ساينس الصف الثاني الاعدادي – الفصل الدراسي الاول ساينس تانية اعدادي – ترم اول In This part we will study : Atmospheric envelope Atmospheric envelope of the Earth It is a gaseous envelope rotating with the Earth around its axis and it extends for about 1000 km above sea level. Atmospheric pressure It is the weight of air column of an atmospheric height on a unit area ( 1 m2 ). Normal atmospheric pressure It is the atmospheric pressure at sea. level and it equals 1013.25 mb . The change of atmospheric pressure with the change in height above sea level • As the elevation (altitude) above sea level decreases , the atmospheric pressure increases due to increasing the length of air column. • As the elevation above sea level increases , the atmospheric pressure decreases due to decreasing the length of air column . Isobar: It is the curved lines that join the points of equal pressure in atmospheric pressure maps. • The center of low atmospheric pressure areas is represented by “L” . • The center of high atmospheric pressure areas is represented by “H” . • The wind moves from the areas of high atmospheric pressure to the areas of low atmospheric pressure . لمتابعة مستر احمد الباشا وكل ما يخص الساينس : جروب الفيس بوك http://bit.ly/2Of1mcN صفحة الفيس بوك http://bit.ly/2Gq5xMo بالتوفيق مستر احمد الباشا