Question
Asked 19th Jan, 2016

What makes equatorial regions to be wettest place on the earth?

It is a common fact that equatorial regions receives highest rainfall (to the tune of 4000 mm in a year). What are the scientific reasons to this fact of nature? Raining occurs everyday or every alternate day over equatorial region making it wettest on earth, resulting them at an average 22 days wet in a month. Some solid scientific reason governs this phenomenon.

Most recent answer

9th Jun, 2016
Radhashyam Muduli
NTPC Limited
Gases in atmospheric air remain in state Nor O2   and not in state 3,......6Nor 4,.....7O2 but water vapour can assume 7,........23H2O form and it condenses in drop lets as rain from this state. These larger particles of moisture migrate with a force greater than g to equatorial region where local force attracting it with force of g only towards centre of the earth. Hence greater force greater than g is effective to carrying water particles to equatorial region from most places on the earth where air circulation(trade wind) is active. This makes greater concentration of moisture over equatorial regions of favourable sites where water droplets condense as rain. This is the actual scientific reason for which daily or on every alternate day(average 20-22 days in a month) raining takes place in equatorial region.
After moisture particles reached this outermost zone(ITCZ) in rotating state, the particles are forced to remain in this zone till they condense as rain. This phenomenon is similar to function of a non-return valve used mostly in unidirectional fluid flow in Engineering practices for safety of a process being carried out.

All Answers (12)

19th Jan, 2016
Reza Safaierad
University of Liège
Dear Radhashyam,
Equatorial regions compared to the other regions of the world receive more solar irradiance and this cause to form a band of the low pressures across the equatorial regions known as Inter-tropical Convergence Zone (ITCZ). Oceans form a big portion of the equatorial area and solar irradiance cause to huge amounts of evapotranspiration over these oceans, in other hand because warm weather has more humidity capacity, thus humidity level in equatorial air is high. When air currents from surrounding high-pressure regions blow toward the ITCZ they bring huge amounts of humidity into ITCZ and this wet air rises in ITCZ and forms Cumulonimbus clouds. Two key factors determine height of the troposphere: amount of Heat and Humidity. Because of warm and humid nature of the equatorial regions troposphere has its maximum height across the equator which is ca. 18 KM and it decreases toward the polar regions to ca. 8 KM. Cumulonimbus clouds produce huge amount of rainfall in these regions. Furthermore, cloud cover decreases evapotranspiration in the equatorial regions. So, equatorial regions are most humid part of the word.
Best, Reza
2 Recommendations
19th Jan, 2016
Bachir Achour
Université de Biskra
Dear Radhashyam,
The rains are more abundant at the equinoxes and take place in the evening. In fact, the hot air becomes laden with moisture and known upward movement. With altitude, there is a cooling (with formation of cumulonimbus cloud type) often causing heavy rains.
With my best regards
Prof. Bachir ACHOUR
2 Recommendations
19th Jan, 2016
Radhashyam Muduli
NTPC Limited
Dear Prof. Bachir ACHOUR,
     Thank you, sir for your idea. Sir, you have stated only how it occurs but the question is why it occurs and what are the scientific reasons for the same.
Thanking you, sir with regards,                                                    R.S.Muduli. 
19th Jan, 2016
Bachir Achour
Université de Biskra
Dear Radhashyam,
Science can only answer "How? ". This is the only field of application where it can intervene: find the mechanisms of life and the universe. In terms of their origin, intent, why, Science can not answer because these issues are outside its domain.
For example, we know that opposites charges attract and the charges of the same sign repel. We know that electrons have a negative charge and protons a positive charge. These properties explain the appearance of certain forces. But all could have been otherwise, and we do not know why the electrons, protons precisely have this property.
With my best regards
Prof. Bachir ACHOUR
1 Recommendation
20th Jan, 2016
Radhashyam Muduli
NTPC Limited
Dear Bachir Achour
   Thank you sir, you are right to state this logic. As researchers, we should go, one step ahead to pick up any available clue within our reach making research activities more lively and active.
Thanking you, sir, with regards,                            R.S.Muduli.  
20th Jan, 2016
Radhashyam Muduli
NTPC Limited
Dear Reza Safaierad,
 Thank you for your ideas. Your points are traditional and usual as supported by all Meteorologists at present. As indicated and mostly accepted, ITCZ is not always a low pressure zone. Particles flowing to this zone are unable to return to any where except to move round in this zone for ever for obvious scientific reasons.This is left out for you to find out with your skills and expertise. 
Thanking you,    with regards,                                   R.S.Muduli.
26th Jan, 2016
Mohamed Elmehdi Saidi
Cadi Ayyad University
I will simply enumerate three reasons:
1- The trade winds from the high subtropical pressures are running into in the equatorial zone and forms a rising air chimney that gives a lot of rain.
2- equatorial regions are an area facing the sun. the air is very well heated and can hold a lot of water vapor. When this vapor is cooled by ascent, it gives a lot of rain.
3- The troposphere which contains the quasitotalité of atmospheric water is thicker in the equatorial regions (15-18 km) compared to other regions of the world (about 10 km). Water vapor has a lot of space to train large cumulonimbus that gives a lot of rain.
Best regards
2 Recommendations
27th Jan, 2016
Radhashyam Muduli
NTPC Limited
 Dear Mohmed El Mehdi Saidi
Sir your  reasons on the subject matter is very nice and logical, but there remains an element from science & technology that will justify the exact fact of nature. You can think in this way, that water particles coming to this zone find  no way to go out to anywhere but to move in this area (ITCZ) till they are condensed into water as rain. 
Thanking you sir,     with regards                                        R.S.Muduli.
8th Jun, 2016
Gil Mahe
Institute of Research for Development
Once the rising air has lost its humidity by condensation within the "chimney" it reaches the top of the troposphere and can not continue upward due to strong stratospheric currents. The dry air then flows towards North and South of the ITCZ and reaches the ground in the tropical belts, creating deserts by dynamic advection of dry air toward the ground surface. This Hadley cell is then completed by tropical trade winds going back toward the ITCZ.
9th Jun, 2016
Radhashyam Muduli
NTPC Limited
Dear Gil Mahe,
                              Thank you for your answer on heavy equatorial rains. Can you please infuse a sense of physics to the process?
Thanks. 
9th Jun, 2016
Gil Mahe
Institute of Research for Development
There are two aspects, the analogic one, what we see, and this is a kind of cell functionning, at the subcontinental scale, and the physics one which is linked to thermodynamic processes both at the local scale (evaporation/condenstion), and at a larger scale, but there we do not know yetexactly what happens between the different part of the world interconnected. I am afraid I am not a physicist... 

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