Technical Note: REFIR-PAD level 1 data analysis and performance characterization

Bianchini, Giovanni; Palchetti, Luca

doi:10.5194/acpd-8-367-2008

Cited by 9 publications

(11 citation statements)

References 15 publications

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“…The total spectral uncertainty σ t ( ν ) is defined as the square root of the squared sum of CAL and NESR. More details about the configuration, data and error analysis can be found in Bianchini and Palchetti []. In this paper the version 2 of the REFIR‐PAD calibrated radiances is used, available since 2015.…”

Section: Experimental Campaign and Instrumentationmentioning

confidence: 99%

One year of downwelling spectral radiance measurements from 100 to 1400 cm⁻¹ at Dome Concordia: Results in clear conditions

et al. 2016

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The present work examines downwelling radiance spectra measured at the ground during 2013 by a Far Infrared Fourier Transform Spectrometer at Dome C, Antarctica. A tropospheric backscatter and depolarization lidar is also deployed at same site, and a radiosonde system is routinely operative. The measurements allow characterization of the water vapor and clouds infrared properties in Antarctica under all sky conditions. In this paper we specifically discuss cloud detection and the analysis in clear sky condition, required for the discussion of the results obtained in cloudy conditions. First, the paper discusses the procedures adopted for the quality control of spectra acquired automatically. Then it describes the classification procedure used to discriminate spectra measured in clear sky from cloudy conditions. Finally a selection is performed and 66 clear cases, spanning the whole year, are compared to simulations. The computation of layer molecular optical depth is performed with line‐by‐line techniques and a convolution to simulate the Radiation Explorer in the Far InfraRed‐Prototype for Applications and Development (REFIR‐PAD) measurements; the downwelling radiance for selected clear cases is computed with a state‐of‐the‐art adding‐doubling code. The mean difference over all selected cases between simulated and measured radiance is within experimental error for all the selected microwindows except for the negative residuals found for all microwindows in the range 200 to 400 cm−1, with largest values around 295.1 cm−1. The paper discusses possible reasons for the discrepancy and identifies the incorrect magnitude of the water vapor total absorption coefficient as the cause of such large negative radiance bias below 400 cm−1.

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Section: Experimental Campaign and Instrumentationmentioning

confidence: 99%

One year of downwelling spectral radiance measurements from 100 to 1400 cm⁻¹ at Dome Concordia: Results in clear conditions

et al. 2016

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“…An accurate characterisation of the Level 1 data analysis, that produced calibrated spectra, can be found in Bianchini and Palchetti (2008). The noise equivalent spectral radiance (NESR) due to the detector noise was found to be in the range of 0.8-2.5 mW/(m 2 sr cm −1 ) for a single spectrum, with the lower values being between 200 and 600 cm −1 .…”

Section: Spectroscopic Measurements Of the Outgoing Longwave Radiationmentioning

confidence: 99%

“…This error is correlated among the different spectral channels. An in-depth analysis of the errors and of their spectral features can be found in Bianchini and Palchetti (2008).…”

Section: Error Budgetmentioning

confidence: 99%

Measurement of the water vapour vertical profile and of the Earth's outgoing far infrared flux

Palchetti

Bianchini²,

Carli³

et al. 2008

Atmos. Chem. Phys.

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Abstract. Our understanding of global warming depends on the accuracy with which the atmospheric components that modulate the Earth's radiation budget are known. Many uncertainties still exist as regards the radiative effect of water in the different spectral regions, among which is the far infrared, where very few observations have been made. An assessment is shown of the atmospheric outgoing flux obtained from a balloon-borne platform with wideband spectrallyresolved nadir measurements at the top of the atmosphere over the full spectral range, from 100 to 1400 cm −1 , made by a Fourier transform spectrometer with uncooled detectors. From these measurements, we retrieved 15 pieces of information regarding water vapour and temperature profiles and surface temperature, with a major improvement in our knowledge of water vapour in the upper troposphere. The retrieved atmospheric state made it possible to calculate the emitted radiance also at frequencies and zenith angles that have not been observed and to determine the outgoing spectral radiation flux. This proves that spectrally resolved observations can be used to derive accurate information on the integrated flux. While the retrieved temperature was in agreement with ECMWF analysis, the retrieved water vapour profile differed significantly; depending on the time and the location, the derived flux in the far infrared (20-600 cm −1 ) differed by 2-3.5 W/m 2 from that calculated using ECMWF. The error with which the far infrared flux is determined by REFIR-PAD is about 0.4 W/m 2 and is caused mainly by calibration uncertainties, while detector noise has a negligible effect. This proves that uncooled detectors are adequate for top-of-the-atmosphere radiometry.

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“…Additionally, FIRST corrects for off-axis frequency shits and vignetting in the scene select mirror and sums multiple detectors for increased precision, AERI corrects for field of view self-apodization instrument line shape (ILS) effects and wavelength scale errors, 13 and REFIR resamples its interferograms from equal-time spaced points to equal position spaced points, corrects its ILS, and estimates the instrument noise equivalent spectral radiance (NESR) and overall calibration errors. 14 In a radiometric sense, the uncertainties quoted above are for stable-source, laboratory radiometric measurements and may be differ in an environment of uncontrolled variables.…”

Section: Instrument Descriptionsmentioning

confidence: 99%

Far-IR measurements at Cerro Toco, Chile: FIRST, REFIR, and AERI

et al. 2010

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In mid-2009, the Radiative Heating in the Underexplored Bands Campaign II (RHUBC-II) was conducted from Cerro Toco, Chile, a high, dry, remote mountain plateau, 23°S , 67.8°W at 5.4km, in the Atacama Desert of Northern Chile. From this site, dominant IR water vapor absorption bands and continuum, saturated when viewed from the surface at lower altitudes, or in less dry locales, were investigated in detail, elucidating IR absorption and emission in the atmosphere. Three FTIR instruments were at the site, the Far-Infrared Spectroscopy of the Troposphere (FIRST), the Radiation Explorer in the Far Infrared (REFIR), and the Atmospheric Emitted Radiance Interferometer (AERI). In a side-by-side comparison, these measured atmospheric downwelling radiation, with overlapping spectral coverage from 5 to100um (2000 to 100cm -1 ), and instrument spectral resolutions from 0.5 to 0.64 cm -1 , unapodized. In addition to the FTIR and other ground-based IR and microwave instrumentation, pressure/temperature/relative humidity measuring sondes, for atmospheric profiles to 18km, were launched from the site several times a day. The derived water vapor profiles, determined at times matching the FTIR measurement times, were used to model atmospheric radiative transfer. Comparison of instrument data, all at the same spectral resolution, and model calculations, are presented along with a technique for determining adjustments to line-by-line calculation continuum models. This was a major objective of the campaign

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Technical Note: REFIR-PAD level 1 data analysis and performance characterization

Cited by 9 publications

References 15 publications

One year of downwelling spectral radiance measurements from 100 to 1400 cm⁻¹ at Dome Concordia: Results in clear conditions

One year of downwelling spectral radiance measurements from 100 to 1400 cm⁻¹ at Dome Concordia: Results in clear conditions

Measurement of the water vapour vertical profile and of the Earth's outgoing far infrared flux

Far-IR measurements at Cerro Toco, Chile: FIRST, REFIR, and AERI

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Technical Note: REFIR-PAD level 1 data analysis and performance characterization

Cited by 9 publications

References 15 publications

One year of downwelling spectral radiance measurements from 100 to 1400 cm−1 at Dome Concordia: Results in clear conditions

One year of downwelling spectral radiance measurements from 100 to 1400 cm−1 at Dome Concordia: Results in clear conditions

Measurement of the water vapour vertical profile and of the Earth's outgoing far infrared flux

Far-IR measurements at Cerro Toco, Chile: FIRST, REFIR, and AERI

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Product

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One year of downwelling spectral radiance measurements from 100 to 1400 cm⁻¹ at Dome Concordia: Results in clear conditions

One year of downwelling spectral radiance measurements from 100 to 1400 cm⁻¹ at Dome Concordia: Results in clear conditions