ExUTLS dynamics and global observations

1
ExUTLS dynamics and global observations Bill
Randel, NCAR ACD
2
ExUTLS dynamics and global observations Bill
Randel, NCAR ACD
3

• Two aspects of ExUTLS transport to explore
• Transport above the subtropical jet
• (links with double tropopauses)
• Tropopause Inversion Layer (TIL)
• (coupling between dynamics and chemical mixing)

4
Extratropical temperature profiles often have
multiple tropopauses
5
Location of double tropopauses for one day (ERA40
data)
PV1-4 (dynamical tropopause)
6
Cross-section near Charleston (ERA40 data)
zonal winds, pot. temp
Charleston
7
Cross-section near Charleston (ERA40 data)
static stability N2
zonal winds, pot. temp
Charleston
8
Cross-section near Charleston (ERA40 data)
static stability N2
zonal winds, pot. temp
Charleston
intrusion of tropical tropospheric air above jet
core
Note double tropopauses occur frequently even at
polar latitudes
9
Where/how often do multiple tropopauses
occur? COSMIC GPS observations for April 2007
10
Double tropopauses for April 30, 2007 (GFS data)
J
11
Differences in ozone for single vs. double
tropopausederived from ozonesondes
lower ozone for double tropopause statistics (cha
racteristic of tropics)
12
Differences in ozone for single vs. double
tropopausederived from SAGE II satellite data
2300 soundings
NH
SH
-gt consistent pattern of less ozone for double
tropopauses
13
Interpretation
transport of air from tropics above jet
core (low stability, low ozone)
Randel, Seidel and Pan, JGR, 2006
14
HIAPER ozone observations during TREX
note ozone decrease above 12 km
stability derived from GFS
ozone
Laura Pan
HIAPER flight track
Andy Weinheimer and Ilana Pollack
15

• 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?)

16
narrow layer of high stability
J
This is a climatological feature of
the extratropical tropopause Birner, 2006
17
examples using GPS data in tropopause-based
coordinate
temp
stability
layer of high stability
height relative to tropopause
18
April 2007 COSMIC climatology
temp
stability
layer of high stability
temp inversion
height relative to tropopause
19
structure of stability in tropopause coordinates
shaded N2 gt 4.5
similar results found for all seasons, and both
hemispheres
3
height relative to tropopause
Randel et al., JAS, 2007
20
TIL coincides with chemical mixing layer
observed profiles in tropopause- based coordinate
note water vapor and ozone transitions occur over
/- 1-2 km (tropopause mixing layer, ala Pan
et al., 2004)
21
TIL coincides with chemical mixing layer
Pan et al., 2006
22
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.
-gt What determines thickness of
the chemical mixing layer? -gt
Is this important to get correct in models?
23
Balanced Structure in Extratropical Cyclone
(Hoskins et al. 1985)
warm
isentropes
cold
winds
low tropopause
24
strength of the inversion vs. circulation
T(ZLRT12km) T(ZLRT1)
systematically stronger for anticyclonic flow
25
Double tropopauses for April 30, 2007