Stratospheric intrusion vorticies

March 16th, 2009 |
GOES-11 / GOES-12 / GOES-13 waver vapor images

GOES-11 / GOES-12 / GOES-13 waver vapor images

Water vapor imagery from the GOES-11, GOES-12, and GOES-13 satellites (above) showed the spin-up of a well-defined “stratospheric intrusion vortex” over western Kansas on 14 March 2009. The imagery from each of those 3 satellites is displayed in its native projection, which helps to demonstrate the difference that satellite viewing angle has on the depiction of features on the water vapor imagery. Also demonstrated is the fact that imagery from GOES-13 was available through the GOES-11 and GOES-12 “Spring eclipse” periods (when the geostationary satellites are in the Earth’s shadow, and their solar panels cannot generate the power necessary to operate the instruments) — larger batteries on-board the GOES-13 satellite allows operation through the Spring and Fall eclipse periods.

A larger-scale view of AWIPS GOES-12 water vapor imagery (below) shows that there was a string of these vorticies forming during the 14-15 March time period, with a pair of smaller, weaker features seen in Iowa. While these stratospheric intrusion vorticies are seen on water vapor imagery from time to time, they usually do not produce much in the way of “sensible weather” (clouds or precipitation). However, they do seem to be capable of producing areas of mid-tropospheric turbulence, which can be a hazard for aviation. Pilot reports of turbulence (below) did show that there were a few scattered reports of light to moderate turbulence in the general vicinity of the vorticies.

GOES-12 water vapor images + pilot reports of turbulence

GOES-12 water vapor images + pilot reports of turbulence

The GOES-12 sounder Total Column Ozone derived product (below) confirms that these water vapor features were indeed stratospheric intrusion vorticies — the warmer/drier water vapor vortex features  corresponded to ozone values in the 375-400 Dobson Unit range (brighter green to red color enhancement).

GOES sounder Total Column Ozone derived product

GOES sounder Total Column Ozone derived product

The largest and most well-defined vortex (which initially formed over western Kansas on 14 March) was fairly long-lived, and was still evident on water vapor imagery over Illinois 48 hours later on 16 March. Surprisingly, this vortex also spawned some small pockets of convection that even produced a handful of cloud to ground lightning strikes (below).

GOES-12 water vapor images + lightnining strikes

GOES-12 water vapor images + lightnining strikes

A GOES-12 water vapor image with an overlay of NAM40 model fields of 500 hPa height (cyan contours) and PV1.5 pressure (red contours) indicated that there was a Potential Vorticity (PV) anomaly associated with the stratospheric intrusion vortex — the height of the “dynamic tropopause” (taken to be the pressure of the PV1.5 surface) was brought downward to near the 500 hPa pressure level over parts of northern Missouri and central Illinois.

GOES-12 water vapor image (with location of NAM40 cross section line)

GOES-12 water vapor image (with location of NAM40 cross section line)

An AWIPS cross section of the NAM40 model fields (below) allows another way to visualize the lowering of the dynamic tropopause with this PV anomaly (PV is depicted as the multi-colored image feature on the cross section).

Cross section of NAM40 model fields

West-to-east cross section of NAM40 model fields