Convective Transport of Water Vapor into the Lower Stratosphere Observed During

Double Tropopause Events

Cameron Homeyer National Center for Atmospheric Research AGU Fall Meeting, 10 December 2013 Collaborators: Laura Pan, Teresa Campos & Andy Weinheimer (NCAR) Sam Dorsi & Linnea Avallone (CU-Boulder), Glenn Diskin (NASA) Mark Zondlo, Anthony O’Brien & Josh DiGangi (Princeton), Tom Ryerson (NOAA)

Image Courtesy of Chris Cantrell

Outline •  Observations from the Deep Convective Clouds and

Chemistry (DC3) experiment

–  May-June 2012

–  NSF-NCAR Gulfstream V (GV) & NASA DC-8

–  Primary goal was to characterize effect of midlatitude convection on UT composition and chemistry

•  Water vapor injection into LS

–  May 19-20 (GV)

–  May 30-31 (GV & DC-8)

Motivation •  Well known: stratosphere-troposphere exchange

modifies UTLS chemistry, radiation budget, and climate •  Potential impacts of STE from extratropical convection:

–  TST: Increase in stratospheric water vapor •  Inorganic chlorine activation and ozone destruction?

(Anderson et al, 2012, Science) –  STT: Increase in tropospheric ozone

•  Problems? –  Convection and associated transport not resolved in global

climate models –  Apart from the identification of overshooting extratropical

convection, little is known about the characteristic depth and frequency, large-scale environments conducive to overshooting, and mechanisms responsible for transport

Transport Mechanisms

Wang, 2003, J. Geophys. Res.

Fujita, 1982, J. Meteorol. Soc. Japan

“Jumping Cirrus”

Direct Overshoot

Mixing

19-20 May 2012

Flight Track & Large-Scale Environment

NCEP-GFS Analysis valid 20 May 2012 at 00 UTC 10

12

1212

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1414

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30

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4040

Lamont, OK Sounding

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Temperature (C)

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5

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Altitu

de

(km

)

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Radar Cross-section (a)

KDDC

LMN

KOUN

A (259.75º E, 35.85º N) B (262.75º E, 35.85º N)

KDDC

LMN

LMN

KOUN

KOUN

A B

(b)

0 15 30 45 60 75

Reflectivity (dB)

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Altitu

de

(km

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Texas

Oklahoma

Kansas

KDDC

In situ Measurements

00:00 00:05 00:10 00:15 00:20Time (UTC)

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Altit

ude

(km

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0.00

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IWC

(g m

ï�)

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Wat

er V

apor

(ppm

v)

Anvil A

B

0 100 200 300 400 500

Water Vapor (ppmv)

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Ozone (

ppbv)

ï� ï� 0 1 2

Tropopause Relative (km)

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Carbon Monoxide (ppbv)

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(a) (b)

A

Anvil

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Tracer-tracer Relationships

Stratosphere

Tropopause Transition Layer

Troposphere

Conclusions •  Observed water vapor mixing ratios up to 200

ppmv above LS background levels (5-10 ppmv) at altitudes 1-2 km above the tropopause – Limited by aircraft ceilings; visual evidence of

transport deeper into the LS •  All cases of injection during DC3 are observed

during double tropopause events from poleward Rossby wavebreaking – Unique stability background may facilitate deep

overshooting – Largely devoid of inorganic chlorine

Transport Illustration