x Abu Dhabi, UAEFriday 28 July 2017

Weatherman says lack of data is a big handicap

Lack of long-term records makes UAE's weather hard to predict says Dubai-based meteorologist.

Sign of the times? There was an unusual snowfall on Jebel Jais in Ras al Khaimah in January.
Sign of the times? There was an unusual snowfall on Jebel Jais in Ras al Khaimah in January.

The lack of historical data makes predicting the weather - at best an inexact science - particularly difficult in the UAE. While last month the heaviest snow in generations fell in Ras al Khaimah, that does not mean the Gulf can expect a milder than usual summer. Or a hotter one, either, said Dave Thomas, a meteorologist who has 25 years of experience in the region. Mr Thomas, senior manager of meteorological services at Dubai International Airport, said part of the difficulty in making accurate long-range predictions was that unlike the West, which has data records stretching back several centuries and highly sophisticated climate modelling systems in place, the UAE has records covering a considerably shorter time, which makes identifying long-term trends more difficult.

"Looking at the data that is available, there is a trend for increasing mean temperatures but that doesn't imply that this summer is going to be the hottest," he said. "People immediately jump to the conclusion that this will result in the next summer producing the highest temperatures ever but it's rare that we break temperature records during the summer months." The rise in the mean annual temperature is at least in part attributable to where it is recorded. Weather data has been collected at Dubai airport since 1967, but during that time the airport has become much bigger.

"Thirty years ago, Dubai airport was outside the city. The location hasn't moved but the amount of tarmac and concrete both at the airport and in the surrounding area has increased dramatically," he said. The pavement acts as a more efficient solar sink than the desert that was there before, absorbing heat during the day and releasing it at night. "It means the minimum temperatures are now considerably higher than previously, although this heat island effect is not entirely responsible for these changes," Mr Thomas said. It has been more than 14 years since a monthly minimum temperature record has been set at the airport.

Even the maximum temperature was not straightforward because high temperatures and comfort levels were at times inversely related. "A temperature of 45°C can be a lot more comfortable than 40°C as the higher temperature will be associated with much lower humidity," he said. "For the temperature to reach 45°C or above the humidity has to be lower. "From one day to the next, the amount of energy reaching the Earth is pretty much the same during the summer, in the absence of clouds. The heat from the Sun warms the earth and the earth warms the air. Water has a very high specific heat capacity and therefore if the air is humid it takes more energy to raise the temperature through each degree. Therefore, temperatures will not be as high if conditions are humid."

jhenzell@thenational.ae