Cloud Population and Deep Convective System Organization in the Tropical Warm Pool Area Affected by the Madden-Julian Oscillation

Deep convective systems are objectively identified by combining data from three A-train satellite instruments: MODIS, AMSR-E and CloudSat CPR. Combining observations from above instruments and CALIPSO CALIOP/IIR the cloud population and deep convective system organization in the tropical warm pool area affected by the Madden-Julian Oscillation (MJO) are investigated. In the Indo-Pacific region, mesoscale convective systems (MCSs) occur in a pattern consistent with the eastward propagation of the large-scale convective envelope of the Madden-Julian oscillation (Fig. 1). MCSs tend to be merged or connected systems over the open ocean, while over the Maritime Continent area they tend to be separated or discrete. Over all regions affected by the MJO, MCSs are major contributors of precipitation. Connected systems increase the most in frequency as well as its relative contribution to the total precipitation during the active phase of the MJO. Characteristics separated and connected MCSs do not vary much over MJO-affected regions though they differ in structure from each other. Connected MCSs have a larger size and produce less but colder-topped anvil cloud. Further analyses show that the relative enhanced large-scale convection, greater frequency of occurrence of connected MCSs, and increased midtroposphere moisture coincide, regardless of the region, season, or large-scale conditions (such as the concurrent phase of the MJO). This suggests that the coexistence of these phenomena is likely the nature of deep convection in this region. The increase of midtroposphere moisture observed in all convective regimes during large-scale convectively active phases suggests that the accumulation of midtroposphere moisture over MJO-affected regions needs to be better understood. Cloud population in association with the MJO represented by its vertical structure obtained from CloudSat and CALIPSO measurements are investigated. The transition from shallower to deep convection in active phases and thick anvils after are recognized. Figure 1. Number concentration of MCSs observed during the eight phases of the MJO. Active MCSs are divided into (from left to right) the smallest 25% of SMCSs, largest 25%of SMCSs and CMCSs . The number concentration is defined as number of systems instantaneously observed in a 1000 km X 1000 km box.