Role of multiscale atmospheric conditions in the evolution of convective organization during MJO-1 of DYNAMO/CINDY/AMIE

Tropical convection;Radar;Dynamics of the Madden-Julian Oscillation (DYNAMO);Madden-Julian Oscillation (MJO)

Thayer, Jeffrey Dale ; Hence ; Deanna A

关键词: Tropical convection;    Radar;    Dynamics of the Madden-Julian Oscillation (DYNAMO);    Madden-Julian Oscillation (MJO);   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/99204/THAYER-THESIS-2017.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Analysis of S-PolKa dual-polarization radar and 6-hourly ERA-interim reanalysis data shows the multiscale atmospheric conditions and changes in convective organization during a central Indian Ocean Madden-Julian Oscillation (MJO) event observed by the DYNAMO/CINDY/AMIE field campaigns in October 2011. Shifts in reflectivity and dual-polarization characteristics of four precipitation types over two time periods, at the beginning and end of the MJO passage over the radar, showed a transition towards shorter bursts of more intense convective precipitation over a smaller portion of the radar domain. These convective elements displayed greater upscale organization as the surrounding environment gradually became more strongly sheared with greater instability, associated with persistent lower-level dry-air advection from the westerly wind burst. These bursts of convection, especially in the first time period, appeared with periodic dry-air intrusions into the central equatorial Indian Ocean.The changes in the vertical distribution of ice particles indicate that graupel progressively occurred over a greater depth, associated with the overall increasing intensity of convective precipitation. As the MJO progressed eastward, other ice particle types occurred over shallower depths with decreased reflectivity values. This change in the aggregates and ice crystals signals a transition towards shorter residence times as a result of weaker stratiform precipitation with smaller or less abundant ice particles.