Research Interests

I am interested in lots of different subjects related to climate, especially topics that relate to land-atmosphere interactions. A (non-exhaustive) list of my research interests is below -- Topics 1-3 form the bulk of my PhD thesis, which I defended and submitted in February 2014.

1) Diurnal Cycle and Island Rainfall

As a dissertation topic, I am studying the impacts of land-atmosphere interactions and the diurnal cycle on the climate system. One goal is to understand whether geologic changes in the island cover and elevation of Indonesia over the past few million years could have moved the climate away from the "permanent El Nino" state that was thought to exist about 5 million years ago. Another goal is understand why islands are typically rainier than nearby ocean areas in the tropics.

To study this problem, I use a combination of models and theory; specifically, I am making heavy use of the SAM (System for Atmospheric Modeling) Cloud-Resolving Model. See the Movies! link for more detail! Some work I've done on the subject of the diurnal cycle and island rainfall:

Cronin, Emanuel, and Molnar (submitted May 2014 to the Quarterly Journal of the Royal Meteorological Society)

Poster at AGU Fall Meeting, December 2012

Talk at the 6th Graduate Climate Conference

AMS Tropical Conference, April 2012
Extended Abstract and Poster

Written Thesis Proposal, January 2012

Thesis Proposal Presentation, February 2012

2) Boundary Layer Sensitivity

The human footprint on the global land surface is large, and rapidly changing, and changes in land surface properties can affect the climate. But real land surfaces are highly complex and heterogeneous, and thus difficult to represent in climate models. The complexity of the land surface formulations used in climate models often makes it difficult to understand what is going on when we attempt to simulate something like the impacts of land cover change on climate. I have developed a (relatively) simple theory which can be used to qualitatively understand how changes in surface wetness, roughness, and reflectivity of the land surface lead to changes in near-surface climate.

Cronin (2013), JAMES

This work ultimately grew out of my generals project (Spring 2011), where I worked on understanding the climate response to "physiological forcing" -- the tendency of plants to close their stomata (leaf pores, through which CO2 enters leaves and water vapor exits them) as the atmospheric CO2 concentration is raised. Some of the earlier work I've done on the subject is available below:

AMS Annual Meeting Poster, January 2012

Generals Presentation, May 2011

Generals Paper, May 2011

3) Notes on Radiative-Convective Equilibrium

Radiative-convective equilibrium (RCE) is a hypothetical state of the atmosphere-surface system where radiative cooling of the atmosphere to space is balanced by convective heating, mainly by rising warm and moist air in clouds, and radiative heating of the surface is balanced primarily by evaporative cooling. Study of RCE has been extremely important for our understanding of sensitivity and stability of climate. However, there are some details of RCE that are not well understood by the field in general.

One element of RCE that seems not to be widely understood is that there is a long approach time scale to equilibrium, and that this long time scale persists even without the thermal inertia of the ocean. See the paper below:

Cronin and Emanuel (2013), JAMES

Often, idealized models use a solar energy input that is averaged over day and night. However, it is not completely obvious how to do this averaging appropriately, since both the sun's angle and intrinsic brightness can be tuned. A short paper on this subject constitutes Chapter 2 in my thesis, and was accepted by the Journal of the Atmospheric Sciences in April 2014.

Cronin (2014, in press), JAS

4) Tropical Cyclones over Land

I did a project for Tropical Meteorology (12.811, Spring 2011) on the unusual reintensification of Tropical Cyclone Erin (2007) over land. My findings were somewhat inconclusive, but I hope to revisit the subject of tropical syslone intensification over land at some point.

Term Paper for 12.811

5) Hadley Circulation and Eddies

Earlier in my time at MIT, I did a few term papers exploring theories of the Hadley circulation. For a Harvard Journal Club last year, I led discussion on a paper about a simple model for the Hadley circulation. See the Code For Numerical Models page for more information.