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 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.

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

2014 ◽  
Vol 14 (7) ◽  
pp. 8963-8996
Author(s):  
J. C. Chiu ◽  
J. A. Holmes ◽  
R. J. Hogan ◽  
E. J. O'Connor
Keyword(s):  
Optical Depth ◽  
Effective Radius ◽  
Liquid Water Path ◽  
Background Signal ◽  
Cloud Optical Depth ◽  
Cloud Properties ◽  
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 signal that is previously unwanted and needs 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, while it increases with optical depth and reaches an asymptote of 10 μm in non-drizzling clouds. This asymptotic behaviour in non-drizzling clouds is found in both 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.

Changes in TOA SW Fluxes over Marine Clouds When Estimated via Semi-Physical Angular Distribution Models

2021 ◽  
Author(s):  
F. Tornow ◽  
C. Domenech ◽  
J. N. S. Cole ◽  
N. Madenach ◽  
J. Fischer
Keyword(s):  
Angular Distribution ◽  
Optical Depth ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Cloud Water ◽  
Effective Radius ◽  
Distribution Models ◽  
Radiative Fluxes ◽  
Cloud Optical Depth ◽  
Aerosol Indirect Effects

AbstractTop-of-atmosphere (TOA) shortwave (SW) angular distribution models (ADMs) approximate – per angular direction of an imagined upward hemisphere – the intensity of sunlight scattered back from a specific Earth-atmosphere scene. ADMs are, thus, critical when converting satellite-borne broadband radiometry into estimated radiative fluxes. This paper applies a set of newly developed ADMs with a more refined scene definition and demonstrates tenable changes in estimated fluxes compared to currently operational ADMs. Newly developed ADMs use a semi-physical framework to consider cloud-top effective radius, , and above-cloud water vapor, ACWV, in addition to accounting for surface wind speed and clouds’ phase, fraction, and optical depth. In effect, instantaneous TOA SWfluxes for marine liquid-phase clouds had the largest flux differences (of up to 25 W m−2) for lower solar zenith angles and cloud optical depth greater than 10 due to extremes in or ACWV. In regions where clouds had persistently extreme levels of (here mostly for <7μm and >15μm) or ACWV, instantaneous fluxes estimated from Aqua, Terra, and Meteosat 8 and 9 satellites using the two ADMs differed systematically, resulting in significant deviations in daily mean fluxes (up to ±10 W m−2) and monthly mean fluxes (up to ±5 W m−2). Flux estimates using newly developed, semi-physical ADMs may contribute to a better understanding of solar fluxes over low-level clouds. It remains to be seen whether aerosol indirect effects are impacted by these updates.

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 Application of a multiple scattering model to estimate optical depth, lidar ratio and ice crystal effective radius of cirrus clouds observed with lidar.

2018 ◽  
Vol 176 ◽  
pp. 05037
Author(s):  
Diego Gouveia ◽  
Holger Baars ◽  
Patric Seifert ◽  
Ulla Wandinger ◽  
Henrique Barbosa ◽  
...  
Keyword(s):  
Multiple Scattering ◽  
Optical Depth ◽  
Single Scattering ◽  
Effective Radius ◽  
Cirrus Clouds ◽  
Ice Crystal ◽  
Backscatter Signal ◽  
Cloud Optical Depth ◽  
Lidar Measurements ◽  
Lidar Ratio

Lidar measurements of cirrus clouds are highly influenced by multiple scattering (MS). We therefore developed an iterative approach to correct elastic backscatter lidar signals for multiple scattering to obtain best estimates of single-scattering cloud optical depth and lidar ratio as well as of the ice crystal effective radius. The approach is based on the exploration of the effect of MS on the molecular backscatter signal returned from above cloud top.

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.

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