Sri Lanka is a tropical country. We do not experience four distinct seasons of weather: spring, summer, autumn and winter. Instead we have two tropical summers and monsoons. The first tropical summer we have been experiencing the past few weeks.
In a previous post titled science: the two summers of colombo, I explained how Colombo experiences two summers. This is because of Earth's tilt relative to the Earth's orbit around the Sun.
Spring begins with the Vernal Equinox, which falls on March, 20 at 11:44 UT this year (2009). For any city in the Equator, Equinoxes will be the days in which they receive the highest amount of Sunlight. Thus, probably the hottest days of the year.
But Sri Lanka is located a few degrees above the Equator in the Northern hemisphere.
Based on the calculation explained in a previous post titled science: the two summers of colombo, lets evaluate the two days where the Sun is directly above an observer at Solar Noon:
δSun = 6.92° N = +6.92°
δSun = 23.44 × sin((360×(284 + N)/365))
N = 98 = 08 April 2009
N = 246 = 03 September 2009
L = 79.86° E = -79.86°
LStd = 82.5° E = -82.5° for +05:30 UT
LStd - L = -2.64°
4 (LStd - L) = 4 min/degree × 10.56° = 42.24 minutes
TSolar= 12 at Solar Noon
B = 360 × (N-81)/364
when N=98, B98 = 16.813
when N=246, B246 = 163.187
E = 9.87 sin(2B) - 7.53cos(B) - 1.5sin(B)
when N=98, E98=-2.17 minutes
when N=246, E246=1.31 minutes
TSolar=TLM + E - 4 (LStd - L)
TLM = TSolar - E + 4 (LStd - L)
when N=98, TLM,98 = 12h - 2.17min + 42.24min = 12:40
when N=246, TLM,246 = 12h + 1.31min + 42.24min = 12:44
Therefore, Colombo will have two Summers with peaks on 08 April 2008 at 12:40 and 03 September 2008 at 12:44.
The hotter Summer being in April since Earth is closer to the Sun.