clouds, aerosols and the directional ......aerosols and radiation • cloud-radiation interactions...
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KRISTIAN PAGH NIELSEN, DANISH METEOROLOGICAL INSTITUTE, [email protected]. ELSA ANDERSEN, SIMON FURBO & JANNE DRAGSTED, TECHNICAL UNIVERSITY OF
DENMARK (DTU). EMILY GLEESON, MET ÉIRANN
CLOUDS, AEROSOLS AND THE DIRECTIONAL DISTRIBUTION OF SOLAR IRRADIANCES
WHY ARE WE INTERESTED IN DIRECTIONAL IRRADIANCES?
• Solar heating and PV panels• Passive solar heating and illumination of
buildings
WHY ARE WE INTERESTED IN DIRECTIONAL IRRADIANCES?
• Solar heating and PV panels• Passive solar heating and illumination of
buildings• The detailed sunshape (important for
CSP) is not a focus here!
CLOUDS AND RADIATION• Cloud-radiation interactions depend on the following steps:
1. Cloud cover
CLOUDS AND RADIATION• Cloud-radiation interactions depend on the following steps:
1. Cloud cover 2. Cloud physical properties: (Gleeson et al. 2015; ALADIN-HIRLAM Newsletter)
a) Liquid water load [kg/m2] b) Ice water load [kg/m2] c) Effective radii [µm]
CLOUDS AND RADIATION• Cloud-radiation interactions depend on the following steps:
1. Cloud cover 2. Cloud physical properties: (Gleeson et al. 2015; ALADIN-HIRLAM Newsletter)
a) Liquid water load [kg/m2] b) Ice water load [kg/m2] c) Effective radii [µm]
3. Cloud optical properties (Nielsen et al. 2014; Geosci. Model Dev.)
CLOUDS AND RADIATION• Cloud-radiation interactions depend on the following steps:
1. Cloud cover 2. Cloud physical properties: (Gleeson et al. 2015; ALADIN-HIRLAM Newsletter)
a) Liquid water load [kg/m2] b) Ice water load [kg/m2] c) Effective radii [µm]
3. Cloud optical properties (Nielsen et al. 2014; Geosci. Model Dev.) 4. Radiative transfer approximations (Nielsen et al. 2014; Geosci. Model Dev.)
AEROSOLS AND RADIATION• Cloud-radiation interactions depend on the
following steps:
1. Aerosol concentration [g/m3] / load [g/m2] 2. Aerosol optical properties ——————-> 3. Radiative transfer approximations
From Gleeson et al. (2015) Atmos. Chem. Physics COST action ES1004 EuMetChem special issue
AEROSOLS AND RADIATION• Cloud-radiation interactions depend on the
following steps:
1. Aerosol concentration [g/m3] and load [g/m2]
2. Aerosol optical properties ——————-> 3. Radiative transfer approximations
From Gleeson et al. (2015) Atmos. Chem. Physics COST action ES1004 EuMetChem special issue
Simulated errors from assuming typical (IFS_land) optical properties:
AODbroadband vs AOD550nm -30% GHI error
AOD* = (1-a·g2)·AOD +15% GHI error
MEASUREMENTS PERFORMED AT DTUAndersen, Nielsen, Dragsted & Furbo (2015), Energy Procedia, 70: 729-736.
Dragsted & Furbo (2012): DTU Byg, report R-275. Available from http://www.byg.dtu.dk/Publikationer/Byg_rapporter
Skalik et al. (2012): “Evaluation of long term global radiation measurements in Denmark and Sweden”. EuroSun 2012 Proceedings
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MEASUREMENTS PERFORMED AT DTUAndersen, Nielsen, Dragsted & Furbo (2015), Energy Procedia, 70: 729-736.
Dragsted & Furbo (2012): DTU Byg, report R-275. Available from http://www.byg.dtu.dk/Publikationer/Byg_rapporter
Skalik et al. (2012): “Evaluation of long term global radiation measurements in Denmark and Sweden”. EuroSun 2012 Proceedings
1-D THEORETICAL STUDY OF RADIANCES• Calculated with
DISORT/libRadtran (Stamnes et al. 1988, 2000, 2015; Mayer & Kylling 2005)
Accuracy of DISORT spectral radiances demonstrated in (Hestenes et al. 2006, Appl. Opt.)
1-D THEORETICAL STUDY OF RADIANCES• Even in the simple
1-D case, the distribution of directional radiances across the sky is never isotropic!
• Key issue: The effects of inhomogeneous clouds on data at high temporal resolution
HOURLY DTU DATAGood models exist for instance: Skartveit et al. (1998)
For tilted surfaces: Perez (1986, 1987, 1993)
2-MINUTE DTU DATAAt high temporal resolution things are more complicated
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SCATTERED HORIZONTAL IRRADIANCE (SHI) AND CLOUD OPTICAL THICKNESS (TAU)
DIRECTIONAL SCATTERED HORIZONTAL IRRADIANCE AND CLOUD OPTICAL THICKNESS (TAU) / COS(SZA)
DIRECTIONAL SCATTERED HORIZONTAL IRRADIANCE AND CLOUD OPTICAL THICKNESS (TAU) / COS(SZA)
DIRECTIONAL SCATTERED HORIZONTAL IRRADIANCE AND CLOUD OPTICAL THICKNESS (TAU) / COS(SZA)
DIRECTIONAL SCATTERED HORIZONTAL IRRADIANCE AND CLOUD OPTICAL THICKNESS (TAU) / COS(SZA)
DIRECTIONAL SCATTERED HORIZONTAL IRRADIANCE AND CLOUD OPTICAL THICKNESS (TAU) / COS(SZA)
DIRECTIONAL SCATTERED HORIZONTAL IRRADIANCE AND CLOUD OPTICAL THICKNESS (TAU) / COS(SZA)
DIRECTIONAL SCATTERED HORIZONTAL IRRADIANCE AND CLOUD OPTICAL THICKNESS (TAU) / COS(SZA)
DIRECTIONAL SCATTERED HORIZONTAL IRRADIANCE AND CLOUD OPTICAL THICKNESS (TAU) / COS(SZA)
CONCLUSION• Based on detailed irradiance measurement at the DTU
measurement site…
• … a new method is suggested, in which the two physical variables:
• Cloud optical thickness and
• Inhomogeneous cloud reflectance
• are used to form a basis for simulating directional irradiances with high temporal resolution.
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