Ah, Hong Kong summer: when you're not leaving us in a hot sweaty mess, you open the heavens, usually when we haven't brought an umbrella, or if we have, leading to epic umbrella battles with everyone on the street. The downpours cause mad traffic jams when we're in a rush, and soak us to the skin, just before we head into the air-conditioning. Summer colds are the worst.
But the cause of this wet weather is also pretty awesome. Here are 11 things you might not know about rain.
1. The scent of the season
After the rain, there is always this fresh, earthy smell in the air - the smell of rain. But if rain is actually just falling water. and water is odorless then why does rain smell? The truth is rain isn’t just water. It contains a bacteria that produces a chemical - Geosmin - which, as it reacts with the oil in plants, creates that aroma. In fact, the ancient Greeks called this scent “petrichor”. So next time you're sheltering from an unexpected shower, take a sniff, and know what you're smelling.
2. Where did my rain go?
In some of the hottest parts of the world, you can't tell if it's rained. That is because the air is so hot and dry that the rain evaporates high in the sky without ever getting to the ground. This phenomenon is often referred to as Phantom Rain. Count your blessings that you are living in Hong Kong where you can still see rain, and see its benefits.
3. Burning up
Acid rain is pretty old school science, but we felt that it is important to keep reminding you of it because it still affects us. It has devastating effects on forests, it acidifies oceans and affects manmade wonders, destroying marble structures and buildings. In the US currently, the annual acidity value of rain averages at about pH 4 and some storms have had pH as low as 2.1. For your reference, the gastric juice in your stomach has pH of 1.5-3.5. That's pretty corrosive.
4. Coloured rain
We all know we can't have a rainbow without rain (they occur when light hits the raindrops and is dispersed, causing a spectrum of light to appear in the sky). But did you know rain can literally be coloured itself? Red, yellow, green and black rain has been recorded in many parts of the world (and no, we're not talking about rainstorm warnings). The colour is due to spores from algae reacting with the water.
5. Hitch-hiking on a raindrop
Humans, apparently, are not the only ones capable of hitch-hiking: bacterias do it, too. Scientists from the Massachusetts Institute of Technology in the US found out that when raindrops land, bacteria in the ground can suspend itself in tiny bubbles inside the raindrops and then float up to the atmosphere when the drop of water evaporates.
6. Places of eternal rain
Ranting on endlessly about the rain and the humidity? You don’t get to do that unless if you live in Mawsynram in the Maghalaya State of India. or Mount Waialeale in Hawaii - the name literally means "rippling water". These two are the wettest places in the world, with both places receiving an astounding average of 11,971 mm and 11,430 mm rainfall respectively each year. In comparison, even with a record-breakingly wet autumn, Hong Kong received 3026.8 mm in 2016.
7. Deluge on demand
Doraemon’s futuristic gadget for creating rain isn’t a fantasy. Thanks to cloud-seeding technology, which utilises silver iodide or potassium iodide, this is fiction made possible. In fact, the US currently spends around US$15 million a year to create 55 billion tonnes of artificial rain per year, and China is following suit.
8. Race to the bottom
It's reassuring to know you're not being a wimp when you feel like the rain is actually stinging. When raindrops hit you, they can possibly be travelling at as many as 9 metres per second, even with air resistance. So yes, it actually hurts. Oh gravity, thou art a heartless force of nature!
9. Raining cats and dogs ... ughhh I mean fish
The saying it "It’s raining cats and dogs", but throughout history, there have been multiple incidences of flightless animals - including fish, frogs, snakes and even tadpoles - "raining" from the sky. While the exact cause for this seemingly supernatural phenomenon is yet to be absolutely confirmed, scientists believe that it is caused by tornadic waterspouts picking up and carrying animals to high altitudes. Gives "flying fish" a whole new set of competitors.
10. Shape of a raindrop
While everyone thinks that a raindrop looks like a comic-book teardrop, that isn’t really the case. As a matter of fact, the shape of a raindrop changes as it falls through the atmosphere. However, due to air resistance, a raindrop is actually flat at the bottom with the shape of a pebble.
11. An alternative type of rain
In a galaxy far, far away, 63 light-years away from Earth, there is a blue planet. Don’t worry,the Sith isn't there, as far as we know, but this huge gas giant (HD 189733b) has an atmosphere of scorching heat of 1,000 degree Celsius where molten glass rains sideways in howling 7,000 kilometre-per-hour winds. Puts summer storms in a bit of perspective when it's only water.