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Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

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Page 1: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Atmospheric Measurements at Capel Dewi field station

Prof. Geraint Vaughan

Page 2: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Where is it?

Page 3: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Aerial view of site

Field of antennae

BungalowLidarcontainer

Page 4: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Instruments on site

• UK Mesosphere-stratosphere-troposphere (MST) radar

• Boundary-layer wind profiler• Surface weather station• Five-wavelength mobile ozone-aerosol lidar • Fixed ozone and water vapour lidars• Lidar ceilometer• GPS receiver (total water vapour column)• Spectrometer for stratospheric measurements

Page 5: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

The MST radar

This is a VHF radar: 47.5 Mhz, or a wavelength of about 6 m. It consists of a field of 400 antennae (the aerial) and transmitter/receiver equipment in the bungalow.

It runs continuously, measuring profiles of winds, atmospheric structure and turbulence every 2 minutes, from 2 to ~16-20 km altitude

Page 6: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Example day: 15 June 2005

Page 7: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Wind measurements

Plot shows 24 hours wind measurements on 15 June 2005.

High winds near 10 km show a jet stream – note that it changes direction over the course of the day.

Note strong wind shear above and below the jet.

Page 8: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Echo power measurements

Same day, 15 June 2005.

Radar measures tropopause height (crosses) where the signal increases with height. Note relation between tropopause and jet stream.Low power at lower levels is due to water vapour, but rain suppresses echoes. Note:Low power 0300 – 0600 as front passes overStrong layering later in the day, indicating descending air and stability to convection

Page 9: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Boundary-layer wind profiler

Similar to MST radar but measures at lower heights – 100 m to around 3 km.

Radar system working at 1.29 GHz – around 24 cm wavelength

Antennae are much smaller and each panel contains an array of 64 of them (8x8)

Three panels pointing in different directions measure winds

Measurements of winds and echo power every 2 minutes, continuously.

Page 10: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Wind profiler measurementsSignal to noise ratio, 15 June 2005

Wind direction,

15 June 2005

Page 11: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Surface Met Data

Campbell Scientific Weather station:

Temperature, rainfall, RH, sunshine

Vector Instruments Anemometer on 10 m tower on top of hill nearby

Page 12: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Surface measurements

Note zero rainfall: rain did not reach ground during frontal passage

Page 13: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Lidar: Basic principles

• LIDAR – Light Detection and Ranging• Similar principle to RADAR – pulses of

light emitted into the atmosphere and scattered back by clouds, aerosols or air molecules.

• Time-of-flight gives scattering height z=½ct

• Light collected by a telescope• Spectrometers or interference filters

isolate wavelength concerned

z

Page 14: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Ceilometer

LIDAR instrument using infra-red wavelengths to measure cloud height

Page 15: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Ceilometer data for 2/4/07

Page 16: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Mobile aerosol-ozone lidar

Lidar using five ultraviolet wavelengths to measure aerosol and ozone profiles

Page 17: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Ozone/aerosol measurements

Black line denotes top of boundary layer – below this the air is polluted with lots of aerosol. But ozone is relatively low: note how the ozone increases above the boundary layer on this day

Page 18: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Raman lidar

Nd-YAG laser (SPECTRON)

355 nm

X10 Beam expander (refracting telescope)

To atmosphere

Transmitter

ReceiverFrom atmosphere

Page 19: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Water vapour measurements by Raman scattering

Aberystwyth Dec 9 2001

Page 20: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Ozone measurements

June 5 2000

Above: tropospheric measurements from 289/299 nm pair.

Below: stratospheric measurements from 299 alone. (We now do DIAL with 299/316 for stratosphere)

Page 21: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

SAOZ spectrometer

Stratospheric Nitrogen dioxide column measurements from Aberystwyth, 1990-2005

0

2

4

6

8

10

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Aberystwyth pmAberystwyth amCamborne pmCamborne amAberdeen pmAberdeen amLerwick pmLerwick am

Year

NO

2 ver

tical

col

umn,

1015

cm

-2

Page 22: Atmospheric Measurements at Capel Dewi field station Prof. Geraint Vaughan

Health and Safety• On entering the site, please report directly to the site bungalow.

Vehicle speed should not excede 10 mph. Do not stray from the track.

• At the site bunglow, please report directly to the site manager (or other representative of the Facility).

• Within the site bungalow, on no account enter the transmitter room, unless given permission to do so by the site manager.

• Outside of the site bungalow, please do not touch any equipment. Do not enter the antenna array unless given permission to do so by the site manager.

• Do not enter cordoned-off areas