TELIS Science cases TErahertz LImb Sounder

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TELIS Science cases(TErahertz LImb Sounder)

• Arno de Lange
• Ruud Hoogeveen, Avri Selig
• 3rd International Atmospheric Limb Workshop
• Montréal, Canada
• 25-28 April 2006

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What is a Terahertz?

• f 1 Terahertz 1012 Hz ? l 300 mm
• 100-1000 THz (UV/Vis/IR) ? optics
• 0.01 THz (10 GHz) ? electronics

• Terahertz signals are hard to detect
• Cannot directly be picked up by electronics
• Optical detectors are blind for THz radiation

• Detection recipe use radio techniques
• Generate THz signal with well known
  characteristics
• Mix atmospheric signal with generated signal ?
• GHz difference frequency
• Analyse difference frequency with conventional
  electronics

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Why being interested in THz?

• Very rich spectrum with well resolved lines
• Almost no Rayleigh scattering (f 4)
• Relative insensitive to PSCs, aerosols, cirrus
  clouds etc
• Audience is this true?
• Thermal emission spectrum ? not dependent on
  light source
• What kind of transitions?
• Electronic 1014 Hz (100 THz)
• Vibrational 1013 Hz (10 THz)
• Rotational 1012 Hz (1 THz)

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500 650 GHz spectrum
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Collaboration TELIS

• 3 channels
• DLR (GER) 1.8 THz
• SRON (NL) 500 650 GHz (and THz)
• RAL (UK) 500 GHz
• Technology driven instrument
• DLR Cryogenic 1.8 THz channel (OH measurements)
• SRON Experience (HIFI) applied to EOS
• RAL Miniaturisation
• Platform
• MIPAS-B stratospheric balloon gondola

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Whats new?

• 1991 UARS MLS (Microwave Limb Sounder)
• 2001 ODIN/SMR
• 2004 EOS MLS (including 1.8 THz channel)
• TELIS in general
• Cryogenic temperatures ? 10x better S/N ratio
• DAC (Digital Auto Correlator) 2x2 GHz bandwidth
  (_at_ 2 MHz)
• Overlapping and complementary with MIPAS-B
• SRON channel
• Low noise amplifier, SIS mixer etc.
• Solid state local oscillator
• SIR (Superconducting Integrated Receiver) ?
  miniaturisation

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Superconducting Integrated Receiver (SIR chip)
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SIR channel
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SIR channel
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SIR channel
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SIR channel First light
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SIR channel OCS spectrum
p 0.23 mbar l 0.50 m LO 625.550 GHz
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Specifications (SIR channel)

• Vertical resolution 1.5 km
• Intensity accuracy 0.2 K _at_ 1 sec integration
  time
• Noise temperature 200 300 K
• Altitude range tropopause platform height (35
  km)
• Frequency range 500 650 GHz
• Single scan 2 GHz (or 2 x 2 GHz) TUNABLE!!
• Frequency resolution 2 MHz
• Species H2O, O3, O2 rare isotopes
• HCl, ClO, HOCl
• N2O, NO, NO2, HNO3, HCN
• CO, H2CO, OCS
• H2O2

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Planned flights MIPAS-B with TELIS

• Qualification flight
• April 2007 Kiruna (Sweden)
• Science flight
• Fall 2007 Terasina (Brazil)

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What to measure?

• Species by SIR channel
• HCl, ClO, HOCl
• (BrO, HBr)
• H2O, O3, O2, (H2O2, HO2)
• NO, N2O, NO2, HNO3
• CO, H2CO, HCN
• OCS, (SO2)
• isotopes H2O, O3, O2
• Science cases pertain to
• Ensemble measurements
• Isotope measurements

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Science cases

• Ozone chemistry
• Stratospheric water
• UTLS transport
• NAT and HNO3

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I. Ozone chemistry
HCl ClONO2 ? HNO3 Cl2 ClONO2 H2O ? HNO3
HOCl
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II. Stratospheric water

• Central questions
• What is the origin of stratospheric water?
• Does the amount of stratospheric water increase?
• If so, why?
• Importance to ozone chemistry
• More stratospheric water more PSCs more
  active Cl
• O(1D) H2O ? 2 OH more O3 depletion by HOx
  cycle

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How to get insight?

• By water isotopes
• All physical and chemical processes have
  different signatures for different isotopes
• Measuring enrichment/depletion gives insight in
  the different processes
• By water and a passive tracer (CO, N2O)
• UTLS transport

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Information by water isotopes

• HDO
• Largest enrichment/depletion (up to -900)
• Good tracer for UTLS water transport
• H217O en H218O
• Measuring both gives insight in chemistry
• Questions
• Is the amount of stratospheric water dependent on
  the temperature of the tropopause?
• Is there an isotope effect with altitude?
• Is there more enrichment in the tropics?

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H2O isotope spectrum
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H2O isotope spectrum (THz channel)
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III. H2O, CO/O3, and/or N2O/O3

• H2O
• Water flux UT ? LS
• CO, N2O
• Total flux UT ? LS
• CO/O3 and/or N2O/O3
• Age of air
• Questions
• When and where comes air (including water) from
  UT in LS?
• How does the water concentration change
• as a function of (tropopause) temperature?
• as function of total air flux?

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IV. PSCs

• Type 1 PSC NAT particles (HNO3.3H2O)
• PSC composition, formation mechanism, and ozone
  depletion processes not entirely understood

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HNO3 and NAT

• Formation/composition
• HNO3(g) and NAT simultaneous measurements
• NO/NO2 ratio ? insight in nitrogen cycle and PSCs
• OH/HO2 ratio ? insight in hydrogen cycle and PSCs
• HNO3, NO/NO2, and OH/HO2
• denitrification of lower stratosphere
• dehydration of lower stratosphere
• Is there also NAT above the tropics?
• Coldest place tropical tropopause

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Conclusion

• TELIS is a sub-mm instrument with excellent
  specifications
• 3 channels
• MIPAS-B balloon
• Qualification flight April 2007
• Promising science cases
• Ozone chemistry
• Stratospheric water
• UTLS transport
• NAT and HNO3

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Ozone isotope anomaly

• Mass dependent fractionation
• Enrichment/depletion of 17O en 18O in fixed ratio
• World wide
• In all kind of materials (water, minerals, ice)
• Main exception
• Atmospheric ozone
• Origin is not entirely clear, but
• O O2 ? O3
• Reaction rate for rare isotopes (w.r.t. 16O3)
  0.90 1.53

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Ozone anomaly as chemistry tracer

• If something reacts with ozone
• the anomaly will (may) be transferred.
• Oxygen isotope measurements are a tracer for
  ozone chemistry.
• H2O and O3 isotopes ? HOx chemistry