Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
It has to do with the equatorial climate - it rains almost everyday there and it's mostly cloudy. If most days of the year are that way I'm sure the temps will be steady all year round.
Over much of the world what matters quite frequently is what air mass you're in at the time. Right now where I am in Texas we were at 80 and humid a few days ago. We had southerly flow bringing warm moist air from the gulf. Today we topped out around 40 thanks to a cold front. Tomorrow will be sunny but still won't get above 60 because of the cold air mass at the surface. Obviously solar angle and day length aren't to blame for the cold weather. Today is little longer than last a day last weekend and the sun is a little bit higher. But because of the cold front it's much cooler. This weekend the south flow will return and we'll be in a warmer air mass. At the equator you've got tropical air to the north and tropical air to the south. Cold air from the poles has a long way to go to make it to the equator so equatorial regions stay in warm tropical air. The equator is never more than 23.5 degrees away from the region of maximum solar intensity and as soon as that max is reached it starts decreasing again. There just isn't time to develop a cold air mass. Also the length of day is always 12 hours at the equator so it's just solar intensity changing.
Some places do have a little seasonal variation. It can be a localized thing. Coastal or island regions have the oceans to moderate temperatures even more than inland places. Wet and dry seasons are also a major reason for any variations like in Nairobi Kenya.
1) The sun angle never decreases much, and its lowest period is for a short time. If you live at 20° the noontime sun angle at winter solistice is 90° - (23.5 - -20°) = 46.5°. At the equator it's 90° - (23.5 - 0°) = 66.5°. The difference in heating from the sun being a bit off of vertical is small compared to lower angles.
2) The period of lower than peak sun angle is short, within a month and a half later or earlier it's not much different from equinox strength.
3) Sun strength is dependent on sun angle and day length. Day length doesn't vary along the equator while it does in the higher latitude tropics, so the change in solar radiation is rather small.
4) Most of the equator falls under rather humid climates. With the high humidity, any extra sun strength mainly goes into evaporating more water rather than increasing the temperature. Any changes from a wet/dry season will be the biggest change in a year.
5) Local air mass patterns (winds and weather from other places to the north and south) probably overwhelm the small changes in sun strength so the pattern you're describing is hard to find.
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.