Gachari, Francis (2014) Impact of Atmospheric Tides on Climate Model. PhD thesis, Jomo Kenyatta University.
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Abstract
The main factor that determines the weather and climate on the surface of the earth is the time variation of the position of the overhead sun. This single factor determines the time of the day or night, variation of earth‘s surface temperature, prevailing wind direction and therefore precipitation, weather and climate. The locus of the overhead sun as described by the solar-declination from a reference point on the earth surface can be accurately calculated astronomically at all times. This makes it possible to predict most weather parameters, using weather and climate models. We have in this study used a second important factor to account for the natural climate variability as the time variation of the overhead moon as described in a similar manner by the lunar declination. This study demonstrates that the presence of enhanced atmospheric tides resulting from lunar-solar geometry is a key factor when used to predict the temporal distribution of rainfall amounts. Solar and lunar declination values obtained from ephemeris available from National Aeronautics Space Agency (NASA) have been used to compute the relative magnitude and duration of the tidal effect in the atmosphere for the period 1959 to 2005 over Nairobi. The impact of the tidal effect has been assessed by statistical modeling of Kenya rainfall against the conventional climate variability indices such as the Southern Oscillation Index (SOI) and Quasi-Biennial Oscillation (QBO) as well as modeling against parameters derived from the tidal effect. We have found that while conventional variability indices provide a method to explain past variability, their values are unknown for the purpose of projection into the future. We have therefore in this study used statistical modeling technique to obtain future rainfall amounts with covariates and factors derived from the lunar-solar geometry. The main advantage of lunar-solar parameters is that their values can be calculated accurately at all times and have therefore been used to carry out a projection of monthly rainfall amounts in Kenya for the period 1901 to 2020. The statistical model reveals an increase in frequency and intensity of severe hydrology events for the period 2018 to 2020.
| Item Type: | Thesis (PhD) |
|---|---|
| Subjects: | Q Science > Q Science (General) Q Science > QC Physics |
| Divisions: | Africana |
| Depositing User: | Mr Nahum Osman |
| Date Deposited: | 07 Jul 2016 13:33 |
| Last Modified: | 07 Jul 2016 13:33 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/723 |
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