OMI follow-on Project Toekomstige missies gericht op troposfeer en klimaat Pieternel Levelt, KNMI.

OMI follow-on Project Toekomstige missies gericht op

troposfeer en klimaat

Pieternel Levelt, KNMI

Toekomstige Troposfeer Missie, SRON, 18 november 2003

Dr. P.F. Levelt (KNMI) Slide 2

Climate Air quality

Anthropogenic influence

Importance of Tropospheric Measurements

Tropospheric chemical science has very strong links to:



Troposphere

Tropospheric measurements needs:

• higher spatial resolution • improved accuracy for O3, NO2, aerosols,

clouds, HCHO• together with CO, CH4, CO2 and H2O• improve aerosol information• improve time-resolution• preference for daily global coverage

(air quality)

GOME Observations of Formaldehyde over North America

Chance et al., Geo. Res. Let. 27, 3461-3464, 2000.

• Next challenge for satellite instrument development is to map the troposphere for air quality monitoring and climate research:



Tropospheric Important Trace Species

(tropospheric) Ozone Aerosols (tropospheric) NO2

SO2

Formaldehyde BrO

UV/VIS

CO CH4

CO2

H2O

NIR



Why these trace species?

• CO indicates combustion; has a chemical role (CO2, CH4)• HCHO indicates VOCs; has role in O3 & aerosols• NO2 indicates NOx; is precursor to O3 & aerosols• SO2 traces combustion, is major aerosol precursor • CO2 is an important greenhouse gas• H2O is an important greenhouse gas

• Ozone is a toxic greenhouse gas.

• Small aerosols are toxic, have direct & indirect global warming effects.

II

II



Climate Forcing

Source: IPCC



Few measurements from space to date: except: MOPITT CO, TOMS residual O3, GOME NO2, BrO, HCHO, MODIS for

aerosols and clouds TES and OMI (Aura) and SCIAMACHY (ENVISAT) will provide many

new measurements Selected OCO NASA mission (2007): Measures CO2 with 1 km2 pixels and

10 km swath. However: Tropospheric chemical science needs more and more accurate

measurements

Currently available or selected tropospheric-climate missions



OMI on EOS Aura Spectrometer in wavelength range 270 – 500 nm

Daily Global Coverage

Small Ground Pixels (13x24 km2)

Polarization Scrambler



OMI Measurement Principle

Courtesy of Dutch Space



New Developments for Polar missions

Smaller Ground Pixels (will also improve accuracy) Extending the Wavelength Range (add IR-channel) Multi-Angle Viewing (for improved aerosol detection)

Assumption: Start from current Leo-OMI optical design:

This means that a smaller spatial resolution of 10 x 10 km2 is not feasible, since this is the optical resolution of the instrument in polar orbit!



Chosen for a module approach:

OMI/SCIAMACHY + instrument is by itself a very complete tropospheric instrument

Depending on missions, channels can be adjusted or skipped



Requirements UV/VIS Ground pixels: decreased to 12 x 13 km2 (except for UV-1,

40 x 40 km2) Spatial sampling: 3 x 270 - 500 nm, preferred extension to 600 nm (O3 and O2-O2) Spectral resolution: minimal OMI, preferred GOME Spectral sampling: 3 x Daily global coverage S/N ratios same as in OMI SRD, except for O3 and NO2

column



Requirements NIR Ground pixels: 12 x 13 km2

Spatial sampling: 3 x 1,6 (CH4 and CO2) and 2,4 mm (CO)

O2A band detection for airmass factor (760 nm)

Spectral resolution: 0.08 nm (CO2), 0.15 nm (CO & CH4) and 0.08 nm for O2A band

Spectral sampling: 3 x Daily global coverage for CO, for CH4 and CO2 not necessary (1000

km swath) S/N ratios: see input SRON



Technical Challenges Identified Size of instrument:

- NIR increases size of instrument - High spectral resolution in combination with high spatial

resolution and broad swath S/N: smaller pixels and same or increased S/N is needed ! CCD’s: CCD with preferred requirements at this moment non-existent; techniques to

built it are however available Scrambler for polarisation insensitivity optimal for UV/VIS and IR Grating: New developed grating needed in order to decrease size of instrument Temperature control of instrument, especially 2,4 mm And more can follow …..Caveat: in case higher spatial resolution is needed for tropospheric trace gases to

obtain needed accuracy.



6 options UV/VIS and IR now studied by industry

(1) Climate mission: Complete UV/VIS and CO, CO2, CH4 and O2A

(2) Air Quality mission: Complete UV/VIS and CO

(3) Climate mission with 1000 km swath for NIR and O2A

(4) Climate mission as (1), without CO

(5) Same as (3) but with 2 telescopes

(6) Same as (1) but with 1000 km swath



Mean aerosol optical depth in August 1997 (monthly average). Retrieved from ATSR-2 image (see Gonzalez et al., Geophys. Res. Lett., 27, 955-958, 2000 )

Monitoring Aerosol



Aerosol retrieval Use dual viewing concept for info on surface albedo for

aerosol retrieval and AMF information for trace gas retrieval

- Current OMI for nadir - Add one viewing angle looking forward - Need for an extra CCD for forward looking

channel, and second telescope Technical Challenge: calibration of those two channels

with high accuracy! Not clear if this is feasible.



Summary OMI Technology is very suitable for remote sensing of the troposphere

- Spatial resolution can be improved to 10 x 10 km2

- Wavelength range can be extended to NIR High-level instrument requirements for UV/VIS and NIR are decided Currently 6 possible instrument designs are studied on feasibility: many

technical challenges are identified Multi angle viewing seems to be more difficult than expected due to

calibration difficulty Caveat: in case higher spatial resolution is needed: new instrument

design probably needed

OMI follow-on Project Toekomstige missies gericht op troposfeer en klimaat Pieternel Levelt, KNMI.

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Transcript of OMI follow-on Project Toekomstige missies gericht op troposfeer en klimaat Pieternel Levelt, KNMI.