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