التباين المكاني و الزماني لغطاء السحب في مصر خلال المدة (1960-2017)‎

الملخص EN

Assessing spatial and temporal variability of cloud cover is of particular importance for understanding climate and its processes.

This study aims to assess spatiotemporal characteristics of cloud cover in Egypt over the period 1960-2017.

Our analysis was based on the monthly gridded data derived from the CRU TS dataset (V.3.26), provided at 0.5° grid interval by the Climate Research Unit (CRU), University of East Angelia, UK.

Changes in cloud cover were assessed using the least squares regression model, while their statistical significance was tested using the non-parametric Spearman's Rho statistic.

The Principal Components Analysis (PCA) was employed to define the dominant spatial patterns of cloud variability in Egypt.

Also, we assessed the links between changes and variability of cloudiness and those of other relevant climatic variables (e.

g.

maximum and minimum air temperatures, diurnal temperature range [DTR], and rainfall).

Results suggest that the amount of cloud cover was mainly higher during spring and winter, especially in the Egyptian Delta, the Nile Valley and its neighboring regions.

Trend analysis indicates a statistically significant decrease in cloud cover over the study period.

Results demonstrate a statistically significant negative feedback between cloud cover and maximum and minimum air temperatures.

For DTR, this dependency was highly variable over space and time.

In contrast, the association was positive and statistically significant between cloud cover and rainfall.

The findings of this study can contribute significantly to better understanding of cloudiness, its variability and thus more reliable diagnosis of atmospheric and hydrological cycles and their possible impacts in Egypt.