Atmospheric measurements at capel dewi field station
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Atmospheric Measurements at Capel Dewi field station. Prof. Geraint Vaughan. Where is it?. Aerial view of site. Lidar container. Bungalow. Field of antennae. Instruments on site. UK Mesosphere-stratosphere-troposphere (MST) radar Boundary-layer wind profiler Surface weather station

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Aerial view of site
Aerial view of site

Lidar

container

Bungalow

Field of antennae


Instruments on site
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


The mst radar
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



Wind measurements
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.


Echo power measurements
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 over

Strong layering later in the day, indicating descending air and stability to convection


Boundary layer wind profiler
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.


Wind profiler measurements
Wind profiler measurements

Signal to noise ratio,

15 June 2005

Wind direction,

15 June 2005


Surface met data
Surface Met Data

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

Campbell Scientific Weather station:

Temperature, rainfall, RH, sunshine


Surface measurements
Surface measurements

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


Lidar basic principles
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


Ceilometer
Ceilometer

LIDAR instrument using infra-red wavelengths to measure cloud height



Mobile aerosol ozone lidar
Mobile aerosol-ozone lidar

Lidar using five ultraviolet wavelengths to measure aerosol and ozone profiles


Ozone aerosol measurements
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


Raman lidar

355 nm

Nd-YAG laser (SPECTRON)

X10 Beam expander (refracting telescope)

Raman lidar

Transmitter

To atmosphere

From atmosphere

Receiver



Ozone measurements june 5 2000
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)


Saoz spectrometer
SAOZ spectrometer

Stratospheric Nitrogen dioxide column measurements from Aberystwyth, 1990-2005


Health and safety
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


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