Jennifer Catto

Supervisors: Len Shaffrey and Kevin Hodges

Extra-tropical cyclones in HiGEM

Outline

Compositing and lifecycles Methodology Results

Vertical Structures Conclusions so far

HiGAM SST experiment Motivation Scientific questions Method

Composite Analysis - Methodology

Step 1: Identify tracks using Kevin’s tracking program

Composite Analysis - Methodology

Step 2: Choose at what stage in the lifecycle to composite the tracks e.g.

Maximum tendency

Maximum intensity

Maximum precipitation

Minimum pressure and identify where

this occurs

Composite Analysis - Methodology

Step 3: Extract the 20o radius around this point and note the direction of propagation of the storms.

Composite Analysis - Methodology

Step 4: Rotate these areas to the same direction of propagation and average them.

+ + =

Composites Analysis – Positions of tracks

HiGEM1.2

HadGEM1.2

Composites Analysis – Wind, pressure and temperature for Atlantic

HadGEM1.2HiGEM1.2

Colours – wind speed

(m/s)

Composites Analysis – Wind, pressure and temperature for Atlantic

HiGEM1.2

Colours – wind speed

(m/s)

ERA-40

Composites Analysis – Vertical Velocity for Atlantic

HadGEM1.2HiGEM1.2

Composites Analysis – Vertical Velocity for Atlantic

HiGEM1.2 ERA-40

Composites Analysis – Differences between Atlantic and Pacific

PacificAtlantic

Lifecycles - Methodology

t=0

Lifecycles – Results

Atlantic

Solid lines – HiGEM

Dashed lines – HadGEM

Dot-dash lines – ERA-40

Lifecycles – Results

Pacific

Solid lines – HiGEM

Dashed lines – HadGEM

Dot-Dash lines – ERA-40

Vertical Structures - Atlantic

HiGEM1.2

Vertical Structures

HadGEM1.2

Conclusions so far

Storm structures in HiGEM1.2 compare better with ERA-40 than those in HadGEM1.2

The resolution has a large effect on the maximum intensity that storms attain.

Differences between Atlantic and Pacific picked up well by both models.

Future Work – HiGAM SST experiment – Motivation 1

HiGEM1.2 HiGAM1.2

Track Density

Future Work – HiGAM SST experiment – Motivation 2

HiGAM - HiGEMHiGEM1.2 – ERA-40

Track Density Difference

Future Work – HiGAM SST experiment – Motivation 3

HiGAM SST experiment

Questions: Is it the tighter SST gradient in the Kuroshio current

that causes the excess cyclones in the Pacific basin in HiGEM?

What effect do the higher resolution SSTs have on the storms in HiGAM?

Is there any effect on the storm structures?

Method: Include a constant DJF SST anomaly in the midlatitude

Pacific Ensemble of 20 simulations beginning in October

HiGAM SST experiment - Method

HiGEM1.2 HiGAM1.2

Track density plots showing densities associated with

genesis in different regions.

Will allow us to identify which (if any) storms are affected by changes in

SSTs applied to the model.