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TELIS – Science cases (TErahertz LImb Sounder) : 

TELIS – Science cases (TErahertz LImb Sounder) Arno de Lange Ruud Hoogeveen, Avri Selig 3rd International Atmospheric Limb Workshop Montréal, Canada 25-28 April 2006

What is a Terahertz?: 

What is a Terahertz? 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 Terahertz signals are hard to detect: Cannot directly be picked up by electronics Optical detectors are blind for THz radiation f = 1 Terahertz = 1012 Hz  l = 300 mm 100-1000 THz (=UV/Vis/IR)  optics 0.01 THz (=10 GHz)  electronics

Why being interested in THz?: 

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)

500 – 650 GHz spectrum: 

500 – 650 GHz spectrum

Collaboration TELIS: 

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

What’s new?: 

What’s 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 (@ 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

Superconducting Integrated Receiver (SIR chip): 

Superconducting Integrated Receiver (SIR chip)

SIR channel: 

SIR channel

SIR channel: 

SIR channel

SIR channel: 

SIR channel

SIR channel – First light: 

SIR channel – First light

SIR channel – OCS spectrum: 

SIR channel – OCS spectrum p = 0.23 mbar l = 0.50 m LO = 625.550 GHz

Specifications (SIR channel): 

Specifications (SIR channel) Vertical resolution 1.5 km Intensity accuracy 0.2 K @ 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

Planned flights MIPAS-B with TELIS: 

Planned flights MIPAS-B with TELIS Qualification flight April 2007 Kiruna (Sweden) Science flight Fall 2007 Terasina (Brazil)

What to measure?: 

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

Science cases: 

Science cases Ozone chemistry Stratospheric water UTLS transport NAT and HNO3

I. Ozone chemistry: 

I. Ozone chemistry HCl + ClONO2  HNO3 + Cl2 ClONO2 + H2O  HNO3 + HOCl

II. Stratospheric water: 

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

How to get insight?: 

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

Information by water isotopes: 

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?

H2O isotope spectrum: 

H2O isotope spectrum

H2O isotope spectrum (THz channel): 

H2O isotope spectrum (THz channel)

III. H2O, CO/O3, and/or N2O/O3: 

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?

IV. PSCs: 

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

HNO3 and NAT: 

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

Conclusion: 

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

Ozone isotope anomaly: 

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

Ozone anomaly as chemistry tracer: 

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

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