Convective Organization & Propagation

This is our one-hour simulation from the System for Atmospheric Modeling (SAM). Individual convective clouds initiate from the bottom, then develop into deep convective clouds, propagate to the periodic boundary on the other side, and finally decay as high-level stratiform clouds. A single cloud rarely lasts more than half an hour, so we can observe multiple generations of clouds within just one hour. But what about the system as a whole?

Another simple question arises: Are the clouds organized? The simple answer is yes. Clouds are not randomly distributed in space; convective clouds often form organized patterns, allowing the convective system to persist for a much longer time. So, how can we quantify convective organization? How can we understand these organized patterns? Is there a relationship between convective organization and propagation? I aim to answer these questions in my research.

Madden-Julian Oscillation (MJO)

The Madden‐Julian Oscillation (MJO) is a tropical eastward-propagating disturbance that originates in the Indian Ocean and repeats for 30–90 days. The MJO has been shown to influence weather and climate phenomena worldwide, but the theories of its propagation and initiation are still under debate, and far less understood than ENSO's. The envelope of the MJO is composed of mesoscale convective systems (MCSs), which in turn are made of individual clouds that organize across space and time. My research focuses on the cloud dynamics in two critical areas for MJO: 1. Central Indian Ocean, where MJO initiates; 2. Maritime Continent, which may break down MJO as a barrier effect.

Lagrangian Particle Dispersion Model (LPDM)

The evolution of various properties makes it difficult to separate cold pools, define their sizes, and determine their role in organizing tropical convection. Therefore, we need a new technique, LPDM! Here are some advantages of Lagrangian tracking for understanding cold pools at a process level: highly intuitive as particles naturally follow the downdrafts, allows continuous tracking of particles throughout the entire dispersal process during the cold pool's life cycle, ensures that information carried by particles remains unaffected by the collision between cold pools or the disintegration of dry-cooled areas, and establishes a more straightforward connection with convective parameterizations.

Cold Pools, Moist Rings & Tropical Cloud Organization

Why focus on the tropics? Tropical convection has weaker updrafts, downdrafts, cold pools, and wind shear, and it was thought to be less organized. However, tropical clouds actually show organization at various scales. Why is this? Do cold pools still play a crucial role? These questions require further investigation. Due to the abundant moisture in the tropics, the evaporative cooling that forms cold pools may not be as strong. However, because of the thermodynamic effects of this moisture, the mature cold pool edges may form moist rings (moist patches) that help generate new convective clouds and organize convective systems. To uncover these secrets, please check our recent publication Tang et al., 2024!