Upper ocean cooling and air‐sea fluxes under typhoons: A case study

Abstract

Direct observations of ocean temperatures and air‐sea energy exchange underneath three typhoons and a tropical storm encountered in the Philippine Sea during the 2010 Pacific typhoon season are examined. Data are reported from two buoys 180 km apart with ocean temperatures recorded to 150 m and wind speeds up to 26 m s−1. A detailed examination of the cold wakes is used to determine the mechanisms though which the ocean cools. The result show that net cooling varied between storms by two orders of magnitude, accounting for between 9 and 1000 MJ m−2 of heat loss, and were a result of entrainment, advection, and surface fluxes. In some cases a marked temperature increase below the mixed layer occurred due to entrainment of warm water across the thermocline. Mixed layer temperature decreases ranged from 0.35 to 1.6°C and found to be well predicted by typhoon translation speed and wind speed. Of the mixed layer heat loss, 12–47% was attributed to enthalpy fluxes, the upper range of which is much greater than previous reports. Results are discussed in terms of their relevance to tropical cyclone and climate modeling.

The role of enhanced velocity shears in rapid ocean cooling during Super Typhoon Nepartak 2016

“…Despite the modeling approach, satellite observations, although powerful, are considerably limited by cloud cover, the spatial and temporal resolutions and are only representative of surface conditions 3,9 . The upper ocean’s temperature, salinity, and velocity profiles before, during, and after the passage of a typhoon can only be obtained by in situ measurements.…”

Observational Evidence of Surface Wave‐Generated Strong Ocean Turbulence

“…Typhoons attack South China Sea every year. Sea surface temperature (SST) was observed to decrease more than 2°after typhoon passed over, which could be attributed to strong turbulence from current shear, wave breaking, and nonbreaking waves in the upper ocean boundary layer (Chiang et al, 2011;Guan et al, 2014;Lin et al, 2017;Potter et al, 2017). Mesoscale eddies were also influenced by typhoons (Lu et al, 2016;Yu et al, 2019).…”

Tropical Cyclone Heat Potential and the Rapid Intensification of Hurricane Harvey in the Texas Bight

“…A strong relationship between SST and maximum potential intensity has been many times demonstrated (e.g., DeMaria & Kaplan, 1994). Surface forcing by TC winds create divergent surface currents which mix the upper ocean reducing the SST and subsequently decreasing enthalpy fluxes (e.g., Potter et al, 2017) which can reduce intensity by up to 70% (Schade & Emanuel, 1999) The decrease in SST is greatest when the mixed layer depth is shallow and when the thermocline gradient is sharp (Price, 1981). In the northern hemisphere ocean cooling is often most pronounced on the right side of the storm track.…”