11:45 AM - 12:00 PM
[MIS21-05] Three-dimensional vortex–vortex interaction between potential vorticity cutoffs and its modulation
Keywords:cutoff lows, potential vorticity, vortex–vortex interaction, diabatic heating
Cyclone vortices sometimes detach from a jet through Rossby wave breaking, and they are usually accompanied by the intrusion of a high potential vorticity (PV) air mass. The vortices are called cutoff lows. They reduce stability below them, which is often associated with unstable weather conditions, including heavy precipitation. Therefore, the maintenance mechanism of cutoff lows is a significant issue. Our group investigated a case over Europe July 2021 (Yamamoto et al. 2024). It is suggested from quantitative analyses that a cutoff low that caused heavy rainfall merged with another low, contributing to maintenance itself. We also found that diabatic heating can affect the merger process. However, we think there is room for further discussion regarding the latter.
Therefore, in this work, we address the same case and conduct ensemble experiments focusing on the parameterizations. Analyses of PV and velocity field reveal that some members involve 1) the direct effect of enhanced positive PV anomalies between the two cutoff lows and 2) the indirect effect of enhanced PV inside the parent cutoff low and then reinforcing cyclonic circulation, which promotes the inflow from the child cutoff low to the parent. These results suggest that the two-dimensional vortex–vortex interaction discussed in previous studies can be applicable to the three-dimensional situations and support the possibility that diabatic heating can modulate the vortex–vortex interaction.
Reference:
Yamamoto, K., K. Iga, and A. Yamazaki, 2024: Mergers as the maintenance mechanism of cutoff lows: A case study over Europe in July 2021. Mon. Wea. Rev., accepted, https://doi.org/10.1175/MWR-D-23-0024.1.
Therefore, in this work, we address the same case and conduct ensemble experiments focusing on the parameterizations. Analyses of PV and velocity field reveal that some members involve 1) the direct effect of enhanced positive PV anomalies between the two cutoff lows and 2) the indirect effect of enhanced PV inside the parent cutoff low and then reinforcing cyclonic circulation, which promotes the inflow from the child cutoff low to the parent. These results suggest that the two-dimensional vortex–vortex interaction discussed in previous studies can be applicable to the three-dimensional situations and support the possibility that diabatic heating can modulate the vortex–vortex interaction.
Reference:
Yamamoto, K., K. Iga, and A. Yamazaki, 2024: Mergers as the maintenance mechanism of cutoff lows: A case study over Europe in July 2021. Mon. Wea. Rev., accepted, https://doi.org/10.1175/MWR-D-23-0024.1.