The aim of this work is to study the variability of winter (monthly mean of DJF) air temperatures in Saudi Arabia. The study of the coefficient of variation (CV) of winter air temperature time series shows that the CV is a function of latitude, decreasing generally gradually from north to south. The highest values of CV during the winter season are mainly because of the migrating extratropical cyclones (Mediterranean cyclones) from west to east, and active subtropical jet, as well as the polar jet. The trend analysis illustrates that all stations have positive trends for the wintertime series. The study of decadal fluctuations in the behavior of winter temperature shows that the period from 1982 to 2010 is characterized in general by negative trend values in most northern stations of Saudi Arabia. In the middle of Saudi Arabia, negative trend values also appear but for the period 1983 to 2003. The southern and middle stations are distinguished by a positive trend during the period from 2003 to 2018.

In this work, analysis of the variability of total column ozone (TCO) over the Kingdom of Saudi Arabia (KSA) has been conducted during the 1979–2020 period based on the ECMWF-ERA5 dataset. It is found that the highest values of TCO appear in the spring and winter months especially over north KSA, while the lowest values of TCO occur in the autumn months. The highest values of the coefficient of variation (COV) for TCO occur in winter and spring as they gradually decrease southward, while the lowest COV values appear in summer and autumn. The Mann–Kendall test indicates that the positive trend values are dominant for the annual and seasonal TCO values over KSA, and they gradually increase southward. The study of long-term variability of annual TCO at KSA stations shows negative trend values are the dominant behavior during the 1979–2004 period, while positive trend values are the dominant behavior during the 2004–2020 period. The Mann–Whitney test assessed the abrupt change of the annual TCO time series at 28 stations in KSA and confirmed that there is an abrupt change towards increasing values around 2000, 2005, and 2014. The climatological monthly mean of the ozone mass mixing ratio (OMR) is studied at three stations representing the north, middle, and south of KSA. The highest values of OMR are found in the layer between 20 and 4 hPa with the maximum in summer and early autumn, while the lowest values are found below 100 hPa.

Heatwave (HW) number (HWN), frequency (HWF), duration (HWD), magnitude (HWM), and amplitude (HWA) are key aspects for interpreting and understanding HW characteristics worldwide. Most previous HW studies over the Kingdom of Saudi Arabia (KSA) focused only on the temperature extremes, so this study aims to assess the decadal changes, anomalies, and spatiotemporal variations in the five HW aspects over KSA during the last four decades (1982–2021) using the ClimPACT2 software. Daily gridded (0.25° × 0.25°) maximum (TX) and minimum (TN) temperatures from the ECMWF-ERA5 reanalysis dataset were used to compute these heat wave (HW) aspects. The HW aspects were derived in ClimPACT2 using the Excess Heat Factor (EHF), the 90th percentile of TX (TX90), and the 90th percentile of TN (TN90), all based on the reference climate period of 1982–2011. The results showed that the decadal sum and anomaly of the five HW aspects increased gradually during the last four decades (1982–2021). The three indices showed that the maximum decadal sum of HWN (42 events), HWF (255 days), and HWD (145 days) occurred in the last decade. Additionally, the last decade has the maximum decadal sum of HWM (175–463 °C) and HWA (189–471 °C) as derived from TX90 and TN90, which is confirmed by EHF, with ranges of 7–58 and 15–185 °C², respectively. Finally, the periods 2015–2021 and 1984–1986 recorded the highest and lowest values of annual HW aspects, respectively, across the study period.

This work aimed to study the synoptic evolution and dynamics of the dust activity associated with the desert cyclone occurring over North Africa and the Arabian Peninsula on 4–8 April 2007 based on ECMWF analysis (ERA5) data. This desert cyclone formed over North Africa (Algeria) in the lee of the Atlas Mountains in response to a powerful upper-level trough transporting cold air into northern Africa coming from high latitudes. The development of the cyclone was initiated when the contrast in temperature between the Mediterranean Sea and northern Africa (the desert) was strong, which increased the meridional temperature gradient. The isobaric vorticity analysis illustrated that the strong advection of positive vorticity and warm air ahead of the cyclone triggered cyclogenesis and low-level jet (LLJ) formation. The strong LLJ maintained the development of the cyclone inside the area of baroclinicity at a low-level. The horizontal divergence of 700 hPa level covered the region downstream of the cyclone trough and is coupled with the lower-level convergence. The study of frontogentical function concluded that the first stage of cyclogenesis is associated with frontogenesis working at the initial front of the cyclone. The vertical motions are then dominated by the direct transverse circulation with the ascent of the warmer and descent of the colder air. The mass transport within the circulation causes pressure falls along the surface front connected with convergence leading to the production of vorticity. The dust emissions linked to the cyclone during its duration and along its path were also investigated.

This paper aimed to investigate the impact of Red Sea topography and water on the development and rainfall of a case of cyclogenesis occurs over Saudi Arabia during the period 16–18 November 2015 using the Weather Research and Forecasting (WRF) model. The WRF Control Run (WRF-CR) experiment was performed with presence of actual topography and surface water of the Red Sea, while the other three sensitivity experiments were carried out without (i) Red Sea Topography (NRST), (ii) Red Sea Water (NRSW), and (iii) Red Sea Topography and Water (NRSTW). The simulated rainfall in the control experiment depicts in well agreement with Tropical Rainfall Measurement Mission (TRMM) rainfall estimates in terms of intensity as well as spatio-temporal distribution. Results demonstrate that rainfall intensity and spatio-temporal distribution significantly changes through each sensitivity experiment compared to the WRF-CR, where the significant variation was found in the NRST experiment. The absence of topography (NRST) leads to formation of strong convergence area over the middle of Red Sea which enhanced uplift motion that further strengthened the low-level jet over Red Sea and the surrounding regions, which enhanced the moisture and temperature gradient and created a conditionally unstable atmosphere that favored the development of the cyclonic system. The absence of Red Sea water (NRSW) changed rainfall spatial distribution and reduced its amount by about 30–40% due to affecting of the dynamics of the upward motion and moisture gradient, suggesting that surface fluxes play an important role in regulating the low-level moist air convergence prior to convection initiation and development.