Outgoing longwave flux estimation: improvement of angular modelling using spectral information

Clerbaux, Nicolas; Dewitte, Steven; Gonzalez, L.; Bertrand, Cédric; Nicula, B.; Ipe, A.

doi:10.1016/s0034-4257(03)00015-4

Cited by 45 publications

(43 citation statements)

References 19 publications

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“…This is a further demonstration that uncooled detectors are adequate for detailed radiometric observations. Radiant Energy System) (Wielicki et al, 1996) experiments, is typically affected by an error of about 4.6 W/m 2 (Clerbaux et al, 2003).…”

Section: Data Analysis: Outgoing Longwave Radiation Fluxmentioning

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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Section: Data Analysis: Outgoing Longwave Radiation Fluxmentioning

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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“…Finally, the instantaneous radiative fluxes are retrieved from the BB radiances using the CERES SW TRMM ADMs [13] for the TRS (see flowchart in Figure 3) and theoretical regressions [24,26] for the TET (see flowchart in Figure 4). The ADMs are used to link the broadband radiances to the hemispheric flux for specific scene types and geometries.…”

Section: Toa Fluxes Processingmentioning

confidence: 99%

“…A theoretical adjustment of the clear ocean ADMs is also performed to account for the reduction of anisotropy in presence of aerosols (see [13]). For the LW, theoretical regressions [24,26] are used to process the instantaneous fluxes. Since no cloud retrieval is available during the night, the best model is selected through an implicit scene identification, i.e., through the analysis of the NB radiances of the imager.…”

Section: Toa Fluxes Processingmentioning

confidence: 99%

The CM SAF TOA Radiation Data Record Using MVIRI and SEVIRI

et al. 2017

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Abstract:The CM SAF Top of Atmosphere (TOA) Radiation MVIRI/SEVIRI Data Record provides a homogenised satellite-based climatology of TOA Reflected Solar (TRS) and Emitted Thermal (TET) radiation in all-sky conditions over the Meteosat field of view. The continuous monitoring of these two components of the Earth Radiation Budget is of prime importance to study climate variability and change. Combining the Meteosat MVIRI and SEVIRI instruments allows an unprecedented temporal (30 min/15 min) and spatial (2.5 km/3 km) resolution compared to, e.g., the CERES products. It also opens the door to the generation of a long data record covering a 32 years time period and extending from 1 February 1983 to 30 April 2015. The retrieval method used to process the CM SAF TOA Radiation MVIRI/SEVIRI Data Record is discussed. The overlap between the MVIRI and GERB instruments in the period 2004-2006 is used to derive empirical narrowband to broadband regressions. The CERES TRMM angular dependency models and theoretical models are respectively used to compute the TRS and TET fluxes from the broadband radiances. The TOA radiation products are issued as daily means, monthly means and monthly averages of the hourly integrated values (diurnal cycle). The data is provided on a regular grid at a spatial resolution of 0.05 degrees and covers the region 70 • N-70 • S and 70 • W-70 • E. The quality of the data record has been evaluated by intercomparison with several references. In general, the stability in time of the data record is found better than 4 Wm −2 and most products fulfill the predefined accuracy requirements.

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“…In the absence of any current spaceborne instrument that isolate the FIR, our new algorithm has the potential to provide valuable proxy measurements, within the limitations of the spectroscopy implemented in the radiative transfer code used to construct the prediction model. To ensure high accuracy, we use the LBLRTM (Clough et al, 1992(Clough et al, , 2005) available publicly at http://rtweb.aer.com, which has a long and successful heritage of being at the leading edge of the field, is continually updated and has been well validated; see for example Shephard et al (2009), Delamere et al (2010 and Alvarado et al (2013). This approach extends existing observations into the far and near infrared using physical knowledge of atmospheric radiative transfer provided by LBLRTM, which we then evaluate using broadband observations from the CERES satellite instrument.…”

Section: Introductionmentioning

confidence: 99%

“…The outgoing radiation field is strongly anisotropic and must be estimated using a predetermined model, of which many exist involving varying degrees of sophistication and assumptions. These can be either theoretically determined using radiative transfer model calculations of flux or empirically derived using satellite measurements over several different viewing angles and locations; see for example Clerbaux et al (2003), Loeb et al (2003) and Kato and Loeb (2005). The resulting angular distribution models (ADMs) relate the radiance measured at a single angle to irradiance estimated over all angles, and as such introduce a further level of uncertainty into the validation, which can be up to 2.3 % for recent satellite products (Instantaneous long-wave TOA flux; see the CERES Terra Edition3A single-scanner footprint (SSF) Data Quality Summary).…”

Section: Introductionmentioning

confidence: 99%

Using IASI to simulate the total spectrum of outgoing long-wave radiances

2015

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Abstract.A new method of deriving high-resolution topof-atmosphere spectral radiances in 10 181 bands, over the whole outgoing long-wave spectrum of the Earth, is presented. Correlations between different channels measured by the Infrared Atmospheric Sounding Interfermeter (IASI) on the MetOp-A (Meteorological Operation) satellite and unobserved wavenumbers are used to estimate far infrared (FIR) radiances at 0.5 cm −1 intervals between 25.25 and 644.75 cm −1 (the FIR), and additionally between 2760 and 3000 cm −1 (the NIR -near infrared). Radiances simulated by the line-by-line radiative transfer model (LBLRTM) are used to construct the prediction model. The spectrum is validated by comparing the Integrated Nadir Long-wave Radiance (INLR) product spanning the whole 25.25-3000 cm −1 range with the corresponding broadband measurements from the Clouds and the Earth's Radiant Energy System (CERES) instrument on the Terra and Aqua satellites at points of simultaneous nadir overpass. There is a mean difference of 0.3 W m −2 sr −1 (0.5 % relative difference). This is well within the uncertainties associated with the measurements made by either instrument. However, there is a noticeable contrast when the bias is separated into night-time and daytime scenes with the latter being significantly larger, possibly due to errors in the CERES Ed3 Spectral Response Functions (SRF) correction method. In the absence of an operational spaceborne instrument that isolates the FIR, this product provides a useful proxy for such measurements within the limits of the regression model it is based on, which is shown to have very low root mean squared errors. The new high-resolution spectrum is presented for global mean clear and all skies where the FIR is shown to contribute 44 and 47 % to the total INLR, respectively. In terms of the spectral cloud effect (Cloud Integrated Nadir Long-wave Radiance -CINLR), the FIR contributes 19 % and in some subtropical instances appears to be negative; results that would go unobserved with a traditional broadband analysis.

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Outgoing longwave flux estimation: improvement of angular modelling using spectral information

Cited by 45 publications

References 19 publications

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

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

The CM SAF TOA Radiation Data Record Using MVIRI and SEVIRI

Using IASI to simulate the total spectrum of outgoing long-wave radiances

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