Hurricane, Tropical Cyclone or Typhones

After Hurricane Sandy, people has been more aware of Hurricanes again. But what's actually a hurricane? You might think it's about the strength of the wind, you're partially correct. It's more complex than that.

A Hurricane is a tropical revolving storm with a warm core.  That's driven by heat from the warm water, which is partially why it has a warm core. This warm core are also partially the reason why they can be so strong. Everyone has heard about the eye, which are the calm and clear center of the storm. To explain this a little further, think about and engine. Instead of gasoline, warm water is the fuel and it's a bit more effective. The calm and dry center is the heat sink, where air that been used land up in, through a slow sinking motion.


The reason behind all the different name is pretty simple, it all depends on where the tropical cyclone can be found. We have hurricane around America, around Japan, China, Indonesia and Northern Australia it's called Typhoons and Tropical Cyclones in the rest of the areas where they can be found.

We have mainly six birth grounds for hurricanes (North Atlantic and Caribbean, Northwest Pacific, Northeast Pacific, Southwest, Southern Indian Ocean and Northern Indian Ocean). Pacific those places are active during a couple of months per year. Most of the Americans know that hurricanes are active during June/August to October. But depending on the water temperature hurricanes can be developed later or earlier.

Here is the time of year when and where hurricanes usually are active:

Northern Tropical Atlantic and Caribbean: June to October
Northwest Tropical Pacific: Mars to December
Northeast Tropical Pacific: June to October
Southwest Tropical Pacific: December to April
South Indian Ocean: November to April
North Indian Ocean: April to May

Those months are when the ocean temperature are most favorable for hurricanes. Which usually means water temperature above 27 degrees Celsius.  And these places are where the environment are the most favorable for hurricane development.

Back to Sandy, I think most of you that reads this already know why it get to be that devastating. But it was mainly because it was really large and that the atmospheric situations forced Sandy to take the track it took.

Hope you liked this post, please comment or Tweet if you have a question about this post.

//Osced

Why does it rain?

Probably everyone have sometime looked up at the clouds. But what is a cloud ? Clouds is a cluster of cloud droplet mainly consisting of condensed water.  A cloud often consists of billions of small cloud droplets, that has been developed because that the air can't take care of more water vapor. When the air is over saturated, water vapor will condense on small particles called aerosol like salt or dust particles.

Because of physical laws that I won't talk about water vapor generally needs those aerosols to condense from vapor to droplets. Depending on the temperature and the amount of excess water vapor in the cloud and the type of particle the droplet will grow differently.

The amount of water vapor the air can hold depends the temperature of the air.  For warmer temperature the air can hold more water vapor. With temperature decreasing with altitude, the air will hold less water higher up in the atmosphere. This means it less likely that a cloud spontaneous appears in the sky. Usually clouds develop because of sudden upward movements in atmosphere.

During the cloud droplets life it will travel upwards until gravity gets to strong, upwards winds is generally not the same in the whole cloud. In some cases the droplet will reach the top of the cloud and start falling down collection smaller cloud droplets. Depending on the upward wind the droplet might stop its fall and either travel upwards or hang still in the cloud.

Sudden upward movement can be caused by several things, usually it is convection or frontal clouds you see in the sky.

We have know learned how a cloud is born, but what happens when it's raining?
In a cloud we have certain upward winds that is working against gravity that wants to push the droplets against the grown. When our droplets reach a certain size they are too big and the gravity wins and our cloud starts to rain.

If you liked this entry or have question, please leave a review. 
//Osced

Weather School: A climate discussion.

It's easy to think that the global warming isn't happening when it gets colder where you live, but we need to remember it's global so even if it gets colder at your place the global temperature can still increase.

Global warming can be divided in two categories; man made and naturally global warming. Many global warming skeptics are using the fact that the sun has different kind of cycles and that for example they say its due to solar spots. Of course solar variability are affecting the climate, but the changes of the temperature can't be fully correlated with the warming. We also has volcano eruptions, but none of the latest volcano did affect the global temperature.

Some of the skeptics even doesn't fully understand the greenhouse effect, and mostly of the scientist that doesn't believe in that the anthropogenic emissions is the cause of the global warming is in a minority. This article (http://www.pnas.org/content/early/2010/06/22/1003187107.abstract) found out that most of the scientist that isn't a 'believer' doesn't actively publishing in this field. I think that's interesting, wonder why? I won't answer that and instead let my readers think about that.

In spirit of the climate discussion I will try to explain the greenhouse effect in several simple ways. I start with the easy and probably the most used way:

We can compare the greenhouse gases with a coat, it works the same way holding the heat inside, making the temperature increasing. This might easily explain the effect, but it can be harder to explain why increased anthropogenic gases would make the temperature increase. The easiest way is to think about it like you another coat on earth. More greenhouse gases means more 'coats'. Pretty simple and explains the essence of the greenhouse effect.

But my favourite explanation is one I learned from one of my teachers. It is still very easy to understand but you can explain a lot more than with the 'coat' explanation. We start with imagining a pub and a little cabin, between the cabin and the pub is a thick forest. If we imagine the forest as the greenhouse gases and the cabin as the open space. The heat or infra-red radiation can then be a drunk person leaving the pub, heading for the cabin. What happens when he walks through the forest? He will have trouble walking in a straight line and 'bounce' between the trees, if the forest is thicker he will have a lot harder to walk through the forest. This is how the greenhouse effect works, with more gases the heat will stay inside the atmosphere longer and heating up it more.

A more scientific explanation talks about 'windows' of radiation that depends on the structure of a molecule. A greenhouse gases has a specific structure that makes it absorb long-wave radiation (heat).

I hope you think this was an interesting reading, please comment and tell me what you thought about it or if you have a question.

//Osced