1. Cirrus Clouds near the mid-latitude tropopause
from CALIPSO
Steven T Massie
ACD/NCAR
January 8, 2008

2. Outline
How likely is it to observe cirrus between
double tropopauses?
Data:
Lidar observations over France
FNL (NCEP) analyses of multiple tropopauses
CALIPSO observations over North America

3. April – May double tropopauses occur ~ 25 % of the time (Paris)
30% 25 20
May
Noel and Haeffeln, Midlatitude cirrus clouds and multiple tropopauses
from a 2002 – 2006 climatology over the SIRTA observatory, JGR,
112, D13206, doe: /2006JD007753, 2007.

4. Lidar observations for a single day
Double tropopause layers are ~ 1.5 km thick
Altitude (km)
Time  15 14 13 12 11 10 9 8 7 6
Noel and Haeffeln, Midlatitude cirrus clouds and multiple tropopauses
from a 2002 – 2006 climatology over the SIRTA observatory, JGR,
112, D13206, doe: /2006JD007753, 2007.

5. Most cirrus cloud tops are
below the tropopause
Z (cloud top) – Z (tropopause)
Noel and Haeffeln, Midlatitude cirrus clouds and multiple tropopauses
from a 2002 – 2006 climatology over the SIRTA observatory, JGR,
112, D13206, doe: /2006JD007753, 2007.

6. Statistical Summary of SIRTA Clouds
Frequency of Cirrus case
occurrence
83% Cloud top > 0.5 km below the tropopuase
10% Cloud top < 0.5 km below the tropopuase
5% Cirrus is at or above the tropopause
2% Cirrus is between a double tropopause
% values are for instances when clouds are observed
Noel and Haeffeln, Midlatitude cirrus clouds and multiple tropopauses
from a 2002 – 2006 climatology over the SIRTA observatory, JGR,
112, D13206, doe: /2006JD007753, 2007.

7. 2nd trop heights are mostly at 16 - 17 km altitudes
2nd Tropopuase Heights from FNL Analyses
2nd trop heights are mostly at km altitudes
Some are between km

8. Calipso Example: May 28 Altitude (km) 30 20 10
N lat :20 – 9:35 UTC

9. Calipso Example: May 25
T = tropopause
height from
FNL analyses

10. CALIPSO and FNL Analyses in 2007
Month % multiple % of time clouds are
tropopauses between multiple tropopause
April 16% 2%
May 10% 1%

11. Summary
Based upon
lidar observations over France
CALIPSO/ FNL (NCEP) data
clouds are between double tropopauses ~ 2% of the time
If you know that a double tropopause will occur, then
you have a roughly 1 in 10 chance of observing
cirrus above the 1st (lowest) tropopause.