AIR Typhoon Model for Japan

AIR Typhoon Model
for Japan
Typhoons are the most frequent cause of property loss in
Japan. The growing number and value of properties in
risk-prone areas of Japan make it essential for companies
operating in this market to have the tools that will
effectively mitigate the impact of winds, precipitationinduced flooding, and storm surge from the next typhoon.
The AIR Typhoon Model for Japan—
part of AIR’s Northwest Pacific Basinwide
Typhoon Model—provides a probabilistic
approach for determining the likelihood
ROBUST CATALOG LEVERAGES DATA FROM LEADING
REGIONAL ORGANIZATIONS
The model features a large catalog of simulated events that
appropriately characterizes the frequency, track, and other
meteorological aspects of potential future storms. To create
this catalog, AIR scientists utilized historical data provided
of losses from typhoon winds,
by leading regional organizations, including the Japan
precipitation-induced flooding, and storm
Meteorological Agency (JMA) and the Shanghai Typhoon
surge. The model incorporates cutting
model features a 10,000-year catalog containing 293,235
edge science that best reflects the current
understanding of the behavior of tropical
Institute (STI). Based on this comprehensive data set, the AIR
simulated events ranging from tropical storm to super
typhoon.
cyclones in this basin, as well as the latest
WIND HAZARD MODELING REFLECTS LATEST
RESEARCH ON REGIONAL TYPHOON BEHAVIOR
engineering research into the response
Observation data indicate that the central pressure–wind
of local construction. Extensive loss data
speed relationship is different in different ocean basins.
from the Japanese insurance market was
the Northwest Pacific tend to have lower wind speeds than
used to validate model results.
For example, for the same central pressure, typhoons in
hurricanes in the North Atlantic. In the AIR model, the
generation of a typhoon’s local wind field involves computing
winds aloft at each point in the model domain using a central
pressure–wind speed relationship that incorporates regionspecific data to best reflect the current understanding of
winds generated by Northwest Pacific typhoons.
A COMPREHENSIVE APPROACH TO ASSESSING REGIONAL RISK
Today, insurers and reinsurers operating globally need the ability
to quantify the risk to policies and portfolios that span multiple
countries—particularly in the Northwest Pacific Basin, where, given
the configuration of landmasses, more than half of all landfalling
typhoons affect more than one country.
To provide a consistent and comprehensive view of risk to companies
with regional portfolios, AIR has developed a unified basinwide
catalog shared by all modeled countries in the Northwest Pacific
basin. The catalog enables seamless risk assessment for multi-country
policies and portfolios, an approach of critical importance to global
companies.
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The majority of storms during the 2007 Northwest Pacific
typhoon season impacted more than one country.
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To ensure the most accurate view of flood risk, AIR’s model
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also accounts for extratropical transitioning, which can lead to
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an increase in the size of a storm’s precipitation shield.
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STORM SURGE MODULE INCORPORATES HIGHRESOLUTION BATHYMETRY AND TERRAIN AND
STORM SURGE ELEVATION DATA
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Although little correlation exists between typhoon wind
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speed and precipitation intensity, storm surge is strongly
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correlated with wind speed. Other factors influencing the
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storm surge threat include bathymetry and tide. A given
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typhoon will typically produce a larger storm surge along
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a coastline with shallow bathymetry than one with steep
Accumulated precipitation in millimeters for 2009’s Typhoon Etau (red circles
indicate storm track). Although Etau never came closer than 300 km to Japan,
flooding from the storm inundated more than 5,000 buildings.
bathymetry. Background astronomical tide level—that is, the
water height that would have been observed in the absence
of a storm—influences the total water level seen during a
The model’s wind field formulation is further supported by
the latest available data and scientific literature on the rate
of decrease in wind speeds after landfall. Overestimating this
rate can significantly underestimate inland losses.
PRECIPITATION-INDUCED FLOOD MODULE
INCORPORATES DETAILED INFORMATION ON SOIL
TYPE, LAND USE/LAND COVER, AND TOPOGRAPHY
Precipitation-induced flooding can be a major driver of
insured loss from Japanese typhoons. Unlike typhoon
winds, which generally decrease as storms move inland, the
intensity of storm-related precipitation can actually increase
in inland regions. Furthermore, the precipitation footprints
of typhoons typically extend for hundreds of kilometers (as
opposed to tens of kilometers, for the wind footprint); thus,
even storms hundreds of kilometers offshore can cause flood
damage on land.
The AIR model employs a separate module that is used to
determine the spatial distribution of accumulated runoff.
High-resolution data on soil type, land use/land cover, and
slope are all used to redistribute precipitation over the model
domain. The fraction of runoff absorbed at a given location
tropical cyclone event. Through the use of high-resolution
bathymetry and terrain elevation data, the storm surge
module simulates a storm surge event from its inception to its
farthest extent inland.
DAMAGE FUNCTIONS PROVIDE ROBUST VIEW OF
WIND, PRECIPITATION-INDUCED FLOOD, AND STORM
SURGE RISK
Based on engineering studies, post-disaster surveys following
recent storms, and analyses of a large set of claims data,
AIR engineers have developed peril-specific functions for
62 different construction classes and 116 occupancy classes
in Japan. Further highlights of the AIR model’s vulnerability
module include:
–– Separate damage functions for the wind, precipitationinduced flood, and storm surge perils
–– Wind, precipitation-induced flood, and storm surge
damage functions that vary by building height,
construction, and occupancy
–– Damage functions that account for the duration of high
winds at a building’s location
–– Method for estimating business interruption that varies
by occupancy and accounts for business characteristics
depends on the porosity of the soil and its saturation level, as
well as the slope of the ground.
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(i.e., resiliency, the ability to relocate) and building size
and complexity
–– Damage functions that capture variability in regional
vulnerability
VARIABILITY IN REGIONAL BUILDING PRACTICES
CAPTURED WITH REGIONAL VULNERABILITIES
By incorporating findings from a comprehensive study of
local construction practices and building codes, regional
–– Detailed age bands for wood frame buildings
vulnerabilities in the AIR model appropriately capture
–– Flood damage estimation that accounts for the existing
the variation in damage from wind. For non-engineered
flood defenses
–– Damage functions that support a variety of specialized
structures (which do not follow prescribed design levels for
environmental loads set out by the country’s national building
risks, including marine cargo, marine hull, railways,
code), these vulnerabilities are based on the composite
buildings under construction, large industrial facilities,
hazard—wind, seismic activity, and snow load. For engineered
additional composite construction classes (to enhance
buildings (which are constructed using the national building
support of Japan’s fire code), and unknown risk
code), regional vulnerabilities were developed using design
characteristics
wind speeds from the Architectural Institute of Japan.
ACCOUNTING FOR JAPAN’S ENGINEERED FLOOD
DEFENSES
Japan continues to invest heavily in flood risk reduction
measures by increasing the level of flood defenses,
including levees, dams, and cisterns. To provide the
most accurate view of flood risk possible, the AIR model
accounts for the flood level that the defenses were
designed to withstand, as well as their current state of
repair, which can differ notably from design conditions.
An underground cistern north of Tokyo (Source: Yomiuri Shimbun).
Photos taken as part of AIR damage surveys; (top) roof and window damage
to a residential structure from Typhoon Ma-on in 2011 and (bottom) damage
to a large mutual line from 2004’s Typhoon Songda.
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VALIDATING INSURED LOSSES USING EXTENSIVE
CLAIMS DATA
Japan differ significantly for water-related perils—including
To produce realistic and robust model results, AIR builds its
compared to the wind peril. Touchstone® allows users to input
models from the ground up, validating each component
separate policy conditions for wind and water-related perils,
independently against multiple sources. AIR modeled wind
and obtain separate loss estimates for the three sub-perils,
speeds, precipitation totals, and storm surge heights are
leading to more accurate loss estimates.
precipitation-induced flood and storm surge perils—as
validated using AMeDAS and buoy data from the Japan
Meteorological Agency.
Results can be made more accurate still if disaggregation is
applied to exposure data submitted at the aggregate level.
AIR also validates top down, comparing modeled losses to
Innovative disaggregation techniques available in Touchstone
industry loss estimates and company data. Modeled losses
distribute prefecture-level, ku-level, or yubin-level exposure
for the AIR Typhoon Model for Japan have been validated
data down to a high resolution grid based on distributions in
against actual loss and claims data from major typhoons
AIR’s detailed industry exposure database for Japan.
since 1991, from companies representing roughly 30% of
Japan premium. AIR’s comprehensive approach to validation
confirms that overall losses are reasonable and that the
final model output is consistent with both basic physical
tested against historical and real-time information.
Regional Vulnerability Factors
Regional Vulnerability Factors
Non-Engineered Buildings
Engineered Buildings
LOWER VULNERABILITY
Gross Losses
expectations of the underlying hazard and unbiased when
LOWER VULNERABILITY
HIGHER VULNERABILITY
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HIGHER VULNERABILITY
Modeled
SEPARATING WIND, PRECIPITATION-INDUCED FLOOD,
AND STORM SURGE LOSSES FOR MORE ACCURATE
MODEL RESULTS
Gross Losses
Regional vulnerabilities for wind of engineered buildings.
Insurance coverage for wind damage is automatically
included in standard fire insurance policies. Flood and
surge coverage are treated as “water” coverage and must
be purchased separately from wind. Policy conditions in
Songda ‘2004
Tokage ‘2004
Chaba ‘2004
Shanshan ‘2004
Modeled losses for select events compare well to observed losses based
on individual company data.
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MODEL AT A GLANCE
MODELED PERILS
Tropical cyclone wind, precipitation-induced flood, and storm surge
MODEL DOMAIN
Northwest Pacific Ocean and the Japanese archipelago
SUPPORTED GEOGRAPHIC
RESOLUTION
Latitude/Longitude, JIS/Ku/Sonpo/Yubin, and Prefecture
STOCHASTIC CATALOG
10,000-year catalog includes 293,235 simulated events
SUPPORTED CONSTRUCTION
CLASSES AND OCCUPANCIES
NUMBER OF SUPPORTED CONSTRUCTION CLASSES: Separate wind, flood, and surge damage
functions for 62 construction types
NUMBER OF SUPPORTED OCCUPANCY CLASSES: 116
UNKNOWN DAMAGE FUNCTION: When detailed exposure data (e.g., construction type or
height) is unavailable, the model applies an “unknown” damage function that takes into
account the building inventory in Japan.
The model supports a wide variety of location, policy, and reinsurance conditions, as well as
SUPPORTED POLICY
CONDITIONS
Extra Expenses and Debris Removal. The complex policies that are commonly used in Japan, such
as endowment or step policy functions, are also supported.
MODEL HIGHLIGHTS
–– Shares a basinwide catalog with other modeled territories in the Northwest Pacific to allow clients to more accurately
model losses to portfolios that cross borders
–– Incorporates central pressure/wind speed relationship specific to Northwest Pacific
–– Explicit modeling of precipitation-induced flooding and storm surge
–– Accounts for damage to building, contents, and business interruption from wind, flood, and surge
–– Accounts for regional variations in building vulnerability due to multi-hazard environment
–– Supports the modeling of specialized risks, including railway, marine cargo, marine hull, and large industrial facilities
–– Accounts for the impact of flood defense systems in mitigating flood risk
–– Touchstone enables users to easily run wind/flood/surge scenarios and can distribute aggregated exposure data down
to a high resolution grid based on distributions in AIR’s detailed industry exposure database
ABOUT AIR WORLDWIDE
AIR Worldwide (AIR) provides catastrophe risk modeling solutions that make individuals, businesses, and society
more resilient. AIR founded the catastrophe modeling industry in 1987, and today models the risk from natural
catastrophes and terrorism globally. Insurance, reinsurance, financial, corporate, and government clients rely
on AIR’s advanced science, software, and consulting services for catastrophe risk management, insurancelinked securities, site-specific engineering analyses, and agricultural risk management. AIR Worldwide, a Verisk
Analytics (Nasdaq:VRSK) business, is headquartered in Boston with additional offices in North America, Europe,
and Asia. For more information, please visit www.air-worldwide.com.
AIR is a Verisk Analytics business.
AIR Worldwide and Touchstone are registered trademarks of AIR Worldwide Corporation.
©2016 AIR WORLDWIDE
Cover Image: Typhoon Jelawat, NASA