Stratosphere-Troposphere Exchange And climate Monitor

Microwave Limb Sounding of the UT/LS: Stratosphere‐Troposphere Exchange And climate Monitor ‐ STEAM
and related projects J. Urban, D. P. Murtagh, P. Eriksson, M. Whale Chalmers University of Technology/ Göteborg / Sweden
U. Frisk, F. von Scheele, A. Emrich
OMNISYS AB / Göteborg & Stockholm / Sweden
Part I: Microwave Limb Sounding
(1) PAST AND PRESENT
Development of mm/sub‐mm Limb Emission Sounder UARS/MLS
MAS/ATLAS
Odin/SMR
Aura/MLS
JEM/SMILES
first satellite mission for “microwave limb emission”.
Millimetre Atmospheric Sounder on the Space Shuttle
first "sub-millimetre wave limb sounder".
first limb mission employing a "THz radiometer".
first limb sounder using SIS detectors.
2001
1991
Odin/SMR Aura/MLS
UARS/MLS
2009
2004
JEM/SMILES
MAS/ATLAS (Space Shuttle)
slide: Y. Kasai
Name of
instrument
Receiver
Trec [K]*
Aura/MLS
Schottky
~6000@650GHz DSB
Odin/SMR
Schottky
~3000@500GHz SSB
JEM/SMILES
SIS
~400@650GHz SSB
Sensitivity
Low
High
Observation geometries The atmosphere from space
thermal emission measurements microwave and infrared range
Line‐of‐sight
limb scan
Limb sounding
Space
illustration adapted from S. Brohede
Microwave limb sounding: major water lines
MLS
SMR
SMILES
183GHz
H2O
H2O
489GHz 557GHz
O2
O2
1991
UARS/MLS 183GHz
MAS/ATLAS (Space Shuttle)
2001
Odin/SMR
489+557GHz
2004
Aura/MLS
183GHz
2009
ISS/SMILES Water line observations
Examples for water line measurements by limb scanning microwave instruments.
Aura/MLS
183 GHz
Odin/SMR
489 GHz
557 GHz
Part I: Microwave Limb Sounding
(2) STRATOSPHERIC WATER VAPOUR
Middle Atmosphere – dynamics and composition
Recent evolution of lower stratospheric water
vapour in the tropics
1992-2014
Earth and Space Sciences
zonal mean
~16.5-18.5 km
Urban et al., Eos Trans. AGU, 95(27), 245, 2014
Contributions of stratospheric water vapour to
decadal changes in the rate of global warming
Do changes of ±0.5 ppmv H2O matter?
[Solomon & Rosenlof, Science 2010]
Earth and Space Sciences
Part II: STEAM ‐ Stratosphere‐Troposphere Exchange And climate Monitor
(1) MOTIVATION AND BACKGROUND
Some history
• SCOPE to ESA Earth explorer mission
• 1998 ‐ MOST proposed to Japanese GEOS‐COM
• 2001 MOST as micro‐satellite to CNES
• 2002 STEAM mission to SNSB
• 2005 STEAM‐R on PREMIER as Earth Explorer core •
•
mission
2008 STEAM‐R on STEP to CSA
2013 STEAM‐R on ALiSS (CSA + SNSB + ?)
Scientific justification
The atmosphere is constantly changing
Atmospheric composition changes are driving climate change
–
–
–
Primary radiative forcing by trace gases & aerosol
Indirect effects through chemistry and aerosol-cloud interactions
Feedbacks via water vapour, cloud & trace gases
Surface temperature sensitivity to composition changes
Ozone
Water Vapour
Methane
pressure (hPa)
~35 km
~25 km
~17 km
~10 km
tropopause
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8
Sensitivity / unit mass (relative radiative forcing)
– Surface temperature change depends on temperature structure and opacity
→ sensitive to height at which composition perturbed
– Region of particular sensitivity: mid–upper troposphere & lower stratosphere
Courtesy Piers Fosters
STEAM – Stratosphere-Troposphere Exchange And climate Monitor
Scientific objectives
• Climate Change
– Detailed measurements of upper tropospheric H2O
– IPCC identified lack of knowledge of the water vapour cycle
particularly in the upper and middle troposphere as a major
uncertainty in climate models
– Water feedback provides a doubling of the CO2 temperature
increase in current climate models
• Stratosphere-Troposphere Exchange
– Highly spatially resolved measurements of O3, H2O, CO, and HCN
in the UT/LS region
• Ozone Changes / Climate-Chemistry Interactions
– Continued surveillance of stratospheric ozone and related species
in post Odin and EOS-Aura era
Earth and Space Sciences
Part II: STEAM ‐ Stratosphere‐Troposphere Exchange And climate Monitor
(2) APPROACH AND CAPABILITIES
Microwave limb sounding: major water lines
MLS
183GHz
STEAM
SMR
SMILES
H2O
H2O
489GHz 557GHz
O2
1991
UARS/MLS
MAS/ATLAS
183GHz
O2
2001
2004
Odin/SMR
Aura/MLS
489+557GHz
Earth and Space Sciences
183GHz
2009
JEM/SMILES
2020?
STEAM
STEAM – Stratosphere-Troposphere Exchange And climate Monitor
STEAM-R / PREMIER
• Optimized 12GHz (DSB) UT/LS channel:
lsb 324.0-336.0 GHz, usb 343.25-355.25 GHz
H2O, HDO, O3, CO, HCN,
N2O, HNO3, CH3CN, CH3Cl, ClO,
temperature
• Sun-synchronous orbit
(820 km as MetOp),
• 14 simultaneous limb views 5-28 km
1.5 - 2 km vertical / ≤ 50 km horizontal sampling
• Auto-correlators: 12 GHz / 25 MHz
• Options: dsb, 2sb
Earth and Space Sciences
STEAM‐R/PREMIER STEAM‐R in PREMIER architecture ‐ courtesy Urban Frisk
STEAM – Stratosphere-Troposphere Exchange And climate Monitor
STEAM-R
12 GHz
bandwidth
UT/LS band
DSB
H2O, HDO,
O3, CO, HCN,
N2O, HNO3,
CH3Cl, ClO
lo 339.625 GHz
DSB
IF 3.625-15.625 GHz
O3
O3
N 2O
HCN
HCN
O 3 H 2O
O
O33
ClO
ClO
O3
N22O
O
N
O3 O3
Earth and Space Sciences
CO
HNO3
NO
CH3CN
CH3CN
CH3CN
O3
ClO
ClO
O
O22
CO
CH3Cl
CH3Cl
HNO3
O3
HDO
Observation geometries from space
The atmosphere from space
Line‐of‐sight
thermal emission measurements microwave and infrared range
Multi‐beam Limb sounding
Multi-beam limb sounding:
STEAM/PREMIER vs STEAM/ALISS
50 km
44 km
short scan:
6-7km
STEAM/PREMIER: Fixed array in 2 stacks,
total of 14 beams in 6-28 km range
28 km
6 km
2 km
Earth and Space Sciences
STEAM/ALISS: Fixed array of 8 beams in
2-44 km range, short scan over 6-7km
STEAM/ALISS nominal capabilities: H2O-16
H2O-16
50km sampling interval: dz = 1.0-1.2km; precision ~10-20%
Earth and Space Sciences
a5 - dsb
mid-latitude night scenario
STEAM – Stratosphere-Troposphere Exchange And climate Monitor
Retrieval simulations for H2O
Scenario M3, monsoon core
dashed white:
tropopause
Test
scenario
grey:
cloud opacity limit
for infrared sensors
Retrieval
simulation
=> Choice of 320-360 GHz range allows measurements in the upper troposphere!
Earth and Space Sciences
Slide: C. Schiller
Comparison Aura/MLS, STEAM-R
approximate vertical (horizontal) resolution in UT/LS region / km
STEAM-R (PREMIER)
H2O
O3
HNO3
HCN
CO
1.5 - 2 (50 - 100)
1.5 - 2 (50 - 100)
1.5 - 2.5
2 - 2.5
2-3
N2O
CH3CN
CH3Cl
ClO
1.5 - 2.5
2.5 - 3.5
2-3
3-4
Horiz. sampling
50 km
Aura/MLS v3.3*
Odin/SMR
2.5 - 3 (200-250)
2 - 2.5 (300-400)
3 - 4 (400-500)
7 - 9 (400-800)
4 - 5 (400-600)
3 - 3.5
1.5 - 2
1.5 - 2
n/a
3-4
4 -5 (400-600)
5 - 6 (400-700)
4 - 6 (450-600)
3 - 4 (300-500)
1.5 - 2
n/a
n/a
1.5 - 2
165 km
600 - 900 km
* according to [EOS MLS Level2 Version 3.3 Data Quality and Description Document, Livesey et al.,
JPL, Jan 18, 2011]
Earth and Space Sciences
Scenario M3, Asian monsoon core:
CO
HCN
CH3CN
 Choice of 320-360 GHz range allows measurements in the presence of clouds
(e.g. Asian monsoon)
Earth and Space Sciences
Scenario P1, Pyro East-Kilmore:
“Black Saturday” pyro-convection scenario
CO
HCN
CH3CN
 Detection of phenomena at tropopause level requires high vertical resolution.
Earth and Space Sciences
Summary
• Microwave limb sounding provides sensitive well resolved measurements of key species for climate and ozone science with global coverage and during day and night. • Several mm‐ and sub‐mm instruments since the early 1990s: UARS/MLS, Odin/SMR, Aura/MLS, SMILES on ISS.
. • STEAM developed for sounding the climate critical UT/LS altitude region using bands in the 320‐360GHz range.
• STEAM based on multi‐beam limb sounding and tomographic retrieval approach for obtaining best sampling, resolution, and sensitivity required for UT/LS. Thank you!
Photo: K. Sagi, Göteborg 2010-12-24

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