 | Reinhardt B. On the retrieval of circumsolar radiation from satellite observations and weather model output: Diss. / Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen. - Köln: DLR, 2013. - x, 127 p.: ill. - (Forschungsbericht; 2013-33). - Res. also Germ. - Bibliogr.: p. 115-124. - ISSN 1434-8454
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Zusammenfassung ............................................... vii
Abstract ....................................................... ix
1 Introduction ................................................. 1
1.1 Circumsolar Radiation and Concentrating Solar
Technologies ............................................ 1
1.2 Aims of this Study ...................................... 3
2 Basic Principles ............................................. 7
2.1 The Radiative Transfer Equation ......................... 7
2.2 Scattering of Sunlight ................................. 10
2.3 Remote Sensing of Clouds from MSG ...................... 12
2.3.1 The SEVIRI Instrument ........................... 12
2.3.2 Retrieval of Cloud Properties from Reflected
Solar Radiation ................................. 15
2.4 Passive Satellite Remote Sensing of Aerosol ............ 17
2.5 The Sunshape ........................................... 19
2.6 The Circumsolar Ratio CSR .............................. 21
2.7 Ground Based Measurements of the Circumsolar
Radiation .............................................. 23
3 Tools and Methods ........................................... 25
3.1 Optical and Mierophysical Properties of Cirrus Clouds .. 25
3.2 Cloud Property Remote Sensing with the APICS
Algorithm .............................................. 27
3.2.1 Algorithm Description ........................... 27
3.2.2 Auxiliary Albedo Dataset ........................ 28
3.2.3 Cirrus Cloud Mask ............................... 31
3.3 Aerosol Input and Processing .......................... 33
3.3.1 Modeled Aerosol Data from the ECMWF IPS ......... 33
3.3.2 Aerosol Optical Properties ...................... 34
3.3.3 Post-Processing of ECMWF Output ................. 39
3.4 Atmospheric Radiative Transfer ......................... 40
3.4.1 The RTE-Solvers DISORT and MYSTIC ............... 40
3.4.2 Adaptation of the RTE-Solver MYSTIC ............. 42
3.4.3 Pseudo-Spectral and Solar Integrated Radiative
Transfer ........................................ 50
3.5 Parametrization of Circumsolar Radiation ............... 52
3.5.1 Concept of the Apparent Optical Thickness ....... 53
3.5.2 Treatment of Multiple Scattering Layers - The
Adding Method ................................... 58
3.5.3 Sensitivity of the CSR Parameterization on Sun
Zenith Angle .................................... 64
3.5.4 Sensitivity of the CSR Parameterization on the
Scattering Layer's Geometry ..................... 65
3.5.5 Further Aspects of the Apparent Optical
Thickness Approach .............................. 60
3.6 Sensitivity of Circumsolar Radiation to Ice Particle
Shape .................................................. 67
3.7 Sensitivity of CSR to Aerosol Particle Shape and
Relative Humidity ...................................... 68
4 Results ..................................................... 73
4.1 Intercomparison of Retrieval Results for Different
Ice Particle Shapes .................................... 73
4.2 Validation ............................................. 76
4.2.1 Validation of Aerosol Related Circumsolar
Radiation ....................................... 79
4.2.2 Validation of Cirrus Related Circumsolar
Radiation ....................................... 82
4.3 Characteristics of Cirrus Related Circumsolar
Radiation .............................................. 89
4.3.1 Spatial Distribution ............................ 89
4.3.2 Irradiance Overestimation by Pyrheliometers ..... 91
4.3.3 Relation of Irradiance and CSR .................. 94
5 Discussion .................................................. 97
5.1 Statistical Post-Processing of IFS Aerosol Output ...... 97
5.2 Uncertainties in the Cirrus Cloud Property Retrieval .. 100
5.2.1 Undetected Cirrus Clouds ....................... 101
5.2.2 Spurious SEVIRI Pixels ......................... 107
5.3 Comparison of the Satellite CSR Retrieval to
a Regression Model .................................... 107
6 Conclusions ................................................ 111
6.1 Synopsis of Findings .................................. 112
6.2 Outlook ............................................... 113
Bibliography .................................................. 115
Glossary ...................................................... 125
Acknowledgements .............................................. 127
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