## 4 The GCC's Solar and Wind Energy Resource Potential
### Effects of Dust and Clouds  
The impact of clouds and dust is identified in relation to the geographical location and local conditions, which are extremely clear in the solar irradiance diurnal variation [57]. Moreover, the clouds, dust particles, and high humidity in the atmosphere eliminate the solar intensity [58]. The solar radiation's intermittencies are related to the issues of dust and sand deposition on PV panels. Moreover, if the dust particles are mixed with severe fog, it could be worse during the winter months, thus affecting the PV panels' performance. However, clouds and dust are the main factors that determine the installation feasibility of solar energy projects [59; 60; 61; 62]. The real challenge is reported by [PERSON] [63] and [PERSON] et al. [64], that is, the Arabian Peninsula (including the circumambient deserts) is one the dustiest areas in the world. The dust emissions are triggered by other external factors, such as regional storms caused by large-scale instabilities of the atmosphere and high-speed wind in some cases [65; 66; 67]. [PERSON] and [PERSON] [68] mention that, as an influence on the strong pressure system gradient between the Arabian Peninsula's thermal low pressure and the Azores' high pressure, a huge amount of dust is transported to Asia from the Northeast African desert. [PERSON] et al. [69] identified three main sources of dust that can impact the region during the year: the Rub Al Khali Desert, which is a large regional  
Figure 3: The monthly performance of GHI (W/m\({}^{2}\)) over 37 years (1980–2017) in the GCC region. Copyright © 2021 Elsevier [55]. source of dust; the deserts of Iraq, which are major dust sources for northern and eastern Saudi Arabia; the Saharan Desert, which is the main remote source of dust for western Saudi Arabia. Moreover, Mashat and Awad [70] categorize Arabian Peninsula locations into permanent and temporary dust locations, and the eastern region is identified as a permanent source of dust. Table 3 provides more details on GCC countries and the effective locations' average annual dust. The presence of clouds and dust over the GCC region is attributable to storms that have a major influence on a substantial portion of the region. Figure 5 shows the coverage of cloud and the aerosol optical depth (AOD) performance, which indicates the areas with high sky index clearness over the GCC region. Mainly, the high values of the AOD across the southern region of the GCC occur during the summer months [55] and are caused by the loads of aerosol and clouds that are correlated with the Indian summer monsoon [71; 72]. A clear sky supported by lower AOD values prevails over the northern region of the GCC, except in some summer months, when the dust is carried by the winds of the Shamal, which act as a solar irradiance opaque filter [73]. The increasing diffuse fraction values are caused by the clouds that occur as a consequence of the mid-latitude weather systems during the winter over the northern region (see Figure 2). Furthermore, seasonal variations in the diurnal patterns of the clearness index that affects the convective cycles' performance are evident in all parts of the region. The northwestern region is characterized by the symmetrical uniform clearness index during the entire year with low difference, excluding the winter period (November to February), while high uncertainty is observable during the daytime. The clearness indicator shows major diurnal variation in the summer (June to September) in southwestern Saudi Arabia and high diurnal variation in the eastern region between October and March [55]. During low-dust periods, the southern surface wind is dominant, while the prevailing wind during heavy-dust activities across the eastern part of the Peninsula is a northern surface wind. The eastern region has high diurnal variabilities during the year, with high cloud coverage and greater AOD values in some cases.