The water budget of a hurricane as dependent on its movement

Abstract

Despite the dangers associated with tropical cyclones and their rainfall, the origins of storm moisture remains unclear. Existing studies have focused on the region 40-400 km from the cyclone center. It is known that the rainfall within this area cannot be explained by local processes alone but requires imported moisture. Nonetheless, the dynamics of this imported moisture appears unknown. Here, considering a region up to three thousand kilometers from storm center, we analyze precipitation, atmospheric moisture and movement velocities for North Atlantic hurricanes. Our findings indicate that even over such large areas a hurricane's rainfall cannot be accounted for by concurrent evaporation. We propose instead that a hurricane consumes pre-existing atmospheric water vapor as it moves. The propagation velocity of the cyclone, i.e. the difference between its movement velocity and the mean velocity of the surrounding air (steering flow), determines the water vapor budget. Water vapor available to the hurricane through its movement makes the hurricane self-sufficient at about 700 km from the hurricane center obviating the need to concentrate moisture from greater distances. Such hurricanes leave a dry wake, whereby rainfall is suppressed by up to 40 per cent compared to its long-term mean. The inner radius of this dry footprint approximately coincides with the radius of hurricane self-sufficiency with respect to water vapor. We discuss how Carnot efficiency considerations do not constrain the power of such open systems that deplete the pre-existing moisture. Our findings emphasize the incompletely understood role and importance of atmospheric moisture supplies, condensation and precipitation in hurricane dynamics.

38 pages, 17 figures, 1 Table; extended analyses: available E/P ratios reviewed and explained (Table 1); rainfall and moisture distributions 3 days before and after hurricanes, propagation velocity and its relationship to radial velocity; efficiency for non-steady hurricanes; hurricane motion and rainfall asymmetries discussed

References in corpus (3)

• The key physical parameters governing frictional dissipation in a precipitating atmosphere
• Heat engines and heat pumps in a hydrostatic atmosphere: How surface pressure and temperature constrain wind power output and circulation cell size
• Comment on "The Tropospheric Land-Sea Warming Contrast as the Driver of Tropical Sea Level Pressure Changes" by Bayr and Dommenget

Cited by in corpus (4)

• The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence
• Hurricane's Maximum Potential Intensity and the Gravitational Power of Precipitation
• Water lifting and outflow gain of kinetic energy in tropical cyclones
• Hurricane's maximum potential intensity and surface heat fluxes