arctas bro measurements from the omi and gome-2 satellite instruments

ARCTAS BrO Measurements from the OMI and GOME-2 Satellite

Instruments

ARC-IONS Data Workshop 7-8 January 2009

University of Toronto

Kelly Chance, Thomas Kurosu, Trevor Beck, Andreas Richter,

Michel van Roozendael, William Simpson, Ross Salawitch, Tim

Canty, Yuhang Wang

• Enhanced tropospheric BrO has long been observed over the Arctic and Antarctic ice pack in the polar spring.

Introduction

BrO has been measured robustly and globally from space since the first GOME measurements in 1998

(Chance, GRL 1998), +, +

OMI BrOOMI BrO Tropospheric Tropospheric Shelf IceShelf Ice

11 March 2005

• BrO is a strong source of O3 destruction in the stratosphere and troposphere.

• BrO is measured globally now by SCIAMACHY, GOME-2, and OMI

OMI BrOOMI BrO Tropospheric Tropospheric Salt LakesSalt Lakes 11stst Observation from Satellite Observation from Satellite

OMI BrOOMI BrO VolcanoesVolcanoes … … 11stst Observation from Satellite Observation from Satellite

Ambrym: First satellite-based BrO observation in volcanic plumes!

GOME/SCIAMACHY/OMI/GOME-2GOME/SCIAMACHY/OMI/GOME-2

Instrument DetectorSpectral Coverage

[nm]

Spectral Resolution

[nm]

Ground Pixel Size [km2]

Global Coverage

GOME(1995)

Lineararray

240-790 0.2-0.440320

(4080 zoom)3 days

SCIAMACHY(2002)

Lineararray

240-2380 0.2-1.5

3030 3060 3090 30120

30240 (depending on

product)

6 days

OMI(2004)

2-DCCD

270-500 0.42-0.63

1530 – 42162

(depending on swath

position)

daily

GOME-2(2006)

Lineararray

240-790 0.24-0.53

4040 (4080 wide-swath, 4010

zoom)

1.5 to 3 days

BestFitting

• Requires precise (dynamic) wavelength and slit function calibration, Ring effect correction, undersampling correction, and proper choices of reference spectra (HITRAN!)

• Best trace gas column fitting results come from direct fitting of satellite radiances

Fitting satellite BrO

GOME BrO fitting for the FIRS-2 overflight on April 30, 1997. The integration time is 1.5s. The fitting precision is 4.2% and the RMS is 2.710-4 in optical depth. Fitting and inversion give a vertical BrO column of 9.31013 cm-2.

• Differences among satellites and algorithms are a 30% or less issue (NB GOME-1).

• Over high albedos, tropospheric and stratospheric AMFs differ by about a factor of two.

Salawitch et al., AGU Fall 2008:ARCTAS & ARCPAC Inorganic Bromine Measurements

April 2008 deployment from Fairbanks, Alaska

Scientific Focus: quantification of the relationship between OMI BrO and the nearly complete removal of ozone in Arctic boundary layer “Ozone Depletion Events”

OMI BrO: New “off line” retrieval that fits 320.5 356.5 nm region for BrO, O3, HCHO, SO2, OClO

Publicly available retrieval: fits 340.5 358.5 nm region for BrO, O3, HCHO, SO2, OClO, and O2-O2

New retrieval: low residuals, much higher signal to noise, but slight correlation with surface albedo

OMI retrievals by Thomas Kurosu GOME-2 retrievals by Trevor Beck

SAO NRT algorithm

SAO new and improved algorithm

NOAA/SAO collaboration

The End!

• Nadir-viewing UV/vis/NIR

• 240-400 nm @ 0.2 nm

• 400-790 nm @ 0.4 nm

• Launched April 1995

• Footprint 320 x 40 km2

• 10:30 am cross-equator time,

descending node

• Global coverage in 3 days

ESA Global Ozone Monitoring Experiment

SCIAMACHY• German/Dutch/Belgian Atmospheric Spectrometer

• 2002 launch on ESA Envisat• Adds (to GOME) continuous coverage to 1700 nm, plus IR bands at 2.0 m (CO2) and 2.4 m (CO, N2O)

• Higher spatial resolution footprint than GOME (as good as 30 60 km2)

• Adds limb scattering and limited solar occultation measurements

- Nadir-limb subtraction improves tropospheric measurements

• Data and validation are still in a preliminary stage

2%

High resolution solar reference spectrum

GOME BrO fitting: Relative contributions absorption by atmospheric BrO (top) and the Ring effect - the inelastic, mostly rotational Raman, part of the Rayleigh scattering – (bottom).

Ambrym Eruption: 4th February 2005, OMI Granule 02968

SO2 courtesy of Simon Carn, UMBC BrO

BrO BrO Tropospheric Tropospheric Volcanoes … Volcanoes … 11stst Observation from Satellite Observation from Satellite

BrO: The FutureBrO: The Future•Polar spring BrO/tropospheric Polar spring BrO/tropospheric O O33

– Higher spatial resolutionHigher spatial resolution

– Better correlation; chemistry Better correlation; chemistry (high latitude Hg deposition)(high latitude Hg deposition)

•Volcanoes!Volcanoes!

•Salt lakes!Salt lakes!

Flight 4: 080404 (Fairbanks to Thule)

Thule

Thule

× OMI Overpass

× OMI OverpassOMI Column (1013 mol/cm2)

↑ DC8 O3

DC8 Alt →

DC8 Br2

T. Kurosu, K. Chance, T. Beck, G. Huey, A. Weinheimer