Figures
Explore figures and images from publications

Context in source publication

Context 1
... the LW a scene dependence is also observed. The results of a similar breakdown of the LW radiance ratio by radiance bin is shown in figure 1. This shows that for warmer scenes with radiances above 60 Wm -2 sr -1 the GERB LW radiance is about 1% lower than the FM2 radiance and 2% lower than the FM3. ...

Similar publications

Book
Full-text available
U S Bureau of Reclamation Filed Manual for engineering geologic logging.
Article
Full-text available
This is a preliminary update of the measurements of αs and the determination of the world average value of αs (M2Z) presented in the 2013/2014 edition of the Review of Particle Properties [1].

Citations

... Refs. [21,22]. The exact threshold may slightly differ from paper to paper; here we use θ , θ vz < 70°. 5 After doing that, we can see that things are already improved (see Figure 1 (b)), but notice that the discrepancies which we identified for the sunglint and the aerosol areas in particular actually remain of the same order, respectively > 0.10 and ∼ 0.05. ...
Article
Full-text available
Geostationary observations offer the unique opportunity to resolve the diurnal cycle of the Earth's Radiation Budget at the top of the atmosphere (TOA), crucial for climate-change studies. However, a drawback of the continuous temporal coverage of the geostationary orbit is the fixed viewing geometry. As a consequence, imperfections in the angular distribution models (ADMs) used in the radiance-to-flux conversion process or residual angular-dependent narrowband-to-broadband conversion errors can result in systematic errors of the estimated radiative fluxes. In this work, focusing on clear-sky reflected TOA observations, we compare the overlapping views from Meteosat Second Generation satellites at 0° and 41.5°E longitude which enable a quantification of viewing-angle-dependent differences. Using data derived from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI), we identify some of the main sources of discrepancies, and show that they can be significantly reduced at the level of one month. This is achieved, separately for each satellite, via a masking procedure followed by an empirical fit at the pixel-level that takes into account all the clear-sky data from that satellite, calculated separately per timeslot of the day, over the month of November 2016. The method is then applied to each month of 2017, and gives a quadratic mean of the albedo root-mean squared difference over the dual-view region which is comparable from month to month, with a 2017 average value of 0.01. Sources of discrepancies include the difficulty to estimate the flux over the sunglint ocean region close to the limbs, the fact that the data processing does not include dedicated angular distribution models for the aerosol-over-ocean case, and the existence of an observer-dependent diurnal-asymmetry artefact affecting the clear-sky-albedo dependence on the solar zenith angle particularly over land areas.
... Refs. [21,22]. The exact threshold may slightly differ from paper to paper; here we use θ , θ vz < 70°. 5 After doing that, we can see that things are already improved (see Figure 1 (b)), but notice that the discrepancies which we identified for the sunglint and the aerosol areas in particular actually remain of the same order, respectively > 0.10 and ∼ 0.05. ...
Preprint
Full-text available
Geostationary observations offer the unique opportunity to resolve the diurnal cycle of the Earth's Radiation Budget at the top of the atmosphere (TOA), crucial for climate-change studies. However, a drawback of the continuous temporal coverage of the geostationary orbit is the fixed viewing geometry. As a consequence, imperfections in the angular distribution models (ADMs) used in the radiance-to-flux conversion process or residual angular-dependent narrowband-to-broadband conversion errors can result in systematic errors of the estimated radiative fluxes. In this work, focusing on clear-sky reflected TOA observations, we compare the overlapping views from Meteosat Second Generation satellites at 0° and 41.5°E longitude which enable a quantification of viewing-angle-dependent differences. Using data derived from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI), we identify some of the main sources of discrepancies, and show that they can be significantly reduced at the level of one month. This is achieved, separately for each satellite, via a masking procedure followed by an empirical fit at the pixel-level that takes into account all the clear-sky data from that satellite, calculated separately per timeslot of the day, over the month of November 2016. The method is then applied to each month of 2017, and gives a quadratic mean of the albedo root-mean squared difference over the dual-view region which is comparable from month to month, with a 2017 average value of 0.01. Sources of discrepancies include the difficulty to estimate the flux over the sunglint ocean region close to the limbs, the fact that the data processing does not include dedicated angular distribution models for the aerosol-over-ocean case, and the existence of an observer-dependent diurnal-asymmetry artefact affecting the clear-sky-albedo dependence on the solar zenith angle particularly over land areas.
... The uncertainty of the unfiltered radiances of the instrument is however further affected by the characterization of the instrument's spectral response, as the calibration sources do not have exactly the same spectra as compared to the actual Earth scenes observed by the instrument. The spectral response uncertainty, estimated at 1.9% for the SW and 0.9% for the LW, is actually the main source of uncertainty for the GERB instrument unfiltered radiances [48]. The calibration source uniformity, the polarisation, the use of SEVIRI data for GERB unfiltering, and the stray-light contamination, have in general a lower contribution to the total uncertainty. ...
... The calibration source uniformity, the polarisation, the use of SEVIRI data for GERB unfiltering, and the stray-light contamination, have in general a lower contribution to the total uncertainty. All together, the uncertainties of the GERB SW and LW unfiltered radiances have been estimated at 2.25% and 0.96% [48]. Several sources of random errors have been identified for the GERB measurements (instrument noise, geolocation, unfiltering, spectral overlap correction, etc.). ...
... Their magnitude is in general small, less than 1%, and they have a negligible effect on the MVIRI/SEVIRI data record given the large quantity of observations (covering almost 2 years) used to derive the empirical relations. A full discussion on the GERB systematic and random errors is provided in the GERB Quality Summary [48]. Next to the use of the GERB data, the empirical NB to BB relations are the source of additional systematic and random errors. ...
Article
Full-text available
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.
... The accuracy of the CERES instrument for OLR and RSR irradi690 ance retrievals is 1% and 0.5%, respectively (Wielicki et al., 1998). The accuracy of GERB does not meet the initial mission target requirements and lies in the range of 1-2% (OLR) and 7-8% (RSR) ( Russell et al., 2006). It must be mentioned that any calibration uncertainty of the SEVIRI instrument 695 would directly affect the derived irradiances. ...
... The accuracy of the CERES instrument for OLR and RSR irradiance retrievals is 1 % and 0.5 %, respectively (Wielicki et al., 1998). The accuracy of GERB does not meet the initial mission target requirements and lies in the range of 1-2 % (OLR) and 7-8 % (RSR) ( Russell et al., 2006). It must be mentioned that any calibration uncertainty of the SEVIRI instrument would directly affect the derived irradiances. ...
Article
Full-text available
A new Rapid Retrieval of Upwelling irradiances from MSG/SEVIRI (RRUMS) is presented. It has been developed to observe the top-of-atmosphere irradiances of small scale and rapidly changing features that are not sufficiently resolved by specific Earth radiation budget sensors. Our retrieval takes advantage of the spatial and temporal resolution of MSG/SEVIRI and provides outgoing longwave and reflected shortwave radiation only by means of a combination of SEVIRI channels. The longwave retrieval is based on a simple linear combination of brightness temperatures from the SEVIRI infrared channels. The shortwave retrieval is based on a neural network that requires as input the visible and near-infrared SEVIRI channels. Both LW and SW algorithms have been validated by comparing their results with CERES and GERB irradiance observations. While being less accurate than their dedicated counterparts, the SEVIRI-based methods have two major advantages compared to CERES and GERB: their higher spatial resolution and the better temporal resolution. With our retrievals it is possible to observe the radiative effect of small-scale features such as cumulus clouds, cirrus clouds, or aircraft contrails. The spatial resolution of SEVIRI is 3 km × 3 km in the sub-satellite point, remarkably better than that of CERES (20 km) or GERB (45 km). The temporal resolution is 15 min (5 min in the Rapid-Scan mode), the same as GERB, but significantly better than that of CERES which, being on board of a polar orbiting satellite, has a temporal resolution as low as 2 overpasses per day.
... InRussell (2011) findet sich hierzu der Satz "Extreme caution is recommended before using the GERB Edition1 flux data to study cirrus cloud radiative effect in the LW". ...
... The accuracy of the CERES instrument for OLR and RSR irradi690 ance retrievals is 1% and 0.5%, respectively (Wielicki et al., 1998). The accuracy of GERB does not meet the initial mission target requirements and lies in the range of 1-2% (OLR) and 7-8% (RSR) ( Russell et al., 2006). It must be mentioned that any calibration uncertainty of the SEVIRI instrument 695 would directly affect the derived irradiances. ...
... The accuracy of the CERES instrument for OLR and RSR irradiance retrievals is 1 % and 0.5 %, respectively (Wielicki et al., 1998). The accuracy of GERB does not meet the initial mission target requirements and lies in the range of 1-2 % (OLR) and 7-8 % (RSR) ( Russell et al., 2006). It must be mentioned that any calibration uncertainty of the SEVIRI instrument would directly affect the derived irradiances. ...
Article
Full-text available
A new Rapid Retrieval of upwelling fluxes from MSG/SEVIRI (RRUMS) is presented. It has been developed to observe the top-of-atmosphere irradiances of small scale and rapidly changing features that are not sufficiently resolved by specific Earth radiation budget sensors. Our retrieval takes advantage of the spatial and temporal resolution of MSG/SEVIRI and provides outgoing longwave and reflected shortwave radiation only by means of a combination of SEVIRI channels. The longwave retrieval is based on a simple linear combination of brightness temperatures from the SEVIRI infrared channels. Two shortwave retrievals are presented and discussed: the first one based on a multilinear parameterisation and the second one based on a neural network. The neural network method is shown to be slightly more accurate and simpler to apply for the desired purpose. Both LW and SW algorithms have been validated by comparing their results with CERES and GERB irradiance observations. While being less accurate than their dedicated counterparts, the SEVIRI-based methods have two major advantages compared to CERES and GERB: their higher spatial resolution and the better temporal resolution. With our retrievals it is possible to observe the radiative effect of small-scale features such as cumulus clouds, cirrus clouds, or aircraft contrails. The spatial resolution of SEVIRI is 3 km &times 3 km in the sub-satellite point, remarkably better than that of CERES (20 km) or GERB (45 km). The temporal resolution is 15 min (5 min in the rapid-scan mode), the same as GERB, but significantly better than that of CERES which, being on board of a polar orbiting satellite, has a temporal resolution as low as 2 overpasses per day.
... A much clearer reliance of OLR dust on τ 067 is seen in the corrected case, and the longwave forcing efficiency, or the rate of change of forcing per unit optical depth, calculated from the bestfit straight line, is 17 ± 5 W m −2 τ 067 −1 . The (1 − σ ) error includes both the impact of uncertainties in the relevant ECMWF fields (Table II) and in the GERB OLR measurements, where the latter uncertainty is assumed to be ±10 W m −2 (Russell, 2006). For completeness, Figure 3(c) shows the time evolution of the dust direct radiative effect over Banizoumbou with and without correction. ...
Article
This paper presents a methodology for estimating the longwave top-of-atmosphere direct radiative forcing due to Saharan dust aerosol from satellite observations made by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) and Geostationary Earth Radiation Budget (GERB) instruments. Narrow-band observations from SEVIRI are used to detect dust presence and quantify its loading, while GERB provides an estimate of the dust impact on the total outgoing longwave radiation. Applying the technique to observations made over the Banizoumbou surface station in Niger through March–June 2006 indicates a midday longwave forcing efficiency of 17 ± 5 W m−2 per unit aerosol optical depth. Copyright © 2007 Royal Meteorological Society