Dear Colleague, in Gabon there are two rainy and two dry seasons, according to the seasonnal latitudinal migration of the ITCZ. The driest period is July-August, which corresponds to the northern location of the ITCZ. So all months do not receive the same amount of rainfall nor have the same amount of rainy days, even if during the dry seasons there are still many rainy days, but with most often low amounts. What happens since climate change hit Africa by the end of the 60s, is that the July-August dry season is more and more humid, like it can be seen in the South Cameroon -see attached papers. The thing is that rainfall data are less available since the 90s in Gabon, which prevents from following accurately how is regionaly distributed the change of rainfall regime. If anyone has more informations about rainfall in Gabon since 1990, please contact me.

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Article Evolution des régimes hydrologiques en région équatoriale ca...

Thanks, Mr.Gil Mahe for your answer and feedback. We are not particularly focusing on Gabon, it is generalized over equatorial regions of the world that remains wet most part of the year and unsuitable for human habitation. It is a boon for Gabon that 2 dry seasons are there in 12 months to plan, cultivate, grow and produce something / agricultural products to feed the populace. Your's Makasu & Makakou are located at 1.630S and 0.560N latitudes respectively have a good pattern of rainfall with only one dry season from July to September as seen from Gaisma/NASA weather monitoring report. During this period ITCZ moves to India and other northern countries of the globe as monsoon to cause raining over these regions. Other places in equatorial habitations are worse for living due to daily and high rainfall. We are in a search to find out the scientific reasons for which these regions remains wet throughout the year. Please help us to find out the same.  

Hello. The classic reasons are :

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.

Otherwise, for Kenya, there's no very heavy rains as in other equatorial countries; because in summer of the northern hemisphere (June to September), the trade winds are deflected to the north where they give monsoon in Southeast Asia. (they are attracted by the continental depression).

Best redards.

Thank you, Mr.Mohamed EI Mehdi, for your welcome answer.Your points are quite traditional and fine. Apart from these points some elements of Physical forces is playing a dominant role for this phenomenon, please try to find out this factor.  

Hi , from Venezuela, near to the equatorial zone , as we know the ecuatorial zone is frequently under the ITCZ influence also this zone is under a low pressure and also receive high irradiation which create convection areas all year round. Also the gradient force from high presure subtripical areas to equatorial zone is transporting humid winds that confront sometimes the effect  of mountains and create clouds an orgraphic rainfall . All these facts make this area quite active in terms of rainfall.  

Thank you, Mr.Jorge Luis for your answer. The presence of ITCZ brings rain,it is understood, but what factors are responsible to install ITCZ permanently at the equatorial region excepting few months in a year over some land masses? Cause of mountains is not accurate as mountains are not present throughout the equatorial regions. 

Normally in Venezuela between 0 and 4 degrees  is the same as you mentioned for AFRICA requatorial regions. Here we assume the effect of  ITCZ is allways present for this area since the effect is delayed and the warm effect and cloud formation is cumulative all year round  even in Summer, and taking the extention of the Convergence activation area  is posible to assume the constant effcet on this equi distnace region form the North -South miigration.  

I mentiones mountains in my last message because we have those in Venezuela, but I understood your idea.

Hope  share more knowledge and to learn from all of you about this area and its climate................Jorge Lopez         

Dear Jorge Luis, thank you for your query, I know the actual scientific reason for which equatorial regions receive year round rainfall. Since presently MYSELF is engaged in this research work to bring out a volume by January,2017 at Chennai chapter of Indian Science Congress Association, I can not say the fact before my publication. Then only I can state/open my theory in general, till such time please bear with me.  Thanks and regards

The equator is where the Earth receives the greatest solar radiations throughout the year, which is transformed in long waves radiations after being absorbed by atmosphere and land components (a part of the solar radiation input of course returns to space without being absorbed ). As such the Equator is the place on earth where the heat received is maximum. Thus evaporation is maximum and warm humid air masses is the thickest on the earth, up to 18 or 20 km height while it is only 6 km at the poles. This leads to convection and heavy rain throughout the year and this is why this is the wettest area on earth, with seasonality due to ITCZ migration following the apparent movement of the sun.   This heat is naturally redistributed towards poles following pression gradients, but due the rotation of earth and the coriolis effect the movement of the air masses follows several cells with upward and downward air currents. The cool and dry air masses coming from the equatorial regions after condensation and rains, come back to ground level in the tropical regions which thus experience dry conditions in the desert tropical belt. From there surface air currents migrate north and south to generate the ground part of the atmospheric cells currents. The winds going back to toward to equator at the ground level are known as trade winds, which willl in turn be warmed and humidified in the equatorial region and be uplift again in the ITCZ, etc. The distribution of land lasses and mountains generates local variability in the spatial distribution of the equatorial rain belt. 

Thank you,Sir, Gil Mahe , you have rightly pointed out the events with cause and effects, Can you please light upon the forces and physics that particles are flowing to this region continuously without any interruption?