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Miserly monsoon drives up mercury

This monsoon, the city has remained high and dry. Blame the unfavourable trough line and deviation of low-pressure belts for the scanty rain and the resultant heat.

The city has experienced just 159mm rainfall between June 1 and July 16 — the second lowest in the period over the past 10 years. In 2009, the city recorded just 158mm rainfall during this period.

The monsoon usually picks up in the city from the first week of July. But this year, it has remained dormant till date. According to records with the Met department, the city recorded 37mm rainfall between July 1 and 15 — the second driest period in the past 10 years. In 2011, the rainfall was 32mm in the same period.

Weathermen have attributed the scanty rainfall in the city to the unfavourable position of the monsoon trough line and the deviation of the low-pressure area to the south from its normal course.

“The eastern tip of the monsoon trough line extended up to Jharkhand over the past three weeks. It normally extends up to the foothill of Himalayas passing through Bihar, causing uniformly good rainfall across the state, including Patna. States north of Odisha, including Bengal, Jharkhand, Assam and Bihar, have experienced deficient monsoon till mid-July this year because of the unfavourable position of the trough line,” said Ashish Sen, director, India Meteorological Department, Patna.

Low-pressure troughs — another key factor of monsoon rainfall — also have bypassed the state this year. “Monsoon rainfall in south and central Bihar, including Patna, mostly depends on low-pressure areas originating from the Bay of Bengal. Normally, two-thirds of the total low-pressure areas originating from the Bay of Bengal in the monsoon follow the route of Bengal-Jharkhand-Bihar. The remaining one-third goes southward via Odisha-Chhattisgarh. But this year, all the five low-pressure areas have gone southward, leading to scanty rainfall in south and central Bihar.

The distribution of monsoon rainfall across the state has been uneven this year. Meteorologists said the north Bihar, especially the north-eastern districts such as Purnea, Katihar and Kishanganj, mostly receive normal or above normal rainfall because they are at the foothills of Himalayas. “The north-eastern parts of the state receive good rainfall even if there is a monsoon lull across the country. The high-level of moisture content in the lower level of the atmosphere collides with Himalayan mountains in this region, leading to uniformly good rainfall throughout the monsoon,” said Sen.

Satellite images on Tuesday evening did not show any cloud cover over Bihar. Weathermen claimed that the dry spell in the city would last at least for four more days. The situation would be the same in the north Bihar districts as well. “The fifth low-pressure area of the season lying over Odisha at present is expected to last for another four days, obstructing the moisture incursion to Bihar. It would reduce the intensity of rainfall in north Bihar as well. The rainfall in the city and other districts in south and central Bihar can be expected only after this low-pressure subsides,” said Sen.