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Vertical diffusion in ERA-40
Dirk Olivié12 November 2003
Vertical diffusion in ERA-40
Overview
• Vertical Diffusion• Louis, Holtslag, ECMW6h
– Kz –profile– Radon distribution– Comparison with measurements
• Ecmwf3h, Ecmwf6h– Radon distribution– Comparison with measurements
What it’s all about …
z
CK
zt
Cz
Kz : diffusion coefficient [m2s-1]
C : tracer concentration
Overview diffusion data
time step
Louis 6h00 instantaneous
Holtslag 3h00 instantaneous
Ecmwf-6h 6h00 accumulated
Ecmwf-3h 3h00 accumulated
Louis – Holtslag – ECMWF6h
• Kz profile
• Global Radon distribution• Comparison with Radon
measurement– daily cycle– correlation
Kz : mean profile
LouisHoltslagEcmwf-6h
August 1993Global meanOver land
Kz : daily cycleLouisHoltslagEcmwf-6h
4h30 7h30 10h30
13h30 16h30 19h30 21h30
1h30
Radon : Holtslag - Louis
Radon : Ecmwf6h - Holtslag
Radon : Ecmwf6h - Louis
Radon : SurfaceLouisHoltslagEcmwf-6h
Measurement
Radon : 1200 m
Louis Ecmwf-6h Measurement Holtslag No diffusion
Correlation : surface
Jan Mar May Jul Sep Nov
LouisHoltslagEcmwf-6h
Correlation : 1200 m
LouisHoltslagEcmwf-6h
Jan Mar May Jul Sep Nov
ECMWF3h-ECMWF6h
• Global Radon distribution• Daily cycle• Correlation