| Abstract: The impact of CO2
-induced global warming on the intensities of strong hurricanes is investigated
using the GFDL regional high-resolution hurricane prediction system. The
large-scale initial conditions and boundary conditions for the regional
model experiments, including SSTs, are derived from control and transient
CO2 increase experiments with the GFDL
R30-resolution global coupled climate model. In a case study approach,
51 northwest Pacific storm cases derived from the global model under present-day
climate conditions are simulated with the regional model, along with 51
storm cases for high CO2 conditions. For
each case, the regional model is integrated forward for five days without
ocean coupling. The high CO2 storms, with
SSTs warmer by about 2.2° C on average and higher environmental convective
available potential energy (CAPE), are more intense than the control storms
by about 3-7 m/s (5%-11%) for surface wind speed and 7 to 24 hPa for central
surface pressure. The simulated intensity increases are statistically significant
according to most of the statistical tests conducted and are robust to
changes in storm initialization methods. Near-storm precipitation is 28%
greater in the high CO2 sample. In terms
of storm tracks, the high CO2 sample is
quite similar to the control. The mean radius of hurricane force winds
is 2 to 3% greater for the composite high CO2
storm than for the control,and the high CO2
storms penetrate slightly higher into the upper troposphere. More idealized
experiments were also performed in which an initial storm disturbance was
embedded in highly simplified flow fields using time mean temperature and
moisture conditions from the global climate model. These idealized experiments
support the case study results and suggest that, in terms of thermodynamic
influences, the results for the NW Pacific basin are qualitatively applicable
to other tropical storm basins. |