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

ECMWF3h-ECMWF6h

Radon - Daily cycle - surface

LouisHoltslagEcmwf-6hEcmwf-3hMeasurement

Radon - Daily cycle – 1200 m

LouisHoltslagEcmwf-6hEcmwf-3hNo diffusionMeasurement

Correlation surface

Jun Jul Aug

LouisHoltslagEcmwf-6hEcmwf-3hNo diffusion

Correlation : 1200 m

LouisHoltslagEcmwf-6hEcmwf-3hNo diffusion

Jun Jul Aug

Radon profile

LouisHoltslagEcmwf-6hEcmwf-3hNo diffusion