The Contribution of Mesoscale Convective Systems to the Thermodynamic Scaling of Extreme Precipitation in the Tropics

Abstract:

The link between Mesoscale Convective Systems (MCS), extreme daily precipitation and surface temperature is investigated in the context of the scaling theory. Satellite-based observations of precipitation are pooled together over the whole tropics and jointly analyzed with satellite-based SST and 2 meters temperature from ERA-5 over land at the 1° 1 day resolution. A newly released database of MCS morphology is also used to relate the scaling to the properties of the MCS.

The study first confirms the thermodynamic scaling rate in the data. The increase of the extreme precipitation rate with temperature in the tropics correlates well with the high cloudiness. The upper level cold cloudiness increase with surface temperature is mainly related to long-lived MCS. It is also shown that cyclone-related MCS account for up to ~60% (~40%) of the total cloudiness over ocean (over land) and are responsible of ~60% (~35%) of the total extreme rainfall amount over ocean (over land).

A dedicated analysis of the coastal regions has also been performed. It reveals that the warmest part of the Clausius Clapeyron scaling regime over the tropical land is indeed linked to the landing of cyclones on the coastal regions.