Humidity is the amount of water vapour in the air. Relative humidity is an important term used in forecasting weather. Humidity indicates the likelihood of precipitation (rain), dew or fog. A high humidity level makes people feel hot because it reduces the ability of the body to sweat and cool down
Have you ever looked out of the window and found it hard to see? It could be because the windows need a good cleaning. Or it could be because of the sudden appearance of fog. Fog can simply be defined as condensation on ground level. Fog or ground clouds are made of millions of tiny drops of water. The ability of fog to form suddenly and disappear as quickly is determined by the ambient temperature or the temperature of the surroundings.
Which is the foggiest place in the world? The foggiest place in the world is Point Reyes, California, USA. It is among the top two foggiest areas in the world where the land is covered with fog for more than 200 days a year.
Have you ever wondered why the windows become foggy when you switch on the airconditioner? Or why your spectacles get foggy when you step out of an air-conditioned car? Well, this foggy factor is seen when an object is colder than the temperature of the area it has been moved to. Water vapour cools on the object and condenses to form fog. This process is also known as condensation.
During the monsoons, you will hear of a lot of aircrafts that have been diverted or delayed because they could not land or take off due to fog. Why does this happen? Simply because pilots cannot see the runway. In order to land safely, a plane has to be lined up on the centre line of the runway at the right altitude and speed. From the sky, the fog looks like a smooth white blanket. Though aircrafts have automatic guidance systems that can guide the aircraft close to the runway, the landing is always done manually. If the pilot cannot see the runway, he/she cannot land the plane.
Our body has an in built cooling mechanism that is triggered by the process of sweating. Did you know that the amount a body sweats is directly proportional to the humidity in the air? Imagine this - you are biking up a hill, pedalling as hard as you can and you're dripping sweat. Why does this happen? Your body works best when its temperature is at 37 degree Celsius. When your body gets hotter than that, like when you are exercising, the body tries to stay cool and comfortable and thus starts sweating. The sweat leaves your skin through tiny holes called pores. When the sweat hits the air, it evaporates (this means it turns from a liquid to a vapour). As the sweat evaporates off your skin, you cool down. You will sweat more if the outside temperature is warm and humid. You will sweat less if the outside temperature is cool and dry.
The next time you walk to school, keep an eye on the blades of grass. Do you see shining drops of water on the grass? These diamond – like drops of water on the leaves are nothing but dew drops. Moist air that settles on plants during the night turns into dew drops in the morning.
DID YOU KNOW?
- Your feet sweat 91 1/4 cups of sweat each year.
- When hippopotamus are upset, their sweat turns red.
- The sweat that oozes from your pores is actually a weak version of urine!