Hurricane research improved by supercomputer simulations

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Information from major hurricanes of the past two decades such as Katrina is being put to good use by scientists striving to understand how hurricanes intensify. A research team led by Jon Reisner of Los Alamos National Laboratory (LANL) is employing the Oak Ridge Leadership Computing Facility’s (OLCF’s) Jaguar supercomputer to use data from lightning detectors and even wind instruments mounted on planes flown into the eye of a hurricane to improve atmospheric models. These simulations may lead to more accurate prediction of hurricane intensities and better preparation of the public for these inevitable disasters.

One challenge for hurricane models has been to successfully integrate the extremely small spatial scales of the condensation process, Reisner said. The particles interact at spatial scales between 10 and 100 nanometers, ranging from the minute size of individual genes and simple viruses to the largest particle size that can slip through a surgical mask.

Reisner’s team is using an atmospheric science model developed at LANL called HIGRAD to simulate and track individual liquid or solid particles on a nanometer scale. HIGRAD is the first atmospheric model capable of simulating liquid or solid phases in either a Lagrangian or Eulerian framework. Simply put, a Lagrangian frame of reference follows an individual fluid parcel as it moves through space and time, whereas a Eulerian framework focuses on a specific location in which the fluid flows over time. The Lagrangian frame of reference allows HIGRAD to look at individual water particles, permitting a more realistic representation of cloud structure within hurricanes.

The virtual particles include those the hurricane has absorbed from the condensation process. These particles can grow, collide, melt, freeze, or otherwise undergo any action or interaction, any microphysical process that occurs in an actual hurricane on this minute spatial scale. In total, HIGRAD used approximately 118,000 Jaguar processors during three separate simulations.

In addition to enabling advances in mirroring microphysical processes, HIGRAD is the first climate tool used to build a three-dimensional model of the lightning activity in a hurricane. Data measured from Rita - the fourth most intense Atlantic hurricane on record (Katrina was the sixth) - by LANL’s lightning-detection network, the Los Alamos Spherical Array (LASA), suggest a correlation between the intensification of lightning activity and the intensification rate of the storm.