Comparison of retrieved noctilucent cloud particle properties from Odin tomography scans and model simulations

Megner, Linda; Christensen, Ole Martin; Karlsson, Bodil; Benze, S.; Fomichev, V. I.

doi:10.5194/acp-16-15135-2016

Cited by 9 publications

(6 citation statements)

References 47 publications

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“…Moreover, the study by Megner et al (2016) suggested that the tomographic algorithm performs well for retrieving number density for small number densities (which usually occur lower in the cloud) but greatly underestimates it for high number densities (which usually occur higher up in the clouds, where the retrieval misses the smaller mode radius).…”

Section: Discussion Of Osiris Tomography Uncertaintiesmentioning

confidence: 99%

“…To overcome the limitation from the assumption of a spatially homogeneous cloud layer and to enable the retrieval of clouds as a function of actual height instead of tangent height, the application of a two-dimensional tomographic retrieval for OSIRIS has been presented by Hultgren et al (2013). The tomographic approach for OSIRIS retrievals (described in Section 2) provides a tool to study both vertical and horizontal variations of cloud microphysical properties on a local scale, which is useful for detailed studies of cloud growth and destruction (Christensen et al, 2016;Megner et al, 2016). An early attempt to apply a direct (tomographic) retrieval for a limb viewing instrument was investigated almost two decades ago.…”

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confidence: 99%

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Common volume satellite studies of polar mesospheric clouds with Odin/OSIRIS tomography and AIM/CIPS nadir imaging

Broman¹,

Benze²,

Gumbel³

et al. 2019

Preprint

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Abstract. Two important approaches for satellite studies of Polar Mesospheric Clouds (PMC) are nadir measurements adapting phase function analysis and limb measurements adapting spectroscopic analysis. Combining both approaches enables new studies of cloud structures and microphysical processes but is complicated by differences in scattering conditions, observation geometry, and sensitivity. In this study, we compare common volume PMC observations from the nadir viewing Cloud Imaging and Particle Size instrument (CIPS) on the AIM satellite and a special set of tomographic limb observations from the Optical Spectrograph and InfraRed Imager System (OSIRIS) on the Odin satellite. While CIPS provides preeminent horizontal resolution, the OSIRIS tomographic analysis provides combined horizontal and vertical PMC information. This first direct comparison is an important step towards co-analyzing CIPS and OSIRIS data, aiming at unprecedented insights into horizontal and vertical cloud processes. We perform the first thorough error characterization of OSIRIS tomographic cloud brightness and cloud ice. We establish a consistent method for comparing cloud properties from limb tomography and nadir observations, accounting for differences in scattering conditions, resolution and sensitivity. Based on an extensive common volume, and a temporal coincidence criterion of only 5 minutes, our method enables a detailed comparison of PMC regions of varying brightness and ice content. We find that the primary OSIRIS tomography product, cloud scattering coefficient, shows very good agreement with the primary CIPS product, cloud albedo with a correlation coefficient of 0.96. However, OSIRIS systematically reports brighter clouds than CIPS and the bias between the instruments (OSIRIS &#8211; CIPS) is 3.4e&#8722;6&#8201;sr&#8722;1 (&#177;2.9e&#8722;6&#8201;sr&#8722;1) on average. The OSIRIS tomography ice mass density agrees well with the CIPS ice water content, with a correlation coefficient of 0.91. However, the ice water content reported by OSIRIS is lower than CIPS, and we quantify the bias to &#8722;22&#8201;g&#8201;km&#8722;2 (&#177;14&#8201;g&#8201;km&#8722;2) on average.

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Section: Discussion Of Osiris Tomography Uncertaintiesmentioning

confidence: 99%

mentioning

confidence: 99%

Common volume satellite studies of polar mesospheric clouds with Odin/OSIRIS tomography and AIM/CIPS nadir imaging

Broman¹,

Benze²,

Gumbel³

et al. 2019

Preprint

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“…The Swedish-led Odin satellite (Murtagh et al, 2002) was launched on 20 February 2001, into an almost Sunsynchronous polar orbit at 600 km with ascending node near 18:00 local solar time. The Odin mission began as a joint project between aeronomy and astronomy, with the primary focus of the aeronomic part of the mission on coupling processes in the atmosphere, better understanding of ozone variation and processes in the middle atmosphere, and processes that govern PMC formation and mesospheric variability.…”

Section: Odin Osirismentioning

confidence: 99%

“…As a consequence, the PMC retrieval cannot separate low-lying clouds from clouds in the foreground or in the background. The PMC retrieval for the limb-viewing Optical Spectrograph and Infrared Imager System (OSIRIS) on the Odin satellite (Murtagh et al, 2002) assumes that the PMC layer is spatially homogeneous along the instrument line of sight (LOS) for the normal limb scans. This assumption is clearly a simplification, and numerous observations from nadir-viewing satellites, lidar and ground-based cameras (e.g.…”

Section: Introductionmentioning

confidence: 99%

Common volume satellite studies of polar mesospheric clouds with Odin/OSIRIS tomography and AIM/CIPS nadir imaging

et al. 2019

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Abstract. Two important approaches for satellite studies of polar mesospheric clouds (PMCs) are nadir measurements adapting phase function analysis and limb measurements adapting spectroscopic analysis. Combining both approaches enables new studies of cloud structures and microphysical processes but is complicated by differences in scattering conditions, observation geometry and sensitivity. In this study, we compare common volume PMC observations from the nadir-viewing Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) satellite and a special set of tomographic limb observations from the Optical Spectrograph and InfraRed Imager System (OSIRIS) on the Odin satellite performed over 18 d for the years 2010 and 2011 and the latitude range 78 to 80∘ N. While CIPS provides preeminent horizontal resolution, the OSIRIS tomographic analysis provides combined horizontal and vertical PMC information. This first direct comparison is an important step towards co-analysing CIPS and OSIRIS data, aiming at unprecedented insights into horizontal and vertical cloud processes. Important scientific questions on how the PMC life cycle is affected by changes in humidity and temperature due to atmospheric gravity waves, planetary waves and tides can be addressed by combining PMC observations in multiple dimensions. Two- and three-dimensional cloud structures simultaneously observed by CIPS and tomographic OSIRIS provide a useful tool for studies of cloud growth and sublimation. Moreover, the combined CIPS/tomographic OSIRIS dataset can be used for studies of even more fundamental character, such as the question of the assumption of the PMC particle size distribution. We perform the first thorough error characterization of OSIRIS tomographic cloud brightness and cloud ice water content (IWC). We establish a consistent method for comparing cloud properties from limb tomography and nadir observations, accounting for differences in scattering conditions, resolution and sensitivity. Based on an extensive common volume and a temporal coincidence criterion of only 5 min, our method enables a detailed comparison of PMC regions of varying brightness and IWC. However, since the dataset is limited to 18 d of observations this study does not include a comparison of cloud frequency. The cloud properties of the OSIRIS tomographic dataset are vertically resolved, while the cloud properties of the CIPS dataset is vertically integrated. To make these different quantities comparable, the OSIRIS tomographic cloud properties cloud scattering coefficient and ice mass density (IMD) have been integrated over the vertical extent of the cloud to form cloud albedo and IWC of the same quantity as CIPS cloud products. We find that the OSIRIS albedo (obtained from the vertical integration of the primary OSIRIS tomography product, cloud scattering coefficient) shows very good agreement with the primary CIPS product, cloud albedo, with a correlation coefficient of 0.96. However, OSIRIS systematically reports brighter clouds than CIPS and the bias between the instruments (OSIRIS – CIPS) is 3.4×10-6 sr−1 (±2.9×10-6 sr−1) on average. The OSIRIS tomography IWC (obtained from the vertical integration of IMD) agrees well with the CIPS IWC, with a correlation coefficient of 0.91. However, the IWC reported by OSIRIS is lower than CIPS, and we quantify the bias to −22 g km−2 (±14 g km−2) on average.

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“…The vertical structure of the NLC is strongly determined by the microphysics that governs cloud growth and sedimentation (Rapp and Thomas, 2006). The tomography will provide detailed insights in this vertical NLC evolution, including its possible modification by wave activity (Hultgren and Gumbel, 2014;Megner et al, 2016;Gao et al, 2018). However, since the vertical structure of the narrow NLC layers is dominated by microphysics rather than dynamical processes, a retrieval of vertical wavelengths of gravity waves will not be feasible from the NLC data.…”

Section: Measurement Conceptsmentioning

confidence: 99%

The MATS Satellite Mission – Gravity Waves Studies by Mesospheric Airglow/Aerosol Tomography and Spectroscopy

Gumbel¹,

Megner²,

Christensen³

et al. 2018

Preprint

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Abstract. Global three-dimensional data are a key to understanding gravity wave interactions in the mesosphere and lower thermosphere. MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a new Swedish satellite mission that addresses this need. It applies space-borne limb imaging in combination with tomographic and spectroscopic analysis to obtain gravity wave data on relevant spatial scales. Primary measurement targets are O2 Atmospheric Band dayglow and nightglow in the near infrared, and sunlight scattered from noctilucent clouds in the ultraviolet. While tomography provides horizontally and vertically resolved data, spectroscopy allows analysis in terms of mesospheric temperature, composition, and cloud properties. Based on these dynamical tracers, MATS will produce a climatology on wave spectra during a 2-year mission. Major scientific objectives concern a characterization of gravity waves and their interactions in the mesosphere and lower thermosphere, as well as their relationship to dynamical conditions in the lower and upper atmosphere. MATS is currently being prepared for launch in 2019. This paper provides an overview over scientific goals, measurement concepts, instruments, and analysis ideas.

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Comparison of retrieved noctilucent cloud particle properties from Odin tomography scans and model simulations

Cited by 9 publications

References 47 publications

Common volume satellite studies of polar mesospheric clouds with Odin/OSIRIS tomography and AIM/CIPS nadir imaging

Common volume satellite studies of polar mesospheric clouds with Odin/OSIRIS tomography and AIM/CIPS nadir imaging

Common volume satellite studies of polar mesospheric clouds with Odin/OSIRIS tomography and AIM/CIPS nadir imaging

The MATS Satellite Mission – Gravity Waves Studies by Mesospheric Airglow/Aerosol Tomography and Spectroscopy

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