ExUTLS dynamics and global observations

Bill Randel, NCAR ACD

ExUTLS dynamics and global observations

Bill Randel, NCAR ACD

Two aspects of ExUTLS transport to explore:

1)Transport above the subtropical jet (links with double tropopauses)

2)Tropopause Inversion Layer (TIL) (coupling between dynamics and chemical

mixing)

Extratropical temperature profiles often have multiple tropopauses

Location of double tropopauses for one day (ERA40 data)

PV=1-4(dynamicaltropopause)

Cross-section near Charleston (ERA40 data)

zonal winds, pot. temp

Charleston

Cross-section near Charleston (ERA40 data)

static stability N2zonal winds, pot. temp

Charleston

Cross-section near Charleston (ERA40 data)

static stability N2zonal winds, pot. temp

intrusion of tropical tropospheric air above jet core

Charleston

Note: double tropopauses occur frequently even at polar latitudes

Where/how often do multiple tropopauses occur?

COSMIC GPS observations for April 2007

Double tropopauses for April 30, 2007 (GFS data)

J

Differences in ozone for single vs. double tropopause

derived from ozonesondes

lower ozonefor doubletropopausestatistics

(characteristicof tropics)

Differences in ozone for single vs. double tropopause

derived from SAGE II satellite data

NH SH

-> consistent pattern of less ozone for double tropopauses

~ 2300 soundings

transport ofair from tropicsabove jet core

(low stability, low ozone)

Interpretation:

Randel, Seidel and Pan, JGR, 2006

HIAPER ozone observations during TREX

stability derived from GFS

HIAPER flight track

ozone

note ozone decrease above 12 km

Andy Weinheimerand Ilana Pollack

Laura Pan

Some Questions:

Why is the transport above the jet mostly poleward rather than equatorward?

How does transport above jet contribute to ventilation of LS? (when and how much?)

What is the origin / age spectrum of air above STJ ? (are there short-lived species in this region?)

J

narrow layer ofhigh stability

This is a climatological feature of theextratropical tropopause

Birner, 2006

examples using GPS data in tropopause-based coordinate

heightrelative totropopause

temp stability

layer ofhigh

stability

April 2007 COSMIC climatology

heightrelative totropopause

temp stability

layer ofhigh

stability

tempinversion

structure of stability in tropopause coordinates

similar resultsfound for

all seasons, andboth hemispheres

shaded:N2 > 4.5

Randel et al., JAS, 2007

heightrelative totropopause

3

observedprofiles in

tropopause-based

coordinate

note water vapor andozone transitions occur

over +/- 1-2 km

(tropopause mixing layer, ala Pan et al., 2004)

TIL coincides with chemical mixing layer

TIL coincides with chemical mixing layer

Pan et al., 2006

Summary:

Tropopause inversion layer is ubiquitous in extratropics and coincides with the chemical mixing layer.

Radiative forcing may help maintain the TIL.

* Detailed structure of ozone and water vapor across the tropopause is important.

-> What determines thickness of the chemical mixing layer?

-> Is this important to get correct in models?

Balanced Structure in Extratropical Cyclone (Hoskins et al. 1985)

cold

warm

low tropopause

isentropes

winds

strength of the inversion vs. circulation

T(ZLRT1+2km) – T(ZLRT1)

systematically stronger for anticyclonic flow

Double tropopauses for April 30, 2007