Investigating CESM1 Ability to Capture Heatwaves

Climate change is influencing the frequency and intensity of heat waves. In the next century, these extreme events are projected to increase in duration, frequency, and intensity, but these events will not occur uniformly in space and time. This project investigates heat waves using data from observations and the Community Earth System Model, version 1 (CESM1). The observational data set contains daily minimum and maximum temperatures from weather stations that have been combined and gridded using a 0.5° latitude-longitude grid. The CESM1 dataset has been regridded to the same 0.5° grid as the observations. From this data we derived the ninetieth percentile (90pp) of daily maximum and minimum temperatures for each day of the year. This was our threshold to define "extreme temperature" at every location across the globe. Events are then defined as consecutive days that are “extreme” and by identifying such events we compile statistics of duration, frequency, and amplitude. We have applied the same approach for both the observations and the model and compared them to evaluate the model’s ability to produce realistic heat wave statistics. The model generally produces realistic statistics of where heat waves occur and the amplitude; the main difference between the model and observational data is the duration of the heat wave. Future work will analyze daily minimum temperature, providing a more complete view of extreme temperature events. Extreme heat events are dangerous for human health, especially if people are not prepared. A better understanding of CESM’s ability to predict extreme temperature events will enable the use of model projections in adaptation decision making.