Turbulence prone areas in the 300 h Pa

Turbulence prone areas in the 300 h. Pa chart (SH) SLIDE 1 W = developing wave depression CF = confluence between two jet streams T = sharp upper trough CL = upper air col. Turbulence in narrow bands along the shear line D= diffluent region of jet stream R = developing upper ridge Adapted from WMO Aviation Hazards ETR-20 J = jet stream turbulence on low pressure side

CIMSS mid-upper level winds, 20 May 2011 12 UTC SLIDE 2 Images courtesy Cooperative Institute for Meteorological Satellite Studies Space Science and Engineering Center / University of Wisconsin-Madison

2 1 19 May 2032 UTC 3 SLIDE 3 20 May 0032 UTC 4 20 May 0432 UTC 5 20 May 0832 UTC 6 20 May 1232 UTC 20 May 1632 UTC

SLIDE 4 Activity 1 questions • Examine slides 1 to 3, showing turbulence prone areas at 300 h. Pa as well as CIMSS mid -upper level winds and also a sequence of enhanced water vapour images from 19 -20 May 2011 • Annotate likely areas of possible mid / upper atmospheric turbulence on slide 3. • We will verify this exercise by examining the NWP output of Ellrod Indices, vertical shear, horizontal temperature gradients and the NMOC Upper Air Analysis Chart

The 6 patterns of mountain waves SLIDE 5 (from Uhlenbrock et al. 2007) 89 wave events over the Colorado Front Range region during 2004 as detected by MODIS channel 27 (6. 7 micron) imagery were correlated with pilot reports of turbulence (within +/- 2 hours of the MODIS image) Most of the radiant energy observed by the satellite is coming from altitudes above approximately 550 h. Pa (or 15 000 ft in a standard atmosphere). Lee waves were grouped into one of six main patterns based on their appearance in the MODIS water vapor imagery. Patterns corresponding to Turbulence Description 0 1 2 None Smooth to light Light 3 4 Light to moderate 5 6 Moderate to severe Severe 7 8 Severe to extreme Extreme

SLIDE 6 The 6 patterns of mountain waves (from Uhlenbrock et al. 2007) 4 K Pattern 1 4 K Pattern 2 100 km 6 K 10 K Pattern 3 Pattern 4 100 km 8 K 8 K Pattern 5 Pattern 6

The 3 patterns of mountain waves most often associated with pilot reports of significant turbulence (from Uhlenbrock et al. 2007) Pattern 3 – herringbone interference pattern. Brightness temperature (BT) 6. 7 variations across the wave pattern are generally < 4 K. Pattern 4 – Have a large BT 6. 7 gradient around the northern Front Range, but have a short extent downstream. The BT 6. 7 gradient across the primary wave is 6 K. Pattern 6 – BT 6. 7 gradient is greater then SLIDE 7 5 K near the Front Range and extends into the Great Plains with a herringbone-type interference pattern.

The 3 patterns of mountain waves most often associated with pilot reports of significant turbulence (from Uhlenbrock et al. 2007) Two characteristics were most coincident with the most turbulent waves. Mountain waves with higher amplitudes were more likely to be more turbulent than average than those with lower amplitudes. Amplitude of the wave depends partly on the size and shape of the mountain. Steep or concave lee slopes produce larger amplitude waves than those that are gentle or convex (Lilly and Klemp 1979, AFH Turbulence Directive) Mountain waves that exhibited interference patterns in the imagery were considerably more likely to be more turbulent than average. Downstream topography can be destructive to waves instigated by upstream terrain when the wavelength is out of phase with the distance between ridges. In this situation, waves may not form beyond the second ridge. When the distance between the ridges is in phase, the downstream topography may amplify the initial wave amplitude (AFH Turbulence Directive). SLIDE 8

South-east Australia, 5 July 2013, 0025 UTC MODIS image SLIDE 9 Visible image 7. 3 micron water vapour Comparing the visible and the 7. 3 micron water vapour image, please annotate areas of possible clear air turbulence Is the turbulence to the lee of the east Australian ranges likely to be severe ? . Why or why not ? . What else would you need to know.

Question – which of Uhlenbrock et al. patterns do the Grampian mountain waves correspond to (morning of the 5 th July – 0025 UTC) ? SLIDE 10 Small downstream extent Large downstream extent (≥ 100 km) Large downstream extent and interference Small amplitude (<4 K) Pattern 1 Pattern 2 Pattern 3 (interfering waves herringbonep attern) Large amplitude (>4 K) Pattern 4 Pattern 5 Pattern 6 (interfering waves) Melbourne 263 K 4 K 257 K 0 distance (km) 120

Activity 2 questions • Examine slides 5 -10 pertaining to mountain wave detection using water vapour imagery. • Please answer the questions at the bottom of slide 9. • On slide 10, please determine which of Uhlenbrock et al. patterns the mountain waves in the cross section correspond to. Do you think the associated turbulence may be severe ? . What other information would you need ? . • We will examine this in more detail during the session.