Hurricanes

Smoking Guns of Climate Change or random occurrences?

Hurricane Attributes

• A Central Pressure• A hurricane wind radius (quite variable)

• A duration• A location• An evolutionary timescale (spin up times)

• A total power at landfall• Need to link all of these together

Emily Chi Thesis

Atlantic Hurricane Formation

Low pressure centers form over Sahara desert and may get amplified as they cross open ocean

Amplification depends critically on SST and available moisture in the atmosphere

Must also have favorable wind conditions (light winds aloft) and weak wind shear

Hurricane Frequency Increasing? This is difficult to establish with a high degree

of statistical confidence; Incompleteness is an important issue

Counting is always noisy

RADAR in the 1950s

Atlantic Multi-decadal Oscillation (AMO)

Frequency Mimics AMO

One Good SimulationOne Good Simulation

Using real fluid dynamics Using real fluid dynamics predicted effect is relatively predicted effect is relatively small in the average but the tails are important!small in the average but the tails are important!

DifficultiesDifficulties

Tropical cyclone wind-speed monitoring has Tropical cyclone wind-speed monitoring has changed dramatically over the last few changed dramatically over the last few decades leading to difficulties in determining decades leading to difficulties in determining accurate trends. accurate trends.

There is an observed multi-decadal There is an observed multi-decadal variability of tropical cyclones in some variability of tropical cyclones in some regions whose causes, whether natural, regions whose causes, whether natural, anthropogenic or a combination, are anthropogenic or a combination, are currently being debated. This variability currently being debated. This variability makes detecting any long-term trends in makes detecting any long-term trends in tropical cyclone activity difficult. . tropical cyclone activity difficult. .

Total Power AttributesTotal Power Attributes

Central pressure; central wind speedCentral pressure; central wind speed Total hurricane wind radiusTotal hurricane wind radius Total moisture contentTotal moisture content We do not have good measurements We do not have good measurements

on the latter two except for the last on the latter two except for the last 15 years or so15 years or so

But, this may be a diagnosticBut, this may be a diagnostic

Track Density Analysis