scholarly journals A microbolometer-based far infrared radiometer to study thin ice clouds in the Arctic

2016 ◽  
Vol 9 (4) ◽  
pp. 1817-1832 ◽  
Author(s):  
Quentin Libois ◽  
Christian Proulx ◽  
Liviu Ivanescu ◽  
Laurence Coursol ◽  
Ludovick S. Pelletier ◽  
...  
Keyword(s):  
Far Infrared ◽  
Frame Rate ◽  
The Arctic ◽  
Spatial Average ◽  
Electronic Noise ◽  
Atmospheric Conditions ◽  
Ice Clouds ◽  
Detector Resolution ◽  
In Situ Experiments ◽  
Infrared Radiometer

Abstract. A far infrared radiometer (FIRR) dedicated to measuring radiation emitted by clear and cloudy atmospheres was developed in the framework of the Thin Ice Clouds in Far InfraRed Experiment (TICFIRE) technology demonstration satellite project. The FIRR detector is an array of 80 × 60 uncooled microbolometers coated with gold black to enhance the absorptivity and responsivity. A filter wheel is used to select atmospheric radiation in nine spectral bands ranging from 8 to 50 µm. Calibrated radiances are obtained using two well-calibrated blackbodies. Images are acquired at a frame rate of 120 Hz, and temporally averaged to reduce electronic noise. A complete measurement sequence takes about 120 s. With a field of view of 6°, the FIRR is not intended to be an imager. Hence spatial average is computed over 193 illuminated pixels to increase the signal-to-noise ratio and consequently the detector resolution. This results in an improvement by a factor of 5 compared to individual pixel measurements. Another threefold increase in resolution is obtained using 193 non-illuminated pixels to remove correlated electronic noise, leading an overall resolution of approximately 0.015 W m−2 sr−1. Laboratory measurements performed on well-known targets suggest an absolute accuracy close to 0.02 W m−2 sr−1, which ensures atmospheric radiance is retrieved with an accuracy better than 1 %. Preliminary in situ experiments performed from the ground in winter and in summer on clear and cloudy atmospheres are compared to radiative transfer simulations. They point out the FIRR ability to detect clouds and changes in relative humidity of a few percent in various atmospheric conditions, paving the way for the development of new algorithms dedicated to ice cloud characterization and water vapor retrieval.

scholarly journals A microbolometer-based far infrared radiometer to study thin ice clouds in the Arctic

2016 ◽  
Author(s):  
Q. Libois ◽  
C. Proulx ◽  
L. Ivanescu ◽  
L. Coursol ◽  
L. Pelletier ◽  
...  
Keyword(s):  
Far Infrared ◽  
Frame Rate ◽  
The Arctic ◽  
Spatial Average ◽  
Electronic Noise ◽  
Atmospheric Conditions ◽  
Ice Clouds ◽  
Detector Resolution ◽  
In Situ Experiments ◽  
Infrared Radiometer

Abstract. A far infrared radiometer (FIRR) dedicated to measure radiation emitted by clear and cloudy atmospheres was developed as a breadboard for the Thin Ice Clouds in Far InfraRed Experiment (TICFIRE) satellite project. The FIRR detector is an array of 80×60 uncooled microbolometers coated with gold black to enhance the absorptivity and responsivity. A filter wheel is used to select atmospheric radiation in 9 spectral bands ranging from 8 to 50 µm. Calibrated radiances are obtained using two well-calibrated blackbodies. Images are acquired at a frame rate of 120 Hz, and temporally averaged to reduce electronic noise. A complete measurements sequence takes about 120 seconds. With a field-of view of 6°, the FIRR is not intended to be an imager. Hence spatial average is computed over 193 illuminated pixels to increase the signal-to-noise ratio and consequently the detector resolution. This results in an improvement by a factor of 5 compared to individual pixel measurements. Another threefold increase in resolution is obtained using 193 non-illuminated pixels to remove correlated electronic noise, leading an overall resolution of approximately 0.015 W m–2 sr–1. Laboratory measurements performed on well known targets suggest an absolute accuracy close to 0.02 W m–2 sr–1, which ensures to retrieve atmospheric radiance with an accuracy better than 1%. Preliminary in situ experiments performed from the ground in winter and in summer on clear and cloudy atmospheres are compared to radiative transfer simulations. They point out the FIRR ability to detect clouds and changes in relative humidity of a few percent in various atmospheric conditions, paving the way for the development of new algorithms dedicated to ice cloud characterization and water vapor retrieval.

scholarly journals Airborne observations of far-infrared upwelling radiance in the Arctic

2016 ◽  
Author(s):  
Quentin Libois ◽  
Liviu Ivanescu ◽  
Jean-Pierre Blanchet ◽  
Hannes Schulz ◽  
Heiko Bozem ◽  
...  
Keyword(s):  
Strong Dependence ◽  
Temperature Stability ◽  
Far Infrared ◽  
Temperature Inversion ◽  
Specific Humidity ◽  
The Arctic ◽  
Ice Clouds ◽  
Airborne Measurements ◽  
Cloud Properties ◽  
Arctic Atmosphere

Abstract. The first airborne measurements of the Far-InfraRed Radiometer (FIRR) were performed in April 2015 during the panarctic NETCARE campaign. Vertical profiles of spectral upwelling radiance in the range 8–50 μm were measured in clear and cloudy conditions from the surface up to 6 km. The clear-sky profiles highlight the strong dependence of radiative fluxes to the temperature inversion typical of the Arctic. Measurements acquired for total column water vapor from 1.5 to 10.5 mm also underline the sensitivity of the far-infrared greenhouse effect to specific humidity. The cloudy cases show that optically thin ice clouds increase the cooling rate of the atmosphere by a factor up to three, making them important pieces of the Arctic energy balance. One such cloud exhibited a very complex spatial structure, characterized by large horizontal heterogeneities at the kilometre-scale. This emphasizes the difficulty to obtain representative cloud observations with airborne measurements, but also points out how challenging it is to model polar clouds radiative effects. These radiance measurements were successfully compared to simulations, suggesting that state-of-the-art radiative transfer models are suited to study the cold and dry Arctic atmosphere. Although FIRR in situ performances compare well to its laboratory performances, complementary simulations show that upgrading the FIRR radiometric resolution would greatly increase its sensitivity to atmospheric and cloud properties. Improved instrument temperature stability in flight and expected technological progress should help meet this objective. The campaign overall highlights the potential for airborne far-infrared radiometry and constitutes a relevant reference for future similar studies dedicated to the Arctic, and for the development of spaceborne instruments.

scholarly journals Simultaneous retrieval of water vapour and temperature profiles and cirrus clouds properties from measurements of far infrared spectral radiance over the Antarctic Plateau

2016 ◽  
Author(s):  
Gianluca Di Natale ◽  
Luca Palchetti ◽  
Giovanni Bianchini ◽  
Massimo Del Guasta
Keyword(s):  
Radiative Transfer ◽  
Water Vapour ◽  
Far Infrared ◽  
Cirrus Clouds ◽  
The Arctic ◽  
Spectral Radiance ◽  
Temperature Profiles ◽  
Ice Clouds ◽  
Antarctic Plateau ◽  
Ice Water

Abstract. The possibility to discriminate the contribution of the atmosphere and ice clouds by using spectral infrared measurements is a fundamental step to quantify the cloud effect in the climate models. The simultaneous retrieval of clouds and atmospheric parameters allows to take into account the possible correlations between the variables. In this paper we describe the development of a routine able to perform the simultaneous retrieval and its application to the analysis of the spectral measurements acquired by the REFIR-PAD (Radiation Explorer Far Infrared – Prototype for Applications and Development) spectroradiometer, operative from Antarctic Plateau since 2012. This routine is able to operate the retrieval with reduced computing time comparable with the REFIR-PAD data acquisition time. The analysis allowed to retrieve the water vapour and temperature profiles and the clouds optical and micro-physical properties, such as the generalised effective diameter (Dge) and the ice water path (IWP), by exploiting the spectral band between 230–980 cm−1. To simulate the radiative transfer, the LBLRTM (Line By Line Radiative Transfer Model) was integrated with a specific code based on the delta-Eddington two-stream approximation, and further the cirrus clouds single scattering properties were derived from a database for hexagonal column habits. In order to identify the ice clouds a back-scattering and depolarisation lidar was available on the site and allowed to infer the position and the cloud thickness used in the simulations. A climatology of the vertical profiles of water vapour and temperature, was performed by using the daily radiosounding available at the base and it was used to build the a priori and initial guess profiles used in the fitting routine. An optimal estimation method with a Levenberg-Marquardt approach was applied to perform the retrieval. The comparison of results with radiosoundings demonstrates that the retrieved atmospheric state is not disturbed by the clouds presence. Finally, the retrieved clouds parameters were compared with the statistical correlation between the cloud temperature (Tc) and the optical depth measured in Antarctica at Dumond D'Urville and the effective diameters with the ice water content (IWC) obtained in the Arctic region finding a general agreement.

scholarly journals Optimal Configuration of a Far‐Infrared Radiometer to Study the Arctic Winter Atmosphere

2020 ◽  
Vol 125 (14) ◽  
Author(s):  
Laurence Coursol ◽  
Quentin Libois ◽  
Pierre Gauthier ◽  
Jean‐Pierre Blanchet
Keyword(s):  
Far Infrared ◽  
Optimal Configuration ◽  
The Arctic ◽  
Infrared Radiometer

scholarly journals Airborne observations of far-infrared upwelling radiance in the Arctic

2016 ◽  
Vol 16 (24) ◽  
pp. 15689-15707 ◽  
Author(s):  
Quentin Libois ◽  
Liviu Ivanescu ◽  
Jean-Pierre Blanchet ◽  
Hannes Schulz ◽  
Heiko Bozem ◽  
...  
Keyword(s):  
Strong Dependence ◽  
Temperature Stability ◽  
Far Infrared ◽  
Temperature Inversion ◽  
Specific Humidity ◽  
The Arctic ◽  
Ice Clouds ◽  
Airborne Measurements ◽  
Cloud Properties ◽  
Arctic Atmosphere

Abstract. The first airborne measurements of the Far-InfraRed Radiometer (FIRR) were performed in April 2015 during the panarctic NETCARE campaign. Vertical profiles of spectral upwelling radiance in the range 8–50 µm were measured in clear and cloudy conditions from the surface up to 6 km. The clear sky profiles highlight the strong dependence of radiative fluxes to the temperature inversion typical of the Arctic. Measurements acquired for total column water vapour from 1.5 to 10.5 mm also underline the sensitivity of the far-infrared greenhouse effect to specific humidity. The cloudy cases show that optically thin ice clouds increase the cooling rate of the atmosphere, making them important pieces of the Arctic energy balance. One such cloud exhibited a very complex spatial structure, characterized by large horizontal heterogeneities at the kilometre scale. This emphasizes the difficulty of obtaining representative cloud observations with airborne measurements but also points out how challenging it is to model polar clouds radiative effects. These radiance measurements were successfully compared to simulations, suggesting that state-of-the-art radiative transfer models are suited to study the cold and dry Arctic atmosphere. Although FIRR in situ performances compare well to its laboratory performances, complementary simulations show that upgrading the FIRR radiometric resolution would greatly increase its sensitivity to atmospheric and cloud properties. Improved instrument temperature stability in flight and expected technological progress should help meet this objective. The campaign overall highlights the potential for airborne far-infrared radiometry and constitutes a relevant reference for future similar studies dedicated to the Arctic and for the development of spaceborne instruments.

Design and instrumentation of an airborne far infrared radiometer for in-situ measurements of ice clouds

2016 ◽  
Author(s):  
Christian Proulx ◽  
Linh Ngo Phong ◽  
Frédéric Lamontagne ◽  
Min Wang ◽  
Bruno Fisette ◽  
...  
Keyword(s):  
Far Infrared ◽  
In Situ Measurements ◽  
Ice Clouds ◽  
Infrared Radiometer

Far-infrared radiometer to map OH in the middle atmosphere

1985 ◽  
Author(s):  
I. NOLT ◽  
J. RADOSTITZ ◽  
K.V. CHANCE ◽  
W. TRAUB ◽  
P. ADE
Keyword(s):  
Middle Atmosphere ◽  
Far Infrared ◽  
Infrared Radiometer

scholarly journals Aerosol distribution around Svalbard during intense easterly winds

2010 ◽  
Vol 10 (4) ◽  
pp. 1473-1490 ◽  
Author(s):  
A. Dörnbrack ◽  
I. S. Stachlewska ◽  
C. Ritter ◽  
R. Neuber
Keyword(s):  
Sea Salt ◽  
Airborne Lidar ◽  
The Arctic ◽  
Aerosol Layer ◽  
Atmospheric Conditions ◽  
Sea Salt Aerosols ◽  
Aerosol Distribution ◽  
Weather Situation ◽  
Low Level Jet ◽  
Aerosol Plume

Abstract. This paper reports on backscatter and depolarization measurements by an airborne lidar in the Arctic during the ASTAR 2004 campaign. A unique weather situation facilitated the observation of the aerosol concentration under strongly forced atmospheric conditions. The vigorous easterly winds distorted the flow past Svalbard in such a way that mesoscale features were visible in the remote-sensing observations: The formation of a well-mixed aerosol layer inside the Adventdalen and the subsequent thinning of the aerosol plume were observed over the Isfjorden. Additionally, mobilization of sea salt aerosols due to a coastal low-level jet at the northern tip of Svalbard resulted in a sloped boundary layer toward north. Mesoscale numerical modelling was applied to identify the sources of the aerosol particles and to explain the observed patterns.

scholarly journals On Aethalometer measurement uncertainties and multiple scattering enhancement in the Arctic

2016 ◽  
Author(s):  
John Backman ◽  
Lauren Schmeisser ◽  
Aki Virkkula ◽  
John A. Ogren ◽  
Eija Asmi ◽  
...  
Keyword(s):  
Detection Limit ◽  
Temporal Resolution ◽  
The Arctic ◽  
Electronic Noise ◽  
Relative Uncertainty ◽  
Post Processing ◽  
Additional Advantage ◽  
Aerosol Absorption ◽  
Threshold Criterion ◽  
Small Aerosol

Abstract. Several types of filter-based instruments are used to estimate aerosol light absorption coefficients.Two significant results are presented based on Aethalometer measurements at six Arctic station from 2012–2014. First, an alternative method of post-processing the Aethalometer data is presented which reduces measurement noise and lowers the detection limit of the instrument more effectively than boxcar averaging. The biggest benefit of this approach can be achieved if instrument drift is minimized. Moreover, by using an attenuation threshold criterion for data post-processing, the relative uncertainty from the electronic noise the instrument is kept constant. This approach results in a time series with a variable collection time (Δt), but with a constant relative uncertainty with regard to electronic noise in the instrument. An additional advantage of this method is that the detection limit of the instrument will be lowered at small aerosol concentrations at the expense of temporal resolution, whereas there is little to no loss in temporal resolution at high aerosol concentrations (>2.1–6.7 Mm−1 as measured by the Aethalometers). At high aerosol concentrations, minimizing the detection limit of the instrument is less critical. Second, utilizing co-located reference methods of aerosol absorption, a multiple cattering enhancement factor (Cref) of 3.10 specific to low elevation Arctic stations is found. Cref is a fundamental part of most of the Aethalometer corrections available in literature, and this is the first time a Cref value has been obtained for the Arctic.

Intercomparison of Bulk Cloud Microphysics Schemes in Mesoscale Simulations of Springtime Arctic Mixed-Phase Stratiform Clouds

2006 ◽  
Vol 134 (7) ◽  
pp. 1880-1900 ◽  
Author(s):  
H. Morrison ◽  
J. O. Pinto
Keyword(s):  
Boundary Layer ◽  
Liquid Water ◽  
Heat Budget ◽  
Cloud Microphysics ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Precipitation Rate ◽  
The Arctic ◽  
Ice Clouds ◽  
Complex Scheme

Abstract A persistent, weakly forced, horizontally extensive mixed-phase boundary layer cloud observed on 4–5 May 1998 during the Surface Heat Budget of the Arctic Ocean (SHEBA)/First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment–Arctic Clouds Experiment (FIRE–ACE) is modeled using three different bulk microphysics parameterizations of varying complexity implemented into the polar version of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5). The two simpler schemes predict mostly ice clouds and very little liquid water, while the complex scheme is able to reproduce the observed persistence and horizontal extent of the mixed-phase stratus deck. This mixed-phase cloud results in radiative warming of the surface, the development of a cloud-topped, surface-based mixed layer, and an enhanced precipitation rate. In contrast, the optically thin ice clouds predicted by the simpler schemes lead to radiative cooling of the surface, a strong diurnal cycle in the boundary layer structure, and very weak precipitation. The larger surface precipitation rate using the complex scheme is partly balanced by an increase in the turbulent flux of water vapor from the surface to the atmosphere. This enhanced vapor flux is attributed to changes in the surface and boundary layer characteristics induced by the cloud itself, although cloud–surface interactions appear to be exaggerated in the model compared with reality. The prediction of extensive mixed-phase stratus by the complex scheme is also associated with increased surface pressure and subsidence relative to the other simulations. Sensitivity tests show that the detailed treatment of ice nucleation and prediction of snow particle number concentration in the complex scheme suppresses ice particle concentration relative to the simpler schemes, reducing the vapor deposition rate (for given values of bulk ice mass and ice supersaturation) and leading to much greater amounts of liquid water and mixed-phase cloudiness. These results suggest that the treatments of ice nucleation and the snow intercept parameter in the simpler schemes, which are based upon midlatitude observations, are inadequate for simulating the weakly forced mixed-phase clouds endemic to the Arctic.

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