Modeling Global Irradiance under All Sky Conditions

2017 ◽  
pp. 65-79
Keyword(s):  
Global Irradiance ◽  
Sky Conditions

scholarly journals Typical distribution of the solar erythemal UV radiation over Slovakia

2008 ◽  
Vol 8 (17) ◽  
pp. 5393-5401 ◽  
Author(s):  
A. Pribullová ◽  
M. Chmelík
Keyword(s):  
Snow Cover ◽  
Total Ozone ◽  
Horizontal Resolution ◽  
Clear Sky ◽  
Global Irradiance ◽  
Daily Dose ◽  
Monthly Total ◽  
Modification Factor ◽  
Typical Distribution ◽  
Sky Conditions

Abstract. Maps of solar erythemal ultraviolet (EUV) irradiance daily doses were created for every month with a horizontal resolution of 500 m at the geographical domain 47.15 N–49.86 N×16.94 E–22.81 E covering the territory of Slovakia. The cloud modification factor for the EUV radiation (cmfUV) was modeled utilizing the relation between the cloud modification factor of global and EUV radiation. The maps of the cmfUV factor were created by utilizing measurements of global irradiance performed at nine observatories during the period 1995–2004 and modeling of the cmfUV dependence on altitude. Maps of the EUV irradiance daily dose corresponded to clear-sky conditions and EUV irradiance daily dose affected by average cloudiness were constructed for mean monthly total ozone, its upper and lower monthly limits, for two probability levels of snow cover occurrence as criteria for the snow effect incorporation in the model and for one day representing typical values for every month. The map-set can be regarded as an atlas of solar EUV radiation over Slovakia.

scholarly journals Spatiotemporal variability of shortwave radiation introduced by clouds over the Arctic sea ice

2019 ◽  
Author(s):  
Carola Barrientos Velasco ◽  
Hartwig Deneke ◽  
Hannes Griesche ◽  
Patric Seifert ◽  
Ronny Engelmann ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Sea Ice ◽  
Spatiotemporal Variability ◽  
Shortwave Radiation ◽  
The Arctic ◽  
Cloud Base ◽  
Small Scale ◽  
Global Irradiance ◽  
Synoptic Conditions ◽  
Sky Conditions

Abstract. The role of clouds in recent Arctic warming is not fully understood, including their effects on the shortwave radiation and the surface energy budget. To investigate relevant small-scale processes in detail, an intensive field campaign was conducted during early summer in the central Arctic during the Physical feedbacks of Arctic planetary boundary layer, Sea ice, Cloud and AerosoL (PASCAL) drifting ice floe station. During this campaign, the small-scale spatiotemporal variability of global irradiance was observed for the first time on an ice floe with a dense network of autonomous pyranometers. 15 stations were deployed covering an area of 0.83 km × 1.3 km from June 4–16, 2017. This unique, open-access dataset is described here, and an analysis of the spatiotemporal variability deduced from this dataset is presented for different synoptic conditions. Based on additional observations, 5 typical sky conditions were identified and used to determine the values of the mean and variance of atmospheric global transmittance for these conditions. Overcast conditions were observed 39.6 % of the time predominantly during the first week, with an overall mean transmittance of 0.47. The second-most frequent conditions corresponded to multi-layer clouds (32.4 %) which prevailed in particular during the second week, with a mean transmittance of 0.43. Broken clouds had a mean transmittance of 0.61 and a frequency of occurrence of 22.1 %. Finally, the least frequent sky conditions were thin clouds and cloudless conditions, which both had a mean transmittance of 0.76, and occurrence frequencies of 3.5 % and 2.4 %, respectively. For overcast conditions, lower global irradiance was observed for stations closer to the ice edge, likely attributable to the low surface albedo of dark open water, and a resulting reduction of multiple reflections between the surface and cloud base. Using a wavelet-based multi-resolution analysis, power spectra of the time-series of atmospheric transmittance were compared for single-station and spatially averaged observations, and for different sky conditions. It is shown that both the absolute magnitude and the scale-dependence of variability contains characteristic features for the different sky conditions.

scholarly journals Spatiotemporal variability of solar radiation introduced by clouds over Arctic sea ice

2020 ◽  
Vol 13 (4) ◽  
pp. 1757-1775 ◽  
Author(s):  
Carola Barrientos Velasco ◽  
Hartwig Deneke ◽  
Hannes Griesche ◽  
Patric Seifert ◽  
Ronny Engelmann ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Sea Ice ◽  
Arctic Sea Ice ◽  
Spatiotemporal Variability ◽  
Cloud Base ◽  
Small Scale ◽  
Global Irradiance ◽  
Synoptic Conditions ◽  
Single Station ◽  
Sky Conditions

Abstract. The role of clouds in recent Arctic warming is not fully understood, including their effects on the solar radiation and the surface energy budget. To investigate relevant small-scale processes in detail, the intensive Physical feedbacks of Arctic planetary boundary layer, Sea ice, Cloud and AerosoL (PASCAL) drifting ice floe station field campaign was conducted during early summer in the central arctic. During this campaign, the small-scale spatiotemporal variability of global irradiance was observed for the first time on an ice floe with a dense network of autonomous pyranometers. A total of 15 stations were deployed covering an area of 0.83 km×1.59 km from 4–16 June 2017. This unique, open-access dataset is described here, and an analysis of the spatiotemporal variability deduced from this dataset is presented for different synoptic conditions. Based on additional observations, five typical sky conditions were identified and used to determine the values of the mean and variance of atmospheric global transmittance for these conditions. Overcast conditions were observed 39.6 % of the time predominantly during the first week, with an overall mean transmittance of 0.47. The second most frequent conditions corresponded to multilayer clouds (32.4 %), which prevailed in particular during the second week, with a mean transmittance of 0.43. Broken clouds had a mean transmittance of 0.61 and a frequency of occurrence of 22.1 %. Finally, the least frequent sky conditions were thin clouds and cloudless conditions, which both had a mean transmittance of 0.76 and occurrence frequencies of 3.5 % and 2.4 %, respectively. For overcast conditions, lower global irradiance was observed for stations closer to the ice edge, likely attributable to the low surface albedo of dark open water and a resulting reduction of multiple reflections between the surface and cloud base. Using a wavelet-based multi-resolution analysis, power spectra of the time series of atmospheric transmittance were compared for single-station and spatially averaged observations and for different sky conditions. It is shown that both the absolute magnitude and the scale dependence of variability contains characteristic features for the different sky conditions.

Enhanced solar global irradiance during cloudy sky conditions

2007 ◽  
Vol 16 (3) ◽  
pp. 295-303 ◽  
Author(s):  
Nils H. Schade ◽  
Andreas Macke ◽  
H. Sandmann ◽  
C. Stick
Keyword(s):  
Global Irradiance ◽  
Sky Conditions

scholarly journals Solar irradiance in the heterogeneous albedo environment of the Arctic coast: measurements and a 3-D-model study

2014 ◽  
Vol 14 (3) ◽  
pp. 3499-3536 ◽  
Author(s):  
A. Kreuter ◽  
R. Buras ◽  
B. Mayer ◽  
A. Webb ◽  
R. Kift ◽  
...  
Keyword(s):  
The Arctic ◽  
Radiative Transfer Model ◽  
Time Shift ◽  
Transfer Model ◽  
Coastal Site ◽  
Global Irradiance ◽  
Model Study ◽  
Arctic Coast ◽  
Sky Conditions ◽  
Model Scenarios

Abstract. We present a unique case study of the solar global irradiance in a highly heterogeneous albedo environment at the arctic coast. Diodearray spectroradiometers were deployed at three sites around Ny Ålesund, Svalbard, and spectral irradiances were simultaneously measured under clear sky conditions during a 24 h period. The 3-D radiative transfer model MYSTIC is applied to simulate the measurements in various model scenarios. First, we model the effective albedos of ocean and snow and consequently around each measurement site. The effective albedos at 340 nm increase from 0.57 to 0.75, from the coastal site in the west towards the site 20 km east, away from the coast. The observed ratios of the global irradiance indicate a 15% higher average irradiance at east relative to west at 340 nm due to the higher albedo. The comparison to our model scenarios suggest a snow albedo of >0.9 and confirm the observation that drift ice has moved into the Fjord during the day. The local time shift between the locations causes a hysteresis-like behavior of these east-west ratios with solar zenith angle (SZA). The observed hysteresis, however, is larger and, at 340 nm, can be explained by the drift ice. At 500 nm, a plausible explanation is a detector tilt of about 1°. The ratios between afternoon and morning irradiances at the same SZA are investigated, which confirm the above conclusions. At the coastal site, the measured irradiance is significantly higher in the afternoon than in the morning. Besides the effect of changing drift ice and detector tilt, the small variations of the aerosol optical depth have to be considered also at the other stations to reduce the discrepancies between model and observations. Remaining discrepancies are possibly due to high thin clouds.

scholarly journals Solar irradiance in the heterogeneous albedo environment of the Arctic coast: measurements and a 3-D model study

2014 ◽  
Vol 14 (12) ◽  
pp. 5989-6002 ◽  
Author(s):  
A. Kreuter ◽  
R. Buras ◽  
B. Mayer ◽  
A. Webb ◽  
R. Kift ◽  
...  
Keyword(s):  
The Arctic ◽  
Radiative Transfer Model ◽  
Time Shift ◽  
Transfer Model ◽  
Coastal Site ◽  
Global Irradiance ◽  
Model Study ◽  
Arctic Coast ◽  
Sky Conditions ◽  
Model Scenarios

Abstract. We present a unique case study of the solar global irradiance in a highly heterogeneous albedo environment at the Arctic coast. Diodearray spectroradiometers were deployed at three sites around Ny Ålesund, Svalbard, and spectral irradiances were simultaneously measured under clear-sky conditions during a 24 h period. The 3-D radiative transfer model MYSTIC is applied to simulate the measurements in various model scenarios. First, we model the effective albedos of ocean and snow and consequently around each measurement site. The effective albedos at 340 nm increase from 0.57 to 0.75, from the coastal site in the west towards the site 20 km east, away from the coast. The observed ratios of the global irradiance indicate a 15% higher average irradiance, at 340 nm east relative to west, due to the higher albedo. The comparison of our model scenarios suggest a snow albedo of > 0.9 and confirm the observation that drift ice has moved into the Fjord during the day. The local time shift between the locations causes a hysteresis-like behavior of these east–west ratios with solar zenith angle (SZA). The observed hysteresis, however, is larger and, at 340 nm, can be explained by the drift ice. At 500 nm, a plausible explanation is a detector tilt of about 1°. The ratios between afternoon and morning irradiances at the same SZA are investigated, which confirm the above conclusions. At the coastal site, the measured irradiance is significantly higher in the afternoon than in the morning. Besides the effect of changing drift ice and detector tilt, the small variations of the aerosol optical depth have to be considered also at the other stations to reduce the discrepancies between model and observations. Remaining discrepancies are possibly due to distant high clouds.

scholarly journals Validation of the McClear clear-sky model in desert conditions with three stations in Israel

2016 ◽  
Vol 13 ◽  
pp. 21-26 ◽  
Author(s):  
Mireille Lefèvre ◽  
Lucien Wald
Keyword(s):  
Correlation Coefficient ◽  
United Arab Emirates ◽  
Ground Level ◽  
Normal Incidence ◽  
Clear Sky ◽  
Global Irradiance ◽  
Desert Areas ◽  
The Mean ◽  
Monitoring Service ◽  
Sky Conditions

Abstract. The new McClear clear-sky model, a fast model based on a radiative transfer solver, exploits the atmospheric properties provided by the EU-funded Copernicus Atmosphere Monitoring Service (CAMS) to estimate the solar direct and global irradiances received at ground level in cloud-free conditions at any place any time. The work presented here focuses on desert conditions and compares the McClear irradiances to coincident 1 min measurements made in clear-sky conditions at three stations in Israel which are distant from less than 100 km. The bias for global irradiance is comprised between 2 and 32 W m−2, i.e. between 0 and 4 % of the mean observed irradiance (approximately 830 W m−2). The RMSE ranges from 30 to 41 W m−2 (4 %) and the squared correlation coefficient is greater than 0.976. The bias for the direct irradiance at normal incidence (DNI) is comprised between −68 and +13 W m−2, i.e. between −8 and 2 % of the mean observed DNI (approximately 840 W m−2). The RMSE ranges from 53 (7 %) to 83 W m−2 (10 %). The squared correlation coefficient is close to 0.6. The performances are similar for the three sites for the global irradiance and for the DNI to a lesser extent, demonstrating the robustness of the McClear model combined with CAMS products. These results are discussed in the light of those obtained by McClear for other desert areas in Egypt and United Arab Emirates.

Evaluation of net shortwave radiation over China with a regional climate model

2020 ◽  
Vol 80 (2) ◽  
pp. 147-163
Author(s):  
X Liu ◽  
Y Kang ◽  
Q Liu ◽  
Z Guo ◽  
Y Chen ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Radiant Energy ◽  
Energy System ◽  
Radiation Budget ◽  
Shortwave Radiation ◽  
Monsoon Region ◽  
Clear Sky ◽  
Sky Conditions

The regional climate model RegCM version 4.6, developed by the European Centre for Medium-Range Weather Forecasts Reanalysis, was used to simulate the radiation budget over China. Clouds and the Earth’s Radiant Energy System (CERES) satellite data were utilized to evaluate the simulation results based on 4 radiative components: net shortwave (NSW) radiation at the surface of the earth and top of the atmosphere (TOA) under all-sky and clear-sky conditions. The performance of the model for low-value areas of NSW was superior to that for high-value areas. NSW at the surface and TOA under all-sky conditions was significantly underestimated; the spatial distribution of the bias was negative in the north and positive in the south, bounded by 25°N for the annual and seasonal averaged difference maps. Compared with the all-sky condition, the simulation effect under clear-sky conditions was significantly better, which indicates that the cloud fraction is the key factor affecting the accuracy of the simulation. In particular, the bias of the TOA NSW under the clear-sky condition was <±10 W m-2 in the eastern areas. The performance of the model was better over the eastern monsoon region in winter and autumn for surface NSW under clear-sky conditions, which may be related to different levels of air pollution during each season. Among the 3 areas, the regional average biases overall were largest (negative) over the Qinghai-Tibet alpine region and smallest over the eastern monsoon region.

Efficient downscaling of satellite oceanographic data with convolutional neural networks

2021 ◽  
Vol 12 (3) ◽  
pp. 46-47
Author(s):  
Nikita Saxena
Keyword(s):  
Neural Networks ◽  
Deep Learning ◽  
Convolutional Neural Networks ◽  
Super Resolution ◽  
Sea Surface ◽  
Clear Sky ◽  
Oceanographic Data ◽  
Computationally Expensive ◽  
Sky Conditions ◽  
Data Inference

Space-borne satellite radiometers measure Sea Surface Temperature (SST), which is pivotal to studies of air-sea interactions and ocean features. Under clear sky conditions, high resolution measurements are obtainable. But under cloudy conditions, data analysis is constrained to the available low resolution measurements. We assess the efficiency of Deep Learning (DL) architectures, particularly Convolutional Neural Networks (CNN) to downscale oceanographic data from low spatial resolution (SR) to high SR. With a focus on SST Fields of Bay of Bengal, this study proves that Very Deep Super Resolution CNN can successfully reconstruct SST observations from 15 km SR to 5km SR, and 5km SR to 1km SR. This outcome calls attention to the significance of DL models explicitly trained for the reconstruction of high SR SST fields by using low SR data. Inference on DL models can act as a substitute to the existing computationally expensive downscaling technique: Dynamical Downsampling. The complete code is available on this Github Repository.

The influence of small cloud covers on the global irradiance at sea

1976 ◽  
Vol 81 (3) ◽  
pp. 395-398 ◽  
Author(s):  
Jack A. C. Kaiser ◽  
Robert H. Hill
Keyword(s):  
Global Irradiance ◽  
Small Cloud
Sign in / Sign up

Export Citation Format

Share Document