Statistical-dynamical Downscaling
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Transcript of Statistical-dynamical Downscaling
Statistical-dynamical Downscaling
Asuka Suzuki-ParkerNCAR Earth System Laboratory
National Center for Atmospheric Research
NCAR is Sponsored by NSF and this work is partially supported by the Willis Research Network and the Research Program to Secure Energy for America
Approach
1. Randomly place a weak
storm
2. Determine trajectory based on
large-scale info and
probabilistic perturbation
3. Calculate intensity based on
large-scale info along the
trajectory
4. Majority of storms don’t
reach TC intensity, but
some do
Large-scale info from bias corrected CCSM
Current: 1950-1999 (20C3M)Future: 2000-2099 (A2)
Genesis Distribution
Pretty good agreement with current observationexcept for tropical Atlantic
North AtlanticTC frequency projection
No trend in annual
frequency
Intensity projection
No change in intensity
either
Genesis location projection
Why no trends?
More favorable
Less favorable
Stat-dyn downscale genesis location Projected large-scale trends
Compared to observation, stat-dyn downscale technique is producing more storms in high latitutdes, and less in tropics
As North Atlantic as a whole, trend gets canceled out
TC duration projection
Increasing average TC
duration
PDI increases
TC size projection
Reduction in TC size
is projected
Summary
• Stat-dyn downscaling is successful in reproducing general global TC formation
• Little TC formation in tropical Atlantic– Fails to capture large-scale trend– No trend in frequency or intensity as
whole North Atlantic
• Storm size and duration trends in agreement with NRCM
Comparisons among three techniques
NRCM Stat-dyn GP
Frequency Increase Steady Depends on area
Intensity Increase Steady
Genesis location Southward shift Steady Southward shift
Size Decrease Decrease
Duration Increase Increase