Answer:
These high mountains and plateau block rains and moisture that would come from the monsoons in the India ocean.
Step-by-step explanation:
Himalayas mountains and Tibetan Plateau block most of the rains coming from the south and cause desert in the northern Himalayas.
Himalayas mountains peak up to 20,000 feet and have a large stretch covering China, India and Pakistan. The lenght and height is enough to encourage changes in the immediate environment.
On the other hand Tibetan plateau is not uniformly flat, it has some high mountains and low river basins.
Together the two cause barriers to moistures that would have flourished the northern Himalayas