Calendar Event Details
Weidong Yang
Affiliation: NASA GSFC, Code 613/USRA
Event Date: Tuesday, February 19, 2019
Location: G133, B33
Time: 11:00 AM
Cloud properties at the edge of clouds; comparison between land and ocean
We use the spectrally invariant method to study the variability of cloud optical thickness (τ) and droplet effective radius (reff) in transition zones between the cloudy and clear sky columns
observed from Shortwave Array Spectroradiometer-Zenith (SASZe) at the Southern Great Plains, Central Facility, Lamont, OK (SGP C1) and during the Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign. The spectrally invariant method approximates the spectra in the cloud transition zone as a linear combination of definitely clear and cloudy spectra, where the coefficients (slope and intercept) characterize the spectrally invariant properties of the transition zone. Similar to the results obtained for the mid-latitude oceanic areas, simulation results from the SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model for the mid-latitude rural vegetation areas demonstrate that (i) the slope of the visible band is positively correlated with τ while the intercept of the near-infrared band has a high negative correlation with reff even without the exact knowledge of τ; (ii) The above properties are valid for all Solar Zenith Angle (SZA) and for different cloud-contaminated skies. In observations of the 22 cases from SGP and MAGIC, we find that during cloudy-to-clear transitions (a) the slopes of the visible band decrease indicating the decrease of τ towards cloud edges, (b) however, the intercepts of the near-infrared band show much more significant increases at SGP than from MAGIC.
These findings suggest that while τ decreases during the cloudy-to-clear transition in all cases, the decrease trend of reff is much more significant in SGP (over land) than at MAGIC (over ocean).
This difference between SGP and MAGIC is consistent with the theoretical understanding of the effect of relative humidity on the types of mixing and contains information for further understanding the roles of aerosol, turbulence and other factors on the entrainmen and mixing process.
Posted or updated: Monday, February 11, 2019
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