Campus Life the secret lives of researchers

Head in the clouds

The mystery of cloud formation precipitates research

As undergraduates at MIT, we whispered under our breaths as we passed the Green Building about the lonely, mysterious graduate students who worked there — “The lights never go off! There is always someone there.” As a graduate student, I’ve had the privilege to meet some of those nocturnal souls. This is one of their stories.
—Emily A. Moberg

My name is Sarvesh Garimella, and I have chosen to lead the mysterious life of a researcher for the next few years. As a graduate student studying climate science in the Earth, Atmospheric, and Planetary Sciences Department (Course 12, for those of you who keep track of such things), I spend the majority of my time running experiments in the MIT Aerosol and Cloud Laboratory and analyzing the data from these experiments.

Basically, I look at how aerosol particles interact with water vapor in the atmosphere to form various types of clouds. I am interested in the microphysics of these interactions and how they affect the formation and persistence of clouds in Earth’s atmosphere. In fact, the lack of understanding on how clouds behave in the climate system is the single largest uncertainty in all of the climate sciences—something we cloud scientists like to call job security.

So here’s what we do know: aerosol particles alone tend to have a net cooling effect on the climate system since they reflect and scatter incoming solar radiation, preventing it from reaching the surface. However, these particles also interact with water in the atmosphere to form various types of clouds through a variety of physical mechanisms. These clouds can either cool or warm the Earth since they can reflect light back to space as well as prevent heat from escaping the Earth.

Because the characteristics of clouds depend on many dynamical and physical factors (like the temperature, relative humidity, aerosol particle number, particle size, and particle composition), we need to perform experiments in the laboratory to determine how, when, and what type of clouds can form under particular conditions. In order to understand how Earth’s climate will evolve as a result of human activities, we need to pin down the role of aerosols and clouds. They are the single largest source of uncertainty in the climate system, especially because of a lack of physical underpinnings to describe their behavior.

On a day-to-day basis, I spend my time in lab using cloud chambers to study droplet or ice crystal formation in the presence of aerosol particles. There are several types of cloud chambers, but all of them allow us to control the temperature and relative humidity that aerosol particles encounter. I look at the data from these experiments to investigate how well various types of particles seed clouds in the atmosphere.

In particular, I am interested in how mineral dust aerosols — those blown from arid regions — affect the ability for clouds to form. They are very abundant in Earth’s atmosphere and are responsible for a great deal of cloud seeding. Often times, mineral dust also has biological or anthropogenic material included in it, which drastically changes this cloud-seeding ability. These changes can have a significant effect on future climate. However, such effects are poorly understood, so I am investigating them in the laboratory.

Overall, I find the topic of cloud formation a fascinating one since it requires a great deal of fundamental research but also has wide societal implications. I have greatly enjoyed the work I have been able to do so far, especially spending a summer doing research in Germany, and I look forward to helping answer some fundamental questions in the field. Luckily for me, answers to these questions are still fairly elusive: as a result, I am guaranteed a mysterious life for years to come.

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