Heat wave melts records | Daily News


 

Heat wave melts records

Last year was the hottest year of the decade for some parts of Sri Lanka, while it was the second hottest year after 2016 for most of other parts of the country. The annual mean temperatures calculated from the data taken from 22 weather stations across the country show that 2019 was the hottest year of the decade for nine areas covered by those stations, namely Mannar, Vavuniya, Puttalam, Kurunegala, Katugastota, Ratmalana, Badulla, Moneragala and Polonnaruwa.

Of them, last year’s annual mean temperature in Badulla and Kurunegala matched the record set in 2016, while the rest set new records. Last year was the second hottest year for Jaffna, Anuradhapura, Batticaloa, Katunayake, Colombo, Nuwara Eliya, Ratnapura, Galle, Hambantota and Pottuvil.

Both the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA) of the United States, following independent analyses, last month announced that Earth’s global surface temperatures in 2019 ranked the second warmest since 1880. The year 2016 has been named the warmest year on record.

Above-average temperatures

As Sri Lanka has different altitudes, the temperature varies accordingly, and therefore coming up with an annual mean temperature for the entire country has been irrational. At the same time, the Meteorological Department does not have its stations to cover six districts, namely Matara, Matale, Kegalle, Kilinochchi, Mullaitivu and Kalutara.

However, last year’s annual mean temperature was higher than the 2010 – 2019 long-term average in all areas of the country, according to the data. Last year’s highest annual mean temperature of 29.2 degrees Celsius had been reported in Trincomalee and Polonnaruwa, while it was 29 degrees Celsius in Vavuniya, and 28.9 degrees Celsius in Mannar, Puttalam and Ratmalana. Trincomalee was an exception when studying the last decade’s data, because its highest annual mean temperature of 30.1 degrees Celsius had been recorded in 2011.

The lowest annual mean temperature of 16.4 degrees Celsius came from Nuwara Eliya as usual. The Meteorological Department takes hourly temperature readings to calculate the daily mean temperature of an area. To calculate the monthly and annual mean temperatures, it adds up all of the temperatures and divides the figure by the total number of days.

The annual mean temperature levels have varied over the decade, but in general, there is a rising trend in many parts of the country. Compared to 2010, the annual mean temperatures in Kurunegala and Katugastota had risen by 1.1 and 1.2 degrees Celsius respectively in 2019. The mean temperature in Polonnaruwa which was 28.3 degrees Celsius in 2011 had risen to 29.2 degrees Celsius (by 0.9 degrees Celsius) in 2019. In the same way, the mean temperature of Puttalam had risen from 28.1degrees Celsius in 2010 to 28.9 degrees Celsius in 2019 and the mean temperature of Moneragala had risen from 27.2 degrees Celsius in 2011 to 28 degrees Celsius in 2019.

Hambantota temperatures show a negative trend with a decrease by 0.2 degrees Celsius in 2019 compared to 2010. The mean temperature in Colombo had increased by 0.2 degrees Celsius from 28 degrees Celsius in 2010 to 28.2 degrees Celsius in 2019. However, data collected in several decades would be required for steadier conclusions on temperature rise.

Extreme weather rising

Speaking to the Daily News, Meteorological Department Director Ajith Wijemannage, who heads the Data Processing, Aviation, International Affairs and Training Division, said the consecutive days without rain or drought periods with which we are familiar, had also increased lately compared to the past.

Last year Sri Lanka faced a long spell of dry weather following below-average rains in the first half of 2019. The country was hit by dry and moderate drought conditions in pockets of the North, North Western, North Central, Uva and Eastern Provinces. As of September 25 last year, more than 780,000 people were affected by drought according to the Disaster Management Centre (DMC). The Northern and Eastern Provinces saw the highest number of affected people. At that time, we were just recovering from a severe drought in 2016 – 2017, that affected over a million people and was said to be the worst in 40 years.

Wijemannage, who has over 22 years’ experience, pointed out that the trend has been that we cover the annual average rainfall, but with less and less number of rainy days. In other words, the intense rainfalls had been increasing lately.

“The annual average rainfall in Sri Lanka is 1,861mm. We have come up with this figure after analysing 30 years of rainfall data. Last year too we covered this average amount, but the worrying factor is that the number of rainy days has been gradually decreasing over the past years. Nowadays, we often get heavier rainfall causing the risk of floods and landslides. We cover the annual average with less number of rainy days,” he explained.

Declining rainy days

The past decades’ data of the number of rainy days draw a negative trend line bolstering the above observation. Compared to 2010, the number of rainy days in Nuwara Eliya and Ratnapura had decreased by 77 days last year.

The number of rainy days in Moneragala had declined by 63 days from 187 days in 2011 to 124 days in 2019. This number in Kurunegala, Trincomalee and Katugastota had decreased by 55, 51 and 48 days respectively in 2019 compared to 2010.

The yearly records of the Mattala weather station, which was established only in 2013, show an increase of rainy days from 111 days in 2013 to 131 days in 2019. The number of rainy days in Hambantota had also increased by three days in 2019 compared to 2010. Except these two stations, all other stations indicate a decrease of rainy days.

It is seen that comparatively Ratnapura, Ratmalana, Galle and Colombo have a higher number of wet days, while Mannar, Jaffna, Trincomalee, Vavuniya, Anuradhapura and Polonnaruwa have more dry days. He said the country’s annual average rainfall varies from about 1,000mm in the driest zones in the northwest and southeast of the island to over 5,000mm in some areas on the western slopes of the central highlands.

According to statistics updated till November, Sri Lanka had received 1,729mm of rainfall in 2019. The data of December were yet to be fed into the system, and the final figure would exceed the annual average given that many parts of the country experienced heavy rainfall leading to floods and landslides in December. The DMC reported that over 71,000 people were affected by the heavy rains, floods and landslides in 13 districts as at December 25. In the last decade, the country’s highest annual rainfall of 2,136mm was in 2014, and the lowest annual rainfall of 1,351mm was in 2016.

Wijemannage said the Department currently has about 500 rain gauge stations throughout the country, and rainfall is measured daily at 8.30 am at these stations. He however pointed out that about 400 rain gauge stations are concentrated in the southwestern part of the country, while the number of stations in the northern and eastern parts of the country is limited. He said, therefore, interpolation is used to estimate values at other unknown points through a geographic information system (GIS).

Cyclones in Bay of Bengal

When it comes to thunder and lightning, Wijemannage said there has been an increase of thunder days over the years, but the fatalities and property damage have been brought down as people are now more aware of the precautions to be taken. The data showed that the number of thunder days in 2019 had increased in 13 areas covered by the 22 weather stations in comparison to 2010, while this number showed a decrease in the remaining nine areas.

There had been 156 thunder days in Ratnapura, 135 in Colombo and 132 in Katunayake last year. Another factor brought out by Wijemannage was that the number of cyclones in the Bay of Bengal has shown a decrease lately, but that their intensity has grown leading to more damage. The cyclone season for Sri Lanka extends from November to January with a peak of cyclone activity during November – December.

Cyclones are generally considered as one of the most dangerous natural disasters of meteorological origin in the tropical region. They are called ‘hurricanes’ in the Atlantic and Eastern Pacific, ‘typhoons’ in the Western Pacific and Far Eastern waters, ‘cyclones’ in the Bay of Bengal and Arabian seas, whereas in the Australian region and the southwest Indian Ocean region they are more specifically termed ‘tropical cyclones’. Tropical cyclones are responsible for significant damage to infrastructure, utilities and agriculture, as well as loss of lives.

Earth’s hottest January

The Meteorological Department has a large database dating back as far as 1869, though it was established as a Department only in 1948. Needless to say, it is a treasure trove for research, and much can be learnt about the future from the trend lines that would appear. Not that there had not been research, but what have we taken from them? Some research papers and studies done by university students were left to gather dust in its cupboards.

Wijemannage pointed out that the Meteorological Department disseminates its seasonal forecast to all other stakeholders such as the Agricultural and Irrigational authorities, Fisheries Department, Aviation sector and the Ceylon Electricity Board, but that these institutions should act upon them to enhance productivity and disaster preparedness. He said better coordination with all these stakeholders would yield better results.

Above average temperatures were reported in many parts of the country last week. The last month was the warmest January on record for the globe, according to a latest report by the NOAA. The globally averaged temperature for January 2020 has surpassed the previous record set in January 2016, and in 141 years of record-keeping from the NOAA, there has never been a warmer January. We are yet to know what more awaits us in 2020 and in the new decade we just stepped into.

The temperature is rising, rainy days are decreasing, and drought periods, intense rainfalls, weather-related disasters, and even thunder are increasing, to recap a few realities. It is time we focussed on environmental conservation and disaster resilience on top of all other matters. In this context, the need for more officers, or rather citizens, like Gampaha District Forest Officer Devani Jayatillake is felt more than ever. Harken to her plea, “we need oxygen, we need more trees”, or face the consequences which are plain to see.


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