Jack Frost hard at work this morning.

That’s true, johnboy, there is a thermal lag that means the temperature keeps dropping until an hour or so after sunrise. However that doesn’t explain why it very suddenly seems to get a few degrees colder just as the sun rises.

I used my ACTEW ice scraper yesterday, it’s very good!

The weather has been really weird. Frosts, but I’ve had brief rain at night, which results in frozen crust over everything (mainly my car, which is wearing a light covering of cardboard tonight). Canberra is dry, but every evening I find the roads are wet, with puddles, out my way every evening. Coastal rain?

That brittle, bright, Canberra cold is missing, and the humidity has been high, as it was in summer. For example, right now it’s 92% here, and 86% down at the BoM’s site in Canberra.

Things are definitely changing.

much simpler explanation.. the sun at dawn is still not heating the earth faster than heat is being lost. At first light it’s even more angled than at the poles. meaning having to work through more atmosphere and hitting a greater surface area with any particular ray of light.

Jivrashia said :

I’m sure there’s a logical scientific explanation but it still threw me off.

I had wondered this a few years back when we started going to the farmers markets before sparrows became flatulent. Here’s two seemingly feasible explanations Google offered me at the time:

~ The suns rays heat moisture suspended in the air causing it to evaporate creating a cooling effect.

~ The rising sun heats the upper atmosphere causing it to expand in turn pushing cold air down from the middle atmosphere, displacing the warmer air at the surface.

Easy! It keeps getting colder until about an hour after sunrise. And the steepest drops in temperature are just before sunrise.

Nice.

Now, allow me to make a long winded observation of the frost and ice forming in the Canberra morning.

I got up at 6am this morning, just in time to remember that I hadn’t put the wheelies out on the kurb. So off I go outside in what I thought was a blithering Canberra chill. To my surprise the air was actually tolerable (even warm) despite the fact that it was still dark, and a bit wet.

Come 7:30am I go out to head to work, to face the shy sun hovering over the horizon. And low and behold… there’s ice forming in the bird bath and frost on the neighbour’s roof tile! Soon I sense that my nose and ears hurt from the chill.

What the…?

I’m sure there’s a logical scientific explanation but it still threw me off.

Beautiful, and my car still looked like that at 8.40am. Would have taken a photo but my hands were too frozen…

Wow!

toriness said :

cool

btw JB i just sent in a photo of a car in a drain – forgot to put my name against it 🙂

haven’t seen it toriness send again to john@the-riotact.com?