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.

This study examines the importance of ground validation to Landsat 5 Thematic Mapper (TM) and Landsat 7 Enhanced Thematic Mapper Plus (ETM+) observations at 2 gas flaring sites in Rivers State, Niger Delta, Nigeria. 12 Landsat imagery (3 Landsat 5 TM and 9 Landsat 7 ETM+) data acquired from 25/03/1987 to 08/03/2013 with < 5 % cloud contamination were used. Both sites are located within a single Landsat scene (Path 188, Row 057). Ground measurements and observations at both sites took place from (04/08/2012-21/09/2012) and (05/08/2019-22/09/2019). Parameters measured are coordinates of points and features, air temperature and relative humidity; and photographs of locations and features were taken. Both air temperature and relative humidity were measured at 3 different levels above the ground surface at 1 minute interval. The results show that the locational error of points and features from Landsat data and fieldwork measurements give negligible difference of 1.0 × 10-6 to 7.3 × 10-6. Also, 4 classes of land use and land cover (LULC) types retrieved from Landsat data are the same with those observed on site during ground measurements. The air temperature (AT) recorded and Land Surface Temperature (LST) retrieved from Landsat data for both sites show that the closer the distance to the flare, the higher the temperature and vice versa. Results show that the spatial variability in ground AT and derived LST from Landsat data differs within 0.8 to 6.0 K because AT is different from LST. Based on the results acquired, it can be concluded that ground validation is essential and required for maximum utilization and exploitation of remote sensing technology applications.

This research investigates the recording of Land Surface Temperature (LST) by Earth Observation (EO) Satellites for four gas flaring sites in Rivers State, Nigeria. Six Landsat 5 Thematic Mapper (TM) and Eleven Landsat 7 Enhanced Thematic Mapper Plus (ETM+) from 17 January 1986 to 08 March 2013 with < 5% cloud contamination were considered. All the sites are located within a single Landsat scene (Path 188, Row 057). Dark Object Subtraction (DOS) method and Atmospheric Correction Parameter (ATMCORR) Calculator were used to obtain atmospheric correction effects parameters for multispectral and thermal bands [Upwelling radiance (L u), downwelling radiance (L d) and transmittance (τ)] of Landsat data respectively. The emissivity (ε) for each site is estimated by using standard values for determined land surface cover from Look Up Table (LUT). The correction obtained from DOS method was applied to the computed reflectance to get the atmospherically corrected reflectance that was used for the classification of land cover. The L u , L d and τ obtained were applied to the calibrated at-sensor radiance band 6 (high gain) data to compute the surface-leaving radiance (L λ) with the ε values obtained for each site. The Planck equation was inverted using the calibration constants to derive LST. Six range of LST values were retrieved for each flaring site, with Bonny Liquefied Natural Gas (LNG) Plant recorded the highest LST (345.0 K) and Umudioga Flow Station with the lowest (293.0 K). LST retrieved from both sensors for the flare hotspots are the highest values compared to other locations within the processing sites, which was clearly shown through Geospatial Information System (GIS) spatial analysis and the transects plots. Furthermore, the closer is the distance to the flare, the higher is the temperature and vice versa. Based on these results, it can be concluded that satellite based sensors, such as Landsat TM and ETM+, have the ability to record LST at gas flaring sites in the Niger Delta.