It now appears that the country may have endured the hottest year in 2010 in recorded history even as cold wave to severe cold wave conditions persist in north and north-west concurrently.
Mean annual temperature for the country as a whole during the last year was +0.93 deg Celsius above the 1961-1990 average.
WARMEST YEAR
It was slightly higher than that of the year 2009, making 2010 as the warmest year on record since 1901, an annual climate summary issued by India Meteorological Department (IMD) said on Friday.
Abnormally warm conditions (heat wave) prevailed over major parts of the country during March and April months claiming more than 300 lives.
The Pre-monsoon season was the warmest since 1901 with mean temperature being 1.8 deg Celsius above normal.
It is also found that the decade 2001-2010 has been the warmest decade with a temperature anomaly of 0.40 C.
LA NINA OUTLOOK
The annual total rainfall for the country as a whole was normal during 2010 with actual rainfall of 121.5 cm against the long period average (LPA) of 119.7 cm.
Monsoon season contributes about 75 per cent of total annual rainfall for the country as a whole. Seasonal rainfall during 2010 was 102 per cent of its LPA.
Significantly, the IMD says that probabilities for La Nina conditions are 94 per cent or more through the January-February-March, 2011.
These conditions, which are considered monsoon-friendly, are forecast to not drop to below 50 per cent until the April-June season, the IMD outlook said.
Analysing the report, sources in the Ministry of Earth Sciences said the hot summer and the eventful wet to wetter season were not confined to India alone.
SYSTEM LOCK-IN
While parts of Europe experienced flooding conditions during the period under reference, Russia underwent the fiercest drought in living memory.
A warming anomaly materialised over India as a semi-permanent ridge (high-pressure system with dry, sinking air in contrast to low-pressure systems with moist, rising air) locked into position across the northwest border.
This had effect of shutting out the calming influence of western disturbances, allowing the hot climes to anchor themselves over the region.
Lesser movement of western disturbances, however, worked to the advantage of the country with the monsoon circulation spared of having to run into the opposing flows associated with western disturbances.
According to sources, this is what helped bring rains in huge quantities over Rajasthan and Gujarat during the monsoon.
Death toll due to heavy rains/floods during the monsoon was more than 500, mostly from northern and northwestern parts, the IMD report said.
A cloud burst in early hours of August 6 in Leh claimed more than 150 lives and more than 500 people are missing.
It is now a given that the atmosphere has warmed up to unprecedented levels, the sources explained. A warmed up atmosphere has the capacity to hold correspondingly larger amount of moisture.
Since the atmosphere cannot hold the moisture for too long, it cannot but precipitate. The air masses transport the moisture from areas of higher pressure to those of lower pressure.
Depending on locally evolving favourable conditions, clouds build up and the moisture gets precipitated.
The spatial distribution is not equal at any given point of time, with seasonal ‘hot spots' receiving the largest precipitation.
The monsoon region offers itself up as a ‘hot spot' and the weather gets amplified over disparate locations depending on extra moisture load in the air mass.
These phenomena are revealed in their gigantic size and scale in the deep ocean basins of the Pacific and the Atlantic where tropical storms and cyclones sustain themselves for up to a week.
Not to the same extent in the rather ‘closed basins' of the Arabian Sea or the Bay of Bengal where these systems can live up to three or four days at the most.
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