Ice cloud imager instrument for MetOp Second Generation

Kangas, V.; D’Addio, Salvatore; Klein, Ulf; Loiselet, M.; Mason, G. R.; Orlhac, J.-C.; Gonzalez, R.; Bergada, M.; Brandt, M.; Thomas, B.

doi:10.1109/microrad.2014.6878946

Cited by 26 publications

(15 citation statements)

References 4 publications

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“…ongoing development and application of ground-based instrumentation in particular for multi-frequency radar Doppler spectra measurements, airborne active/passive instrument packages and satellite measurements which will be further extended into the sub-millimeter range, i.e by the Ice Cloud Imager (ICI; Kangas et al, 2014) including channels up to 664 GHz.…”

Section: Summary and Future Perspectivesmentioning

confidence: 99%

PAMTRA 1.0: A Passive and Active Microwave radiative TRAnsfer tool for simulating radiometer and radar measurements of the cloudy atmosphere

Mech¹,

Maahn²,

Kneifel³

et al. 2020

Preprint

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Abstract. Forward models are a key tool to generate synthetic observations given the knowledge of the atmospheric state. In this way they are an integral part of inversion algorithms that aim to retrieve geophysical variables from observations or in data assimilation. Their application for the exploitation of the full information content of remote sensing observations becomes increasingly important when these are used to evaluate the performance of cloud resolving models (CRMs). Herein, CRMs profiles or fields provide the input to the forward model whose simulation results are subsequently compared to the observations. This paper introduces the freely available comprehensive microwave forward model PAMTRA (Passive and Active Microwave TRAnsfer), demonstrates its capabilities to simulate passive and active measurements across the microwave spectral region for up- and downward looking geometries, and illustrates how the forward simulations can be used to evaluate CRMs and to interpret measurements to improve our understanding of cloud processes. PAMTRA is unique as it treats passive and active radiative transfer (RT) in a consistent way with the passive forward model providing up- and down-welling polarized brightness temperatures and radiances for arbitrary observation angles. The active part is capable of simulating the full radar Doppler spectrum and its moments. PAMTRA is designed to be flexible with respect to instrument specifications, interfaces to many different formats of in- and output type, especially CRMs, spanning the range from bin-resolved microphysical output to one- and two-moment schemes, and to in situ measured hydrometeor properties. A specific highlight is the incorporation of the self-similar Rayleigh--Gans Approximation (SSRGA) both for active and passive applications which becomes especially important for the investigation of frozen hydrometeors.

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Section: Summary and Future Perspectivesmentioning

confidence: 99%

PAMTRA 1.0: A Passive and Active Microwave radiative TRAnsfer tool for simulating radiometer and radar measurements of the cloudy atmosphere

Mech¹,

Maahn²,

Kneifel³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…This can be best seen for the outermost 183±7.5 GHz and the window channel at 243 GHz. This channel is of particular interest as it will also be flown on the Ice Cloud Imager (ICI; Kangas et al, 2014) onboard of MetOP-SG to be launched in 2023. Scattering by ice particles strongly increases with increasing frequency and therefore a brightness temperature depression can occur.…”

Section: Case Studymentioning

confidence: 99%

Microwave Radar/radiometer for Arctic Clouds MiRAC: First insights from the ACLOUD campaign

Mech¹,

Kliesch²,

Anhäuser³

et al. 2019

Preprint

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Abstract. The Microwave Radar/radiometer for Arctic Clouds (MiRAC) is a novel instrument package developed to study the vertical structure and characteristics of clouds and precipitation onboard the Polar 5 research aircraft. MiRAC combines a frequency modulated continuous wave (FMCW) radar at 94 GHz including a 89 GHz passive channel (MiRAC-A) and an eight channel radiometer with frequencies between 175 and 340 GHz (MiRAC-P). The radar can be flexibly operated using different chirp sequences to provide measurements of the equivalent radar reflectivity with different vertical resolution down to 5 m. MiRAC is mounted for down-looking geometry on Polar 5 to enable the synergy with lidar and radiation measurements. To mitigate the influence of the strong surface backscatter the radar is mounted with an inclination of about 25° backward in a belly pod under the Polar 5 aircraft. Procedures for filtering ground return and range side-lobes have been developed. MiRAC-P frequencies are especially adopted for low humidity conditions typical for the Arctic to provide information on water vapor and hydrometeor content. MiRAC has been operated on 19 research flights during the ACLOUD campaign in the vicinity of Svalbard in May/June 2017 providing in total 48 hours of measurements from flight altitudes > 2300 m. The radar measurements have been carefully quality controlled and corrected for surface clutter, mounting of the instrument, and aircraft orientation to provide measurements on a unified, geo-referenced vertical grid allowing the combination with the other nadir pointing instruments. An intercomparison with CloudSat shows good agreement in terms of cloud top height of 1.5 km and radar reflectivity up to −5 dBz and demonstrates that MiRAC is able to fill the gap in observing low level clouds with its more than ten times higher vertical resolution down to about 150 m above the surface. This is especially important for the Arctic as about 45 % of the clouds during ACLOUD showed cloud tops below 1200 m, i.e., the blind zone of CloudSat.

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“…The ICI is a conical scanning millimeter‐/submillimeter‐wave radiometer that is being developed for the Meteorological Operation Second Generation (MetOp‐SG) mission (Kangas et al, ). It will provide continuity and enhancement of operational meteorological observations from 2020 to 2040.…”

Section: Ice Cloud Imagermentioning

confidence: 99%

Ensemble Optimization Retrieval Algorithm of Hydrometeor Profiles for the Ice Cloud Imager Submillimeter‐Wave Radiometer

et al. 2018

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In this paper, we propose an ensemble optimization algorithm to retrieve the hydrometeor profiles for the upcoming Ice Cloud Imager submillimeter‐wave radiometer. The algorithm combines the database approach with local optimization under a framework of Bayesian Monte Carlo methodology. It first builds a retrieval database with atmospheric parameters obtained from prior information, and then it conducts ensemble optimization to minimize the cost function when too few database cases match the observations. The ensemble approach does not use the gradient information. Instead, it learns what the optimum's posterior distribution looks like, and then tries to estimate this distribution directly. The algorithm represents the unknown continuous posterior distribution with an ensemble of discrete cases, and it iteratively decreases the estimate uncertainties by generating a new ensemble from the learned distribution. Once the termination criterion is met, retrieval results and uncertainties are derived by integration over the final ensemble. We conduct retrieval experiments using simulated noisy brightness temperatures. Retrieved profiles are compared to the true values, and the results are statistically analyzed. The ensemble optimization algorithm is demonstrated to be an effective objective value minimization technique that avoids the complexity of gradient radiative transfer calculations. The algorithm also shows a satisfactory water content profile retrieval performance for frozen hydrometeors.

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Ice cloud imager instrument for MetOp Second Generation

Cited by 26 publications

References 4 publications

PAMTRA 1.0: A Passive and Active Microwave radiative TRAnsfer tool for simulating radiometer and radar measurements of the cloudy atmosphere

PAMTRA 1.0: A Passive and Active Microwave radiative TRAnsfer tool for simulating radiometer and radar measurements of the cloudy atmosphere

Microwave Radar/radiometer for Arctic Clouds MiRAC: First insights from the ACLOUD campaign

Ensemble Optimization Retrieval Algorithm of Hydrometeor Profiles for the Ice Cloud Imager Submillimeter‐Wave Radiometer

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