June 2012 Featured Scientist – Benjamin Kirtman, PhD

Dr. Benjamin Kirtman

June  2012

Overview – Dr. Benjamin Kirtman is the Program Director for the Physical Science and Engineering at the Center for Computational Science. He is also a Professor in the Division of Meteorology and Physical Oceanography at the University of Miami Rosenstiel School for Marine and Atmospheric Science (RSMAS), where he also serves as the Associate Dean for Research. Prior to joining the University of Miami, Dr. Kirtman was a Professor at George Mason University.

Dr. Kirtman received his Bachelor’s degree from the University of California at San Diego in Applied Mathematics. He holds  Masters and PhD degrees in Meteorology and Physical Oceanography from the University of Maryland – College Park. Dr. Kirtman is very active in scientific leadership both internationally and nationally. Currently, Dr. Kirtman is co-Chair of the World Climate Research Program (WCRP) Working Group on Seasonal to Interannual Prediction (WGSIP) and is a Coordinating Lead Author of the Intergovernmental Panel of Climate Change (IPCC) Assessment Report (AR) Five that is currently in progress. Professor Kirtman is also an Executive Editor of Climate Dynamics one the most prestigious peer reviewed journals in the field. Professor Kirtman is the author and/or co-author of over 100 peer reviewed papers focused on understanding and predicting climate variability on time scales from intra-seasonal to decadal. More recently, Dr. Kirtman published on understanding how climate variability might change in a warmer climate. He currently advises and continues to work with several PhD students.

Research Interests

Dr. Kirtman’s research is a wide-ranging program to understand and quantify the limits of climate predictability from days to decades. The research also involves understanding how the climate will change in response to changes in anthropogenic (e.g., greenhouse gases) and natural (e.g., volcanoes) forcing. This research involves hypothesis testing numerical experiments using sophisticated state-of-the-art climate models and experimental real-time prediction. The group uses and has access to a suite of climate models, climate data and high performance computational platforms. Some results from various projects are briefly summarized here.

Figures 1 and 2: Surface current speeds in a high-resolution simulation

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One of Dr. Kirtman’s projects is a collaborative effort including scientist from George Mason University and the National Center for Atmospheric Research seeks to understand how ocean eddies impact large-scale climate variability. This requires global climate simulations conducted at resolutions that have never before been attempted. Figures 1 and 2 show a snap shot of the surface current speeds in this high-resolution simulation compared to the typical resolutions used. Capturing the details of these currents has been shown to dramatically affect the global distribution of rainfall.

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Dr. Kirtman’s research group is also leading an effort to develop a US National Multi-Model Ensemble prediction system for intraseasonal-to-interannual prediction. Figure 3 shows the forecast skill (as measured by the correlation between the predictions and observations. Figure 4 shows the forecast skill for global sea surface temperatures. The new prediction system has considerable skill in the southern tier of the US and is being used to understand the mechanisms for persistent drought and the limits of predictability.

We have also developed a new ocean-atmosphere-sea-ice-land coupling system called the “interactive ensemble” that is specifically designed to diagnose coupled feedback between the component models and estimate how high frequency variability in one component affect the other components. In the example shown below we have used the interactive ensemble to diagnose how atmospheric weather impacts the low frequency meridional overturning circulation in the Atlantic Ocean. This meridional overturning circulation is critical for maintaining the relatively warm climate over Europe. The top two panel show the mean meridional overturning circulation from a simulation with realistic atmospheric weather (left panel) and from the interactive ensemble simulation with reduce atmospheric weather (right panel). The bottom panel shows how this meridional overturning circulation changes with time (blue control and red interactive ensemble). The result suggests that atmospheric weather is an important factor in the overturning circulation.

Dr. Kirtman is also the lead developer a new ocean-atmosphere-sea-ice-land coupling system called the “interactive ensemble” that is specifically designed to diagnose coupled feedback between the component models and estimate how high frequency variability in one component affect the other components. In the example shown below we have used the interactive ensemble to diagnose how atmospheric weather impacts the low frequency meridional overturning circulation in the Atlantic Ocean. This meridional overturning circulation is critical for maintaining the relatively warm climate over Europe.The top two panel show the mean meridional overturning circulation from a simulation with realistic atmospheric weather (Figure 5) and from the interactive ensemble simulation with reduce atmospheric weather (Figure 6).

Figure 5

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Figure 7 shows how this meridional overturning circulation changes with time (blue control and red interactive ensemble). The result suggests that atmospheric weather is an important factor in the overturning circulation.

Figure 7