Hans Chen

Ph.D. student in atmospheric sciences at Penn State

  • Hans W. Chen
  • Doctoral Graduate Student
  • Department of Meteorology
  • The Pennsylvania State University


I am a Ph.D. student in the Department of Meteorology at Penn State, working with my advisor Fuqing Zhang and my co-advisor Richard Alley. My research interests include climate variability on interannual to decadal time scales, synoptic-scale atmospheric dynamics, and interactions between regional climate variability and the general circulation of the atmosphere. At the moment my research focuses on improving our understanding of the links between reduced Arctic sea ice and the weather in the Northern Hemisphere mid-latitudes.


2013–present Ph.D. in Atmospheric Sciences and Meteorology, Department of Meteorology, The Pennsylvania State University, University Park, Pennsylvania, United States.
2010–2012 M.S. in Atmospheric Sciences, Oceanography and Climate, Department of Meteorology, Stockholm University, Stockholm, Sweden.
2007–2010 B.S. in Meteorology, Department of Meteorology, Stockholm University, Stockholm, Sweden.

More information can be found in my CV.

Research interests

The focus of my research is to improve our understanding of climate variability on interannual to decadal time scales, from a large-scale to regional-scale perspective. I approach the problems using a combination of observational data, numerical models, and statistical methods. The research topics I am interested in include:

  • Synoptic-scale atmospheric dynamics and teleconnection patterns
  • Interactions between large-scale circulation and regional climate
  • Data assimilation, ensemble techniques, and predictability

Current research projects

Mid-latitude atmospheric response to Arctic sea-ice loss

I am currently investigating the impact of reduced Arctic sea ice on the weather and climate variability in the Northern Hemisphere mid-latitudes. More information about this project will be up soon.

Past research projects

A robust mode of climate variability in the Arctic: The Barents Oscillation

Worldmap of Köppen types

This project is based on my Master's thesis and examines the robustness of an atmospheric mode known as the Barents Oscillation (BO). The BO was originally identified as the second Empirical Orthogonal Function (EOF) of monthly wintertime sea level pressure anomalies north of 30°N. Contrary to the dominant Arctic Oscillation/North Atlantic Oscillation (AO/NAO) mode, the BO has mainly a meridional structure and was speculated to be important for the heat transport into the Arctic. A subsequent study, however, showed that an artificial BO-like mode could arise purely due to non-stationary in the spatial pattern of the AO/NAO. Thus, it became unclear whether the BO could be considered independently from the AO/NAO. The objective of this study was to investigate if the BO is a real physical mode of atmospheric variability or an artifact of EOF analysis. On the project page you can find more information about the BO and obtain the BO index.

Go to project page

Using the Köppen classification to quantify climate variation and change

Worldmap of Köppen types

When trying to quantify the impact of climate variation and climate change, it is common to use a single scalar variable such as surface temperature. However, it is not given that a change in e.g. surface temperature will have the same impact everywhere; some ecosystems are relatively stable, while others are more sensitive to changes in the regional climate. This project explores a different approach, using the Köppen climate classification to identify the climatic condition in different regions over various time scales. The Köppen classification system was developed empirically based on the vegetation distribution on Earth and combines surface temperature and precipitation into one single metric. The results of this project suggest that the Köppen classification can be used as a diagnostic tool to examine climate variation and climate change.

Go to project page


  • Chen, H. W., Q. Zhang, H. Körnich, and D. Chen, 2013: A robust mode of climate variability in the Arctic: The Barents Oscillation. Geophysical Research Letters, 40, 2856-2861, 10.1002/grl.50551.
  • Chen, D. and H. W. Chen, 2013: Using the Köppen classification to quantify climate variation and change: An example for 1901–2010. Environmental Development, 6, 69-79, 10.1016/j.envdev.2013.03.007.



Presentation slides



Here I have listed various free software I have found useful in my research.

Atmospheric science


  • Python - My programming language of choice for performing analyses. Useful packages:
  • Git - Powerful version control system. I keep most of my work in Git repositories.
  • Zotero - Reference management software for collecting and organizing bibliographic data.