Effects of horizontal resolution and air–sea flux parameterization on the intensity and structure of simulated Typhoon Haiyan (2013)
In: Natural hazards and earth system sciences: NHESS, Band 19, Heft 7, S. 1509-1539
Abstract
Abstract. This study investigates the effects of horizontal
resolution and surface flux formulas on typhoon intensity and structure
simulations through the case study of the Super Typhoon Haiyan (2013). Three
sets of surface flux formulas in the Weather Research and Forecasting Model
were tested using grid spacings of 1, 3, and 6 km. Increased resolution and
more reasonable surface flux formulas can both improve typhoon intensity
simulation, but their effects on storm structures differ. A combination of a
decrease in momentum transfer coefficient and an increase in enthalpy
transfer coefficients has greater potential to yield a stronger storm. This
positive effect of more reasonable surface flux formulas can be efficiently
enhanced when the grid spacing is appropriately reduced to yield an intense
and contracted eyewall structure. As the resolution increases, the eyewall
becomes more upright and contracts inward. The size of updraft cores in the
eyewall shrinks, and the region of downdraft increases; both updraft and
downdraft become more intense. As a result, the enhanced convective cores
within the eyewall are driven by more intense updrafts within a rather small
fraction of the spatial area. This contraction of the eyewall is associated
with an upper-level warming process, which may be partly attributed to air
detrained from the intense convective cores. This resolution dependence of
spatial scale of updrafts is related to the model effective resolution as
determined by grid spacing.
Problem melden