Mucky rain

While the south of New Zealand has been struggling with too much rain in recent days, here in the north we are so very short of it (though Saturday’s forecast looks promising).  Basically, we have had almost none since Christmas. As someone who relies on rain to wash the car, this means my car is now looking rather mucky. The carwash at the petrol station I use most is not in action any more – I don’t know whether that is to save water or for some other reason – so this means I might actually have to get a bucket or two of water and clean the thing myself, while trying to keep water use to a minimum. (Yes, I know that sounds like a totally selfish perspective and please be assured I don’t actually rate the state of cleanliness of my car above the problems faced by local farmers with the drought. There are a lot of people in Waikato and the rest of the North Island who have it really tough at the moment with lack of water.)

But yesterday it rained! Not very much, but there was certainly some rainfall. And what did it do to my car? Clean it? Just a little? No. Just the opposite. Arriving back at my car after work, I discovered large round splats of muck all over the windscreen, roof and bonnet.

When it rains, the falling water droplets collect particulates in the atmosphere as they fall. These particulates could be pollen, dust (I think there’s a lot of that), industrial pollutants or smoke particles. The droplets hit the car and then the water quickly evaporates, leaving the splatter behind. Thus, rather than cleaning the car, in this case they add to the problem.

One could conceivable collect some of this splatter and analyze where it has come from. How much of it has come from the Australian bush fires, for example, and how much has come from the dust blown up from large areas of dead grass that surround Cambridge?

While the muck doesn’t cause too much issue most of the time, it can cause serious problems when driving towards a light source (i.e. the sun). In this case the small particulates on the windscreen scatter the incoming light in all directions, leading to the ‘whiteout’ effect. When that happens suddenly, at high speed, you could be in trouble. On the positive side, the rainfall clears pollutants out of the atmosphere. I’m hoping the air is going to feel much fresher on Sunday, after the promised front blows through.


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