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9月中下旬,湖南大部分地区先后进入初秋季节,出现“秋风阵阵凉”、“一场秋雨一场寒”的天气。自秋分以后,太阳直射点逐渐南移,加之昼短夜长,北半球获得的热量不断减少,特别是高纬度地区,空气变得愈来愈冷,气压升高,形成一个深厚而广阔的冷气团,气象上称它为极地高压,也就是我们常说的西伯利亚冷高压。到了秋末时节,南方暖湿气团逐渐南退,北方冷气团乘机南下,其前沿与暖湿气团常在湖南上空交锋,形成降水,其雨量较
Late September, most parts of Hunan have entered the early autumn season, there “autumn cool”, “a cold autumn,” the weather. Since the autumn equinox, the direct point of the sun gradually moved southward. In addition to the short day and long night, the heat gained in the northern hemisphere has been declining. Especially in the high latitudes, the air becomes colder and colder with the pressure rising to form a deep and broad air- Meteorologically referred to as the polar high pressure, that is, we often say that the Siberian cold. In the late autumn season, the southern warm and humid air mass gradually southward, the northern air mass air south, its front and warm air mass often confrontation over Hunan, the formation of precipitation, the rainfall is more