NERSCPowering Scientific Discovery Since 1974

User-Submitted Publications (2017)

Timmermans

Impact of tropical cyclones on modeled extreme wind-wave climate

The extremes of ocean wave climate, including contributions from tropical cyclones, were investigated by examining the effect of ocean wave simulation resolution increase.

The first ever long climatological wave simulations at 0.25o resolution, based upon previous high resolution climate modeling (Wehner et al. 2015), allowed us to identify the effects of tropical cyclones.

Making use of HPC facilities at NERSC, long simulations of global wave climate were run using NCEP's Wavewatch III model, driven by climatological wind data previously generated from Community Atmosphere Model (CAM5). The effect of tropical cyclones is clearly seen to impact wave height, but uncertainty due to sampling is a problem. This study highlights the importance of resolution when simulating extreme sea states in certain regions.

Resources Used: Cori Phase 1 - Cray XC40 (Haswell), Edison - Cray XC30, Hopper - Cray XE6

Diagnosing conditional anthropogenic contributions to heavy Colorado rainfall in September 2013

We find an attributable influence of climate change on the September 2013 Colorado flood event, with a 30% (+/- 9%) increase in rainfall. As a best estimate, we find that anthropogenic climate change doubled the conditional probability of the event’s occurrence. In addition, the lower bound on this “risk ratio” is insensitive to uncertainty in the definition of this extreme event and is greater than one.

This research revealed that climate change can intensify rare extreme precipitation events beyond magnitudes that would be expected by the Clausius-Clapeyron scaling of increased temperature alone.