Remote sensing of cloud droplet radius profiles using solar reflectance from cloud sides – Part 1: Retrieval development and characterization
<p>Convective clouds play an essential role for Earth's climate as well as for regional weather events since they have a large influence on the radiation budget and the water cycle. In particular, cloud albedo and the formation of precipitation are influenced by aerosol particles within c...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/12/1183/2019/amt-12-1183-2019.pdf |
| _version_ | 1811198212259708928 |
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| author | F. Ewald F. Ewald T. Zinner T. Kölling B. Mayer |
| author_facet | F. Ewald F. Ewald T. Zinner T. Kölling B. Mayer |
| author_sort | F. Ewald |
| collection | DOAJ |
| description | <p>Convective clouds play an essential role for Earth's
climate as well as for regional weather events since they have a large
influence on the radiation budget and the water cycle. In particular, cloud
albedo and the formation of precipitation are influenced by aerosol particles
within clouds. In order to improve the understanding of processes from
aerosol activation, from cloud droplet growth to changes in cloud radiative
properties, remote sensing techniques become more and more important. While
passive retrievals for spaceborne observations have become sophisticated and
commonplace for inferring cloud optical thickness and droplet size from cloud
tops, profiles of droplet size have remained largely uncharted territory for
passive remote sensing. In principle they could be derived from observations
of cloud sides, but faced with the small-scale heterogeneity of cloud sides, “classical” passive remote sensing techniques are rendered inappropriate.
In this work the feasibility is demonstrated to gain new insights into the
vertical evolution of cloud droplet effective radius by using reflected solar
radiation from cloud sides. Central aspect of this work on its path to a
working cloud side retrieval is the analysis of the impact unknown cloud
surface geometry has on effective radius retrievals. This study examines the
sensitivity of reflected solar radiation to cloud droplet size, using
extensive 3-D radiative transfer calculations on the basis of realistic
droplet size resolving cloud simulations. Furthermore, it explores a further
technique to resolve ambiguities caused by illumination and cloud geometry by
considering the surroundings of each pixel. Based on these findings, a
statistical approach is used to provide an effective radius retrieval. This
statistical effective radius retrieval is focused on the liquid part of
convective water clouds, e.g., cumulus mediocris, cumulus congestus, and
trade-wind cumulus, which exhibit well-developed cloud sides. Finally, the
developed retrieval is tested using known and unknown cloud side scenes to
analyze its performance.</p> |
| first_indexed | 2024-04-12T01:28:06Z |
| format | Article |
| id | doaj.art-0afb80481cac42caafe578140461c572 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-04-12T01:28:06Z |
| publishDate | 2019-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-0afb80481cac42caafe578140461c5722022-12-22T03:53:34ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482019-02-01121183120610.5194/amt-12-1183-2019Remote sensing of cloud droplet radius profiles using solar reflectance from cloud sides – Part 1: Retrieval development and characterizationF. Ewald0F. Ewald1T. Zinner2T. Kölling3B. Mayer4Meteorologisches Institut, Ludwig-Maximilians-Universität, Munich, GermanyDeutsches Zentrum für Luft und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, GermanyMeteorologisches Institut, Ludwig-Maximilians-Universität, Munich, GermanyMeteorologisches Institut, Ludwig-Maximilians-Universität, Munich, GermanyMeteorologisches Institut, Ludwig-Maximilians-Universität, Munich, Germany<p>Convective clouds play an essential role for Earth's climate as well as for regional weather events since they have a large influence on the radiation budget and the water cycle. In particular, cloud albedo and the formation of precipitation are influenced by aerosol particles within clouds. In order to improve the understanding of processes from aerosol activation, from cloud droplet growth to changes in cloud radiative properties, remote sensing techniques become more and more important. While passive retrievals for spaceborne observations have become sophisticated and commonplace for inferring cloud optical thickness and droplet size from cloud tops, profiles of droplet size have remained largely uncharted territory for passive remote sensing. In principle they could be derived from observations of cloud sides, but faced with the small-scale heterogeneity of cloud sides, “classical” passive remote sensing techniques are rendered inappropriate. In this work the feasibility is demonstrated to gain new insights into the vertical evolution of cloud droplet effective radius by using reflected solar radiation from cloud sides. Central aspect of this work on its path to a working cloud side retrieval is the analysis of the impact unknown cloud surface geometry has on effective radius retrievals. This study examines the sensitivity of reflected solar radiation to cloud droplet size, using extensive 3-D radiative transfer calculations on the basis of realistic droplet size resolving cloud simulations. Furthermore, it explores a further technique to resolve ambiguities caused by illumination and cloud geometry by considering the surroundings of each pixel. Based on these findings, a statistical approach is used to provide an effective radius retrieval. This statistical effective radius retrieval is focused on the liquid part of convective water clouds, e.g., cumulus mediocris, cumulus congestus, and trade-wind cumulus, which exhibit well-developed cloud sides. Finally, the developed retrieval is tested using known and unknown cloud side scenes to analyze its performance.</p>https://www.atmos-meas-tech.net/12/1183/2019/amt-12-1183-2019.pdf |
| spellingShingle | F. Ewald F. Ewald T. Zinner T. Kölling B. Mayer Remote sensing of cloud droplet radius profiles using solar reflectance from cloud sides – Part 1: Retrieval development and characterization Atmospheric Measurement Techniques |
| title | Remote sensing of cloud droplet radius profiles using solar reflectance from cloud sides – Part 1: Retrieval development and characterization |
| title_full | Remote sensing of cloud droplet radius profiles using solar reflectance from cloud sides – Part 1: Retrieval development and characterization |
| title_fullStr | Remote sensing of cloud droplet radius profiles using solar reflectance from cloud sides – Part 1: Retrieval development and characterization |
| title_full_unstemmed | Remote sensing of cloud droplet radius profiles using solar reflectance from cloud sides – Part 1: Retrieval development and characterization |
| title_short | Remote sensing of cloud droplet radius profiles using solar reflectance from cloud sides – Part 1: Retrieval development and characterization |
| title_sort | remote sensing of cloud droplet radius profiles using solar reflectance from cloud sides part 1 retrieval development and characterization |
| url | https://www.atmos-meas-tech.net/12/1183/2019/amt-12-1183-2019.pdf |
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