Professor, Department of Earth and Atmospheric Sciences, Saint Louis University, Missouri, USA

Dr. Pan’s research includes climate change, land surface processes, plant disease forecast, extreme precipitation, and aerosol-clouds-climate interaction. He has published over 100 scientific papers in J. Climate, J. Atmospheric Sci., Monthly Weather Review, and Plant Disease among others. Dr. Pan’s research on global warming effects on the central U.S. climate was reported by national and international news media outlets including the Washington Post, the New York Times, and ABC News.

Speech Title: Regional "warming holes" under global warming environment

Abstract: One of the global warming features is that continents are expected to warm faster than oceans and continental centers should warm fastest. However, the 20th-century warming pattern seems to defy this belief with major continental centers (e.g., south-central China, Central U.S., and southern-central South America) being warm less or even cooling. This abnormal summer daytime less warming or cooling in the middle of the continents has been termed as “warming hole (WH)”. The WHs occur 1) to the east of major mountain ranges whose blocking of tropical easterly winds favors a southerly (northerly) flow in the northern (southern) hemisphere, 2) in heavily cultivated agricultural regions where deep crop roots can extract stored soil moisture, and 3) near the terminus of the low-level jets where converged moisture generates cloudiness and precipitation. Studies have attributed WHs to the Pacific Decadal Oscillation (PDO), regional atmospheric-hydrological feedbacks and aerosol loading, among others. Here we found that i) the temperature trends and spatial patterns in WH regions correlates closely with cloudiness and solar radiation, ii) the trend of WH temperature has a large Atlantic Multidecadal Oscillation (AMO) component that affects moisture transport and thus cloud, precipitation, and solar radiation, and iii) the cooling in the WHs is modulated by the AMO and as AMO shifts to positive phase at the turn of the century, the WH phenomenon has also weakened in recent decade or so.