Seasonal variations in SAGE II background

aerosols in the upper troposphere and lower

stratosphere

SAGE II 論文の要点まとめ庭野　将徳

2 Sep, 2007

Stratospheric Background Aerosol (SBA)- Mean Vertical profiles of SBA:

Vertical decrease in the number of particles at larger mode in the lower stratosphere [Thomason & Peter, 2006]

Vertical decrease of the amount of carbonaceous aerosols in the lower stratosphere [Murphy et al., 2007]

=> How is the vertical profile of SAGE II Reff ?- Seasonal cycle in SBA: [Hitchman et al., 1994]

Above 26 km, the enhanced uplift of aerosols in summer with the suppressed uplift or horizontal mixing in winter (contrast of winter vs summer)

At 16-22 km, rapid horizontal transport and mixing

=> How is the role of microphysics and dynamics ? (Also how is the hemispheric difference and tropical varia

tions ?)

Aerosol formation in tropical upper troposphere (TUT)

- In UTU, cold temperature, much water in the cloud region =>Aerosol formation: the production of OH, and

consequently of gaseous H2SO4

Aerosol loss: the uptake of gaseous H2SO4 & SO2, and the homogeneous freezing of aerosol particles to form cirrus clouds

However, the horizontal distribution of aerosols on the whole global in UTU is still unclear …

& Reff (2.5S-N) at 24 km (Fig.1)Before Pinatubo:

& Reff are larger than those in 2000-2003

After Pinatubo:

-1998~ for &

-2000~ for & Re

=> use data for 1998-2004 to remove interannual variability

3.1. Time variation

↑El Reventador (Nov 2002)

↑ Pi

↑ Ruiz

↑ Rev

Seasonal Amplitude (Fig.2)

0.452 (%)

Reff (%)

　 3.2. Seasonal Cycle

Large amplitude > 15%1) at 45S-40N above 26

km2) at 14-21km & 15S-30N3) over high latitudes above

18 km4) Below 14 km in subtropics

to mid-latitudes -> 1), 2) のみ注目

0.452 (%)

Reff (%)

Hemispheric Asymmetry, & a comparison with qw :

- Above 26 km, large in SH for , but in NH for qw

- Below 20 km: larger in NH for (& qw from other study)

qw (ppmv)

Seasonal Amplitude (Fig.2)

Climatological0.452 (Fig. 3) 20-30S 5S-SN 20-30N

30 km: be out-of-phase between NH & SH18 km: be in-phase between NH, Eq, and SH

30 km

18 km

Min In late spring

Max In early winter

Min In late winter

Max In early winter

Min In Apr-Aug

Min In Apr-Aug

Min In Apr-Aug

0.452 (Fig. 4)

Jan Apr

Jul Oct

32

16

0

km

90S Eq 90N

3. Very small value at 20-30o below 16 km in winter-spring

2.Decline of isolines from winter to spring (most robust in spring-summer)

1. Peak value and altitude over tropics decrease toward higher latitudes

Reff (m) (Fig. 5)

32

16

0

km

small

largevertical decrease ~26km: steadily exists even in 2000-2003

A isoline gap depelops with the isoline decline from local fall to winter, and is prominent in local winter-spring

Reff value ranges in 0.19-0.20 below 28 km

0.452 & Reff over 10S-N (Fig.6)

32

24

16

km

Jan 　 　　　　　　　 Jan

0.452: Tape recorder signal up to 24 km (qw~32 km),

0.452, qw : in phase

Dry Wet

Smallvalues

Largevalues

Reff & 0.452: the uplift of isoline in Jan-Mar, anomalies in Jan-Jun & Jun-Jan

0.452: Phase reversal at the peak altitude (28 km)

--

-

Month-altitude sections of 0.452

(Fig.7)km30

20

10

Downward propagation of positive/negative anomalies down to 26 km

Above 26 km, the decline of E0452 peak altitude in local fall-spring (28-23 km in SH, 27-24 km in NH) => larger decline in SH ! => larger amplitude of E in SH

Negative in local winter-summer & positive in local summer-winter at 30 km

20-30S

Month-altitude sections of 0.452

(Fig.7)

km30

20

10

negative negative

negative positve

20-30N

Upward phase propagation only in NH

Below 16 km: a negative in local winter

At 16-18 km: a negative in Mar-Jul both in NH & SH with large amplitude in NH

positve negative

Horizontal map of 0.452 at 14 km(Fig. 8)

Feb

Aug

H H

H H

Very small value of in the winter subtropics at 14km

Corresponding to anti-cyclonic outflow from convective area

Summer value: larger value than winter value