Advancing Tropical Cyclone Forecasts Using Aircraft Observations - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 174

Fig. 5: Drawings of the three varieties of floats and a surface drifter deployed.
surface air flowing inward over relatively cool water can lessen the enthalpy
flux from the ocean into the atmosphere, thereby becoming cooled and reducing
buoyancy in the eyewall. The left front quadrant had only a very small SST
decrease. Black et al. (1988) and Shay et al. (1992) further documented the
significant impact TCs have on the upper ocean. Cione and Uhlhorn (2003)
showed that SST reduction near the TC centre is modest (~0.2-1.2 K), and that
much of the observed 4-6 K cooling occurs long after TC passage. The
magnitude of the SST change was statistically linked to subsequent intensity
changes, suggesting that SST measurements in regions over which the TC
core will pass, and during passage, will aid in intensity forecasts. These issues
were investigated in flights supporting the Coupled Boundary Layer Air-Sea
Transfer (C-BLAST) experiment during the 2000-04 Atlantic hurricane seasons
(Black et al., 2007).
Careful analysis of data from dropwindsondes and ocean expendable probes
released from the P-3s is elucidating the ways in which TCs interact with the
underlying ocean to cause intensity changes. Cione et al. (2000) and Cione
and Uhlhorn (2003) found that low-level inflow into the TC centre was not
isothermal, that surface moisture was not constant, and that the air near the
surface was not in thermodynamic equilibrium with the sea. The surface air
temperature drops as the air flows toward the TC centre; this drop occurs far
from the eyewall where the largest pressure drops occurred, so the change is
not adiabatic. This allows surface heat and moisture fluxes to be much higher
near the eyewall than further away; the fluxes are thus greater than previously
believed, and more energy is provided to the TC from the underlying ocean.
Since the eyewall is nearly saturated, the surface air temperature near the TC
centre was relatively constant with distance from the centre despite the potential