Aviation Department

02 - 2009© DWD

......Preconditions for the development of mountain waves

• General weather conditions

Surface– anticyclonal curve of the isobars on the edge of a high

pressure area ( inversion between 1500 and 2500 m)– Gradient of wind 36 km/h– Weak frontal system in parallel to the isobars

( increase of wind with the height constant wind direction)

Aviation Department

02 - 2009© DWD

Mountain Waves

© Copyright: Bernhard Mühr

Aviation Department

02 - 2009© DWD

Kinds of waves

• Mountain Waves– Obstacles for the undisturbed airstream are

hills or mountains

• Shear waves– Caused by vertical or horizontal wind shear

• Thermal waves– Obstacle is a thermal updraft

Aviation Department

02 - 2009© DWD

Preconditions for the development of mountain waves

• Topographical Conditions– Mountain ridge located diagonally to the wind direction

(deviation of the wind direction max. +/- 30º from the perpendicular direction)

• Vertical profile of temperature– stable layer of air mass at and above the height of the mountain

ridges

• Vertical profil of wind– Perpendicular components 15-27 kt– Linear increase of wind with the height (min. constancy)

Aviation Department

02 - 2009© DWD

...... Preconditions for the development of mountain waves

• General weather conditions

Higher levels– anticyclonal flank of the yet stream– Constant wind direction above mountain level– Wind speed at 500 hPa level: 60-115 km/h– Wind speed at 300 hPa level: 80-150 km/h– Narrow trough (SW-stream at the front of a trough)

Aviation Department

02 - 2009© DWD

Yearly statisticof days with mountain waves

In Europe

Aviation Department

02 - 2009© DWD

Ideal Mountain Wave

Aviation Department

02 - 2009© DWD

Vertical profileof the

Wind speedand there effect

on theair stream

a. laminar air streamb. standing eddyc. mountain wave streamd. rotor streame. Rotor stream

Aviation Department

02 - 2009© DWD

Influenceof the

profiles of obstacleson the development

of waves

(Wallington)

to short

to long

ideal obstacle

to long despite height

ideal chain of obstacles with resonance effects

= wave length

Aviation Department

02 - 2009© DWD

Possibilities to forecast mountain waves• Surface weather forecast charts, upper level

forecast charts (500 und 300 hPa)

• Lester-Harrison-Nomogram

• Analysis of TEMPs: – Vertical profile– Scorer parameter

• Direct model output (SkyView, SkyView LMK)

Aviation Department

02 - 2009© DWD

LME 7 kmGME 40 km LMK 2.8 km

The operational model chain of DWD, consisting of GME, LME und LMK

Aviation Department

02 - 2009© DWD

2,8 km grid

40 km grid

DWD – model LMK

Aviation Department

02 - 2009© DWD

Forecast of vertical movement with LMKForecast of vertical movement with LMK

m N

N

Thüringer Wald Erzgebirge

Aviation Department

02 - 2009© DWD

Example of 26.10.06:

• Harz` wave up to 5000 m

• more than 100 wave flights in the NW part of Germany

Aviation Department

02 - 2009© DWD

Example 21 November 2006:

• Max. altitude Riesengebirge up to 7000 m

• 500 km out and return flight Klix- Riesengebirge and back home

Aviation Department

02 - 2009© DWD

Cross section of the Riesengebirge 16 November 2007

Aviation Department

02 - 2009© DWD

Thermal Waves

Aviation Department

02 - 2009© DWD

The cumulus wave

Aviation Department

02 - 2009© DWD

The cloud street wave