The Energy-Pump Mechanism Behind Dubai ‘16•4’ Record-Breaking Rainfall

Located in the subtropics, the record-breaking extreme rainfall (ER) that struck Dubai on April 16, 2024, provides a high-impact case for diagnosing subtropical jet–moist-convection coupling from an energetics perspective. This study applies the perturbation potential energy (PPE) framework to diagnose the energetics of this event. We develop an energetically closed, self-reinforcing energy-pump feedback mechanism, identify extreme conditions using the Rank Attribution Method relative to the 1979–2024 baseline, and quantify moisture source contributions using the Water Accounting Model (WAM). The energetics exhibit clear precursors, with stratospheric PPE and upper-tropospheric perturbation kinetic energy (PKE) becoming significantly anomalous 24–48 h before rainfall onset. Critically, as the bridge between PPE and PKE, the perturbation conversion from PPE to PKE term (PCK) leads to rainfall by about 2 h and effectively anchors both subsequent intensity and the primary rainband. When PCK intensifies, PKE increases in both the upper and lower troposphere, enhancing upper-tropospheric divergence and lower-tropospheric convergence; ascent then accelerates and rainfall amplifies. Latent heating (LH) further warms the column, increases PPE, and strengthens conversion, closing the positive energy-pump feedback loop (LH–PPE–PCK–PKE–LH) that sustains deep convection. Two distinct episodes in this event share this mechanism but differ dynamically: Process I is upper-level dominated and primarily jet-divergence forced, whereas Process II is lower-tropospheric dominated with stronger moisture transport, producing a more rapid rise to peak intensity. Moisture sourcing is dominated by the northwestern Arabian Sea (50.4%), with secondary contributions from the Red Sea (8.2%), the Gulf of Aden (6.7%), and the eastern Mediterranean (4.5%). These results deepen understanding of the energetics of ER over the Arabian Peninsula and highlight PCK as a physically based early-warning indicator for forecasting and risk assessment.