This study analyzes the spatiotemporal variations of seasonal Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue (DB) AOD at 550 nm from the Aqua satellite over Saudi Arabia for the period 2002-2013. Satellite retrieved AOD is also compared with AERONET AOD over the Solar Village and KAUST station. The result of the seasonal AOD spatial distribution shows that the peak AOD value of 0.6 is observed over Hafr Al Batin, Riyadh, and the Rub Al Khali desert during spring, whereas the Gizan area shows the peak AOD during summer. In contrast, the autumn shows the peak AOD value of 0.5 over Dhahran and in the proximity of Jeddah, whereas Hafr Al Batin, Al Khafji, Al Jubail, and the Rub Al Khali desert show the peak AOD value of 0.4 in winter. Regression analysis shows the AOD increasing trends during spring, summer, and autumn (except for winter) over the entire Saudi Arabia. Over the Solar Village, the AOD increasing trends are also noted during spring and summer, whereas autumn and winter display the AOD decreasing trends. The AOD increasing trends are displayed in all seasons over KAUST. Hence, the AOD increasing/decreasing trends indicate that the number of dust storms either increases or decreases over these regions. Over the Solar Village, the correlation values for MODIS DB AOD versus AERONET AOD are 0.77 (spring), 0.62 (summer), 0.65 (autumn), and 0.75 (winter). Likewise, over KAUST, the correlation values for the same pairing are 0.85 (spring), 0.71 (summer), 0.81 (autumn), and 0.89 (winter). The incorrect aerosol model selection and imperfect surface reflectance calculation are responsible for reducing the correlation. Therefore, this study recommends that the DB algorithm can be used effectively to detect AOD over Saudi Arabia, which will further help to improve the MODIS DB AOD product utilizing the next version of the algorithm.

Madden-Julian Oscillation (MJO)-like disturbances with features similar to observations, although slightly weaker. Conclusions The Saudi-KAU CGCM ability to simulate the ENSO and the MJO suggests that it is capable of making useful predictions on subseasonal to seasonal timescales.

Purpose Urbanization may be the most measured form of permanent land transformation. Jeddah, the second largest city of Saudi Arabia, has witnessed an unprecedented rate of growth over the last 40 years. In cities like Jeddah, the rapid increase in population along with the consequent urban development may have impact on the environment. Methods Data from various sensors on the Landsat satellite have been used to monitor urban expansion in Jeddah for 41 years. For this study, eight images, three each from the Multispectral Sensor and Thematic Mapper as well as two from the Enhanced Thematic Mapper Plus between the years 1973 and 2014, were acquired and analyzed to monitor the spatial and temporal changes in Jeddah. Information on land use with regard to vegetation, bare soil, sand, urban area, rocks, road/ concrete structures, and water bodies was extracted. ResultsThe results of our analysis show that urbanization in the study area increased by 109.76 km 2 for the period 1973-2014, and in some areas has altered the structure and spatial pattern of the city. However, analyses of the impact of urban growth on temperature variations show that urban sprawl has a minimal impact on land surface temperature in the city. Conclusions This study indicates that the most efficient way to determine the environmental impacts of urban sprawl is through the use of satellite data.

ABSTRACT:The synoptic characteristics and statistical variability of seasonal dust over southwestern Saudi Arabia are studied for the period from 1979 to 2006 using the aerosol index (AI) from the Total Ozone Mapping Spectrometer (TOMS) satellite, dust observations from surface stations, and meteorological data from the National Center for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) reanalysis data set.The seasonal AI distribution indicates that approximately 80% of each year was dusty and that most of the dust occurred during hot months. In addition, the surface observations of the dust types show that the stations with the largest number of dust observations throughout the year were close to the desert, except during the summer, when the stations near the Red Sea had the largest number of dust observations.The synoptic forces that influenced the dust cases were the relative positions of high-pressure systems (Azores or Siberian) and low-pressure systems (Sudan or Indian), alongside their interactions. The relative positions of the atmospheric systems are highly pronounced at a pressure level of 850 hPa; at this pressure, the systems are oriented from north (anticyclonic system) to south (cyclonic system), turn anticlockwise to become oriented from west (anticyclonic system) to east (cyclonic system) during the summer, and then turn clockwise during the winter. Moreover, the interaction of the atmospheric systems influences the wind pattern of the seasonal composition over the southern Arabian Peninsula, which produces an anticyclonic wind pattern during winter, a cyclonic wind pattern during spring, a northerly/northwesterly wind pattern during summer and an anticyclonic wind pattern during autumn.The dust sources changed because of the relative positions of these atmospheric systems, in which the 'Toker Gap' Sudan was the summer/autumn dust source, and the 'central and eastern' Arabian Peninsula was the winter/spring dust source.

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