Climate Variability and Extreme Events: Droughts and Typhoons
Stefan Liess, Postdoctoral Researcher in the Department of Earth Sciences at the University of Minnesota
Link to Video
https://umn.webex.com/umn/ldr.php?RCID=7f08e51907ff4e1aeb95f26369176827
During winter, Minnesota is the fastest warming state of the contiguous U.S. since the 1970s. This is related to the influence from strongly warming Arctic conditions, also known as Arctic amplification. We show with regional and global model simulations that this amplification can be enhanced by increased vegetation growth around the Arctic circle. In addition to temperature changes, increased moisture availability is an important factor related to vegetation growth. Invasive species such as the brown marmorated stink bug might be able to thrive in future climates. We project regional climate change over Minnesota by using globally available projections and down-scale these with a regional model to make these projections useful for local policy makers. These projections need to account for variability in the ocean circulation such as the El Nino mSouthern Oscillation (ENSO), which can be related to observed droughts over Minnesota for the last century.
Reliable observations for more than a century are necessary to detect multidecadal climate variability. The Atlantic Multidecadal Oscillation (AMO) has a period of 60-80 years and is thought of as a main driver for the Sahel drought from the 1970s to the 1990s. We show that the extent of this oscillation can reach East Africa and even the Indian summer monsoon. We identify a teleconnection between the Tasman sea and the Southern ocean that describes the multidecadal drought cycle over Australia and that is statistically correlated to the AMO, but no physical explanation for the latter connection has been found so far. We show in a regional simulation how atmospheric moisture content over Australia, East Africa, and India are connected via the monsoon circulation. This circulation converges with tropical easterlies over the west Pacific warm pool, where our simulation shows a series of three strong tropical cyclones, which have observed counterparts as typhoons Frankie, Gloria, and Herb during the 1996 typhoon season.