Author(s): Luis Angel Espinosa; Maria Manuela Portela; Jose Pedro Matos

Linked Author(s): Maria Manuela Portela, Luis Angel Espinosa

Keywords: Climate change; Climate trends; Heatwaves; Diurnal temperature range; Lisbon Metropolitan Are

Abstract: Understanding regional changes in rainfall and temperature can aid adaptation and enhance resilience in coastal cities vulnerable to climate change. This study examined temporal changes using the non-parametric Mann-Kendall (MK), Sen's slope, and sequential Mann-Kendall (SQMK) tests in annual series of rainfall, minimum and maximum surface temperatures (Tmin and Tmax) over the periods 1864 to 2021 in the Lisbon Metropolitan Area (Portugal). The available data included high-quality daily records from a representative climatological station in the urban area. The results revealed non-statistically significant changes in long-term rainfall but statistically significant ones in temperature, with increasing trends in both Tmin and Tmax. Overall, the coastal area has warmed by 2.0°C over the 157-year period. Additionally, annual series of the diurnal temperature range (DTR, i. e., the difference between the daily Tmin and Tmax) and heatwave days of Tmax were investigated using the same models. The SQMK results indicated a positive DTR trend for the first half of the 20th century; however, a dramatic reversal in DTR change occurred in the early 1950s, exhibiting a shift from increasing to decreasing trends. This is in accordance with a number of climatological studies from other regions reporting a decrease in DTR over the past few decades. In general, most of the series denoted anomalies clearly escaping their long-term natural variability, for instance, when comparing their trends and standard deviations. The number of heatwave days in Tmax has increased representing 10% of the days in the last 15 years. The key message of this communication is that the Lisbon area is (i) warming with heatwaves that are more frequent and (ii) exhibiting a sustained decrease in DTR.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0536-cd

Year: 2023