Changes in the Characteristic Features of Disturbances Appearing in the Baiu Frontal Zone over Western Japan Due to Global Warming

Numerical experiments are performed using a non-hydrostatic regional climate model with a horizontal resolution of 5 km to study changes in the characteristic features of disturbances appearing over the Baiu frontal zones due to global warming. In this study, disturbances are defined as those with precipitation greater than 20 mm/6 hr within a radius of 100 km. An increase in the number of disturbances is found in the Baiu frontal zone over western Japan in the warming climate. The increase is caused by the lengthening of the Baiu duration. In addition, the disturbances are likely to be much more detected by the intensification of precipitation. Among such disturbances, those with intense precipitation and eastward-tilting vertical structures in high-pass-filtered fields are more frequently seen in the warming climate. They are considered to be meso-alpha-scale baroclinic instability modified by diabatic heating due to large precipitation. Our results suggest that the changes in the numbers of disturbances are induced by an increase in the supply of water vapor to the Baiu frontal zone and convectively unstable stratifications in the lower atmosphere.