Retrievals of Cloud Droplet Size from the RSP Data: Validation Using in Situ Measurements
We present comparisons of cloud droplet size distributions retrieved from the Research Scanning Polarimeter (RSP) data with correlative in situ measurements made during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). This field experiment was based at St. Johns airport, Newfoundlan...
Main Authors: | , , , , , , , , , |
---|---|
Format: | Other/Unknown Material |
Language: | unknown |
Published: |
2016
|
Subjects: | |
Online Access: | http://hdl.handle.net/2060/20160014659 |
id |
ftnasantrs:oai:casi.ntrs.nasa.gov:20160014659 |
---|---|
record_format |
openpolar |
spelling |
ftnasantrs:oai:casi.ntrs.nasa.gov:20160014659 2023-05-15T17:23:01+02:00 Retrievals of Cloud Droplet Size from the RSP Data: Validation Using in Situ Measurements Stamnes, Snorre Hair, John Sinclair, Kenneth Crosbie, Ewan Alexandrov, Mikhail D. Wasilewski, Andrzej P. Hostetler, Chris Hu, Yongxiang Ziemba, Luke Cairns, Brian Unclassified, Unlimited, Publicly available December 12, 2016 application/pdf http://hdl.handle.net/2060/20160014659 unknown Document ID: 20160014659 http://hdl.handle.net/2060/20160014659 Copyright, Distribution as joint owner in the copyright CASI Earth Resources and Remote Sensing Meteorology and Climatology GSFC-E-DAA-TN38026 AGU Fall Meeting 2016; 12-16 Dec. 2016; San Francisco, CA; United States 2016 ftnasantrs 2019-07-20T23:42:19Z We present comparisons of cloud droplet size distributions retrieved from the Research Scanning Polarimeter (RSP) data with correlative in situ measurements made during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). This field experiment was based at St. Johns airport, Newfoundland, Canada with the latest deployment in May - June 2016. RSP was onboard the NASA C-130 aircraft together with an array of in situ and other remote sensing instrumentation. The RSP is an along-track scanner measuring polarized and total reflectances in9 spectral channels. Its unique high angular resolution allows for characterization of liquid water droplet size using the rainbow structure observed in the polarized reflectances in the scattering angle range between 135 and 165 degrees. A parametric fitting algorithm applied to the polarized reflectances provides retrievals of the droplet effective radius and variance assuming a prescribed size distribution shape (gamma distribution). In addition to this, we use a non-parametric method, Rainbow Fourier Transform (RFT), which allows us to retrieve the droplet size distribution (DSD) itself. The latter is important in the case of clouds with complex structure, which results in multi-modal DSDs. During NAAMES the aircraft performed a number of flight patterns specifically designed for comparison of remote sensing retrievals and in situ measurements. These patterns consisted of two flight segments above the same straight ground track. One of these segments was flown above clouds allowing for remote sensing measurements, while the other was at the cloud top where cloud droplets were sampled. We compare the DSDs retrieved from the RSP data with in situ measurements made by the Cloud Droplet Probe (CDP). The comparisons show generally good agreement with deviations explainable by the position of the aircraft within cloud and by presence of additional cloud layers in RSP view that do not contribute to the in situ DSDs. In the latter case the distributions retrieved from the RSP data were consistent with the multi-layer cloud structures observed in the correlative High Spectral Resolution Lidar (HSRL) profiles. The comparison results provide a rare validation of polarimetric droplet size retrieval techniques, which can be used for analysis of satellite data on global scale. Other/Unknown Material Newfoundland North Atlantic NASA Technical Reports Server (NTRS) Canada |
institution |
Open Polar |
collection |
NASA Technical Reports Server (NTRS) |
op_collection_id |
ftnasantrs |
language |
unknown |
topic |
Earth Resources and Remote Sensing Meteorology and Climatology |
spellingShingle |
Earth Resources and Remote Sensing Meteorology and Climatology Stamnes, Snorre Hair, John Sinclair, Kenneth Crosbie, Ewan Alexandrov, Mikhail D. Wasilewski, Andrzej P. Hostetler, Chris Hu, Yongxiang Ziemba, Luke Cairns, Brian Retrievals of Cloud Droplet Size from the RSP Data: Validation Using in Situ Measurements |
topic_facet |
Earth Resources and Remote Sensing Meteorology and Climatology |
description |
We present comparisons of cloud droplet size distributions retrieved from the Research Scanning Polarimeter (RSP) data with correlative in situ measurements made during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). This field experiment was based at St. Johns airport, Newfoundland, Canada with the latest deployment in May - June 2016. RSP was onboard the NASA C-130 aircraft together with an array of in situ and other remote sensing instrumentation. The RSP is an along-track scanner measuring polarized and total reflectances in9 spectral channels. Its unique high angular resolution allows for characterization of liquid water droplet size using the rainbow structure observed in the polarized reflectances in the scattering angle range between 135 and 165 degrees. A parametric fitting algorithm applied to the polarized reflectances provides retrievals of the droplet effective radius and variance assuming a prescribed size distribution shape (gamma distribution). In addition to this, we use a non-parametric method, Rainbow Fourier Transform (RFT), which allows us to retrieve the droplet size distribution (DSD) itself. The latter is important in the case of clouds with complex structure, which results in multi-modal DSDs. During NAAMES the aircraft performed a number of flight patterns specifically designed for comparison of remote sensing retrievals and in situ measurements. These patterns consisted of two flight segments above the same straight ground track. One of these segments was flown above clouds allowing for remote sensing measurements, while the other was at the cloud top where cloud droplets were sampled. We compare the DSDs retrieved from the RSP data with in situ measurements made by the Cloud Droplet Probe (CDP). The comparisons show generally good agreement with deviations explainable by the position of the aircraft within cloud and by presence of additional cloud layers in RSP view that do not contribute to the in situ DSDs. In the latter case the distributions retrieved from the RSP data were consistent with the multi-layer cloud structures observed in the correlative High Spectral Resolution Lidar (HSRL) profiles. The comparison results provide a rare validation of polarimetric droplet size retrieval techniques, which can be used for analysis of satellite data on global scale. |
format |
Other/Unknown Material |
author |
Stamnes, Snorre Hair, John Sinclair, Kenneth Crosbie, Ewan Alexandrov, Mikhail D. Wasilewski, Andrzej P. Hostetler, Chris Hu, Yongxiang Ziemba, Luke Cairns, Brian |
author_facet |
Stamnes, Snorre Hair, John Sinclair, Kenneth Crosbie, Ewan Alexandrov, Mikhail D. Wasilewski, Andrzej P. Hostetler, Chris Hu, Yongxiang Ziemba, Luke Cairns, Brian |
author_sort |
Stamnes, Snorre |
title |
Retrievals of Cloud Droplet Size from the RSP Data: Validation Using in Situ Measurements |
title_short |
Retrievals of Cloud Droplet Size from the RSP Data: Validation Using in Situ Measurements |
title_full |
Retrievals of Cloud Droplet Size from the RSP Data: Validation Using in Situ Measurements |
title_fullStr |
Retrievals of Cloud Droplet Size from the RSP Data: Validation Using in Situ Measurements |
title_full_unstemmed |
Retrievals of Cloud Droplet Size from the RSP Data: Validation Using in Situ Measurements |
title_sort |
retrievals of cloud droplet size from the rsp data: validation using in situ measurements |
publishDate |
2016 |
url |
http://hdl.handle.net/2060/20160014659 |
op_coverage |
Unclassified, Unlimited, Publicly available |
geographic |
Canada |
geographic_facet |
Canada |
genre |
Newfoundland North Atlantic |
genre_facet |
Newfoundland North Atlantic |
op_source |
CASI |
op_relation |
Document ID: 20160014659 http://hdl.handle.net/2060/20160014659 |
op_rights |
Copyright, Distribution as joint owner in the copyright |
_version_ |
1766109988498964480 |