Les travaux de Jean-François Geleyn sur la paramétrisation du rayonnement atmosphérique

2021 ◽  
pp. 068
Author(s):  
Ján Mašek
Keyword(s):  
Numerical Weather Prediction ◽  
State Of The Art ◽  
Weather Prediction ◽  
Radiative Effects ◽  
Distribution Method ◽  
Numerical Weather ◽  
Cloud Radiative Effects ◽  
Temps Reel ◽  
Rayonnement Solaire ◽  
Radiation Scheme

Cet article résume les activités de Jean-François Geleyn qui ont abouti à un schéma de rayonnement de pointe adapté à la prévision numérique du temps. L'objectif principal - traiter les interactions nuage-rayonnement - a été atteint grâce à une amélioration considérable de l'approche à bandes larges (la vision avec deux seuls intervalles spectraux, l'un pour les courtes longueurs d'onde pour le rayonnement solaire, l'autre pour les grandes longueurs d'onde pour le rayonnement thermique), en ouvrant la voie à un appel intermittent du schéma dans le temps. Le schéma qui en résulte offre une alternative compétitive par rapport aux approches traditionnelles en « k-distribution corrélée » utilisant des méthodes plus précises mais plus coûteuses, méthodes qui ne permettent pas la mise à jour en temps réel des effets radiatifs des nuages. The paper summarizes the activities of Jean-François Geleyn leading to a state-of-the-art radiation scheme tailored for numerical weather prediction. The main goal - dealing with cloud-radiation interactions - was reached thanks to significant improvements to the broadband approach allowing for single shortwave and single longwave intervals, opening a way to selective intermittency. The resulting scheme offers an alternative competitive to the mainstream approach that uses very accurate but expensive correlated k-distribution method, not allowing for timely update of cloud radiative effects.

scholarly journals Impact of the 4 April 2014 Saharan dust outbreak on the photovoltaic power generation in Germany

2017 ◽  
Vol 17 (21) ◽  
pp. 13391-13415 ◽  
Author(s):  
Daniel Rieger ◽  
Andrea Steiner ◽  
Vanessa Bachmann ◽  
Philipp Gasch ◽  
Jochen Förstner ◽  
...  
Keyword(s):  
Power Generation ◽  
Solar Radiation ◽  
Numerical Weather Prediction ◽  
Mineral Dust ◽  
Weather Prediction ◽  
Aerosol Particles ◽  
Saharan Dust ◽  
Radiative Effects ◽  
Numerical Weather ◽  
The Impact

Abstract. The importance for reliable forecasts of incoming solar radiation is growing rapidly, especially for those countries with an increasing share in photovoltaic (PV) power production. The reliability of solar radiation forecasts depends mainly on the representation of clouds and aerosol particles absorbing and scattering radiation. Especially under extreme aerosol conditions, numerical weather prediction has a systematic bias in the solar radiation forecast. This is caused by the design of numerical weather prediction models, which typically account for the direct impact of aerosol particles on radiation using climatological mean values and the impact on cloud formation assuming spatially and temporally homogeneous aerosol concentrations. These model deficiencies in turn can lead to significant economic losses under extreme aerosol conditions. For Germany, Saharan dust outbreaks occurring 5 to 15 times per year for several days each are prominent examples for conditions, under which numerical weather prediction struggles to forecast solar radiation adequately. We investigate the impact of mineral dust on the PV-power generation during a Saharan dust outbreak over Germany on 4 April 2014 using ICON-ART, which is the current German numerical weather prediction model extended by modules accounting for trace substances and related feedback processes. We find an overall improvement of the PV-power forecast for 65 % of the pyranometer stations in Germany. Of the nine stations with very high differences between forecast and measurement, eight stations show an improvement. Furthermore, we quantify the direct radiative effects and indirect radiative effects of mineral dust. For our study, direct effects account for 64 %, indirect effects for 20 % and synergistic interaction effects for 16 % of the differences between the forecast including mineral dust radiative effects and the forecast neglecting mineral dust.

scholarly journals The Usefulness of Piecewise Potential Vorticity Inversion

2012 ◽  
Vol 69 (3) ◽  
pp. 934-941 ◽  
Author(s):  
Bjørn Røsting ◽  
Jón Egill Kristjánsson
Keyword(s):  
Numerical Weather Prediction ◽  
Potential Vorticity ◽  
State Of The Art ◽  
Weather Prediction ◽  
Specific Region ◽  
Critical View ◽  
Numerical Weather ◽  
Boundary Temperature ◽  
Potential Vorticity Inversion ◽  
Dynamic Meteorology

Abstract It is today widely accepted that potential vorticity (PV) thinking is a highly useful approach for understanding important aspects of dynamic meteorology and for validation of output from state-of-the-art numerical weather prediction (NWP) models. Egger recently presented a critical view on piecewise potential vorticity inversion (PPVI). This was done by defining a PV anomaly by retaining the observed PV field in a specific region, while changing the observed PV fields to zero elsewhere. Inversion of such a modified PV field yields a flow vastly different from the observed. On the basis of this result it was argued that PPVI is useless for understanding the dynamics of the flow. The present paper argues that the results presented by Egger are incomplete in the context of PPVI, since the complementary cases were not considered and that the results also depend on the idealized model formulations. The complementary case is defined by changing the observed PV to zero in the specific region, while retaining the observed PV field elsewhere. By including the complementary cases, it can be demonstrated that the streamfunction fields associated with the PV and boundary temperature anomalies presented by Egger add up to yield the observed streamfunction field, as expected if PPVI is to be valid. It follows that PPVI is indeed valid and useful in these cases.

scholarly journals Machine Learning Emulation of 3D Cloud Radiative Effects

2021 ◽  
Author(s):  
David Meyer ◽  
Robin J. Hogan ◽  
Peter D. Dueben ◽  
Shannon L. Mason
Keyword(s):  
Climate Models ◽  
Weather Prediction ◽  
Radiative Effects ◽  
Weather Forecasts ◽  
Medium Range ◽  
Cloud Radiative Effects ◽  
The Difference ◽  
The Cost ◽  
Radiation Scheme ◽  
Operational Scheme

<p>The treatment of cloud structure in radiation schemes used in operational numerical weather prediction and climate models is often greatly simplified to make them computationally affordable. Here, we propose to correct the current operational scheme ecRad – as used for operational predictions at the European Centre for Medium-Range Weather Forecasts – for 3D cloud radiative effects using computationally cheap neural networks. The 3D cloud radiative effects are learned as the difference between ecRad’s fast Tripleclouds solver that neglects 3D cloud radiative effects, and its SPeedy Algorithm for Radiative TrAnsfer through CloUd Sides (SPARTACUS) solver that includes them but increases the cost of the entire radiation scheme. We find that the emulator increases the overall accuracy for both longwave and shortwave with a negligible impact on the model’s runtime performance.</p>

scholarly journals Effects of aerosols on clear-sky solar radiation in the ALADIN-HIRLAM NWP system

2016 ◽  
Vol 16 (9) ◽  
pp. 5933-5948 ◽  
Author(s):  
Emily Gleeson ◽  
Velle Toll ◽  
Kristian Pagh Nielsen ◽  
Laura Rontu ◽  
Ján Mašek
Keyword(s):  
Optical Properties ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Radiative Effect ◽  
Aerosol Optical Properties ◽  
Numerical Weather ◽  
Clear Sky ◽  
Radiation Scheme

Abstract. The direct shortwave radiative effect of aerosols under clear-sky conditions in the Aire Limitee Adaptation dynamique Developpement InterNational – High Resolution Limited Area Model (ALADIN-HIRLAM) numerical weather prediction system was investigated using three shortwave radiation schemes in diagnostic single-column experiments: the Integrated Forecast System (IFS), acraneb2 and the hlradia radiation schemes. The multi-band IFS scheme was formerly used operationally by the European Centre for Medium Range Weather Forecasts (ECMWF) whereas hlradia and acraneb2 are broadband schemes. The former is a new version of the HIRLAM radiation scheme while acraneb2 is the radiation scheme in the ALARO-1 physics package. The aim was to evaluate the strengths and weaknesses of the numerical weather prediction (NWP) system regarding aerosols and to prepare it for use of real-time aerosol information. The experiments were run with particular focus on the August 2010 Russian wildfire case. Each of the three radiation schemes accurately (within ±4 % at midday) simulates the direct shortwave aerosol effect when observed aerosol optical properties are used. When the aerosols were excluded from the simulations, errors of more than +15 % in global shortwave irradiance were found at midday, with the error reduced to +10 % when standard climatological aerosols were used. An error of −11 % was seen at midday if only observed aerosol optical depths at 550 nm, and not observation-based spectral dependence of aerosol optical depth, single scattering albedos and asymmetry factors, were included in the simulations. This demonstrates the importance of using the correct aerosol optical properties. The dependency of the direct radiative effect of aerosols on relative humidity was tested and shown to be within ±6 % in this case. By modifying the assumptions about the shape of the IFS climatological vertical aerosol profile, the inherent uncertainties associated with assuming fixed vertical profiles were investigated. The shortwave heating rates in the boundary layer changed by up to a factor of 2 in response to the aerosol vertical distribution without changing the total aerosol optical depth. Finally, we tested the radiative transfer approximations used in the three radiation schemes for typical aerosol optical properties compared to the accurate DISORT model. These approximations are found to be accurate to within ±13 % even for large aerosol loads.

scholarly journals Impact of the 4 April 2014 Saharan dust outbreak on the photovoltaic power generation in Germany

2017 ◽  
Author(s):  
Daniel Rieger ◽  
Andrea Steiner ◽  
Vanessa Bachmann ◽  
Philipp Gasch ◽  
Jochen Förstner ◽  
...  
Keyword(s):  
Power Generation ◽  
Solar Radiation ◽  
Numerical Weather Prediction ◽  
Mineral Dust ◽  
Weather Prediction ◽  
Aerosol Particles ◽  
Saharan Dust ◽  
Radiative Effects ◽  
Numerical Weather ◽  
The Impact

Abstract. The importance for reliable forecasts of incoming solar radiation is growing rapidly, especially for those countries with an increasing share in photovoltaic (PV) power production. The reliability of solar radiation forecasts depends mainly on the representation of clouds and aerosol particles absorbing and scattering radiation. Especially under extreme aerosol conditions, numerical weather prediction has a systematic bias in the solar radiation forecast. This is caused by the design of numerical weather prediction models, which typically account for the direct impact of aerosol particles on radiation using climatological mean values and the impact on cloud formation assuming spatially and temporally homogeneous aerosol concentrations. These model deficiencies in turn can lead to significant economic losses under extreme aerosol conditions. For Germany, Saharan dust outbreaks occurring 5 to 15 times per year for several days each are prominent examples for conditions, under which numerical weather prediction struggles to forecast solar radiation adequately. We investigate the impact of mineral dust on the PV power generation during a Saharan dust outbreak over Germany at 4 April 2014 using ICON-ART, which is the current German numerical weather prediction model extended by modules accounting for trace substances and related feedback processes. We find an overall improvement of the PV power forecast for 65 % of the pyranometer stations in Germany. Of the nine stations with very high differences between forecast and measurement, eight stations show an improvement. Furthermore, we quantify the direct radiative effects and indirect radiative effects of mineral dust. For our study, direct effects account for 64 %, indirect effects for 20 % and synergistic interaction effects for 16 % of the differences between the forecast including mineral dust radiative effects and the forecast neglecting mineral dust.

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