Extra-tropical Cyclones in

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Extra-tropical Cyclones in




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Presentations text content in Extra-tropical Cyclones in

Slide1

Extra-tropical Cyclones in Recent Re-Analyses

Kevin HodgesLennart Bengtsson and Robert Lee

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Slide2

Motivation

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Extra-tropical cyclones:-

Important components of the general circulation.

How should they be verified for distribution and properties?

Observations are highly inhomogeneous.

No long term observational record.

Re-analyses:-

Best available, 4D, homogeneous data sets constrained by observations.

What are the uncertainties?

Slide3

New Re-Analyses

ERA-Interim (ECMWF)T255L60 (~80km) spectral, 4D Var., 1989-2009.Modern Era Retrospective Re-Analysis (MERRA)0.50x0.670L72(~74km) finite volume, Grid-point Statistical Interpolation (GSI, 3D Var.), 1979-2009. Japanese 25 Year Re-Analysis (JRA25)T106L40 (~125km) spectral, 3D Var., 1979-2009. NCEP Coupled Re-analysisT382L64 (~38km), GSI, 1979-2009.20th Century Re-AnalysisSurface only observations, 1891-2008, ensemble kalmen filter, T63.

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Slide4

Comparison Methodology

Identify and track cyclones – synoptic.MSLP – T63.ξ850 – T42.Compare using:-INTERIM as base (1989-2006).Spatial statistics.Intensity pdf’s.Cyclone matching.Composites.

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Slide5

Spatial Statistics

NH, DJF

SH, JJA

Track Density

Genesis Density

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Slide6

Older Re-analyses

Track Density Differences (1979-2002)

NH

SH

NCEP-ERA40

JRA25-ERA40

Slide7

General Results

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Number per month

Slide8

INTERIM-JRA25

NH, DJF

SH, JJA

Track Density

Genesis Density

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Slide9

INTERIM-MERRA

NH, DJF

SH, JJA

Track Density

Genesis Density

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Slide10

INTERIM-NCEP

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NH, DJF

SH, JJA

Track Density

Genesis Density

Slide11

Intensity-MSLP

NH, DJF

SH, JJA

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Slide12

Intensity Winds, Vorticity

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NH

SH

925hPa Winds

850hPa

Vorticity

Slide13

Cyclone Matching

Vorticity,T42 IntensitiesMean seperation ≤ 40Time overlap > 60% points

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Slide14

Separation, Vorticity

NH DJF

SH JJA

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JRA25-ERA40, 1979-2002.

Slide15

Intensity

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Slide16

Observations-Quickscat

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Max. Intensities

Instantaneous Differences

Slide17

Lifecycles

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Slide18

ATHENA-Intensities

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T159 Intensities

Slide19

ATHENA-Distributions

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Slide20

Future Work

Apply same methods directly to satellite data to verify cyclone structure in NWP (directly) and climate models (statistically).Apply to other weather system types, e.g. TC including examining the transition of EW to TC; the extra-tropical transition of TC and polar lows.Extend to energetics.

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