Estimation of land surface Temperature of Maiduguri Metropolitan Area: A Case Study of Jere & some part of Mafa using Landsat 8 Operational Land Image (OLI)

Estimation of land surface Temperature of Maiduguri Metropolitan Area: A Case Study of Jere & some part of Mafa using Landsat 8 Operational Land Image (OLI) the research revealedmean solar radiance as 10.54 W/m 2 /str/μm the calculated minimum and maximum NDVI values are respectively -0.01674 and 0.5489, used to obtain proportion to vegetation which is then used to determine the emmissivity of the area having minimum emmissivity of 0.986 and maximum of 0.99, the minimum and maximum land surface temperature of Maiduguri Metropolitan areas are respectively 41.16 o C and 26.11 o C.


INTRODUCTION
Temperature is simply the average translational kinetic energy of a particular body of day to day basis. The weather aspect of temperature can be varied throughout the day. Cold and hot waves are factors that affect the temperatures of particular climates. Satellite Thermal Infrared sensors measure top atmosphere irradiances, from which temperatures can be determined using Plank's law (Ifatimehin, 2007).
Land surface temperature would provide vital information about climate changes which plays a role in many environmental processes (Dousset and Gourmelon, 2003). Temperature, controlled by atmospheric, thermal properties of the surface and subsurface media, is an important factor controlling most physical, chemical, and biological aspect of the Earth (Becker et al, 1990).
Surface temperature could be emphased as the temperature of any object recorded and is determined by the varying patterns of spectral responses of each object. Considering the resolution of satellite data, the surface temperature can be defined as the average surface temperature of the ground under the pixel scale mixed with different fractions of surface types.
Numerous factors need to be measured in order to estimate the surface temperature from satellite thermal data.
Digital number from Landsat 8 Operational Land Image (OLI) with wavelength range of 10·4-12·5 µm was applied in order to calculate surface temperatures using equation 6, which state the radiance emitted from an object at a certain wavelength and its temperature (Shindell et al 2001). In the estimation of surface temperature from Advances in Physics Theories and Applications www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.83, 2020 46 satellite thermal data, the Digital Number (DN) of image pixels first needs to be converted into spectral radiance using the sensor calibration data (Markham and Barker, 1986).
However, the radiance converted from digital number does not represent a true surface temperature but a mixed signal or the sum of different fractions of energy. These fractions include the energy emitted from the ground, up welling radiance from the atmosphere, as well as the down welling radiance from the sky integrated over the hemisphere above the surface. Therefore, the effects of both surfaces emissivity and atmosphere must be corrected in the accurate estimation of Surface Temperature (Qin et al, 2001).
At infrared wavelengths the concept of surface temperature is useful for remote temperature measurements. At terrestrial IR wavelengths most land and water surfaces as well as dense cloud layers have a nearly constant emissivity ε > 0.95. Therefore, in case of a transparent atmosphere, the brightness temperature of the surface is very close to its thermodynamic temperature (Petty, 2004). Land surface emissivity is a key parameter for determination of Surface Temperature as well as in the environmental studies. Most natural surfaces are able to emit only part of their potential radiant energy (Caselles et al, 1997).
The aim of this research is to estimate the land surface temperature of Maiduguri Metropolitan area: a case study of Jere & some part of Mafa using Landsat 8 Operational Land Image.

Data Used
Landsat 8 satellite images data of Borno state, primarily downloaded from United States Geological Survey

Solar Radiance
Using the rescaling factor from MTD file, (TIR) Digital Numbers can be converted to solar radiance.

Brightness Temperature:
Solar radiance would be converted to brightness temperature using the thermal constant Values in MTD file (Qin, et-al (2001) Where: BT = Brightness temperature (°C)

Normalized Differential Vegetation Index (NDVI):
To determine NDVI standardized vegetation index which will be calculated using Near Infra-red (Band5) and Red Where: e = Land Surface Emissivity

Fig. 3: Land Surface Emmissivity Maps of Maiduguri Metropolitan Area
The emmissivity were determined in order to calculate the accurate land surface temperature from the solar radiant and brightness temperature, while we have the minimum value of 0.986 and maximum value of 0.99.

3.4
Land Surface Temperature