud envelope obtained from 2 simultaneous images. The retrieved cloud
topography as well as the velocities are in good agreement with the estimates obtained from the
physical models.
Heather Guy, David D. Turner, Von P. Walden, Ian M. Brooks, and Ryan R. Neely
Atmos. Meas. Tech., 15, 5095–5115, https://doi.org/10.5194/amt-15-5095-2022, https://doi.org/10.5194/amt-15-5095-2022, 2022
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Fog formation is highly sensitive to near-surface temperatures and humidity profiles. Passive remote sensing instruments can provide continuous measurements of the vertical temperature and humidity profiles and liquid water content, which can improve fog forecasts. Here we compare the performance of collocated infrared and microwave remote sensing instruments and demonstrate that the infrared instrument is especially sensitive to the onset of thin radiation fog.
Matthias Tesche and Vincent Noel
Atmos. Meas. Tech., 15, 4225–4240, https://doi.org/10.5194/amt-15-4225-2022, https://doi.org/10.5194/amt-15-4225-2022, 2022
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Mid-level and high clouds can be considered natural laboratories for studying cloud glaciation in the atmosphere. While they can be conveniently observed from ground with lidar, such measurements require a clear line of sight between the instrument and the target cloud. Here, observations of clouds with two spaceborne lidars are used to assess where ground-based lidar measurements of mid- and upper-level clouds are least affected by the light-attenuating effect of low-level clouds.
Michael Schäfer, Kevin Wolf, André Ehrlich, Christoph Hallbauer, Evelyn Jäkel, Friedhelm Jansen, Anna Elizabeth Luebke, Joshua Müller, Jakob Thoböll, Timo Röschenthaler, Bjorn Stevens, and Manfred Wendisch
Atmos. Meas. Tech., 15, 1491–1509, https://doi.org/10.5194/amt-15-1491-2022, https://doi.org/10.5194/amt-15-1491-2022, 2022
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The new airborne thermal infrared imager VELOX is introduced. It measures two-dimensional fields of spectral thermal infrared radiance or brightness temperature within the large atmospheric window. The technical specifications as well as necessary calibration and correction procedures are presented. Example measurements from the first field deployment are analysed with respect to cloud coverage and cloud top altitude.
Matthew S. Norgren, John Wood, K. Sebastian Schmidt, Bastiaan van Diedenhoven, Snorre A. Stamnes, Luke D. Ziemba, Ewan C. Crosbie, Michael A. Shook, A. Scott Kittelman, Samuel E. LeBlanc, Stephen Broccardo, Steffen Freitag, and Jeffrey S. Reid
Atmos. Meas. Tech., 15, 1373–1394, https://doi.org/10.5194/amt-15-1373-2022, https://doi.org/10.5194/amt-15-1373-2022, 2022
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A new spectral instrument (SPN-S), with the ability to partition solar radiation into direct and diffuse components, is used in airborne settings to study the optical properties of aerosols and cirrus. It is a low-cost and mechanically simple system but has higher measurement uncertainty than existing standards. This challenge is overcome by utilizing the unique measurement capabilities to develop new retrieval techniques. Validation is done with data from two NASA airborne research campaigns.
Alessandro Battaglia
Atmos. Meas. Tech., 14, 7809–7820, https://doi.org/10.5194/amt-14-7809-2021, https://doi.org/10.5194/amt-14-7809-2021, 2021
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Space-borne radar returns can be contaminated by artefacts caused by radiation that undergoes multiple scattering events and appears to originate from ranges well below the surface range. While such artefacts have been rarely observed from the currently deployed systems, they may become a concern in future cloud radar systems, potentially enhancing cloud cover high up in the troposphere via ghost returns.
Richard J. Roy, Matthew Lebsock, and Marcin J. Kurowski
Atmos. Meas. Tech., 14, 6443–6468, https://doi.org/10.5194/amt-14-6443-2021, https://doi.org/10.5194/amt-14-6443-2021, 2021
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This study describes the potential capabilities of a hypothetical spaceborne radar to observe water vapor within clouds.
Katia Lamer, Mariko Oue, Alessandro Battaglia, Richard J. Roy, Ken B. Cooper, Ranvir Dhillon, and Pavlos Kollias
Atmos. Meas. Tech., 14, 3615–3629, https://doi.org/10.5194/amt-14-3615-2021, https://doi.org/10.5194/amt-14-3615-2021, 2021
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Observations collected during the 25 February 2020 deployment of the VIPR at the Stony Brook Radar Observatory clearly demonstrate the potential of G-band radars for cloud and precipitation research. The field experiment, which coordinated an X-, Ka-, W- and G-band radar, revealed that the differential reflectivity from Ka–G band pair provides larger signals than the traditional Ka–W pairing underpinning an increased sensitivity to smaller amounts of liquid and ice water mass and sizes.
Inderpreet Kaur, Patrick Eriksson, Simon Pfreundschuh, and David Ian Duncan
Atmos. Meas. Tech., 14, 2957–2979, https://doi.org/10.5194/amt-14-2957-2021, https://doi.org/10.5194/amt-14-2957-2021, 2021
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Currently, cloud contamination in microwave humidity channels is addressed using filtering schemes. We present an approach to correct the cloud-affected microwave humidity radiances using a Bayesian machine learning technique. The technique combines orthogonal information from microwave channels to obtain a probabilistic prediction of the clear-sky radiances. With this approach, we are able to predict bias-free clear-sky radiances with well-represented case-specific uncertainty estimates.
Frédéric Szczap, Alaa Alkasem, Guillaume Mioche, Valery Shcherbakov, Céline Cornet, Julien Delanoë, Yahya Gour, Olivier Jourdan, Sandra Banson, and Edouard Bray
Atmos. Meas. Tech., 14, 199–221, https://doi.org/10.5194/amt-14-199-2021, https://doi.org/10.5194/amt-14-199-2021, 2021
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Spaceborne lidar and radar are suitable tools to investigate cloud vertical properties on a global scale. This paper presents the McRALI code that provides simulations of lidar and radar signals from the EarthCARE mission. Regarding radar signals, cloud heterogeneity induces a severe bias in velocity estimates. Regarding lidar signals, multiple scattering is not negligible. Our results also give some insight into the reliability of lidar signal modeling using independent column approximation.
Jörn Ungermann, Irene Bartolome, Sabine Griessbach, Reinhold Spang, Christian Rolf, Martina Krämer, Michael Höpfner, and Martin Riese
Atmos. Meas. Tech., 13, 7025–7045, https://doi.org/10.5194/amt-13-7025-2020, https://doi.org/10.5194/amt-13-7025-2020, 2020
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This study examines the potential of new IR limb imager instruments and tomographic methods for cloud detection purposes. Simple color-ratio-based methods are examined and compared against more involved nonlinear convex optimization. In a second part, 3-D measurements of the airborne limb sounder GLORIA taken during the Wave-driven ISentropic Exchange campaign are used to exemplarily derive the location and extent of small-scale cirrus clouds with high spatial accuracy.
Felipe Toledo, Julien Delanoë, Martial Haeffelin, Jean-Charles Dupont, Susana Jorquera, and Christophe Le Gac
Atmos. Meas. Tech., 13, 6853–6875, https://doi.org/10.5194/amt-13-6853-2020, https://doi.org/10.5194/amt-13-6853-2020, 2020
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Cloud observations are essential to rainfall, fog and climate change forecasts. One key instrument for these observations is cloud radar. Yet, discrepancies are found when comparing radars from different ground stations or satellites. Our work presents a calibration methodology for cloud radars based on reference targets, including an analysis of the uncertainty sources. The method enables the calibration of reference instruments to improve the quality and value of the cloud radar network data.
Alexander Myagkov, Stefan Kneifel, and Thomas Rose
Atmos. Meas. Tech., 13, 5799–5825, https://doi.org/10.5194/amt-13-5799-2020, https://doi.org/10.5194/amt-13-5799-2020, 2020
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This study shows two methods for evaluating the reflectivity calibration of W-band cloud radars. Both methods use natural rain as a reference target. The first method is based on spectral polarimetric observations and requires a polarimetric cloud radar with a scanner. The second method utilizes disdrometer observations and can be applied to scanning and vertically pointed radars. Both methods show consistent results and can be applied for operational monitoring of measurement quality.
Bernd Kaifler, Dimitry Rempel, Philipp Roßi, Christian Büdenbender, Natalie Kaifler, and Volodymyr Baturkin
Atmos. Meas. Tech., 13, 5681–5695, https://doi.org/10.5194/amt-13-5681-2020, https://doi.org/10.5194/amt-13-5681-2020, 2020
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The Balloon Lidar Experiment was the first lidar dedicated to measurements in the mesosphere flown on a balloon. During a 6 d flight, it made high-resolution observations of polar mesospheric clouds which form at high latitudes during summer at ~ 83 km altitude and are the highest clouds in Earth's atmosphere. We describe the instrument and assess its performance. We could detect fainter clouds with higher resolution than what is possible with ground-based instruments.
Hannes J. Griesche, Patric Seifert, Albert Ansmann, Holger Baars, Carola Barrientos Velasco, Johannes Bühl, Ronny Engelmann, Martin Radenz, Yin Zhenping, and Andreas Macke
Atmos. Meas. Tech., 13, 5335–5358, https://doi.org/10.5194/amt-13-5335-2020, https://doi.org/10.5194/amt-13-5335-2020, 2020
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In summer 2017, the research vessel Polarstern performed cruise PS106 to the Arctic north of Svalbard. In the frame of the cruise, remote-sensing observations of the atmosphere were performed on Polarstern to continuously monitor aerosol and clouds above the vessel. In our study, we present the deployed instrumentation and applied data analysis methods and provide case studies of the aerosol and cloud observations made during the cruise. Statistics of low-cloud occurrence are presented as well.
Alessandro Battaglia, Pavlos Kollias, Ranvir Dhillon, Katia Lamer, Marat Khairoutdinov, and Daniel Watters
Atmos. Meas. Tech., 13, 4865–4883, https://doi.org/10.5194/amt-13-4865-2020, https://doi.org/10.5194/amt-13-4865-2020, 2020
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Warm rain accounts for slightly more than 30 % of the total rain amount and 70 % of the total rain area in the tropical belt and usually appears in kilometer-size cells. Spaceborne radars adopting millimeter wavelengths are excellent tools for detecting such precipitation types and for separating between the cloud and rain components. Our work highlights the benefits of operating multifrequency radars and discusses the impact of antenna footprints in quantitative estimates of liquid water paths.
Linda Forster, Meinhard Seefeldner, Andreas Baumgartner, Tobias Kölling, and Bernhard Mayer
Atmos. Meas. Tech., 13, 3977–3991, https://doi.org/10.5194/amt-13-3977-2020, https://doi.org/10.5194/amt-13-3977-2020, 2020
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We present a procedure for both the geometric and absolute radiometric characterization of the weather-proof RGB camera HaloCamRAW, which is part of our automated halo observation system HaloCam, designed for the quantitative analysis of halo displays. By comparing the calibrated HaloCamRAW radiances of a 22° halo scene with radiative transfer simulations, we demonstrate the potential of developing a retrieval method for ice crystal properties, such as size, shape, and surface roughness.
Katia Lamer, Pavlos Kollias, Alessandro Battaglia, and Simon Preval
Atmos. Meas. Tech., 13, 2363–2379, https://doi.org/10.5194/amt-13-2363-2020, https://doi.org/10.5194/amt-13-2363-2020, 2020
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According to ground-based radar observations, 50 % of liquid low-level clouds over the Atlantic extend below 1.2 km and are thinner than 400 m, thus limiting their detection from space. Using an emulator, we estimate that a 250 m resolution radar would capture cloud base better than the CloudSat radar which misses about 52 %. The more sensitive EarthCARE radar is expected to capture cloud cover but stretch cloud. This calls for the operation of interlaced pulse modes for future space missions.
Sung-Ho Suh, Masayuki Maki, Masato Iguchi, Dong-In Lee, Akihiko Yamaji, and Tatsuya Momotani
Atmos. Meas. Tech., 12, 5363–5379, https://doi.org/10.5194/amt-12-5363-2019, https://doi.org/10.5194/amt-12-5363-2019, 2019
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This is a fundamental study on the features of aerodynamic parameters: terminal velocity, axis ratio, and canting angle. These are necessary for developing a quantitative ash fall estimation method based on weather radar. They were analyzed under controlled conditions from laboratory free-fall experiments, since the aerodynamic properties of the particles are highly dependent on external conditions. These results will help in the development of quantitative ash estimation.
Mario Mech, Leif-Leonard Kliesch, Andreas Anhäuser, Thomas Rose, Pavlos Kollias, and Susanne Crewell
Atmos. Meas. Tech., 12, 5019–5037, https://doi.org/10.5194/amt-12-5019-2019, https://doi.org/10.5194/amt-12-5019-2019, 2019
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An improved understanding of Arctic mixed-phase clouds and their contribution to Arctic warming can be achieved by observations from airborne platforms with remote sensing instruments. Such an instrument is MiRAC combining active and passive techniques to gain information on the distribution of clouds, the occurrence of precipitation, and the amount of liquid and ice within the cloud. Operated during a campaign in Arctic summer, it could observe lower clouds often not seen by spaceborne radars.
Emma Hopkin, Anthony J. Illingworth, Cristina Charlton-Perez, Chris D. Westbrook, and Sue Ballard
Atmos. Meas. Tech., 12, 4131–4147, https://doi.org/10.5194/amt-12-4131-2019, https://doi.org/10.5194/amt-12-4131-2019, 2019
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Ceilometers are laser cloud base recorders which retrieve information about atmospheric aerosol and differing cloud types. In order to ensure the information retrieved from the ceilometer is correct and comparable with other ceilometers in an observation network, a calibration is needed. Presented here is a novel automated calibration method, which includes a correction for the effects of water vapour in the atmosphere and shows its application on the UK Met Office's ceilometer network.
Alessandro Battaglia and Pavlos Kollias
Atmos. Meas. Tech., 12, 3335–3349, https://doi.org/10.5194/amt-12-3335-2019, https://doi.org/10.5194/amt-12-3335-2019, 2019
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This work investigates the potential of an innovative differential absorption radar for retrieving relative humidity inside ice clouds. The radar exploits the strong spectral dependence of the water vapour absorption for frequencies close to the 183 GHz water vapour band.
Results show that observations from a system with 4–6 frequencies can provide
novel information for understanding the formation and growth of ice crystals.
Ann M. Fridlind, Marcus van Lier-Walqui, Scott Collis, Scott E. Giangrande, Robert C. Jackson, Xiaowen Li, Toshihisa Matsui, Richard Orville, Mark H. Picel, Daniel Rosenfeld, Alexander Ryzhkov, Richard Weitz, and Pengfei Zhang
Atmos. Meas. Tech., 12, 2979–3000, https://doi.org/10.5194/amt-12-2979-2019, https://doi.org/10.5194/amt-12-2979-2019, 2019
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Weather radars are offering improved capabilities to investigate storm physics, which remain poorly understood. We investigate enhanced use of such data near Houston, Texas, where pollution sources often provide a convenient contrast between polluted and clean air. We conclude that Houston is a favorable location to conduct a future field campaign during June through September because isolated storms are common and tend to last an hour, allowing frequent observations of a full life cycle.
Kevin Wolf, André Ehrlich, Marek Jacob, Susanne Crewell, Martin Wirth, and Manfred Wendisch
Atmos. Meas. Tech., 12, 1635–1658, https://doi.org/10.5194/amt-12-1635-2019, https://doi.org/10.5194/amt-12-1635-2019, 2019
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Using passive spectral solar radiation and active lidar, radar, and microwave measurements with HALO during NARVAL-II, the cloud droplet number concentration of shallow trade wind cumulus is estimated. With stepwise inclusion of the different instruments into the retrieval, the benefits of the synergetic approach based on artificial measurements and two cloud cases are demonstrated. Significant improvement with the synergetic method compared to the solar-radiation-only method is reported.
Paolo Dandini, Zbigniew Ulanowski, David Campbell, and Richard Kaye
Atmos. Meas. Tech., 12, 1295–1309, https://doi.org/10.5194/amt-12-1295-2019, https://doi.org/10.5194/amt-12-1295-2019, 2019
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The halo ratio indicates the strength of the 22° cirrus halo and gives valuable information on cloud properties. We obtain it from all-sky images by applying a range of transformations and corrections and averaging brightness azimuthally over sun-centred images. The ratio is then taken at two angles from the sun, 20° and 23°, in variance from previous suggestions. While we find ratios > 1 to be linked to halos, they can also occur under scattered cumuli as artefacts due to cloud edges.
Tobias Kölling, Tobias Zinner, and Bernhard Mayer
Atmos. Meas. Tech., 12, 1155–1166, https://doi.org/10.5194/amt-12-1155-2019, https://doi.org/10.5194/amt-12-1155-2019, 2019
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Imaging technology allows us to quickly gather information on larger cloud fields. Unlike using lidar or radar, it is difficult to obtain accurate position information about the observed clouds. This work presents a method to retrieve the missing position information using RGB images from an airborne video camera. Using field campaign data, we observe and explain a median offset of 126 m compared to lidar data and show that systematic errors across the measurement swath are well below 50 m.
Cristofer Jimenez, Albert Ansmann, Ronny Engelmann, Moritz Haarig, Jörg Schmidt, and Ulla Wandinger
Atmos. Meas. Tech., 12, 1077–1093, https://doi.org/10.5194/amt-12-1077-2019, https://doi.org/10.5194/amt-12-1077-2019, 2019
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We propose an extended formalism for a full instrumental characterization of a three-channel lidar system, allowing the retrieval of highly accurate linear depolarization profiles. The results obtained at several depolarizing scenarios, the good agreement with the retrievals of a second collocated calibrated lidar system, and the long-term stability of the calibration parameters corroborate the potential and robustness of the new technique.
Ryan R. Neely III, Lindsay Bennett, Alan Blyth, Chris Collier, David Dufton, James Groves, Daniel Walker, Chris Walden, John Bradford, Barbara Brooks, Freya I. Addison, John Nicol, and Ben Pickering
Atmos. Meas. Tech., 11, 6481–6494, https://doi.org/10.5194/amt-11-6481-2018, https://doi.org/10.5194/amt-11-6481-2018, 2018
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Mobile X-band radars are widely used by atmospheric scientists to observe clouds and make estimates of rainfall. Here we describe the National Centre for Atmospheric Science's mobile X-band dual-polarisation Doppler radar (NXPol). NXPol is the first radar of its kind in the UK. To demonstrate the radar’s capabilities, we present examples of its use in three field campaigns as well as an example from ongoing observations at the National Facility for Atmospheric and Radio Research.
Takuo T. Tsuda, Yuta Hozumi, Kento Kawaura, Keisuke Hosokawa, Hidehiko Suzuki, and Takuji Nakamura
Atmos. Meas. Tech., 11, 6163–6168, https://doi.org/10.5194/amt-11-6163-2018, https://doi.org/10.5194/amt-11-6163-2018, 2018
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Polar mesospheric clouds (PMCs) or noctilucent clouds (NLCs) are the highest clouds in the Earth's atmosphere. In this paper, we introduce new PMC observations by the Japanese Geostationary Earth Orbit (GEO) meteorological satellite Himawari-8, which was launched in October 2014.
Martin Radenz, Johannes Bühl, Volker Lehmann, Ulrich Görsdorf, and Ronny Leinweber
Atmos. Meas. Tech., 11, 5925–5940, https://doi.org/10.5194/amt-11-5925-2018, https://doi.org/10.5194/amt-11-5925-2018, 2018
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Ultra-high-frequency radar wind profilers are widely used for remote sensing of horizontal and vertical wind velocity. They emit electromagnetic radiation at a wavelength of 60 cm and receive signals from both falling particles and the air itself. In this paper, we describe a method to separate both signal components with the help of an additional cloud radar system in order to come up with undisturbed measurements of both vertical air velocity and the fall velocity of particles.
Madhu Chandra R. Kalapureddy, Patra Sukanya, Subrata K. Das, Sachin M. Deshpande, Govindan Pandithurai, Andrew L. Pazamany, Jha Ambuj K., Kaustav Chakravarty, Prasad Kalekar, Hari Krishna Devisetty, and Sreenivas Annam
Atmos. Meas. Tech., 11, 1417–1436, https://doi.org/10.5194/amt-11-1417-2018, https://doi.org/10.5194/amt-11-1417-2018, 2018
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A new technique to separate cloud and non-hydrometeor returns from a cloud radar high-resolution reflectivity measurements is proposed. The TEST algorithm potentially identifies cloud height with the theoretical echo sensitivity curves and observed echo statistics for the cloud height tracing. TEST is more robust in identifying and filtering out the biota contributions by constraining further with spectral width and LDR measurements. This algorithm improves the monsoon cloud characterization.
Robert A. Stillwell, Ryan R. Neely III, Jeffrey P. Thayer, Matthew D. Shupe, and David D. Turner
Atmos. Meas. Tech., 11, 835–859, https://doi.org/10.5194/amt-11-835-2018, https://doi.org/10.5194/amt-11-835-2018, 2018
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This work focuses on making unambiguous measurements of Arctic cloud phase and assessing those measurements within the context of cloud radiative effects. It is found that effects related to lidar data recording systems can cause retrieval ambiguities that alter the interpretation of cloud phase in as much as 30 % of the available data. This misinterpretation of cloud-phase data can cause a misinterpretation of the effect of cloud phase on the surface radiation budget by as much as 10 to 30 %.
Pierre Crispel and Gregory Roberts
Atmos. Meas. Tech., 11, 593–609, https://doi.org/10.5194/amt-11-593-2018, https://doi.org/10.5194/amt-11-593-2018, 2018
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In this study, we use an all-sky stereo camera network to perform geolocation of individual elements of a cloud field in order to track individual clouds and estimate some of their morphological characteristics and their evolution in time. Furthermore, this allows use of cloud geolocation for cloud airborne measurements. For example, in the case of instrumented UAVs, the GPS coordinates of the target cloud may be communicated in real time to the autopilot.
Emily M. McCullough, Robert J. Sica, James R. Drummond, Graeme Nott, Christopher Perro, Colin P. Thackray, Jason Hopper, Jonathan Doyle, Thomas J. Duck, and Kaley A. Walker
Atmos. Meas. Tech., 10, 4253–4277, https://doi.org/10.5194/amt-10-4253-2017, https://doi.org/10.5194/amt-10-4253-2017, 2017
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CRL lidar in the Canadian High Arctic uses lasers and a telescope to study polar clouds, essential for understanding the changing global climate. Hardware added to CRL allows it to measure the polarization of returned laser light, indicating whether cloud particles are liquid or frozen. Calibrations show that traditional analysis methods work well, although CRL was not originally set up to make this type of measurement. CRL can now measure cloud particle phase every 5 min, every 37.5 m, 24h/day.
Linda Forster, Meinhard Seefeldner, Matthias Wiegner, and Bernhard Mayer
Atmos. Meas. Tech., 10, 2499–2516, https://doi.org/10.5194/amt-10-2499-2017, https://doi.org/10.5194/amt-10-2499-2017, 2017
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Halo displays are produced by scattering of sunlight by smooth, hexagonal ice crystals. Consequently, the presence of a halo should contain information on particle shape. This study presents HaloCam, a novel sun-tracking camera system, and an automated detection algorithm to collect and evaluate long-term halo observations. Two-year HaloCam observations revealed that about 25 % of the detected cirrus clouds occurred together with a 22° halo indicating the presence of smooth, hexagonal crystals.
Stuart Fox, Clare Lee, Brian Moyna, Martin Philipp, Ian Rule, Stuart Rogers, Robert King, Matthew Oldfield, Simon Rea, Manju Henry, Hui Wang, and R. Chawn Harlow
Atmos. Meas. Tech., 10, 477–490, https://doi.org/10.5194/amt-10-477-2017, https://doi.org/10.5194/amt-10-477-2017, 2017
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In this paper we present the ISMAR instrument, a new airborne submillimetre radiometer designed for cloud ice remote sensing. We discuss the instrument calibration and evaluate the main sources of bias and the radiometric sensitivity in different measurement scenarios. We also compare clear-sky zenith measurements from high altitude with radiative transfer simulations to demonstrate the performance of ISMAR in flight.
Edward R. Niple, Herman E. Scott, John A. Conant, Stephen H. Jones, Frank J. Iannarilli, and Wellesley E. Pereira
Atmos. Meas. Tech., 9, 4167–4179, https://doi.org/10.5194/amt-9-4167-2016, https://doi.org/10.5194/amt-9-4167-2016, 2016
Penny M. Rowe, Christopher J. Cox, and Von P. Walden
Atmos. Meas. Tech., 9, 3641–3659, https://doi.org/10.5194/amt-9-3641-2016, https://doi.org/10.5194/amt-9-3641-2016, 2016
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Clouds play an important role in the rapid climate change occurring in polar regions, yet cloud measurements are challenging in such harsh, remote environments. Here we explore how well a proposed low-power infrared spectrometer, which would be highly portable, could be used to determine cloud height. Using simulated data, we estimate retrieval accuracy, finding that such an instrument would be able to constrain cloud height, particular for low, thick clouds, which are common in polar region.
Martin de Graaf, Holger Sihler, Lieuwe G. Tilstra, and Piet Stammes
Atmos. Meas. Tech., 9, 3607–3618, https://doi.org/10.5194/amt-9-3607-2016, https://doi.org/10.5194/amt-9-3607-2016, 2016
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The shapes and sizes of the FoV from the OMI satellite instrument were determined with extensive lab tests but never verified after launch. Here, collocated measurements from MODIS, flying in formation, were used to find the most optimal shape of the OMI FoV. This shape is not quadrangular, as suggested by the provided corner coordinates of a pixel, but rather super-Gaussian shaped and overlapping with the FoV of neighbouring pixels.
Luis Millán, Matthew Lebsock, Nathaniel Livesey, and Simone Tanelli
Atmos. Meas. Tech., 9, 2633–2646, https://doi.org/10.5194/amt-9-2633-2016, https://doi.org/10.5194/amt-9-2633-2016, 2016
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We discuss the theoretical capabilities of a radar technique to measure profiles of water vapor in cloudy/precipitating areas. The method uses two radar pulses at different frequencies near the 183 GHz H2O absorption line to determine water vapor profiles by measuring the differential absorption on and off the line. Results of inverting synthetic data assuming a satellite radar are presented.
Florian Ewald, Tobias Kölling, Andreas Baumgartner, Tobias Zinner, and Bernhard Mayer
Atmos. Meas. Tech., 9, 2015–2042, https://doi.org/10.5194/amt-9-2015-2016, https://doi.org/10.5194/amt-9-2015-2016, 2016
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The new spectrometer of the Munich Aerosol Cloud Scanner (specMACS) is a
multipurpose hyperspectral cloud and sky imager which is designated, but not limited, to investigations of cloud-aerosol interactions in Earth's atmosphere. This paper describes the specMACS instrument's hardware and software design and
characterizes the instrument performance. Initial measurements of cloud sides are presented which demonstrate the wide applicability of the instrument.
Quentin Libois, Christian Proulx, Liviu Ivanescu, Laurence Coursol, Ludovick S. Pelletier, Yacine Bouzid, Francesco Barbero, Éric Girard, and Jean-Pierre Blanchet
Atmos. Meas. Tech., 9, 1817–1832, https://doi.org/10.5194/amt-9-1817-2016, https://doi.org/10.5194/amt-9-1817-2016, 2016
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Here we present a radiometer, FIRR, aimed at measuring atmospheric radiation in the far infrared, an underexplored region of the Earth spectrum. The FIRR is a prototype for the planned TICFIRE satellite mission dedicated to studying thin ice clouds in polar regions. Preliminary in situ measurements compare well with radiative transfer simulations. This highlights the high sensitivity of the FIRR to water vapor content and cloud physical properties, paving the way for new retrieval algorithms.
Kerry Meyer, Yuekui Yang, and Steven Platnick
Atmos. Meas. Tech., 9, 1785–1797, https://doi.org/10.5194/amt-9-1785-2016, https://doi.org/10.5194/amt-9-1785-2016, 2016
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This paper presents the expected uncertainties of a single-channel cloud opacity retrieval technique and a temperature-based cloud phase approach in support of the Deep Space Climate Observatory (DSCOVR) mission; DSCOVR cloud products will be derived from Earth Polychromatic Imaging Camera (EPIC) observations. Results show that, for ice clouds, retrieval errors are minimal (< 2 %), while for liquid clouds the error is limited to within 10 %, although for thin clouds the error can be higher.
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Short summary
A model relating the position of objects in the 3-D world to their pixel coordinates has been developed for a fixed-focal length fisheye lens camera. An associated automated method to calibrate model parameters has been developed for a daytime skyward-pointing camera. The position of the sun throughout the day is used as input to the calibration algorithm. The accuracy of the calibration was found to be on the same order as the accuracy of sun position detection in an image.
A model relating the position of objects in the 3-D world to their pixel coordinates has been...
