mipas discovers antarctic nitric acid trihydrate (nat) polar...
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AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Michael Höpfner, Michael Höpfner, NielsNiels Larsen, Reinhold Larsen, Reinhold SpangSpang, , BeiBei Ping Ping LuoLuo, Jun Ma, , Jun Ma, SynneSynne H. H. SvendsenSvendsen, Stephen D. , Stephen D. EckermannEckermann, ,
Paola Paola MassoliMassoli, Francesco Cairo, Marcel , Francesco Cairo, Marcel SnelsSnels, Guido , Guido didiDonfrancescoDonfrancesco, , BjoernBjoern Knudsen, Knudsen, UtaUta BiermannBiermann, Gabriele , Gabriele
Stiller, Thomas von Stiller, Thomas von ClarmannClarmann, Herbert Fischer, Herbert Fischer
MIPAS discovers Antarctic MIPAS discovers Antarctic nitric acid nitric acid trihydratetrihydrate (NAT) (NAT)
polar stratospheric cloud beltpolar stratospheric cloud belt
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
•• What is the composition of solid What is the composition of solid nitric acid containing (Type 1a) nitric acid containing (Type 1a) PSCs?PSCs?
•• How do these particles nucleate?How do these particles nucleate?
QuestionsQuestions
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Analysis of space-borne mid-infrared limb-emission measurements during the initial PSC formation in the Antarctic stratosphere in May/June 2003.
Approach
Space borne → global view of PSC distributionMid-infrared → possibility to identify PSC composition
through spectroscopic signaturesLimb → good sensitivity to thin clouds through long optical pathEmission → visibility of PSCs also during polar night Antarctic stratosphere → ideal natural laboratory for PSC studies
MIPAS on Envisat
14.6 µm 4.15 µm
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
MIPAS PSC observations over MIPAS PSC observations over McMurdoMcMurdo on 4 Aug 2003 on 4 Aug 2003
800 850 900 9500
200
400
600
800
1000
Tangent altitude 13.1 km 16.1 km 19.2 km
Rad
ianc
e [n
W/(c
m2 sr
cm
-1)]
Wavenumber [cm-1]
CFC-11
HNO3
CFC-12
SF6
CO2
???
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Spang and Remedios, 2003:
Spectral feature around 820 cm-1 attributed to NAT indirectly by HNO3-temperature relationship and occurrence temperature of the band
CRISTA PSC observations in August 1997
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Refractive indices
ν3(NO3-)
ν2(NO3-) ν1(NO3
-) ν2(H3O+)
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Bierm.98 smoothed
780 800 820 840 860 880 9000
200
400
600
800
1000Tangent altitude
13.1 km 16.1 km 19.2 km
Wavenumber [cm-1]
ν2(NO3-)
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Spectral fit to the measurement
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
MIPAS measurement
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
MIPAS measurement
ν3(NO3-)
ν3(NO3-)
ν3(NO3-)
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Observed positions of the ν2(NO3-)-band of NAD and NAT
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Search for NAT in MIPAS observationsSearch for NAT in MIPAS observations
SimulationSimulationββ--NATNATSTSSTSIceIceββ--NAT: R < 3 µmNAT: R < 3 µmββ--NAT: R > 3 µmNAT: R > 3 µm
Observation Observation
0.2 - 1 µm
2 µm
3 - 4 µm5 - 6 µm
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Comparison: MIPAS PSC composition Comparison: MIPAS PSC composition ↔↔ LidarLidar PSC typesPSC types
MIPAS closestmatch
MIPAS closestmatch but one
Temperature
McMurdo LidarRed: Type 1aGreen: Type 1bBlue: Type 2
Red: NATGreen: STSBlue: IceBlue-green: ?
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Development of PSC Types over AntarcticaDevelopment of PSC Types over Antarctica
First First NATNATafterafter~20 ~20
days!days!
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
First ice observations
NAT only downwind the Antarctic Peninsula
Oscillatory ECMWF temperature contours
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Naval Research Laboratory Mountain Wave Forecast Model Naval Research Laboratory Mountain Wave Forecast Model
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
ΔT [K]
Backward trajectoriesBackward trajectories
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
Microphysical PSC model runsMicrophysical PSC model runsMeasurementMeasurement ModelModel
without without with with mountain wavesmountain waves
AtmosphericAtmospheric Science Science ConferenceConference, ESA ESRIN , ESA ESRIN FrascatiFrascati, 11 May 2006, 11 May 2006
SummarySummary• Spectroscopic evidence for β-NAT as constituent of Type 1a PSC
• No indication for NAD found in MIPAS PSC observations
• Detection of a NAT belt in the early Antarctic stratospheric vortex 2003: 20 days after first PSC observation
• Mountain wave activity over the Peninsula and the Ellsworth Mountains explains the sudden NAT formation
→ Trigger for subsequent frequent vortex-wide NAT observations?
→ No freezing mechanism of NAT above the ice frost point necessary to explain the observed ‘denitrification before dehydration’ in the Antarctic vortex?
Spectroscopic Evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds M. Höpfner, et al., Atmos. Chem. Phys., 6, 1201-1219, 2006.
MIPAS detects Antarctic stratospheric belt of NAT PSCs caused by mountain waves M. Höpfner et al., Atmos. Chem. Phys., 6, 1221-1230, 2006.
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