# Estimation of Direct Normal Irradiance at Antarctica for Concentrated Solar Technology
## 2 Materials and Methods  
### The Antarctic Climate  
The climate of the Antarctic continent is strongly influenced by astronomical factors, its geographical position, the average altitude and its ice cover. Since the Earth, during the winter season of the southern hemisphere, is at the maximum distance from the Sun, this season is longer than in the northern hemisphere. Therefore, this long polar night and the Sun's low inclination angle makes Antarctica a less heated continent even in the summer. In addition, the surface is almost completely covered by ice or by snow, which reflects most of the incident solar energy. Moreover, the average altitude of the continent exceeds 2000 m, contributing to a reduction in the thickness of the atmospheric troposphere, which normally acts as a heat source.  
All these factors make Antarctica the coldest place on Earth, with a very short summer and very long winter, where temperatures reach winter minimum values even in autumn. In winter, the average temperatures range between \(-20\)\({}^{\circ}\)C in the coastal strip and \(-70\)\({}^{\circ}\)C in the continent, while in the summer the average temperatures range between \(0\)\({}^{\circ}\)C along the coast and \(-35\)\({}^{\circ}\)C in the continent.  
The orography of the continent presents a vast central elevated landform, the plateau, with a slope towards the ocean. MZS, located on the coast of the Ross Sea, is separated from the plateau by the Transantarctic Chain. The heat loss caused by surface albedo acts in the formation of an intense thermal inversion near the ground, with the consequent formation of very cold air that moves from the plateau by gravity towards the coastal areas, forming the katabatic winds. These winds, which often exceed 100 km/h, give rise to snowstorms that can persist for long periods; once they reach the coastal strip, they encounter more humid and warm air masses generating violent disturbances. Precipitation, in Antarctica, is generally scarce and more concentrated along the coastal strip, so that we may consider the Antarctic continent a cold desert. The area surrounding MZS is in fact considered one of the windiest places on Earth.  
The trend of average monthly temperatures shows a maximum corresponding to the months of December and January, when temperatures are close to \(0\)\({}^{\circ}\)C. A sudden drop in temperatures occurs between February and March, reaching average values of around \(-20\)\({}^{\circ}\)C in April. The temperatures continue to reach minimal values until July and August with the lowest temperatures recorded throughout the year, reaching \(-22\)\({}^{\circ}\)C in average values with extreme peaks of \(-40\)\({}^{\circ}\)C. In September the temperatures start to increase, which continues until December. The predominant winds measured at MSZ are oriented in a west and north-west direction. Those wind directions are the most intense winds coming from the glacial valleys of the Reeves and Priestley glaciers, the area that connects the Antarctic Plateau with the Ocean. In general, in this area, eastern and southern winds are rare. Days with no wind are very frequent [3].