Atmospheric sampling of Supertyphoon Mireille with NASA ...

NEWELL ET AL' DC-8 SAMPLING OF TYPHOON MIREILLE
net income flux net income flux
-0.137
-0.338 -0.201 5.576
1.451
-4.124
lflO hPa lot hPa
II
-5.032 -
150 hPa
- -5.309
+
-1.202
+
-
15fl hPa
= -2.253
+
-7.424 -
2fit hPa
- -10.224
+
-1.726
+
-
200 hPa
-- -5.329
+
-6.155 -
258 hPa.
- -4.167
+
-0.679
+
-
25fl hPa
-- -5.928
+
-4.096
+
-
3Off hPa
- 0.471
+
0.230
+
-
300 hPa
-- -3.377
+
-3.894
q-
-
4tO hPa
- 0.299
+
-0.685
+
-
4fir hPa
-- -3.187
+
0.710 -
5fit hPa
- 0.872
+
-0.578
+
-
5fit hPa
-- -0.360
q-
7.730 -
7fit hPa
- 4.894
+
3.296
+
-
' 7fit hPa
-+- 4.703
7.722 -
850 hPa
- 4.372
+
3.149
+
-
850 hPa
-- 5.231
+
10.302 -
1 tilt hPa
- 8.591 3.771 -
1 tilt hPa
-.- 6.375
W E S N
Figure 19. Example of mass flux components across the walls of the box in Figure 16 for September
27, 1991, based on divergent wind calculated from ECMWF data. Units, 10 9 kg s -1 .
appear to be only a small fraction of that carded upward in
the cloud regions. In an effort to estimate the vertical
motion in central core, it is assumed that the heat balance
within the core is between adiabatic compression and
radiative cooling. The relationship is
to 3p
RT Q
pCp = p = W[Fd- F]
(4)
1867
The ECMWF cross section of vertical motion through
the storm (Figure 18) is not inconsistent with these low
values. In fact, the subsidence in the eye is rather limited,
and the cylindrical volume shown could be regarded as a
Taylor column, as outlined further below. These
conclusions do not agree with the relatively large sinking
motion at 5 km in the core suggested by Willoughby
[19881.
6. Large-Scale Mass Flux
where F 4 is the dry adiabatic lapse rate (= g/Cv, about
10øC km 4) and F = - 3T/3z. Q was calculated from the
nearest radiosonde to the eye with good data. Station A 17 1/2 ø x 17 1/2 ø latitude-longitude box was drawn
47807 at 33.5øN, 130.4øE at 0600 UT was used. To surrounding the typhoon (Figure 16), and flow into and out
simulate conditions in the eye, air temperature was of the box was evaluated each day from the divergem wind
increased by 6øC at 250 hPa between the environment and component. An example appears in Figure 19 where it is
the eye, tapering to IøC at 100 hPa and 3øC at 700 hPa. evident that the majority of the ifflow occurs below 500
Specific humidity was taken directly from the sounding. hPa. We are interested here in the mass flux passing
Cooling rates calculated for the upper troposphere were between the boundary layer and the free troposphere and
about 3.3øC d 'l. The local lapse rate was 7.7øC km 'l. The have therefore calculated the vertical flux through 850 hPa.
value for w was thus -1.7 cm s-l, a small subsidence. Values in Table 2 show that Mireille was sampled on the
day of maximum mass flux, 29 x 109 kg s -1 These values
Table 2. Mass Flux From Lower to Upper Troposphere
are compared with Typhoon Orchid sampled on October 8,
in Table 2; Mireille has about double the flux by Orchid
but clearly a larger sample needs to be studied and
1991
Flux per Unit Area
10 -3 kg m '2 s '1
Total Flux
10 9 kg s 4
compared with the flux by middle-latitude cyclones before
the overall significance of these values from Mireille can
be assessed. It would also be valuable to make an estimate
September 24
Supertyphoon Mirei lle
5 20
of the actual area involved in the rising motion, perhaps by
using weather radar. It is also worth noting from Figure 19
that as well as the boundary layer, the next two layers
September 25
September 26
September 27
September 28
September 29
6
6
9
5
3
21
27
29
19
13
above also contribute substantially to the mass flux through
the system. For example, the 700- to 500-hPa layer
contributes about 20 x 10 v kg s - with at least one third of
this material coming in from the adjacent Asian continent
to the west, as may be seen from Figure 17.
Typhoon Orchid
Is the typhoon important in the general circulation in
carrying trace constituents into the upper troposphere?
October 5
October 6
October 7
October 8
October 9
October 10
3
4
5
5
4
5
14
17
20
18
15
16
This question is examined below for the case of DMS.
The PEM-West missions showed that DMS only
reached the free troposphere from the boundary layer on
three occasions: on September 16 over the North Pacific on
a day of very strong convection as seen from the cloud
videos; on September 27 in association with typhoon
Mireille; and on October 8 in association with typhoon