Orlanski, I., and J. J. Katzfey, 1987: Sensitivity of model simulations
for a coastal cyclone. Monthly Weather Review, 115(11),
2792-2821.
Abstract: A nested global, limited-area model was used to predict
the Presidents' Day cyclone of 18-19 February 1979. Both a low (~150 km)
and a high (~50 km) horizontal resolution version were used. The model
has full physics with a planetary boundary layer, moisture, moist convective
adjustment, and radiation.
The low-resolution model, using a global analysis for initial and boundary
conditions (termed a simulation), was able to capture the general development
and movement of the cyclone. Some discrepancies were noted for the intensity
of upper-air features between the analyses and the model solution during
the first 24 hours. The primary focus of this paper is to determine the
effect of initial and boundary conditions, as well as model parameterizations
on the accuracy of the predictions. The evolution of the storm is discussed
with an emphasis on the quality of the numerical simulation.
The impact of the initial conditions on the model solution was tested by
using four different global analyses. It was found that the variability
between the solutions was less than the variability between the analyses.
Varying the horizontal diffusion in the model produced stronger development
with weaker diffusion, but the character of the development did not change
significantly. The sensitivity of the simulation to latent heat was tested
by running the model without latent heating. A low did develop in this
model solution, although it was much weaker and it did not develop vertically
as in the cases with latent heating.
The most significant improvement in accuracy in this sensitivity study
occurred when the horizontal resolution was increased from 1.25°
x 1.0° (~150 km) to 0.4° x 0.32° (~50 km). The position
and intensity of the surface low were much closer to reality, as indicated
by comparison with a mesoanalysis and to satellite pictures.
The nested model was also run in forecast mode with boundary conditions
for the limited-area model supplied by the (Geophysical Fluid Dynamics
Laboratory) GFDL global spectral model forecast. In general, the quality
of the limited-area forecast compared very well with the simulations. The
overall character and intensity of the development were similar.
The role of lateral boundary conditions was demonstrated by comparing forecasts
and simulations with identical initial conditions. The results suggest
the increasing importance of the boundary data with time in the limited-area
forecast and show high correlation between the errors in the limited-area
forecast and the global forecast within the limited-area domain.