Enhanced solar global irradiance during cloudy sky conditions

Schade, Nils H.; Macke, Andreas; Sandmann, H.; Stick, C.

doi:10.1127/0941-2948/2007/0206

Cited by 59 publications

(64 citation statements)

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“…In our data, in Davos the maximum cloud enhancement with Cc-Ac is a SCE value of 477 Wm −2 and in Payerne it is 440 Wm −2 under Ci-Cs conditions. Schade et al (2007) showed that the largest cloud enhancements can be registered at near-overcast situations. However, our data show a maximum in cloud enhancement cases for a fractional cloud coverage of 3 to 4 oktas in Davos and 1 to 3 oktas in Payerne.…”

Section: Shortwave Cloud Effectmentioning

confidence: 99%

“…For St-As clouds there is no case observed with a cloud enhancement of more than 40 % SCE rel . Schade et al (2007) also showed that altocumulus is the cloud type that produces most of the downward solar cloud enhancement. They demonstrated that altocumulus clouds can be responsible for temporary enhancements of up to 500 Wm −2 .…”

Section: Shortwave Cloud Effectmentioning

confidence: 99%

“…Several studies (e.g. Robinson, 1966;Schade et al, 2007;Thuillier et al, 2013;Calbo et al, 2017) show the influence of the magnitude of cloud enhancement events and its duration. To compare our results with these analyses on the duration of cloud enhancement events, the resolution of 1-min images needs to be increased to the seconds range and will be the subject of a subsequent study.…”

Section: Shortwave Cloud Effectmentioning

confidence: 99%

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Cloud radiative effect, cloud fraction and cloud type at two stations in Switzerland using hemispherical sky cameras

et al. 2017

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Abstract. The current study analyses the cloud radiative effect during the daytime depending on cloud fraction and cloud type at two stations in Switzerland over a time period of 3 to 5 years. Information on fractional cloud coverage and cloud type is retrieved from images taken by visible all-sky cameras. Cloud-base height (CBH) data are retrieved from a ceilometer and integrated water vapour (IWV) data from GPS measurements. The longwave cloud radiative effect (LCE) for low-level clouds and a cloud coverage of 8 oktas has a median value between 59 and 72 Wm −2 . For midand high-level clouds the LCE is significantly lower. It is shown that the fractional cloud coverage, the CBH and IWV all have an influence on the magnitude of the LCE. These observed dependences have also been modelled with the radiative transfer model MODTRAN5. The relative values of the shortwave cloud radiative effect (SCE rel ) for low-level clouds and a cloud coverage of 8 oktas are between −90 and −62 %. Also here the higher the cloud is, the less negative the SCE rel values are. In cases in which the measured direct radiation value is below the threshold of 120 Wm −2 (occulted sun) the SCE rel decreases substantially, while cases in which the measured direct radiation value is larger than 120 Wm −2 (visible sun) lead to a SCE rel of around 0 %. In 14 and 10 % of the cases in Davos and Payerne respectively a cloud enhancement has been observed with a maximum in the cloud class cirrocumulus-altocumulus at both stations. The calculated median total cloud radiative effect (TCE) values are negative for almost all cloud classes and cloud coverages.

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Section: Shortwave Cloud Effectmentioning

confidence: 99%

Section: Shortwave Cloud Effectmentioning

confidence: 99%

Section: Shortwave Cloud Effectmentioning

confidence: 99%

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Cloud radiative effect, cloud fraction and cloud type at two stations in Switzerland using hemispherical sky cameras

et al. 2017

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“…The OLR is invariant to the cloud cover and cancels out. In general clouds have a surface SW cooling effect (negative SW CRE), although radiation enhancements due to the broken cloud effect can even lead to occasional and local larger fluxes at the surface than at the top of atmosphere (see Schade et al, 2007). Therefore, on short time-scales convective clouds can have a positive CRE.…”

Section: Cloud Radiative Effectmentioning

confidence: 99%

“…To correct for such errors, direct sun situations have been identified from light dispersion on the acrylic glass dome, and the calculated cloud amount was reduced by 9 % (Kalisch and Macke, 2008). No cosine-weighting of horizontal near pixel has been performed in order to minimize the influence of cloud sides on the total cloud cover (Schade et al, 2007).…”

Section: Cloud Covermentioning

confidence: 99%

Radiative budget and cloud radiative effect over the Atlantic from ship-based observations

2012

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Abstract. The aim of this study is to determine cloud-type resolved cloud radiative budgets and cloud radiative effects from surface measurements of broadband radiative fluxes over the Atlantic Ocean. Furthermore, based on simultaneous observations of the state of the cloudy atmosphere, a radiative closure study has been performed by means of the ECHAM5 single column model in order to identify the model's ability to realistically reproduce the effects of clouds on the climate system.An extensive database of radiative and atmospheric measurements has been established along five meridional cruises of the German research icebreaker Polarstern. Besides pyranometer and pyrgeometer for downward broadband solar and thermal radiative fluxes, a sky imager and a microwave radiometer have been utilized to determine cloud fraction and cloud type on the one hand and temperature and humidity profiles as well as liquid water path for warm nonprecipitating clouds on the other hand.Averaged over all cruise tracks, we obtain a total net (solar + thermal) radiative flux of 144 W m −2 that is dominated by the solar component. In general, the solar contribution is large for cirrus clouds and small for stratus clouds. No significant meridional dependencies were found for the surface radiation budgets and cloud effects. The strongest surface longwave cloud effects were shown in the presence of low level clouds. Clouds with a high optical density induce strong negative solar radiative effects under high solar altitudes. The mean surface net cloud radiative effect is −33 W m −2 .For the purpose of quickly estimating the mean surface longwave, shortwave and net cloud effects in moderate, subtropical and tropical climate regimes, a new parameterisation was created, considering the total cloud amount and the solar zenith angle.The ECHAM5 single column model provides a surface net cloud effect that is more cooling by 17 W m −2 compared to the radiation observations. This overestimation in solar cooling is mostly caused by the shortwave impact of convective clouds. The latter show a large overestimation in solar cooling of up to 114 W m −2 . Mean cloud radiative effects of cirrus and stratus clouds were simulated close to the observations.

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Radiative effect of aerosols above the northern and southern Atlantic Ocean as determined from shipborne lidar observations

et al. 2013

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[1] The direct solar radiative effect of aerosols over the Atlantic Ocean was investigated on the basis of aerosol Raman/polarization lidar observations aboard the research vessel Polarstern between Germany (50 ı N) and either South America (50 ı S) or South Africa (40 ı S) in 2009 and 2010. First, a case study of complex aerosol conditions with marine aerosol, dust, and smoke particles in the boundary layer and free troposphere is presented to demonstrate that detailed knowledge of aerosol layering (boundary layer, free troposphere) and aerosol mixing state is required for an accurate determination of the resulting radiative effects. A statistical analysis based on all lidar observations revealed the highest daily mean radiative effect (-43˙59 W m -2 at the surface, -14˙18 W m -2 at top of atmosphere) in the latitudinal belt from 0 ı N-15 ı N in the Saharan dust outflow region. Mean aerosol radiative effects of the polluted northern and clean southern midlatitudes were contrasted. In the northern midlatitudes, the averaged aerosol radiative effect of all simulations was -24˙33 W m -2 at the surface which is a factor of 1.6 higher than at similar southern hemispheric latitudes. The simulations based on the lidar observations are in good agreement with colocated pyranometer measurements.

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Enhanced solar global irradiance during cloudy sky conditions

Cited by 59 publications

References 0 publications

Cloud radiative effect, cloud fraction and cloud type at two stations in Switzerland using hemispherical sky cameras

Cloud radiative effect, cloud fraction and cloud type at two stations in Switzerland using hemispherical sky cameras

Radiative budget and cloud radiative effect over the Atlantic from ship-based observations

Radiative effect of aerosols above the northern and southern Atlantic Ocean as determined from shipborne lidar observations

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