Warm conveyor belts in present-day and future climate simulations – Part 2: Role of potential vorticity production for cyclone intensification

Abstract. Warm conveyor belts (WCBs) are strongly ascending, cloud- and precipitation-forming airstreams in extratropical cyclones. The intense cloud-diabatic processes produce low-level cyclonic potential vorticity (PV) along the ascending airstreams, which often contribute to intensification of associated cyclone. This study investigates how climate change affects cyclones' WCB strength importance WCB-related diabatic PV production for cyclone intensification, based on present-day (1990–1999) future (2091–2100) simulations Community Earth System Model Large Ensemble (CESM-LE). In each period, a large number cyclones their trajectories have been identified both hemispheres during winter season. as air parcels that rise at least 600 hPa 48 h. Compared ERA-Interim reanalyses, able capture structure WCBs reasonably well, gives confidence projections with CESM-LE. However, amplitude diabatically produced anomaly centre is underestimated simulations, most likely because reduced vertical resolution compared ERA-Interim. comparison two climates reveals an increase rate Southern Hemisphere (SH) climate. also increases Northern (NH) but smaller degree, not projected considerably. Hence, responds differently strength. Cyclone deepening correlates positively intensity WCB, Spearman correlation coefficient 0.68 (0.66) NH (future) 0.51 (0.55) SH. explosive strong WCBs, referred C1 cyclones, hemispheres, while weak (C3 cyclones) decrease. A composite analysis will be even stronger more production, formation tower, precipitation. They become warmer, moister, slightly intense. findings indicate (i) latent heating (as our method) increase, (ii) important than climate, (iii) interplay between dry moist dynamics crucial understand intensification.