1. LATMOS-IPSL, CNRS/UVSQ
Dehydration, hydration and horizontal transport in the tropical UT/LS from high-resolution in situ observations
Sergey M. Khaykin
LATMOS-IPSL, CNRS/UVSQ
J.-P. Pommereau, E. Riviere, N. Amarouche, M. Ghysel, A. Hauchecorne, J.-P. Vernier, F.G. Wienhold, H. Vömel, G. Held, S. Evan, T. Thornberry, A. Rollins, D. Fahey, K. Rosenlof,, M. Fujiwara.
Strateole-2 workshop, Paris, March

2. TRO-Pico balloon campaigns, Brazil, 22°S, Feb-Mar 2012, Jan-Feb 2013
Experimental setup
TRO-Pico balloon campaigns, Brazil, 22°S, Feb-Mar 2012, Jan-Feb 2013
to study the impact of convective overshooting on stratospheric water budget
Zero-pressure plastic 500 and 1500 m3 balloons
500, 800 and 1200 g Totex rubber balloons
Flight train
Species
Nb of flights in 2012, 2013
Pico-SDLA H2O + LOAC
H2O and aerosol 1 2
Pico-SDLA CH4
CH4
Pico-SDLA CH4 +Pico-SDLA H2O
H2O and CH4
Pico-SDLA CO2 +Pico-SDLA H2O
H2O and CO2 3
Pico-SDLA H2O
H2O
pico-SDLA H2O dry wet / wet dry transition period (SMOP) 4 7
Mini-SAOZ
O3, NO2, H2O, H2CO, BrO
FLASH and COBALD 6 13
FLASH + COBALD + LOAC
COBALD
aerosol
RS92 radiosonde, series of ~4 RS a day (in number of days)
P, T, U 10 15 25
Plastic balloons
Rubber balloons

3. TroPico-I balloon campaign, Brazil, 22°S, Feb-Mar 2012
Hydration by convective overshooting
TroPico-I balloon campaign, Brazil, 22°S, Feb-Mar 2012
Balloon sounding (FLASH hygrometer)
Radar echo tops and trajectories
ascent
descent
Balloon trajectory
WV enhancements are associated with convective overshooting cells upwind (reaching 17 km) detected by the radar 6 hours before the sounding
Injection of water into the stratosphere: hydration at local / mesoscale.

4. TroPico-I balloon campaign, Brazil, 22°S, Feb-Mar 2012
Hydration by convective overshooting
TroPico-I balloon campaign, Brazil, 22°S, Feb-Mar 2012
Balloon sounding (FLASH hygrometer)
Radar echo tops and trajectories
ascent
descent
WV enhancements are associated with convective overshooting cells upwind (reaching 17 km) detected by the radar 6 hours before the sounding
Injection of water into the stratosphere: hydration at local / mesoscale.

5. Hydration by convective overshooting: CRM modeling
Hydration by convective overshooting: CRM modeling
Tro-Pico-I balloon campaign, Brazil, 22°S, Feb-Mar 2012
BRAMS CRM simulation for 13 Mar 2012
Hydration by overshooting
Courtesy of
Emmanuel Riviere, GSMA
CRM reproduces the injection of water into the stratosphere

6. Horizontal transport (in-mixing) in the tropical LS
Horizontal transport (in-mixing) in the tropical LS
sounding location
Circles = trajectories initialized from the WV/BSR enhancement (18.5 km); Triangles = trajectories initialized at other levels.

7. In-mixing of extra-tropical air affects tropical LS composition
Horizontal transport (in-mixing) in the tropical LS
In situ, satellite and CTM
CLaMS CTM simulation: 420 K
H2O
Horiz. transport
Vertical transport
Filament of humid air above Bauru captured by CTM
In-mixing of extra-tropical air affects tropical LS composition

8. Water vapour intercomparison
TroPico-II balloon campaign, Brazil, 22°S, Jan-Feb 2013
Comparison between FLASH-B and Pico-SDLA hygrometers
Excellent agreement between FLASH and PicoSDLA

9. Temperature anomaly at CPT level
Anomalous cooling and dehydration in Jan 2013
Temperature anomaly at CPT level
Exceptionally cold tropopause (- 4 K) in January 2013

10. Dehydration TroPico-II balloon campaign, Brazil, 22°S, Jan-Feb 2013
TroPico-II balloon campaign, Brazil, 22°S, Jan-Feb 2013
Dehydration
Local scale
Hydration 18 26 27 31 02 06 10 11 13
Synoptic scale
Significant dehydration of TTL (-2 ppmv) above S. America:
regional or planetary scale event?

11. SSW and TTL cooling/dehydration
SSW and TTL cooling/dehydration
Change of 10 hPa temperature during SSW, 2012/13 winter
Zonal mean H2O, H2O anomaly and T anomaly
MLS and COSMIC,
Arctic
Tropics
Cold point T and Z
CPZ
SSW onset, Jan 6
CPT
Evan et al., QJRMS, in review
Khaykin et al., in prep.
Enhanced tropical upwelling and convection during SSW
resulted in TTL cooling and extreme dehydration

12. SSW and TTL cooling/dehydration
SSW and TTL cooling/dehydration
CFH and MLS H2O
10 Jan 2014, Biak, Indonesia
CFH and MLS H2O
12 Jan 2014, Hanoi, Vietnam
0.5 ppmv (!!!)

13. Clouds and dehydration
Pre-dehydration phase: formation of subvisible cirrus clouds at CPT level with extreme supersaturation and low backscatter
Tmin=187.8 K
Cirrus with extreme supersaturation (165 %) and low backscatter
Subsaturated cirrus with very high backscatter

14. Light-weight instrumentation for water vapour and aerosol
FLASH-B
Fluorescence Lyman-Alpha Stratospheric Hygrometer
COBALD
Compact Optical Backscatter AerosoL Detector
Range of water vapour measurements
Detection limit
Integration time
Vertical resolution
Measurement precision
Total uncertainty
Height range
Weight
ppmv
0.1 ppmv
4 s
~ m
5 %
<10 % (1σ)
350… 5 hPa
0.4 kg w/out batteries
Light sources
Detector
Angle
Response time
Weight
2 LED’s λ1 = 455 nm,
λ2 = 870 nm
Wide range silicon detector
θ = 174°.. 180° 1s
~ 0.5 kg

15. Courtesy of A. Lykov and D. Efremov (Roshydromet)
Unmanned aircraft (UAV) droppable from meteo balloon
FLASH
COBALD
Courtesy of A. Lykov and D. Efremov (Roshydromet)

16. Summary and proposal for Strateole-II
In situ balloon soundings of H2O and aerosol show high potential for studying the mechanisms controlling tropical UT/LS composition (cross-tropopause overshooting, horizontal transport/in-mixing, dehydration, cloud formation etc.)
Excellent agreement between FLASH-B and Pico-SDLA hygrometers
Proposal for Strateole-II:
validation flights with FLASH, COBALD and any other sensors
=> during or after the main phase of Strateole-II
=> equatorial site (same as Strateole ?)
=> small plastic or weather balloons
=> balloon-lifted UAV (cost-efficient soundings, indispensable for island sites)
=> funding to be raised (ANR, CNES, … ?)

17. SSW and lower stratosphere composition
SSW and lower stratosphere composition
Tape recorder signal in zonal mean H2O from Aura MLS
Zonal hPa
H2O zonal mean latitude 82 hPa No
SSW
Major
Interannual variability of H2O is governed by the extra-tropical dynamics and QBO

18. Extratropical dynamics is an important driver of global LS composition
SSW and lower stratosphere composition
Tape recorder signal in zonal mean H2O from Aura MLS
Zonal hPa
Zonal hPa
CO zonal mean latitude 68 hPa No
SSW
Major
Extratropical dynamics is an important driver of global LS composition

19. SSW and lower stratosphere composition
SSW and lower stratosphere composition
Tape recorder signal in zonal mean H2O from Aura MLS
CMIP5 H2O
Zonal hPa
AOGCM INM
Institute of Numerical Mathematics, Russia
Courtesy of P. Vargin and E. Volodin
Jiang et al., 2012
Interannual variability of H2O is not correctly reproduced by CMIP5 models

20. SSW and TTL cooling/dehydration
SSW and TTL cooling/dehydration
SSW onset
Increase of tropical upwelling and convection after SSW
Enhanced transport of CO into the stratosphere above most convective region
SH Africa
Enhanced transport of H2O into the TTL and freezing at CPT
Net effect = LS dehydration

21. Deep convection and LS water vapour
Deep convection and LS water vapour
H2O zonal anomaly in SH tropics (25°S - 15°S) from Aura MLS
Wet signal above continents during convective season
Hydration of LS at synoptic scale seen by MLS.
What is its contribution compared to dehydration?

22. Coincident cooling and drying above Brazil during Tropico-2013
Temperature
Water vapour