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Science Page for ACCENT

Flight of 19990915 Over Hurricane Floyd


Figure 1a. (Click to enlarge) LR, pALT, Zt, and OAT vs UT(ks)
for the ACCENT WB-57F flight of 1999.09.15.
Figure 2a. (Click to enlarge) WB-57F Flight Track for 1999.09.15

 

Figure 3a. (Click to enlarge) Isentropes from 58-63 ks UT.
Figure 4a. (Click to enlarge) Isentropes from 63-68 ks UT.

The CTC plot for this flight.

Figure 3a and 4a plot isentropes for the ACCENT WB-57F flight of 1999.09.15 from 58 ks to 68 ks over Hurricane Floyd. As shown in Figure 2a, the most easterly point was reach at about 63 ks, so Figure 3a can be viewed as the east bound leg, and Figure 4a as the west bound leg. Examining Figure 3a, there is a sharp 1.2 km jump in the tropopause height (from 15.2 km to 16.4 km) at 59.2 ks, which appears to be associated with isentrope wave activity that has a significantly sloped phase line. This jump cannot be questioned because it is so close to flight level (~15.8 km) which varied little until the aircraft began a climb at 61 ks). At 60.2 ks (about 1000 s after it jumped up) the tropopause returned to 15. km, it's pre-jump value.

As can be seen in Figure 4a, the isentrope wave activity returned at 65.5 ks when the WB-57 descended from 18 km to 15.8 km. Also, the tropopause was at 15.4 km, close to its pre-climb value. (The slight increase in the tropopause altitude as the aircraft climbed from 15.8 km to 18 km is to be expected since as the plane climbs the MTP less able to resolve the sharp tropicl tropopause, which was apparent when the aircraft was near the tropopause. At 66.7 ks the tropopause again does a relatively sharp jump, this time from 16.2 km to 15.2 km, reversing the jump that was seen at 59.2 ks on the east bound leg! Note that in both cases the wave activity appears to start east of the sharp tropopause jump. Also, 66.7 ks the aircraft is about 110 km (70mi) south of where it was on the east bound leg.

Another interesting observation is that the outside air temperature changed little during the ascent of the WB57 to 18 km. There was a 0.5 K jump when the tropopause jumped, but then the OAT settled back and remained relatively constant even though the aircraft climbed 2 km. This is consistent with the MTP observation that temperature profile was nearly isothermal from ~15 km to 17 km within the region bounded by the tropopause jumps.

Flight of 19990913 Two Days before Hurricane Floyd Landfall

The figures below convey the same information as above, but for the flight of 1999.09.13. It had a very similar flight track, but occurred before the Hurricane Floyd landfall, so it represents a useful reference to assess the significance of features associated with Hurricane Floyd. The figures a numbered 1b-4b, and correspond to figures 1a-4a above.
 

Figure 1b. (Click to enlarge) LR, pALT, Zt, and OAT vs UT(ks)
for the ACCENT WB-57F flight of 1999.09.13.
Figure 2b. (Click to enlarge) WB-57F Flight Track for 1999.09.13

 

Figure 3b. (Click to enlarge) Isentropes from 58-63 ks UT.
Figure 4b. (Click to enlarge) Isentropes from 63-68 ks UT.

The CTC plot for this flight.