FAAM Sortie Brief

VISURB-UK: Assessment of aerosol properties related to urban visibility.

Flight No: B254 Date: 19th Dec 2006

Trial objectives:

To carry out in-situ sampling of aerosol properties and their effect on visibility.

Location:

Following a path round the north sea and English Channel, from Flamborough head through toDorset.

Points:

#80: 5405N, 0E.

#87: 53N, 1E.

#40: 5250N, 1.5E.

#41: 5153N, 1.47E.

#42: 5105N, 1.3E.

#43: 5040N, 1.0W.

#44: 5040N, 1.00W.

#45: 5001N, 2.0W.

#46: 5001N, 3.25W.

Weather:

High loadings of atmospheric aerosols trapped in shallow boundary layer. Fog and stratocumulus with very low cloud base may be a problem, particularly over the north sea.

Special requirements:

Check the mesoscale model forecast for extent of fog and position of aerosol plumes before flying.

Instruments of particular importance:

PCASP

Nephelometer/Wet-nephelometer

PSAP

AMS – possibly not available due to lack of staff from Manchester

Flight pattern:

  1. Take off from Cranfield at 11:00Z (11:00L).
  2. Transit north towards the north sea coast, heading for an initial operating point of off Flamborough head (#80) [30 mins].
  3. Perform a profile descent at 1000ft/min to 50ft aiming to arrive at #80 at the end of the profile, T=30 mins.
  4. Ascend to a suitable operating altitude (suggest 500ft, but possibly lower if aerosol layer is very shallow, or if necessary to keep below marine stratus/stratocumulus).
  5. Turn southwards and perform a SLR on a track around the UK coastline. If fog or very low cloud are a problem try to deviate further from the coastline where fog and low cloud will probably lift.
  6. Continue on a course round the coast using the following points:

#80 -> #87 [10mins, T=40mins].

#87 -> #40 [10mins, T=50mins].

#40 -> #41 [20mins, T=70mins].

#41 -> #42 [20mins, T=90mins].

  1. Interrupt the SLR at #42 (or somewhere along the south coast in a region of high aerosol concentrations) to perform a vertical profile through the boundary layer. This would consist of a descent to 50ft then an ascent up to 5000ft (or a level above the aerosol layer), followed by a profile descent back to the operating altitude. Aircraft should return to the point where the profile was starting before continuing its track around the UK. This could be achieved by making a reciprocal turn after the ascent and back-tracking for a few minutes before making another reciprocal turn and descending back to the starting point of the profile [10 mins, T=100mins].
  2. Continue track along south coast as far as #46:

#42 -> #43 [10mins, T=110mins].

#43 -> #44 [20mins, T=130mins].

#44 -> #45 [20mins, T=150mins].

#45 -> #46 [15mins, T=165mins].

  1. At point #46 make a reciprocal turn and retrace the track back along the English channel to point #87, or as far as possible given time restrictions[T=270mins].
  2. Return to Cranfield, profiling up through boundary layer at 1000ft/min on leaving the operating region [20mins, 290mins].