Absolute Pressure vs. Relative Pressure: What’s the Difference?
Absolute pressure is the raw, unadjusted air pressure measured at your location, right where your weather station is sitting. It’s the actual pressure exerted by the atmosphere, plus the weight of the air column above it. This reading doesn’t care if you’re at sea level or halfway up a mountain.
Relative pressure, on the other hand, is what you see on weather reports. It’s adjusted to sea level, so no matter how high up you live, the reading makes sense when you compare it to other places. Why? Because air pressure decreases as you go higher, and if everyone reported unadjusted readings, it’d be chaos! You’d never be able to tell if a low-pressure system was coming through or if someone’s backyard weather station just happened to be perched on a hill.
Why Does Relative Pressure Matter in New Zealand?
New Zealand’s landscape is anything but flat. Whether you’re by the beach in Auckland or tucked away in the mountains of Queenstown, your absolute pressure will vary just because of elevation. To make your readings line up with official weather reports or forecasts (which use relative pressure at sea level), you’ll want to set your station to display relative pressure.
How to Set Relative Pressure in NZ (It’s Easy!)
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Check the current sea-level pressure for your location.
- The easiest way? Head to MetService or WeatherWatch and find the current pressure for a nearby town or airport. They report relative (sea-level) pressure.
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Adjust your weather station’s pressure reading to match.
- Your station is probably showing absolute pressure straight out of the box.
- Look in your weather station’s manual for how to calibrate or set relative pressure. Usually, there’s a setting where you can dial it in to match what you saw on MetService.
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Done! Now your station shows relative pressure, and you’re ready to track those classic NZ weather mood swings like a pro.
Quick Example
Let’s say your weather station shows 1015 hPa absolute pressure. You hop on MetService and see the sea-level pressure nearby is 1021 hPa. You’d adjust your station’s relative pressure setting until it matches that 1012 hPa reading, either by directly entering that number, or by setting a offset (of +6 in this example)