Abdallah Abdeldym

On April 4-8, 2007, a desert depression swept across North Africa and the Arabian Peninsula, bringing sweltering temperatures, fierce winds, and vast dust clouds that significantly impacted life in the region. This article gives a diagnostic investigation of this Saharan dust storm utilizing diabatic heating (DH) and kinetic energy budget in isobaric coordinates. It also looks at the connection between kinetic energy (KE) generation and DH. Horizontal temperature advection plays the dominant role throughout the depression's life cycle. While cold advection reigns supreme during the first two times, warm advection takes the lead during peak development. The term for adiabatic temperature changes and the vertical advection term have opposing effects. The contribution of the local temperature term to the change in DH is relatively minimal. All terms, excluding the local one, generally decrease in magnitude as they ascend from lower to upper layers. Interestingly, while the peak values for all other terms occur at the surface (1000 hPa), the local temperature change reaches its maximum at higher levels. The top layers contribute the most to KE. The temporal variations in the kinetic energy budget terms track the storm's life cycle. Peak intensity coincides with maximal generation, flux divergence, and dissipation, reflecting vigorous energy exchange. These terms decline during decay, mirroring the waning energy dynamics. Cross-contour flow is the key driver of KE generation, particularly during a depression's growth stage. The analysis of DH and KE generation reveals a strong association between their spatial patterns. The movement of heating or cooling regions closely mirrors the movement of zones of positive or negative generation, and both exhibit a clear connection to the depression's movement.

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.

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.

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.

The aim of this work was to study the variation in the total ozone column amount (TOC) during the life cycle of the tropical cyclone (TC) that occurred over the northwest Indian Ocean from 14 to 25 October 2008. This goal was achieved through examining the behavior of the tropical cyclone tilt under vertically varying background flows in association with the cyclone development. Thus, the vertical wind shear (VWS) was estimated as one of the most important dynamical parameters related to TC formation and intensity changes. Moreover, we estimated the variations in the daily values of TOC during the period of cyclone activity. We found that the magnitude of VWS increased during the growth period, and VWS weakened during the decay period. Anomalies of daily TOC were found to reduce steadily before and during the cyclone formation, followed by an increasing trend after the dissipation of cyclone. It was also found that during the development of the tropical cyclone, an outflow developed in the upper levels, having high velocities that extended beyond the tropopause up to the lower stratosphere. As a result, the lowest value of TOC during the tropical cyclone was due to a large amount of injected water vapor from the troposphere into the stratosphere through the convection processes. This was mostly photo-dissociated into OH and atomic O by deep solar radiation in the upper and lower stratosphere, leading to a severe reduction in stratospheric ozone.

This paper aimed to study the variation in the total ozone column amount (TOC) during the life cycle of the tropical cyclone (TC) that occurred over the northwest Indian Ocean in October 2008. The characteristics of TC tilts with vertically varying background flows were inspected preliminarily also in the current study. The vertical wind shear (VWS) was estimated as one of the most important dynamical parameters of the large-scale environment related to TC formation, structure, and intensity changes. It is found that the magnitude of VWS increased during the growth period, meanwhile, VWS weakened during the decay period. Anomalies of daily TOC have been calculated and found related to the strengthening of the cyclonic system. During the development of the tropical cyclone, an outflow develops in the upper levels with high velocities that can extend beyond tropopause up to the lower stratosphere. As a result, the lowest value of TOC during the tropical cyclone was owing to a large amount of injected water vapor from the troposphere into the stratosphere through the convection processes which was mostly photo-dissociated into OH plus atomic O by deep solar radiation in the upper and lower stratosphere leading to severe reduction of stratospheric ozone