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.

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.

In this study monthly, seasonal and annual values of temperature have been analyzed over Egypt during the period 1960-2016. It is found that the temperature is a function of latitudes where the values of temperature increase gradually from north to south. The trend analysis illustrates that there is a significant increase in seasonal and annual values of temperature over Egypt. The annual wave dominates at all stations; its amplitude for the northern stations is smaller than those for the southern stations. The analysis of the spatial distribution of the monthly average of temperature (1960 – 2016) for each month of the year has been made. It is found that Latitudinal gradients in temperature are strong in winter and spring seasons with particular increase over the north of Egypt due to the effect of mid-latitude travelling depressions from west to east over Egypt. The climatological distribution of temperature throughout the months of the year reflects the effect of meteorological factors and pressure systems affecting the weather and climate in the study area. The warmest areas in summer are the middle and the south eastern parts of Egypt.

This research aims to study and discuss the diabatic heating at the different isobaric levels during interaction between mid-latitude (southward extension of 500 hPa trough) and extra-tropical (northward extension of Sudan monsoon low) cyclones over Egypt and east Mediterranean during the period 3-6 November 2015. Also, relationship between diabatic heating and kinetic energy generation were illustrated. The cyclogenesis of this case is associated with maximum heavy rainfall over northern part of Egypt during growth stage (4-5 November). Throughout the life cycle of cyclone, the vertical advection term ((T/P)) is the significant term that plays an important role in diabatic heating calculation and opposite to adiabatic term (-(/Cp)). The largest contribution of the horizontal cold advection occurs during the pre-storm stage, while the largest warm advection occurs during the growth stage. Finally, it is found also that the area of diabatic cooling (heating) is synchronized with destruction (generation) of kinetic energy.

Ozone variation during a case of cyclogenesis

The variability of ozone over Egypt has been studied in this work. Higher values of coefficient of variation (COV) at eight stations occur at winter while lowest values occur at summer. The COV is function of latitude in annual, winter and spring where it decreases gradually from the north to south of Egypt. The trend analysis of ozone over the eight stations indicates negative trends over northern stations for both annual and seasonal time series with the greatest one at winter. The horizontal distribution of ozone trend values is negative over all Egypt in winter while it positive over middle and south Egypt in the other seasons. The long-term variability of the behavior of the annual ozone shows positive trend values in ozone are the dominant features during the period 1979- 1989 at the most stations. Negative trend values in ozone are the dominant features during the period 1990- 2014 at all stations. The Mann–Kendall test confirms that there is an abrupt change towards decreasing of ozone occurs in 1981, 1984, 2012, 1999, 2000, 1998 and 2010, while a change towards increasing of ozone appears in 2006, 2014, 1993 and 1989.