Which of the four geographical regions (northern region, southern region, northwest region and Qinghai-Tibet region) is Yumenguan talking about?

Select the northwest region. Reason: Spring breeze is not enough to cross Yumen Pass (spring breeze means that warm and humid air cannot cross Yumen Pass, thus excluding northern and southern regions and Qinghai-Tibet region: Linzhi region in Tibet is actually a subtropical maritime monsoon climate affected by warm and humid air in the Indian Ocean). There is also the ancient Yumen Pass, which is located in the northwest border. Remember to choose me to be satisfied.