What is it about?
The slow-moving large storm systems over the tropics from the Indian Ocean to the Western Pacific Ocean have drawn the attention of meteorologists for a few decades, because the behaviors of such strong storm systems, such as their moving speed and occurrence frequency, can not be obtained by solving the conventional wave equations. Previous studies suggest that the greenhouse effect of the high ice clouds is important in controlling the moving speed of such strong storm systems. Our study shows that the ice cloud greenhouse effect is underestimated in many current models, which neglect the backscattered surface-emitted electromagnetic energy by clouds in their calculations. Neglecting the cloud scattering makes the heating gradient from cloud base to cloud top less sharp. We also find increased ice cloud coverage up to 5 days before the strong storm systems come.
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Why is it important?
The simulated behaviors of tropical large storm systems are sensitive to how much energy is trapped by the ice clouds associated with the systems (i.e., the ice cloud greenhouse effect). Our results may help meteorologists improve the simulations of the tropical large storm systems that significantly impact the weathers over the tropics and the subtropics.
Perspectives
The large storm systems are strongest in the Indian Ocean and Southeast Asian but become weak when they move to the Pacific Ocean. One difference in the meteorological conditions between the eastern Indian Ocean and the western Pacific Ocean is the large-scale mean flow direction. If the increased ice cloud coverage before the arrival of the storm systems we find in this study plays a role in the intensification of the storm systems, then the decay of such storm system over the Pacific Ocean may be linked to the large-scale mean flow through the lag between the increased ice cloud coverage and the storm system intensification.
Tong Ren
Texas A&M University System
Read the Original
This page is a summary of: 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, June 2020, American Geophysical Union (AGU),
DOI: 10.1029/2020jd032591.
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