Annual precipitation decreasing

Islamabad

Annual precipitation now averages to less than 250 mm, decreasing from north to south but in all more than three-fourth of the country has less than 300 mm annually while about 7 per cent of the country, mostly mountain slopes, has more than 500 mm.

A working paper compiled by the climate change ministry stated about 20 per cent of the total area has less than 125 mm total annual rainfall, with a high variability as a rule and great climatic differences prevail from the northern mountains down to the seacoast in the extreme south, but the country's general climatic character is arid.

It said on the basis of annual rainfall maximum increase in precipitation has been observed at Rawalpindi while the minimum has been observed at Faisalabad and no city in the Punjab has shown the negative trend.

Water whether in liquid or solid form falling from the clouds is termed as ‘precipitation.’ That is rain, snow, hail, sleet and fog and it is the yielding component of a hydrological cycle. It is due to lower temperatures vapours combine to make droplets or ice crystals heavier and heavier in clouds, which finally drop in the form of precipitation when gravity overcomes buoyancy.

The time series of precipitation over this region for the last 109 years shows slightly increasing trend but not a well-marked change when compared with the centurion scales.