DIAMET Data Handling

DIAMET Data

The following tables and Excel files contain longitude (aircraft position), air temperature, wind measurements and height data from one of the DIAMET research flights.

The aircraft flew westwards along the same line of latitude from the southwest of England out into the Celtic Sea. It then returned eastwards along the same path. The flight path is shown in Figure 1 below.

Figure 1

One data set is from a westward low level leg of the flight at a height of approximately 350 metres above the sea. The other data set comes from an eastward higher level leg of the flight at a height of approximately 4450 metres above sea level.

Temperature is given in Degrees Kelvin and both the eastward (horizontal) and northward (vertical) component of the wind speed is given in metres per second.

Low Level Flight Data

Higher Level Flight Data

Low Level Flight Data

Higher Level Flight Data

Figure 1 below is a pressure chart of the weather situation on 12th December 2011 when the DIAMET research flight collected the data provided.

Figure 1

By comparing the flight path diagram in Figure 2 to the pressure chart, it is clear that the research plane flew across a warm front at upper, and then lower levels. Plotting the temperature data against longitude for both the high and low level flights, reveals a temperature gradient normally associated with a frontal boundary.

Figure 2

Wind Shear

Wind shear refers to a change in wind speed, and/or direction with distance in the atmosphere. Vertical wind shear is a change in a wind over a vertical distance.

Plots of the Easterly and Northerly wind components from both flights show a marked difference in wind speed values between the high and low levels. This is indicative of vertical ‘wind shear’.

Significant shear is normally observed when the temperature difference across a front is 5 °C or more, and the front is moving at 30 knots or faster.

Wind shear is a hazard for aircraft, gliders and parachutists.

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