Wednesday, August 12, 2009

Bangalore has had no deficit in rainfall

Bangalore has had no deficit in rainfall

El Nino effect reduced the rainfall caused by southwest monsoon

Bosky Khanna

Even though the temperature in the city remains pleasant, many are of the opinion that southwest monsoon showers have mostly eluded Bangalore, thus resulting in a deficit of rainfall. But Dr A Muthachami, director, Indian Meteorological Department, Bangalore, said that south and coastal Karnataka, including Bangalore, are better positioned but it is the north-interior Karnataka that is suffering from real deficit of rainfall. He spoke to Bosky Khanna on the issue.

With the monsoon season almost nearing its end, is Bangalore experiencing a deficit in rainfall?
There is still one-and-a-half months left for the southwest monsoon to cause rainfall in the city. Though Bangalore is experiencing lesser rainfall this year when compared to last year, there has not been any deficit. The normal rainfall for the month of June is 8 cm but Bangalore has received almost 20 cm of rainfall. For July, the normal rainfall is 12 cms and Bangalore received 2 cms. For August, the normal rainfall is 16 cms and Bangalore till date has experienced 4 cms with 20 days still remaining. So by the end off August, Bangalore will have received near to normal rainfall.

Why is it that when the other parts of the state receive heavy rainfall, Bangalore does not and vice versa?
Bangalore is located in the rain shadow region of Western Ghats and when the wind blows from the west, it gets obstructed by the hills. Thus the moisture laden wind blows to the windward side of the ghats, causing heavy rainfall in the coastal region and ghat areas and the rainfall in Bangalore is limited. But during weak monsoon condition when there is ample sunshine, the lower levels of the atmosphere are warm which gives rise to convection current. The air goes up leading to the formation of clouds, resulting in rainfall in the city.

Which parts of Karnataka have been worst hit by scarce rainfall?
Most parts of north-interior Karnataka have received deficit rainfall (-20%). Rainfall has been very scarce in Bidar, Gulbarga, Bijapur and Raichur districts. From June till August (till date), Bidar has received 148 mm of rainfall as against the normal of 399 mm. Bijapur has received 113 mm as against the normal of 203 mm. Gulbarga has received 148 mm as against the normal of 332 mm and Raichur has received 89 mm as against normal of 242 mm.

Will the present rainfall pattern have an effect on the forthcoming northeast monsoon conditions?
It is ideally seen that when monsoon is affected by the EL Nino phenomenon — severe atmospheric and oceanic disturbance in the Pacific Ocean — the after effects are seen in the northeast monsoon conditions. India, including Karnataka, experienced the EL Nino effect which reduced the rainfall during southwest monsoon. This will be made up in the northeast monsoon from October to December, when the state will receive good rainfall. But the quantity cannot be forecast now.

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