|
The Esperance Meteorological Office (MO) opened on 28 June
1969. Synoptic observations had previously been taken at the
Esperance Post Office beginning in 1883.
The Esperance MO is one of 14 Bureau staffed stations in
Western Australia providing a vital role in Australia's
surface and upper-air measurement network. Weather balloons
are released 4 times per day at 12:15am, 7:15am, 1:15pm and
7:15pm. Information about temperature, humidity, pressure and
wind profiles from the surface to a height of about 27kms
(90,000ft) is gathered from these balloon flights. Surface
observations of wind, pressure, temperatures, visibility,
precipitation, weather phenomena, evaporation, etc, are
recorded at regular intervals throughout the day and night.
Limited observations are recorded and transmitted by an
automatic weather station when staff are not present.
Meteorological Technical Officers (Observers) staff the
office seven days a week and provide coverage for most of the
day. At times the hours of coverage are reduced to cater for
leave and training requirements.
Radar
The radar is used to automatically track a target suspended
under a balloon and compute the wind speed, wind direction
and the height of the balloon as it ascends through the
atmosphere. Typical balloon flights last about 90 minutes,
reach heights up to 27 km and the balloon can often travel
200 km downwind before it bursts. Balloons are normally
released four times each day.
Apart from tracking weather balloons, the radar is used to
detect precipitation (rain, snow and hail). It estimates
precipitation intensity from the strength of the returned
echoes. It can detect light rain to a distance of about 200km
and severe thunderstorms to over 300km, limited mainly by the
earth's curvature. The radar displays a map of colour graded
precipitation distribution and intensity on a PC monitor in
the MO. This image is updated every 10 minutes when the radar
is not being used for balloon tracking.
Radiosonde
Radiosondes are small battery powered radio transmitters
that are carried through the atmosphere under a weather
balloon. The radiosonde contains a small aneroid barometer
and temperature & humidity sensing elements. When
operating, the radiosonde transmits radio signals indicating
pressure, temperature and humidity to a receiver in the MO.
Radiosondes are released world wide at scheduled times. In
WA, radiosondes are released daily at 7.15am. At Esperance,
additional radiosonde flights are also released on Sunday and
Thursday evenings at 7.15pm. The signals that the radiosonde
transmits back to the MO are processed by a computer and
displayed graphically on the computer screen. The data
received from the radiosonde enables a temperature and
moisture profile of the atmosphere to be calculated. As the
data is displayed it is manually scrutinised and modified if
necessary before being encoded and transmitted to the
Bureau's communications network for national and
international distribution.
Weather Balloons
Meteorological balloons are inflated with hydrogen. They are
filled with sufficient gas to cause them to ascend through
the atmosphere at about 300m (1,000ft) per minute. As air
pressure decreases with height, the balloon expands in size
until it finally bursts. During the hours of darkness
balloons are released with a small torch attached under the
target to allow visual tracking for the first few minutes
before the radar acquires and automatically tracks the
reflective target suspended under the balloon. The hydrogen
used to inflate the balloon is a highly flammable gas and
safety precautions must be strictly followed when inflating
and handling weather balloons. These precautions include the
wearing of an anti-flash coat, goggles, gloves and antistatic
boots. As the balloon is inflated, overhead sprinklers ensure
the balloon and surrounds are wet in order to reduce the
chance of static electricity build-up.
Marine Radio Broadcast ( 27 Meg & VHF Radio )
"Esperance Whr" is a limited coastal radio station.
Our frequencies are:
- 27 Meg Radio - calling ch 88, working ch 96.
- VHF Radio - calling ch 16, working ch 72.
Coastal waters forecasts (Bremer Bay to Israelite Bay) &
current weather conditions are transmitted from the MO by
duty staff daily at 0635, 1235 & 1635 WST. Warnings are
transmitted upon receipt.
Feedback or suggestions are welcomed.
|
