Abstract
This research examines the effects of South prevailing wind on Land Surface Temperature (LST) retrieved from Earth Observation (EO) Satellites at 11 gas flaring sites in Rivers State, Niger Delta region, Nigeria. 7 Landsat 5 Thematic Mapper (TM) and 18 Landsat 7 Enhanced Thematic Mapper Plus (ETM+) from 17/01/1986 to 08/03/2013 with < 5 % cloud contamination were considered. All sites are located within a single Landsat scene (Path 188, Row 057). The atmospherically corrected reflectance was used for the classification of 4 land cover (LC) types at each site. The emissivity (ε) for each site is estimated by using standard values for determined LC from Look Up Table (LUT). The surface-leaving radiance (Lλ) is computed from the atmospherically corrected thermal band 6 (High gain) and the emissivity (ε) values. The Planck equation was inverted using Landsat calibration constants to derive LST. Geospatial analysis of LST results using ArcGIS show 6 ranges of LST values for all sites. For both sensors LST retrieved for the flare stack sources are the highest values compared to other locations within the sites. Wind directions and wind speeds for Landsat data acquisitions dates and the South prevailing wind were applied to the LST for assessing their effects on it. The results show that for Eleme I and II, and Onne, the p-values results showed that no statistically significant relationships between δLST values in different directions (δLSTNE, δLSTNS and δLSTNW) existed. For Obigbo site, the wind direction (South) for data acquisition date combined with the South prevailing wind to generate a noticeable impact on the LST towards the North-East and the North-West directions. For Alua, Bonny, Chokocho, Rukpokwu, Umurolu and Sara sites, the p-value obtained is statistically significant for all the 3 (δLSTNE, δLSTNS and δLSTNW) relationships; therefore, producing a circle flare δLST footprint. For Umudioga site, only δLSTN versus δLSTW is statistically significant, causing a noticeable effect on the flare δLST in the North-West direction. Based on these results, it can be concluded that the volume and rate of burning gas, and the speed of the South wind at the time of satellite overpass are major factors that determine the influence of the South prevailing wind on the LST retrieved at the flaring sites in the Niger Delta.