Question

give reason why there is a seasonal shifting in pressure belts

Answer 1

The earth resolves on its orbit round the sun in 365 days. The earth is inclined on its axis at an angle of 23.5 degrees. Thus, the relative position of the earth with the sun changes. In consequence, the position of all the pressure belts change with the northward and southward migration of the sun.
Thus there is a seasonal shifting in pressure belts.