MAG: F.M. Breon, H. Dolman, G. Ehret, P. Flamant,N. Gruber, S. Houweling, M. Scholze, R.T. Menziesand P. Ingmann (ESA)

A-Scope Measuring CO2 Using a space-based Lidar

A-SCOPE: F. M. Breon, H. Dolman, G. Ehret, P. Flamant, N. Gruber, S. Houweling, M. Scholze, R.T. Menzies and P. Ingmann (MAG)

ASCENDS: P. Rayner

Outline• Introduction: Active remote sensing

• A-SCOPE

• ASCENDS

• Instrument Requirements

• Prospects for launch

Measurement methods:1. Passive: Thermal IR

• e.g. AIRS, IASI

• Information on vertical profile

• But, low sensitivity to the surface

• Application: T retrieval (ECMWF)

AIRS CO2, July - August 2003

Tiwari et al, JGR, 2006

Measurement methods:2. Passive: Short Wave IR

• e.g. Sciamachy, OCO, GOSAT

• Sensitive to the PBL

• Aim: Estimation of CO2

sources & sinks

• Critical: Aerosols, thin clouds

SCIAMACHY CO2, July - October

ppm Buchwitz et al, ACP, 2007

Measurement methods:3. Active: Diff. Absorption Lidar

• Carries own light source (laser)

• Day + night time measurements

• Always nadir (glint, high lats)

• Detects aerosols, thin clouds

DIAL

Wavelength selection

H2O

CO2

onoff

• Low T sensitivity

• Low contribution

H2O

• Line wing = High surface

sensitivity

Aerosol correction 1; Passive

• Problem: Optical path

• Solution: measure CO2 & O2, wide wavelength range

• Determine CO2/O2 + aerosol parameters

Sciamachy CO2

Houweling et al., ACP, 2005

Aerosol correction 2; Active

• Solution: pulsed laser

• Select surface echo from pulse delay time

• Potentially: use aerosol echo for CO2 vertical profile

A-SCOPE

• Pulsed Laser CO2 (1.6 or 2.0 micron)

• Altimeter: Vegetation vertical distribution

• Aerosols & clouds

Among the 6 ESA Earth explorer missions (Phase 0) Launch (if succesful): ~2015

Proposed instrument:

Note: ECMWF(H2O, T, p) needed for conversion to XCO2

Canopy Lidar

Harding & Carabajal (GRL, 2005)

Can

op

y heig

ht d

istribu

tion

ASCENDS

• CO2 (1.6 micron), O2 (0.76 micron)

• CW laser (not pulsed)

Proposed instrument:

Status: No call yet but: US Decadal Survey: 2013 - 2016

A-SCOPE: Accuracy requirements

• Target requirement on surface flux estimation (level 3):

0.02 PgC/yr over 106 km2

(or ~ 50% of the annual flux)

Translation to XCO2 (level 2)• Inverse modelling simulations

Required precision:

0.5 - 1.5 ppm

Systematic error:10% of precision

Performanceestimation

OCO:

DIAL (no pressure broadening):

Chevallier et al., 2007

Rayner, pers. comm.

Performanceestimation

DIAL, no pressurebroadening:

DIAL, + pressurebroadening:

Rayner, pers. comm.

Summary

• DIAL: Promising technique for measuring CO2

• Technological challenge

• Will A-Scope fly? => ESA User Consultation Mtg

Granada, Oct. 2008