Retrievals of thin cloud optical depth from a multifilter rotating shadowband radiometer

2004 ◽  
Vol 109 (D2) ◽  
Author(s):  
Qilong Min
Keyword(s):  
Optical Depth ◽  
Cloud Optical Depth ◽  
Thin Cloud ◽  
Multifilter Rotating Shadowband Radiometer

scholarly journals A method to retrieve super-thin cloud optical depth over ocean background with polarized sunlight

2015 ◽  
Vol 15 (15) ◽  
pp. 21959-21982
Author(s):  
W. Sun ◽  
R. R. Baize ◽  
G. Videen ◽  
Y. Hu ◽  
Q. Fu
Keyword(s):  
Solar Radiation ◽  
Optical Depth ◽  
Ocean Surface ◽  
Sensitivity Study ◽  
Meridian Plane ◽  
Polarization Angle ◽  
Cloud Optical Depth ◽  
Surface Conditions ◽  
Reflected Light ◽  
Thin Cloud

Abstract. In this work, an algorithm that uses the polarization angle of the backscattered solar radiation to detect clouds with optical depth (OD) < ~ 0.3 is further developed. We find that at viewing angles within ± ~ 8° around the backscattering direction, the p-polarized intensity that is parallel to the meridian plane of reflected light from surface is sensitive to and nearly linearly related to the optical depth of super-thin clouds. Moreover, our sensitivity study suggests that the p-polarized intensity at these viewing angles is not sensitive to the ocean surface conditions. Using this property of p-polarized intensity, super-thin clouds' optical depth can be retrieved.

scholarly journals A method to retrieve super-thin cloud optical depth over ocean background with polarized sunlight

2015 ◽  
Vol 15 (20) ◽  
pp. 11909-11918 ◽  
Author(s):  
W. Sun ◽  
R. R. Baize ◽  
G. Videen ◽  
Y. Hu ◽  
Q. Fu
Keyword(s):  
Solar Radiation ◽  
Optical Depth ◽  
Ocean Surface ◽  
Sensitivity Study ◽  
Meridian Plane ◽  
Polarization Angle ◽  
Cloud Optical Depth ◽  
Surface Conditions ◽  
Reflected Light ◽  
Thin Cloud

Abstract. In this work, an algorithm that uses the polarization angle of the backscattered solar radiation to detect clouds with optical depth (OD) < ~ 0.3 is further developed. We find that at viewing angles within ± ∼ 8° around the backscattering direction, the p-polarized intensity that is parallel to the meridian plane of reflected light from the surface is sensitive to, and nearly linearly related to, the optical depth of super-thin clouds. Moreover, our sensitivity study suggests that the p-polarized intensity at these viewing angles is not sensitive to the ocean surface conditions. Using this property of p-polarized intensity, super-thin clouds' optical depth can be retrieved.

Retrievals of cloud optical depth and effective radius from Thin-Cloud Rotating Shadowband Radiometer measurements

2011 ◽  
Vol 116 (D23) ◽  
pp. n/a-n/a ◽  
Author(s):  
Bangsheng Yin ◽  
Qilong Min ◽  
Minzheng Duan ◽  
M. J. Bartholomew ◽  
A. M. Vogelmann ◽  
...  
Keyword(s):  
Optical Depth ◽  
Effective Radius ◽  
Cloud Optical Depth ◽  
Thin Cloud

Design of a Shadowband Spectral Radiometer for the Retrieval of Thin Cloud Optical Depth, Liquid Water Path, and the Effective Radius

2011 ◽  
Vol 28 (11) ◽  
pp. 1458-1465 ◽  
Author(s):  
M. J. Bartholomew ◽  
R. M. Reynolds ◽  
A. M. Vogelmann ◽  
Q. Min ◽  
R. Edwards ◽  
...  
Keyword(s):  
Optical Depth ◽  
Liquid Water ◽  
Effective Radius ◽  
Liquid Water Path ◽  
Cloud Optical Depth ◽  
Water Path ◽  
Cloud Properties ◽  
Radiative Intensity ◽  
Thin Cloud ◽  
Aerosol Properties

Abstract The design and operation of a Thin-Cloud Rotating Shadowband Radiometer (TCRSR) described here was used to measure the radiative intensity of the solar aureole and enable the simultaneous retrieval of cloud optical depth, drop effective radius, and liquid water path. The instrument consists of photodiode sensors positioned beneath two narrow metal bands that occult the sun by moving alternately from horizon to horizon. Measurements from the narrowband 415-nm channel were used to demonstrate a retrieval of the cloud properties of interest. With the proven operation of the relatively inexpensive TCRSR instrument, its usefulness for retrieving aerosol properties under cloud-free skies and for ship-based observations is discussed.

scholarly journals A 12-year long global record of optical depth of absorbing aerosols above the clouds derived from the OMI/OMACA algorithm

2018 ◽  
Vol 11 (10) ◽  
pp. 5837-5864 ◽  
Author(s):  
Hiren Jethva ◽  
Omar Torres ◽  
Changwoo Ahn
Keyword(s):  
Atlantic Ocean ◽  
Optical Depth ◽  
Frequency Of Occurrence ◽  
Cloud Optical Depth ◽  
Low Level ◽  
Aerosol Cloud ◽  
Aerosol Absorption ◽  
The World ◽  
Absorbing Aerosols

Abstract. Aerosol–cloud interaction continues to be one of the leading uncertain components of climate models, primarily due to the lack of adequate knowledge of the complex microphysical and radiative processes of the aerosol–cloud system. Situations when light-absorbing aerosols such as carbonaceous particles and windblown dust overlay low-level cloud decks are commonly found in several regions of the world. Contrary to the known cooling effects of these aerosols in cloud-free scenario over darker surfaces, an overlapping situation of the absorbing aerosols over the cloud can lead to a significant level of atmospheric absorption exerting a positive radiative forcing (warming) at the top of the atmosphere. We contribute to this topic by introducing a new global product of above-cloud aerosol optical depth (ACAOD) of absorbing aerosols retrieved from the near-UV observations made by the Ozone Monitoring Instrument (OMI) onboard NASA's Aura platform. Physically based on an unambiguous “color ratio” effect in the near-UV caused by the aerosol absorption above the cloud, the OMACA (OMI above-cloud aerosols) algorithm simultaneously retrieves the optical depths of aerosols and clouds under a prescribed state of the atmosphere. The OMACA algorithm shares many similarities with the two-channel cloud-free OMAERUV algorithm, including the use of AIRS carbon monoxide for aerosol type identification, CALIOP-based aerosol layer height dataset, and an OMI-based surface albedo database. We present the algorithm architecture, inversion procedure, retrieval quality flags, initial validation results, and results from a 12-year long OMI record (2005–2016) including global climatology of the frequency of occurrence, ACAOD, and aerosol-corrected cloud optical depth. A comparative analysis of the OMACA-retrieved ACAOD, collocated with equivalent accurate measurements from the HSRL-2 lidar for the ORACLES Phase I operation (August–September 2016), revealed a good agreement (R = 0.77, RMSE = 0.10). The long-term OMACA record reveals several important regions of the world, where the carbonaceous aerosols from the seasonal biomass burning and mineral dust originated over the continents are found to overlie low-level cloud decks with moderate (0.3 < ACAOD < 0.5, away from the sources) to higher levels of ACAOD (> 0.8 in the proximity to the sources), including the southeastern Atlantic Ocean, southern Indian Ocean, Southeast Asia, the tropical Atlantic Ocean off the coast of western Africa, and northern Arabian sea. No significant long-term trend in the frequency of occurrence of aerosols above the clouds and ACAOD is noticed when OMI observations that are free from the “row anomaly” throughout the operation are considered. If not accounted for, the effects of aerosol absorption above the clouds introduce low bias in the retrieval of cloud optical depth with a profound impact on increasing ACAOD and cloud brightness. The OMACA aerosol product from OMI presented in this paper offers a crucial missing piece of information from the aerosol loading above cloud that will help us to quantify the radiative effects of clouds when overlaid with aerosols and their resultant impact on cloud properties and climate.

Retrieval of Cloud Optical Depth: Synergies between Whole Sky Imagers and Radiative Transfer Modeling.

2021 ◽  
Author(s):  
Caterina Peris-Ferrús ◽  
José Luís Gómez-Amo ◽  
Francesco Scarlatti ◽  
Roberto Román ◽  
Claudia Emde ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Optical Depth ◽  
Cloud Optical Depth ◽  
Radiative Transfer Modeling

scholarly journals The interdependence of continental warm cloud properties derived from unexploited solar background signals in ground-based lidar measurements

2014 ◽  
Vol 14 (16) ◽  
pp. 8389-8401 ◽  
Author(s):  
J. C. Chiu ◽  
J. A. Holmes ◽  
R. J. Hogan ◽  
E. J. O'Connor
Keyword(s):  
Optical Depth ◽  
Effective Radius ◽  
Liquid Water Path ◽  
Cloud Optical Depth ◽  
Cloud Properties ◽  
Warm Cloud ◽  
Lidar Measurements ◽  
Atmospheric Radiation Measurement ◽  
Ground Based Lidar ◽  
Geometric Thickness

Abstract. We have extensively analysed the interdependence between cloud optical depth, droplet effective radius, liquid water path (LWP) and geometric thickness for stratiform warm clouds using ground-based observations. In particular, this analysis uses cloud optical depths retrieved from untapped solar background signals that are previously unwanted and need to be removed in most lidar applications. Combining these new optical depth retrievals with radar and microwave observations at the Atmospheric Radiation Measurement (ARM) Climate Research Facility in Oklahoma during 2005–2007, we have found that LWP and geometric thickness increase and follow a power-law relationship with cloud optical depth regardless of the presence of drizzle; LWP and geometric thickness in drizzling clouds can be generally 20–40% and at least 10% higher than those in non-drizzling clouds, respectively. In contrast, droplet effective radius shows a negative correlation with optical depth in drizzling clouds and a positive correlation in non-drizzling clouds, where, for large optical depths, it asymptotes to 10 μm. This asymptotic behaviour in non-drizzling clouds is found in both the droplet effective radius and optical depth, making it possible to use simple thresholds of optical depth, droplet size, or a combination of these two variables for drizzle delineation. This paper demonstrates a new way to enhance ground-based cloud observations and drizzle delineations using existing lidar networks.

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