TEMPERATURE: (normally shown on graphs as red - bold for outside temperature)
This measures how much heat energy something has. Something with a higher temperature tends to lose its heat energy to things with lower temperature in three main ways (that we understand at present, but also magnetic fields also transfer energy(heat) - see electric toothbrush picture below)
(a) Conduction - when we touch something cold, heat is transferred from our hand to it
(b) Convection - when a gas or fluid passes by something - eg hot air rises to the top of a room
(c) Radiation - when heat is transferred through space - we feel a fire's warmth across a room
note: a dull black object transmits / absorbs heat radiation best - shiny white things reflect it
We measure a number of different temperatures:
(1) TEMP - Outside air temperature (shaded in a white ventilated box 1200mm above ground level)
(2) Soil - Soil temperature 300mm below ground - it remains much more stable
(3) Black plate temp - heats up in the sun and gets colder than outside temp on clear frosty nights
(4) Classroom 1 temperature - allows us to see when heaters are left on after school
(5) eg Classroom 2 temperature - a portable sensor we can use for experiments
(6) eg Ponga Whare) temperature - another portable sensor (coming)
(7) Pole top Temperature - measured by the anemometer
Wind Chill Temperature - We calculate this from the anemometer pole top outside temperature and wind speed This indicates the extra risk we face from hypothermia in high winds particularly if we are wet
Frost: Caused by surface heat radiated out into space on clear nights
HUMIDITY: (Normally shown on graphs as blue - bold for outside humidity)
This measures how much moisture (dampness) the air holds. As the temperature of air rises it can hold more water vapour. When it holds the maximum it can for that temperature it is said to have reached its "saturation" point . Our humidity sensors actually measure "relative humidity" which is a percentage of saturation ( eg 60% means the air is holding 60% of the total amount of water it could hold at the current temperature). This means that when the temperature rises (eg when the sun come out) the humidity goes down. We measure
!1) Outside air humidity (shaded in a ventilated white box 1200mm above ground)
(2) Classroom 1 humidity - allows us to see when heaters are left on after school
(3) eg Classroom 2 humidity - a portable sensor we can use for experiments
eg Ponga Whare humidity - another portable sensor (coming)
Dew Point Temperature - The temperature at which dew forms - calculated by anemometer on pole top
RAINFALL (normally shown on graphs as light green)
Rain, hail and snow and snow works in a similar way to above. Clouds coming in from the across the sea arrive carrying a lot of moisture. When they hit the cold air above our forest clad mountains the water condenses out and falls as rain. If it freezes in the clouds it falls as snow, if the rain freezes on the way down, it falls onto us as hail.
We measure and accumulate data for this
RAIN / 1Hh - rain for last hour included in retained statistics and graphs
Rain / 24 hr - rainfall readings for the last hour
Historical rainfall records by month, year etc
On our weather page we point to the Metview 7 day rain forecast map. Be sure to check this if you want to go tramping in our area.
BAROMETRIC PRESSURE: (normally shown on graphs boldly in dark green)
As air gets warmer by getting heat from the sun, from the warmer ground or wherever other means, it expands in volume so it tends to rise. This means that the air pressure around the globe varies. It is measured as maximum at sea level reducing as our altitude increases and moving towards zero at the outer edge of our earth's atmosphere.
The Barometric Pressure is actually the weight of the column of air above it divided by the area of the bottom of the column eg it has a unit of Kilograms per square metre or equivalent.
Our weather station adjusts the actual pressure measured at the altitude the station is at to an equivalent sea level reading so different results from different places and altitudes can be compared.
Generally speaking, if the barometric pressure is rising, then we probably have good sunny weather with clear skies coming. If it is falling, we can normally expect lots of clouds and rain. Before we had a weatherstaion to graph this, we used to tap the barometer on the wall to see if the pressure needle moved in the rising or falling direction.
WIND: (normally shown purple on graphs)
If the barometric pressure is high at one place the air will tend to flow to other places where the pressure is lower. We call that wind. The Metrological Service publish a weather map where the lines "Isobars" join points where the pressure is the same. Where the isobay lines are close together, we can expect a lot of air movement, winds and storms. In high pressure regions the wind tends to rotate clockwise in the Southern hemisphere and anti clockwise in the Northern hemisphere. We have anticyclones where the pressure is low that bring bad weather whereas in the northern hemisphere we hear about cyclones bringing storms and tornados.
The Anemometer (Wind gauge) is on the pole top 9 metres high and measures:
(1) hourly wind velocity.
(2) wind gust velocity,
(3) Wind direction
UV RADIATION: (normally shown bold yellow/gold on graphs)
Our weather station measures Ultraviolet levels using a sensor on the top of our pole to try to reduce its measurements being effected by ground level morning mist.
The UV Index tells us when the risk of skin cancer is highest, warning us to shield and protect ourselves from the sun. On the positive side it also is a source of Vitamin D
BLACK PLATE ABSORBTION AND RADIATION (Something special we measure)
We have built our own black plate sensor to try to learn about the level of radiation we get from the sun by day and what happens to it. This causes the temperature of the plate (which we measure and compare with the ambient air temperature) to rise , particularly if there are no clouds in the way. This you can see in the following daily reading graph. We found this on an amateur weather guru discussion group where they called this sensor a "Black plate in a jam jar sensor " or "A night-time cloud detector"
c) Daytime UV peaks at different times - also the difference between frosty and snowy morning