A wet 2022 for Singapore, even as temperatures soared
Despite the high rainfall, Singapore’s annual mean temperature in 2022 was the tenth highest on record.
SINGAPORE: With above-average rainfall for most months, it was a very wet 2022 for Singapore, which also saw temperature levels reaching new highs in some categories.
In its annual climate assessment report issued on Thursday (Mar 23), the Meteorological Service Singapore (Met Service) said average annual rainfall for 2022 was nearly 18.8 per cent above the long-term average - defined as the 30-year period between 1991 and 2020.
This was partly influenced by prevailing La Nina conditions along with a negative Indian Ocean Dipole, which refers to a broad pattern of temperature differences in the western and eastern Indian Ocean.
2022 was ranked as the sixth wettest year in the past 40 years and the tenth warmest year since temperature records began in 1929.
SIXTH WETTEST YEAR SINCE 1980
October was the year’s wettest month, with total rainfall of 412mm - about twice the month’s long-term average.
This exceeded the previous high of 389.3mm in 2011, making October 2022 the wettest October in the last four decades.
The highest daily total rainfall for the month was 138.1mm, recorded at Pasir Panjang.
It is not common for the year’s wettest month to fall in October, with the previous occurrence in 1985, the Met Service said.
October 2022 was exceptionally wet, with a high number of Sumatra squalls affecting Singapore.
Several tropical cyclones had formed in the South China Sea and western Pacific Ocean, contributing to the formation of these squalls. The convergence of winds in the area caused by these cyclones led to the formation of Sumatra squalls, which typically bring widespread showers and gusty winds to Singapore in the early morning hours.
March 2022 was also the wettest March since 2009, it added.
The wet weather in March 2022 was mainly due to strong solar heating of land areas coupled with the convergence of winds over the island.
March was also among the wettest months of 2022, with most parts of the island receiving above-average rainfall.
Thundery showers forming over southwestern Singapore on Mar 7, 2022 led to the second wettest day in March in the last 10 years, with the highest daily total rainfall of 134.2mm recorded at Jurong West.
The above-average rainfall in both 2021 and 2022 has led to questions about whether this increase represents a long-term trend in Singapore's climate.
Although there has been a gradual increase in the annual total rainfall of Singapore by 78mm per decade from 1980 to 2022, this trend is not considered statistically significant, the Met Service said.
Years that have predominantly experienced La Nina conditions, such as 2022, 2021, and 2011, tend to be wetter, while years with El Nino conditions, such as 1982, 1997, and 2015, tend to be drier, it added.
The Met Service also noted that 2022 marked the third year in a row where La Nina conditions were present, making this the first triple year La Nina since at least the 1960s.
RISING TEMPERATURES, SCORCHING MAY
In 2022, Singapore experienced its tenth warmest year on record, tied with 2021, 2018, 2014, 2009, and 2004.
The mean temperature for the year 2022 was recorded at Changi climate station at 27.9 degrees Celsius, which is 0.1 degrees Celsius above the long-term average of 27.8 degrees Celsius. The mean temperature for the last decade (2013 to 2022) reached a new high of 28.01 degrees Celsius, which is 0.04 degree Celsius higher than the previous record of 27.97 degrees Celsius for the decade from 2012 to 2021.
The highest temperature recorded islandwide during the year was 36.8 degrees Celsius at Admiralty on April 1. This was the second-highest recorded temperature for Singapore, with the highest being 37 degrees Celsius in Tengah in April 1983.
May 2022 was ranked the fifth warmest May on record, with the warmest day in May recorded on May 13, 2022.
Daily maximum temperatures were recorded to be above 34 degrees Celcius for 22 days in May, and out of these, the temperatures exceeded 35 degrees Celcius on 13 days.
Singapore's average rainfall for the month was close to the long-term average, but there were 11 days with little or no rain, the Met Service said.
“In the second half of the month, the presence of dry air over equatorial Southeast Asia coincided with the dry phase of the Madden-Julian Oscillation, which resulted in very warm weather over Singapore,” it added.
On May 13, the highest daily maximum temperature of 36.7 degrees Celsius recorded at Admiralty made it the hottest day on record for the month of May. This surpassed the previous high of 36.5 degrees Celcius on May 16, 2010 and May 3, 2016.
May is statistically the warmest month of the year, the Met Service said.
It also said that the daily mean temperatures have been steadily rising at the Changi climate station. From 1984 to 2022, the Changi climate station has seen an increase of 0.24 degrees Celsius on average per decade.
The number of "very warm" days in Singapore has also increased, which refers to days when the daily maximum temperature exceeds 34 degrees Celsius.
The Urban Heat Island (UHI) effect is particularly noticeable during the night, when temperatures in more developed urban areas can be several degrees higher than in less developed areas surrounded by trees and water bodies, according to the Met Service. The UHI effect is a phenomenon where towns and cities experience significantly higher air temperatures compared to their greener surroundings.
Singapore's long-term temperature trend can be attributed to a combination of factors, including global warming and the UHI effect, it added.