Research Areas

The Climate and Radiation Lab (CRL) has a very active group studying the climate and health impacts of airborne particles ("aerosols"). Aerosol particles reflect sunlight, which tends to cool surfaces locally. Some also absorb sunlight, warming and stabilizing the ambient atmosphere while still cooling the surface below, sometimes suppressing cloud formation, and even affecting large-scale atmospheric circulation...

The goal of climate analysis is to better understand the Earth’s past and present climate, and to predict future climate response to changes in natural and human-induced factors, such as the Sun, greenhouse gases (e.g., water vapor, carbon dioxide and methane), and aerosols (e.g., from dust storms, pollution, fires, sea spray or volcanic eruptions). Climate analysis studies are routinely carried out using a mix of data from diverse sources including historical climate data, current and past satellite instruments, field campaigns, and outputs from regional and global numerical models.

Clouds play a critical role in the Earth's hydrologic cycle and in the energy balance of the climate system. They have a strong effect on solar heating by reflecting part of the incident solar radiation back to space...

The Sun is a distant source of energy that reaches the Earth as solar radiation. Solar radiation has a rich spectral structure. It consists of ultra-violet radiation largely absorbed by stratospheric ozone, visible radiation to which the atmosphere is mostly transparent, and near-infrared and solar infrared radiation where some absorption by atmospheric water vapor occurs.

The Sun’s illumination is the ultimate energy source for the Earth's biosphere, and the ultimate driving force for atmospheric, and oceanic circulations. The Sun is a variable star as one can see from sunspots recorded back to Galileo’s time in the early 1600s. Satellite observations over the past three decades show that the sunspot activity is associated with changes in solar output energy.

The reflectance of natural surfaces depends on the view geometry, i.e., the position of the observer or measuring instrument relative to the Sun. Land surfaces usually appear darker in the forward scattering direction (i.e, with the Sun in front of the observer) and significantly brighter in the backscattering direction (i.e., with the Sun behind the observer).

70% of the Earth’s surface is covered by oceans. It is the only inner planet where all three phases of water (liquid, ice, and vapor) coexist. The movement of water in its different forms, and the perpetual water phase changes are essential ingredients of the planetary water cycle (also known as the hydrological cycle). Precipitation is a major component of the water cycle, and is responsible for most of the fresh water on the planet.