Impact of Cloud Longwave Scattering on Radiative Fluxes Associated With the Madden-Julian Oscillation in the Indian Ocean and Maritime Continent Academic Article uri icon

abstract

  • AbstractPrevious studies suggested that cloud longwave radiation contributes to the development and maintenance of the MaddenJulian Oscillation (MJO) and modelbased 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 onelayer 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 satellitedetected onelayer cloud area consists primarily of ice clouds, particularly during the boreal winter in the 4year study period. An increased ice cloud area fraction of onelayer cloud groups is present up to 5days before the onset of MJO events. If longwave scattering is neglected, the composite mean OLR overestimation over the onelayer ice cloud area from 5days before to 4days after the MJO passage is approximately 3.5 to 5.0Wm2. Neglecting longwave scattering also leads to a HR underestimation at cloud base and an overestimation at cloud top, making the basetotop heating gradient less sharp at the cloudresolving scale.

published proceedings

  • JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES

author list (cited authors)

  • Ren, T., Yang, P., Schumacher, C., Huang, X., & Lin, W.

citation count

  • 5

publication date

  • July 2020