My main research interests are focused on large-scale dynamics and transport in the atmosphere and oceans, and its controls on the distribution of trace constituents. This is important for several different aspects of global change, including stratospheric ozone depletion, air pollution, and global warming. In recent years research activities have expanded to include the atmosphere of Mars, air quality, and urban heat.

Current Projects
Polar Vortices
Width of the Tropics
Impact of Ozone on Climate
Ocean Ventilation
Tropospheric Transport
Air Quality
Urban Heat

Past Projects
Chemistry-Climate Coupling
Upper Tropospheric Water Vapor
Stirring and Mixing
Transport Timescales

Current Projects

strat_vortexPOLAR VORTICES

Polar vortices are a prominent winter feature in the atmospheres of Earth, Mars, and several other planets. On Earth there are distinct stratospheric and tropospheric polar vortices (What is a polar vortex?). The stratospheric polar vortex plays a key role in ozone depletion, and can also influence surface weather (including extreme events).  Extreme surface weather events are often related to transient, localized displacements of the edge of the tropospheric polar vortex.




The width of the tropical circulation is a fundamental aspect of Earth’s climate, with potential societal impacts (e.g. through changes in precipitation). Recent evidence has shown that the edge of the tropics has been expanding, but with a large range in expansion rates between studies. We are examining the relationships between different metrics of tropical expansion, and the possible causes for expansion.


The build up of CFCs and other chlorine and bromine containing species in the atmosphere has lead to significant stratospheric ozone depletion, especially over Antarctic during spring. This ozone depletion leads not only to changes in UV radiation reaching the surface, but also changes in changes in tropospheric weather systems and climate, and ocean circulations. Using observations and a hierarchy of numerical models we are examining the impact of the ozone hole on southern hemisphere weather and climate.


The transport of surface waters into the interior (”ventilation”) of the southern oceans plays an important role in global climate and the cycling of carbon, oxygen, and nutrients in the oceans. We are using observations and models to explore changes in this ventilation. Analysis of measurements of the man-made compounds CFC-12 and SF6 shows large-scale coherent changes in ventilation times, with decreases in the subtropical thermocline and intermediate waters and increases in circumpolar deep waters. These inferred changes are consistent with expected response due to the changes in surface winds that have been linked to the formation of the Antarctic ozone hole.


The tropospheric distributions of chemically and radiatively important constituents such as ozone, water vapor, carbon dioxide, and aerosols are strongly influenced by transport, and quantifying this transport is central to understanding and predicting air quality and climate change. We are using trace gas measurements and model simulations to quantify the transit-time distribution (TTD) for transport from NH populated regions.

  • Scott, AA, DW Waugh, BF Zaitchik, 2018, Reduced Urban Heat Island intensity under warmer conditions, Environmental Research Letters 13 (6).
  • Scott, A. A., Zaitchik, B., Waugh, D., & O’Meara, K. (2017). Intra-urban temperature variability in Baltimore. Journal of Applied Meteorology and Climatology, 56, 159-171.
  • Zaitchik BF, K O’Meara, K Baja, MC McCormack, AA Scott and DW Waugh (2016) B’more Cool: Monitoring the Urban Heat Island at High Density for Health and Urban Design. Earthzine.

Past Projects

ozone_hole Chemistry – Climate Coupling

We are collaborating with scientists at NASA Goddard Space Flight Center (GSFC) and other institutes in several different activities using multi-dimensional coupled chemical – physical models to understand past changes and predict future changes in stratospheric composition and global climate.

Tropiwvaporcal Upper Tropospheric Water Vapor

Water vapor plays a crucial role in Earth’s climate system, and it is important to know the water vapor distribution and processes controlling this distribution. We are performing research to better quantify the distribution and key processes using a combination of satellite observations, theory, and transport models.

seawifsStirring and mixing

Transport and mixing play key roles in determining the distribution of important tracers in the atmosphere and oceans. For example, quantifying the mixing of different stratospheric air masses is important for understanding the observed ozone depletion, which quantifying mixing in the ocean is important for understanding ocean color. We use high-resolution simulations together with observations to quantify stirring and mixing in the stratosphere and oceans. More

cfchistory2Timescales and Tracers

Quantifying the timescales for transport into and through the stratosphere, oceans, lakes and groundwater is important for understanding/modeling the flow, biochemical cycling, and distribution of constituents. Research in this area uses theory, models and observations to determine transit time distributions (TTDs) and the infiltration of tracers (e.g. ozone-depleting substances into the stratosphere, and carbon into the oceans). More