Climate and Catastrophe Risk Assessment - Asia
Federal Ministry
Met Office
cars
for the Environment, Nature Conservation
and Nuclear Safety
Summary of Key Points
part of the Oasis Platform for Climate and Catastrophe Risk Assessment -
Asia, a project funded by the International Climate Initiative (IKI)
1)
Model fits are done for each named storm, and a posterior
predictive distribution for each cell obtained by simulating random
deviates with a mean and standard deviation based on 1000
simulations of the posterior distribution of the model parameters.
Chittagong and Cox's Bazar are particularly at risk of maximum
tropical cyclone wind speeds exceeding 45 m/s (87 kts) and 60 m/s
(116 kts) respectively, in 5% of tropical cyclones making landfall
Areas within 30 km of the coastline of southern provinces (Khulna,
Barisal and Chittagong) will experience maximum windspeed in
excess of very severe cyclonic storm condition ≥ 33 m/s (64 kts)
with a likelihood of 20-50% per tropical cyclone event
Chittagong and Cox's Bazar are roughly x2.5 and x4.8 more likely to
experience tropical cyclones exceeding Very Severe cyclonic storm
conditions than Dhaka, for a landfalling cyclone.
Combing our Bayesian predictive hazard distribution with a loss
function (describing the relative loss experienced for different
actions and magnitude of event) we can create a warning model
based on decision theory
All our data associated with this project will be made available under
Cc-by 4.0.
a)
Model output is available at 4.4km (0.0405°) and 1.5km (0.0135°)
over two nested domains
k)
b)
We run a 9-member ensemble, designed to limit the free-running
model time to 72 hours
Differences in maximum gust speed footprints, for the 1st to 80th
percentiles, of the 1.5km data are roughly O(0.5 m/s) faster than the
4.4km data
d)
Extreme lows of the 1.5km data are [50, 87] hPa and [10, 37] hPa
shallower for the 1st and 5th percentiles
m)
e)
This comparisons suggests that 1.5km storms must also be smaller
in size than the 4.4km storms.
f)
Peak gust speeds are typically 50 - 150 knots (25 - 80 m/s) faster
than ERA5 & minimum MSLP is typically 20 - 50 hPa deeper than
ERA5 in the 4.4km model.
n)
g)
Unfortunately there are no reliable source of observational data in
this region to verify these results against.
i)
==
h)
Initialisation time has significant influence on storm track.
However each footprint is a physically plausible realization of how
the storm could have evolved.
p)
j)
To integrate information from all 9 ensemble members into a
coherent spatial prediction we use a generalise additive models
(GAM)
www.metoffice.gov.uk
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