## 1 Introduction  
Solar energy systems, especially photovoltaic (PV) systems, have become one of the main electricity providers in the last decade, because the cost of their components and installation has dropped dramatically since the 1990s [1; 2]. However, climatic, environmental and operative conditions, as well as geographical locations, play crucial roles in the energy yield of such systems. This fact has triggered the motivation for research into quantifying and modeling the output power/efficiency of PV systems as a function of such conditions. Researchers are investigating dust accumulation, soiling effects and temperature on PV performance and are trying to maximize the energy yield and minimize the power loss due to these factors. The country of Jordan is one of the Middle East and North Africa (MENA)-region countries and has some of the highest dust emission and deposition flux in the world [3]; in addition, this region controls dust distribution in other parts of the world [3; 4]. Due to its importance and influence on PV performance, several review papers have been published that target the classification and categorization of the work accomplished in this field. For instance, in [5], the published work since 2010 was summarized. In their review, [PERSON] and [PERSON] [6] reviewed the work done before and after 1990, and they came up with general recommendations for different temperature ranges and amounts of annual precipitation. As far as the country of Jordan is concerned, they recommended a cleaning frequency of once a week or two times a week based on the rate of dust accumulation. In their review paper [7], a summary of dust effects on PV performance and the chemistry and physics of dust particles along with restoration and preventive mitigation is presented. [PERSON] et al. [8] concluded that cell technology, the selection of equipment, temperature and dust have a huge influence on the PV efficiency. A review that deals with the mechanisms of dust accumulation, rebound and resuspension is shown in [9]; they discussed the effects of air velocity and direction, and humidity for each mechanism. It was concluded that soiling is greatly affected by the module tilt angle while the resuspension mechanism is the most sensitive to wind velocity and has the highest dependence on the particle size. A balance between dust losses and cleaning expenses is presented in [10]. Different models were developed to predict the variable power output of PV. A detailed review of these models is presented in [11]. They reported that the regression models have an advantage as far as the metrological variables are concerned, while intelligent learning techniques can offer improved nonlinear approximation performance. In their review, [PERSON] et al. [12] show that harsh environmental conditions could reduce the reliability of sensors used for PV parameters measurements, increasing malfunction. [PERSON] et al. [13] stated that humidity affects the incident irradiance as well as the dust accumulation. Moreover, they concluded that increasing air velocity decreases the cell temperature and increases dust accumulation. Since PV technology is booming in the MENA region, many researchers in the region have worked on trying to investigate the effect of dust and soiling on PV performance. For example, a study in a controlled experimental setup to investigate the effect of dust on the reduction of PV efficiency was conducted in Baghdad, Iraq in [14]. It was concluded that efficiency reduced by 6.24%, 11.8% and 18.74% for dust exposures of one day, one week and one month respectively. Their results are in excellent agreement with the results obtained mathematically in [15]. In their work, [PERSON] et al. [16] investigated the effects of Khamaseen (Haboob) dust storms coming to Jordan from the Arab Peninsula on PV performance as well as the environmental and health issues caused by such storms. They found that the major particles in such storms are aluminosilicates with a particle size of 5-20 mm.