Criteria for defining tropical storms in AGCMs

• After Bengtsson et al. 1995 and Vitart et al. 1997
  1. Relative vorticity $\xi$ at 850mb: $\xi_{NH}^{}$ > 3.510^-5s^-1, $\xi_{SH}^{}$ < - 3.510^-5s^-1.

  2. A maximum speed of at least 15m/s within a 7X7 grid point box, around the grid point the fulfills condition (1).

  3. The closest local minimum sea level pressure within a 7X7 grid point box, around the grid point the fulfills condition (1) is defined as the center of the storm.

  4. The maximum of sum of the temperature anomalies (deviation from the mean within the 7X7 grid point box around the center of the storm) at 700mb, 500mb and 300mb is greater than 3^oC.

  5. The temperature anomaly at 300mb is greater than the temperature anomaly at 850mb for all grid points in the 7X7 grid point box around the center of the storm.

  6. The mean speed (within at 7X7 grid point box around the center of the storm) at 850mb greater than the mean speed at 300mb.

  7. Minimum duration of the storm: 2 days.