Can Satellite-Based Thermal Anomalies Be Indicative of Heatwaves? An Investigation for MODIS Land Surface Temperatures in the Mediterranean Region

Abstract

In recent years, an exceptional number of record-shattering temperature extremes have been observed, resulting in significant societal and environmental impacts. The Mediterranean region is particularly thermally vulnerable, frequently suffering from intense and severe heatwaves. Using daily temperature observations from 58 weather stations (NOAA Global Historical Climatology Network daily database) in the Mediterranean area, past heatwave episodes were initially detected. A daily LST time series was developed using Land Surface Temperature (LST) products from Moderate Resolution Imaging Spectroradiometer (MODIS) (Terra & Aqua satellites) for a 19-year period (2002–2020) at the station locations. LST anomalies were identified using percentile-based indices. It was found that remotely sensed-based LST presents the potential for understanding and monitoring heatwave events, as surface thermal anomalies were generally indicative of heatwaves. Approximately 42% (39%) of heatwave days during daytime (nighttime) coincided with LST anomalies; conversely, 51% of daytime LST anomalies overlapped with the exact days of a heatwave (38% at night). Importantly, the degree of association was significantly higher for extremely hot days (up to an 80% match) and long-lasting heatwaves (up to an 85% match). Rising trends in frequency and duration were observed for both heatwaves and LST anomalies. The results advance the understanding of surface-atmosphere coupling during extreme temperature days and reflect the suitability of thermal remote sensing in heatwave preparedness strategies.

Satellite-Derived Land Surface Temperature Dynamics in the Context of Global Change—A Review

“…During the study period between 2002 and 2020, they noticed an increase in positive LST anomalies of 1.35 days/10 years during the daytime and 1.64 days/10 years during the nighttime, which was in line with the increase in heat wave days. Major events, such as the European heat wave in 2003, could be clearly detected from the number of LST anomaly days [19]. The global analysis of yearly maximum LST by Mildrexler et al [180] showed spatially continuous patches of positive LST anomalies over Europe in 2003 and Siberia in 2010, which corresponds to the reported heat waves.…”

“…Heat wave metrics, therefore, are mostly based on positive LST or air temperature anomalies in the warm season. Agathangelidis et al [19] showed that, for the Mediterranean region, there is a high coincidence rate between heat wave days, detected with air temperature station measurements and LST anomalies. The match percentage was lower on the first days of the heat wave and increased as the heat wave evolved.…”

“…Similar to droughts, heat waves are extreme climatic events that have severe impacts on a wide range of societal and environmental domains. They are linked to increased mortality rates, stress on animal populations and ecosystems and a higher probability of energy infrastructure failures [19]. The occurrence of heat waves has increased in recent decades due to climate change.…”

“…While again, the most studied topic in this category is SUHI (17 studies), topics from the sphere of 'Atmosphere' were overrepresented (eight studies). These studies include the examination of the Mediterranean and North American heatwaves [18,19] and climatological long-term trends over east Africa [3] and the Tibetan Plateau [61]. The third most-studied spatial scale is regional small' (21 studies, 13%).…”

“…Figure 1 provides an overview of the application fields of LST. LST has been used to study global warming [3][4][5][6][7][8][9][10][11][12][13][14][15][16], interannual climate variabilities [5,[7][8][9][10]14,17], heat waves [18][19][20], droughts [21][22][23][24][25], soil moisture dynamics [22,23,[26][27][28][29], forest dynamics [28,[30][31][32][33][34][35][36][37][38][39], general vegetation-temperature interactions [15,20,[24]…”