What do the following indicate in a barometer regarding weather — (a) gradual fall in the mercury level, (b) sudden fall in the mercury level, (c) gradual rise in the mercury level ?

(b) If the barometric height at a height suddenly falls, it means that the pressure at that place has suddenly decreased which indicates the coming of a storm or cyclone.

(c) A gradual increase in the barometric height means that the moisture in air is decreasing. This indicates the coming of dry weather.