Premium
Cloud Edge Properties Measured by the ARM Shortwave Spectrometer Over Ocean and Land
Author(s) -
Yang Weidong,
Marshak Alexander,
Wen Guoyong
Publication year - 2019
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2019jd030622
Subject(s) - shortwave , zenith , radiative transfer , magic (telescope) , physics , atmospheric radiative transfer codes , spectrometer , sky , solar zenith angle , infrared , cloud computing , spectroradiometer , atmospheric sciences , remote sensing , environmental science , meteorology , geology , astrophysics , optics , reflectivity , computer science , operating system
We use the spectrally invariant method to study the variability of cloud optical thickness (τ) and droplet effective radius ( r eff ) in transition zones between the cloudy and clear‐sky columns observed by Shortwave Array Spectroradiometer‐Zenith at the Southern Great Plains Central Facility site (SGP C1) and during the Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign. The spectrally invariant method approximates the spectra in the transition zone as a linear combination of definitely clear and definitely cloudy spectra. The slope and intercept of the linear relations characterize τ and r eff in the transition region, respectively. The radiative transfer model simulations show that that (i) the slope of the visible band is positively correlated with τ, while (ii) the intercept of the near‐infrared band has a high negative correlation with r eff . We have analyzed 22 cloud edge cases from the SGP and MAGIC and found that from cloud to clear in the transitions, (a) the slopes of the visible band decrease, indicating the decrease of τ toward cloud edges, and (b) the intercepts of the near‐infrared band show a much more significant increase at the SGP than from the MAGIC. The results from observed cases suggest that while τ decreases for all cases, the decrease in r eff is much more significant for cloud over land at the SGP site compared to the ocean counterpart during the MAGIC campaign.