Marine heat waves [MHW] occur when ocean water temperatures are much warmer than normal (above the 90th percentile of the climatological distribution and so-called marine heat spikes [MHS]) for at least five consecutive days (Hobday et al., 2016).
The MHWs are computed using sea surface temperature (SST) from the daily near real-time (1/16º) and reprocessed (1/20º) satellite products in the Mediterranean Sea distributed by the Copernicus Marine Service (Pisano et al., 2016, Buongiorno Nardelli et al., 2013). The reference period chosen for the climatology is 1982-2015.

The daily bulletin provides daily map of MHS in the Mediterranean (for the last available day) and time series of sub-regional SST and MHS over the current year.

Annual MHW indices have been defined to estimate the long-term evolution of sub-regional MHW characteristics over the last four decades: total days, mean and maximum intensities (above the mean), mean duration and frequency.

Daily bulletin

Map of daily marine heat spike w.r.t. the daily 90th percentile climatology for the last available day (left).
Timeseries of the sub-regional daily SST for the current year, the daily mean and 90th percentile climatologies, with marine heat spikes highlighted (right).

Marine heat wave indices (1982-2023)

MHW total days

Map of the annual MHW total days in 2023 (left) and time series of the sub-regional annual total days from 1982 to 2023 (right)

MHW mean amplitude

Map of the annual MHW mean amplitude in 2023 (left) and time series of the sub-regional annual mean amplitude from 1982 to 2023 (right)

MHW maximum intensity

Map of the annual MHW maximum intensity in 2023 (left) and time series of the sub-regional annual maximum intensity from 1982 to 2023 (right)

MHW mean duration

Map of the annual MHW mean duration in 2023 (left) and time series of the sub-regional annual mean duration from 1982 to 2023 (right)

MHW frequency

Map of the annual MHW frequency in 2023 (left) and time series of the sub-regional annual frequency from 1982 to 2023 (right)