Abstract
Recent research suggests atmospheric cloud radiative effect (ACRE) acts as an important feedback mechanism for enhancing the development of convective self‐aggregation in idealized numerical simulations. Here, we seek observational relationships between longwave (LW) ACRE and the spatial organization of mesoscale convective systems (MCSs) in the tropics. Three convective organization metrics that are positively correlated with the area of MCS, that is, convective organization potential, the area fraction of precipitating MCS, and the precipitation fraction of MCS, are used to indicate the degree of convective organization. Our results show that the contrast in the LW ACRE inside and outside an MCS is consistent across different MCS precipitation intensities throughout the life cycle of an MCS, typically 90–100 W/m2, and provides important positive feedback to the circulation of the given MCS. However, the LW ACRE inside and outside an MCS as well as their difference are not strongly related to the degree of organization, suggesting that the LW cloud radiative feedback may be supportive of MCS formation and maintenance without necessarily being a dominant factor for spatial organization of MCSs. The domain average vertical velocity does tend to be related to the measures of convective organization, suggesting that factors that favor large‐scale low‐level convergence may exert a leading effect in creating an environment favorable for mesoscale organization of deep convection.
Plain Language Summary
The difference between radiative cooling in the dry regions and radiative heating in the moist clusters encourages self‐generated radiative circulations in numerical models, which drives scattered moist clusters into organized moist patches. We examine the observed relationship between the spatial organization of mesoscale convective systems (MCSs) and cloud‐related radiative heating/cooling. The difference between cloud‐related heating inside and outside MCSs is found to be important for the development of individual MCSs, but it still cannot explain the organizational behavior of MCSs in the real world. The organization of MCSs seems to be strongly tied to the external factors in their large‐scale environment, such as large‐scale low‐level convergence.
Key Points
Longwave cloud radiative heating observations are consistent with a positive feedback supporting individual mesoscale convective systems (MCSs)
Observed cloud‐related radiative heating does not exert a strong influence on the spatial organization of MCSs
Observed mesoscale convective organization is closely related to large‐scale low‐level convergence