Comparing the decade 1997-2006 to the decade 1967-1976, average annual rainfall has decreased by 11.7 per cent – from 570.81 mm in the earlier period to 503.89 mm in the later, the National Statistics Office reported yesterday, World Meteorological Day.

A news release issued on the day took a decennial approach to the five main climatic parameters: rainfall, air temperature, hours of sunshine, humidity and wind.

Taken at 10-year intervals, 1976 was by far the wettest of the four, while 2006 was characterised by a greater quantity of rain than both 1986 and 1996. January 2006 was the wettest of its four counterparts under review, while February 2006 was the driest.

At 19.35 degrees Celsius, the mean annual air temperature was highest last year when compared to the three other years under review. This represented a rise of two per cent when compared to 1996 and of eight per cent when compared to 1976.

Likewise, average daily hours of bright sunshine per year in 2006 showed an increase in comparison to the three other years.

Conversely, mean annual humidity, which was calculated at more or less 83 per cent in 1976, 1986 and 1996, fell to 78 per cent in 2006. Humidity levels in these years fell noticeably in May, June and August and, to a lesser extent, in September and November.

Wind speed is the rate at which the wind blows, measured in knots. Of the four years under review, the wind in Malta blew strongest in 1976, at an average of 9.2 knots.

Average annual wind speed was lowest in 2006, less than both in 1976 and 1996 by around 20 per cent.