Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Impact of Cloud Longwave Scattering on Radiative Fluxes Associated With the Madden‐Julian Oscillation in the Indian Ocean and Maritime Continent

TitleImpact of Cloud Longwave Scattering on Radiative Fluxes Associated With the Madden‐Julian Oscillation in the Indian Ocean and Maritime Continent
Publication TypeJournal Article
Year of Publication2020
JournalJournal of Geophysical Research: Atmospheres
Volume125
Number13
Abstract / Summary

Previous studies suggested that cloud longwave radiation contributes to the development and maintenance of the Madden-Julian Oscillation (MJO) and model-based convection is highly sensitive to the radiation scheme. However, currently used radiation schemes do not take cloud longwave scattering into account, resulting in an overestimation of the outgoing longwave radiation (OLR) and an underestimation of the downward longwave flux at the surface. We use combined active and passive satellite cloud property retrievals to quantify the one-layer cloud OLR and heating rate (HR) biases introduced by neglecting cloud longwave scattering in the Indian Ocean and Maritime Continent in the context of MJO, with a focus on its phases 3, 5, and 6. The results show that the satellite-detected one-layer cloud area consists primarily of ice clouds, particularly during the boreal winter in the 4-year study period. An increased ice cloud area fraction of one-layer cloud groups is present up to 5 days before the onset of MJO events. If longwave scattering is neglected, the composite mean OLR overestimation over the one-layer ice cloud area from 5 days before to 4 days after the MJO passage is approximately 3.5 to 5.0 W m(-2). Neglecting longwave scattering also leads to aHRunderestimation at cloud base and an overestimation at cloud top, making the base-to-top heating gradient less sharp at the cloud-resolving scale.

URLhttp://dx.doi.org/10.1029/2020jd032591
DOI10.1029/2020jd032591
Journal: Journal of Geophysical Research: Atmospheres
Year of Publication: 2020
Volume: 125
Number: 13
Publication Date: 07/2020

Previous studies suggested that cloud longwave radiation contributes to the development and maintenance of the Madden-Julian Oscillation (MJO) and model-based convection is highly sensitive to the radiation scheme. However, currently used radiation schemes do not take cloud longwave scattering into account, resulting in an overestimation of the outgoing longwave radiation (OLR) and an underestimation of the downward longwave flux at the surface. We use combined active and passive satellite cloud property retrievals to quantify the one-layer cloud OLR and heating rate (HR) biases introduced by neglecting cloud longwave scattering in the Indian Ocean and Maritime Continent in the context of MJO, with a focus on its phases 3, 5, and 6. The results show that the satellite-detected one-layer cloud area consists primarily of ice clouds, particularly during the boreal winter in the 4-year study period. An increased ice cloud area fraction of one-layer cloud groups is present up to 5 days before the onset of MJO events. If longwave scattering is neglected, the composite mean OLR overestimation over the one-layer ice cloud area from 5 days before to 4 days after the MJO passage is approximately 3.5 to 5.0 W m(-2). Neglecting longwave scattering also leads to aHRunderestimation at cloud base and an overestimation at cloud top, making the base-to-top heating gradient less sharp at the cloud-resolving scale.

DOI: 10.1029/2020jd032591
Citation:
Ren, T, P Yang, C Schumacher, X Huang, and W Lin.  2020.  "Impact of Cloud Longwave Scattering on Radiative Fluxes Associated With the Madden‐Julian Oscillation in the Indian Ocean and Maritime Continent."  Journal of Geophysical Research: Atmospheres 125(13).  https://doi.org/10.1029/2020jd032591.