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(1)我国北方干旱产生的自然原因和人为原因有哪些? _________________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________(2)据多年统汁,图中①②两地区旱灾发生的季节不同,试分析两地区旱灾季节差异的原因。 _________________________________________________________________________________________(3)这次旱灾可能对我国带来哪些不利影响? _________________________________________________________________________________________