Why did Shandong have more rain before 1990s and less rain in recent decades?

This is mainly because of global warming and abnormal climate, and now it can only snow a little, mainly because the water container that has been in the Pacific Ocean is dry, but it is in the westerlies. The drier the westerlies are, of course, he won't be in too much water vapor. Recently, the northwest of Shandong Province is more serious, and the clouds never come, and the dark clouds collapse when they move here. This is a true story. Once here, it's gone, either in Hebei or around the Yellow River. I'm not a meteorological major, so I can't know the details.