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Research highlight

Convective storms can self-aggregate, forming large-scale overturning circulations. What physical processes can lead to self-aggregation of convection? A paper in GRL shows that convective heating and its feedback with large-scale circulations can lead to self-aggregation even in the absence of radiative, surface-flux, and moisture-entrainment feedbacks. 
What sets the spatial scale of convective self-aggregation? A paper in JAS presents a boundary layer theory for the horizontal scale of 2D (x, z) convective self-aggregation by considering both the momentum and energy constraints for steady circulations. This theory is verified using a suite of cloud-resolving simulations. 
What leads to convective self-aggregation? Combining energetic analyses and mechanism-denial experiments, a paper in JAMES proposes that the development of self-aggregation requires the generation of available potential energy (APE), and that boundary layer diabatic processes dominates the APE production. 
Pritchard_Yang_2016MJO.jpg
The Madden-Julian Oscillation (MJO) is often described as a planetary-scale phenomenon that only occurs over the warmest water on Earth. However, a paper in JCLI shows that the MJO can still occur even over an extremely cold ocean surface, and that the spatial scale of the MJO shrinks to the synoptic scale in cold climates. 
What sets the spatial scale of the Madden-Julian Oscillation (MJO)? A paper in GRL presents a scaling theory for the zonal scale of the MJO based on a suite of shallow water model simulations and dimensional analysis. Our results suggest that the zonal scale of the MJO increases with the gravity wave speed and decreases with the number density of convection.  
The Madden-Julian Oscillation (MJO) is a month-long, planetary-scale phenomenon in the tropical atmosphere. Although it was first discovered about 50 years ago, there is no widely-accepted theory, and many climate models do not capture it. In a paper in JAS, we present a one-layer shallow water model that can successfully simulate the MJO. Based on the simulation results, we propose that the MJO is a large-scale envelope of short-lived, small-scale gravity waves.