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- Title
The Influence of Cloud Types on Cloud‐Radiative Forcing During DYNAMO/AMIE.
- Authors
Najarian, Hrag; Sakaeda, Naoko
- Abstract
Cloud‐radiative feedback is known to be an important process for the Madden‐Julian Oscillation (MJO) and its accurate representation in general circulation models. The MJO is known to have a stronger cloud‐radiative feedback compared to higher frequency convectively coupled equatorial waves (CCEW), for reasons that remain unclear. The objective of this study is to use data from the Dynamics of the MJO/Atmospheric Radiation Measurement MJO Investigation Experiment field campaign to investigate how cloud type evolution and their associated cloud‐radiative forcing (CRF) differ between the MJO and CCEWs and their application to MJO dynamics under moisture mode theory. This study finds that the amplitude of CRF is the largest within the MJO compared to the higher frequency CCEWs, and CRF maximizes after the maximum precipitation (enhanced phase) of the MJO. We suggest this delay in the timing of maximum CRF occurs because most cloud types (congestus, deep, anvil, and cirrus) simultaneously maximize in frequency after the enhanced phase of the MJO, which is not seen for the higher frequency CCEWs. These specific cloud types help maintain the MJO through their radiatively‐driven moistening which acts to prolong the enhanced phase of the MJO. The decomposition of radiatively‐driven moistening by cloud types shows that simultaneous moistening by deep, anvil, and congestus clouds are particularly responsible for the maintenance of the MJO under moisture mode theory. This analysis suggests the importance of capturing the correct evolution of different cloud types and their associated radiative effects to better understand the thermodynamics of the MJO. Plain Language Summary: Large‐scale atmospheric disturbances in the tropics influence weather locally and globally, therefore it is important for numerical models to accurately represent these disturbances. Previous studies suggest that slower and larger‐scale disturbances trap more radiative heat than faster and smaller disturbances. To understand why this unique relationship exists, we utilize high resolution observational data collected between October and December 2011, located in the Maldives. We found that the slowest and largest disturbance, the Madden‐Julian Oscillation (MJO), had nearly all cloud types most frequent after its rainiest period, while faster and smaller disturbances had clouds frequent during their rainiest period. Atmospheric cloud‐radiative heating followed a similar trend, with the MJO trapping the most radiative heat, and it was after its rainiest period, unlike the faster/smaller waves. We reconstructed the close relationship between cloud occurrence and cloud‐radiative heating to isolate the cloud‐radiative heating induced by each cloud type (shallow, congestus, deep, mid, anvil, cirrus). Rainy (congestus and deep) and thick high (anvil) clouds trapped the most radiative heat within the atmosphere after the rainiest period of the MJO. The added radiative heat drives upward motion that acts to moisten the atmosphere, prolonging the rainy period of the MJO. Key Points: Most cloud types maximize in frequency after the maximum precipitation for the Madden‐Julian Oscillation (MJO), which is unique compared to higher frequency wavesDeep convective and anvil clouds lead to the strong cloud radiative forcing of the MJO that lags its precipitation maximumThe radiative effects of those clouds lead to moistening, implying that the effect of cloud organization is important to the MJO
- Subjects
MALDIVES; ATMOSPHERIC radiation measurement; MADDEN-Julian oscillation; GENERAL circulation model; ELECTRIC generators; RADIATIVE forcing
- Publication
Journal of Geophysical Research. Atmospheres, 2023, Vol 128, Issue 8, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2022JD038006