Complex sentence: Precipitation generally decreases from east to west with increasing distance from the Bay of Bengal, source of the summer monsoontata adabiatic effects as rising air masses cool and drop their moisture content on windward slopes, then warm up as they descend so relative humidity drops.
Split into simpler sentences: Precipitation generally decreases from east to west with increasing distance from the Bay of Bengal, source of the summer monsoon. This pattern is modified by adabiatic effects as rising air masses cool and drop their moisture content on windward slopes, then warm up as they descend so relative humidity drops.