FTIR campaigns at Ile de la Réunion Corinne Vigouroux, Martine De Mazière, A.C. Vandaele, E. Neefs, F. Scolas, T. Egerickx, C. Hermans, K. Janssens Belgian Institute of Space Aeronomy, Brussels, Belgium B. Barret, P.F. Coheur, S. Fally, M. Carleer, R. Colin Université Libre de Bruxelles, Brussels, Belgium and J. Leveau Université de La Réunion, S t Denis, Ile de La Réunion / France

Measurement site locations Site 1: Université de La Réunion Altitude: 50 m 20°54’ S – 55°29’ E Site 2: Piton du Maïdo Altitude: 2203 m 21°04’ S – 55°23’ E

Solar tracker Site 1: Université de La Réunion Site 2: Piton Maïdo

Solar Tracker Meteo Station FTS inside cabin: Bruker IFS 120 M Site 2: setup at Piton Maïdo

Scientific : –Initiate long-term monitoring of the atmospheric composition at a (sub)tropical site by FTIR remote- sensing, in the frame of NDSC. –Validation of satellite experiments, in particular ACE/SciSAT1. Technological : –test BARCOS (Bruker Automation and Remote COntrol System, Neefs et al., 2003 ) at Maïdo. Campaigns Objectives

Purpose : Measurements in an automatic mode – including remote control options :  Run several days without human assistance, at any time and any geographical location. Working principle : Each day: finds, loads and executes a script for that day. Script : list of commands wearing a tag (time or zenith angle) to indicate when the command has to be executed. BARCOS

BARCOS includes : An elementary scripting language Solar tracker Meteorological station to condition the observations (rain detector, sensors for wind, ambient pressure and direct solar irradiance) A data logger and a GPS receiver Software (in Labview) for housekeeping, suntracker commanding and interaction with the FTS software (OPUS) Parallel manual and remote/automatic control are possible

BARCOS solar tracker : Can be : - Bruker solar tracker (BST) - Denver solar tracker(DST) (collaboration with T. Stephen and T. Hawat of Denver Univ.) Operating options for DST : - tracking mode : on CCD image of target = sun, moon, star,... - calculated mode - automatic mode DST : Image allows cloud detection

Under development Automatic Liquid N 2 filling Wireless access to internet for remote control and data exchange Exploitation of meteo data to condition the choice of used spectra: Time h,min,sec Time measurement of a spectrum: a few minutes

SCIENTIFIC DATA

Maïdo (2203 m) University (50 m) MOPD = / /250 82/125/250 Strong absorption of Water Vapor near the sea level Spectral regions (NDSC filters) Near- and mid-IR, covering cm -1. Best spectral resolution = cm -1 (MOPD=250 cm)

Large number of stratospheric and tropospheric gases : – HCl, HF, HNO3,… – O3, CH4, N2O, CFC-11, HCFC-22, CO, HCN, OCS, C2H6,... Spectra are retrieved by SFIT2 program :  Vertical total column abundances.  Low vertical resolution profiles: - Based on dependence of absorption line shape on pressure - Using Optimal Estimation Method (Rodgers). Retrievals

Sensitivity and Vertical Resolution : Are given by Averaging Kernels = rows of A matrix  Trace of A: Degrees Of Freedom (if =1 : only total column) Ex: CO ~ 2  Amplitude of A: sensitivity ~ 5 km, 9 km, CO: ~ 5 km, 9 km, no sensitivity above 20 km. no sensitivity above 20 km.  Width of A: vertical resolution

 Molecule :O3 : DOF ~ 5 HNO3 : DOF ~ 1 (only total column!)  Solar zenithal angle : ex : DOF of N2O at Maïdo  SNR, … + other retrievals parameters to be optimized Sensitivity and Vertical resolution depend on:

Profile retrievals are being optimized (O3, N2O, CO, HNO3,…) - But… one month : not enough for geophysical conclusions! Ground-Based validation of satellite: - Only FTIR provide correlative data for N2O, HNO3, CH4 profiles. - Intercomparisons with MIPAS and Odin data are being performed. Scientific Results of our first campain Sept Oct. 29, 2002

Example of Odin Validation : O3 FTIR Odin A priori Odin Smoothed With FTIR Aver. Kern. A priori far from real profile – still both retrievels agree well Total column (FTIR-Odin)/Odin = 5.6%

MIPAS FTIR Example of MIPAS Validation : HNO3 A priori far from real profile – still both retrievels agree well

Future in La Réunion island 2 nd campaign planned for Aug-Nov. 2004, at St Denis, for validation of ACE (overpasses in August and October) 3 rd campaign planned in the frame of a major tropical campaign in the frame of the EC project SCOUT-O3, in Long-time monitoring needed for geophysical work :  waits for NDSC infrastructure at Reunion Island By when ?

Our Role in STAR Support FTIR pilot study in Paramaribo : Technical : - Supporting installation and operation of UBremen FTS - Implementation of BARCOS ? Scientific : - Contribution to data retrieval and interpretation

THE END

A priori profile Retrieved profile Example: Retrieval of O3 at Maido

Example: Retrieval of CO at St-Denis A priori profile Retrieved profile

Example of Odin Validation : O3 Odin FTIR A priori Odin Smoothed With FTIR Aver. Kern. A priori far from real profile – still both retrievels agree well Total column (FTIR-Odin)/Odin = 3.3 %

Example of Odin Validation : O3 A priori far from real profile – still both retrievels agree well Total column (FTIR-Odin)/Odin = 9.9 %

FTIR retrievals have 2.5 – 3 independent information elements, situated around 5, 13 and 20 km altitude; ~ no sensitivity above 25 km Both retrievals confirm maximum of N 2 O VMR profile around 22 km altitude in UT/LS where both are sensitive. MIPAS FTIR Example of MIPAS Validation : N2O