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The impact of seasonalities on direct radiative effects and radiative heating rates of absorbing aerosols above clouds
Author(s) -
Chang Ian,
Christopher Sundar A.
Publication year - 2017
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.3012
Subject(s) - noon , radiative transfer , aerosol , atmospheric sciences , solar zenith angle , environmental science , zenith , atmospheric radiative transfer codes , optical depth , effective radius , cloud cover , atmosphere (unit) , meteorology , physics , cloud computing , optics , astrophysics , galaxy , computer science , operating system
The impact of seasonalities on direct radiative effects ( DREs ) and radiative heating rates ( RHRs ) of absorbing aerosols above clouds in the southeast Atlantic is examined using radiative transfer calculations. For an aerosol optical thickness of 0.6 located between 0 and 4 km, a cloud optical thickness of 9.0 and a cloud effective radius of 12.8 µm at 0.55 µm located between 1 and 2 km, the diurnally averaged RHR at noon in the aerosol layer increases from ∼6.6 K day −1 in June to ∼8.9 K day −1 in October. In June (October), the RHR in the cloud layer at noon is 1.3 (1.7) K day −1 higher than the case of pristine clouds. However, an elevated aerosol layer (2–4 km) reduces the RHR by ∼0.2 K day −1 in the cloud layer relative to a pristine cloudy case. The DRE at top‐of‐atmosphere ( TOA ) reaches its peak when the solar zenith angle ( SZA ) is 54°. The DRE increases (decreases) with SZA for SZA less (greater) than 54°. The primary peak DRE is ∼29.5 W m −2 at 5.0°S 5.0°E, occurring at 0800 UTC . At noon, the DRE at TOA is ∼18.9, ∼20.5 and ∼23.1 W m −2 at 5.0°S, 15.0°S and 25.0°S along 5.0°E, respectively. This study provides data and theoretical understanding to help positioning science flights that target measurements of above‐cloud aerosol radiative effects.