Duration of heat waves
The duration of heat waves is an indicator of the heat in the atmosphere. This indicator describes heat wave trends in terms of their duration in the Basque Country between 1971 and 2016. This is an important index when applied to fields such as agriculture, tourism or human health.
- Between 1971 and 2016, there was no positive or negative trend in the duration of heat waves for the Basque Country as a whole, with the trend being almost non-existent and insignificant.
- At a spatial level, positive rates of change in terms of the duration of heat waves can only be seen in the Ebro axis and around the Baias and Oria basins, although the level of significance is not uniform.
Relationship of the indicator to climate change
A heat wave is a sustained period of unusually hot days. Heat waves can result in illness and death, particularly among the elderly, the very young and other vulnerable population groups. Prolonged exposure to excessive heat can also have other effects. For example, it can damage crops, injure or kill livestock and increase the risk of forest fires. Prolonged periods of extreme heat can also lead to power outages, as the high demand for air conditioning can put a strain on the power grid. Climate change is associated with a global increase in the duration of heat waves, which is why it is necessary to analyse its impact on the duration of heat waves in the Basque Country.
Figure 1. Time series of the duration of heat waves in the period 1971-2016 for the Basque Country as a whole.
This section details the evolution of the duration of heat waves in the Basque Country between 1971 and 2016.
The annual time series of the duration of heat waves does not show any significant variation (p=0.49) for the Basque Country as a whole in the data period observed (Figure 1). The correlation coefficient near 0 shows that there is no linear relationship between the duration and the evolution over time, meaning that there is no significant variation in this indicator for the Basque Country as a whole.
Figure 2. Rate of change in the duration of heat waves in the Basque Country, 1971-2016.
In line with the overall results, there is no spatial trend in terms of the duration of heat waves in the Basque Country since 1971, with the exception of small areas spread out across the region. Consequently, a positive trend can be seen along the axis of the Ebro and around the basins of the Baias and Oria, although the level of significance is not uniform (Figure 2).
Air temperature in the Basque Country is measured in both manual and automatic weather stations managed by different institutions (Basque Government, Provincial Councils, AEMET, URA).
In daily resolution data sets the minimum temperature refers to the lowest temperature value in a day, which is often recorded just after sunrise, when the Sun becomes visible over the horizon.
Data series have been fed into spatial prediction models to generate a daily resolution cartographic database, which is the starting point for the calculation of this climate change indicator. Static covariates, derived from digital terrain models, have been included in this prediction to explain air temperature.
The cartographic database comes from Phase II of the KLIMATEK project “High Resolution Climate Change Scenarios for the Basque Country”.
These maps are used to calculate the duration (in days) for each year of the longest heat wave identified by the ‘number of heat waves’ indicator, defined as those events that occur in the warm period (May - September) where the daily maximum temperature on 3 or more days exceeds the 90th percentile of the maximum temperature calculated from the base period 1971-2000.
Decadal trends (Sen’s slope), i.e. magnitude of mean temperature increases/decreases over a decade, is also calculated; and it is checked whether the trend is statistically significant or whether it is actually the result of the variability of the thermometric series itself using the Mann Kendall (MK) test.
Gaztelumendi S., Otxoa de Alda K., R. Hernández, M. Maruri, J.A. Aranda, P. Anitua (2018) “The Basque Country Automatic Weather Station Mesonetwork in perspective”. WMO/CIMO Technical Conference on Meteorological and Environmental Instruments and Methods of Observation (CIMO TECO-2018). 8 - 11 October 2018. Amsterdam, The Netherlands.
Hernández R., M. Maruri, K. Otxoa de Alda, J. Egaña, S. Gaztelumendi. (2012) “Quality Control Procedures at Euskalmet Data Center”. Advances in Science and Research – Topical Library, Volume 8, 2012, pp. 129-134.
Herrera, S., J. M. Gutiérrez, R. Ancell, M. R. Pons, M. D. Frías and J. Fernández. 2012. Development and analysis of a 50-year high-resolution daily gridded precipitation dataset over Spain (Spain02). Int. J. Climatology, 32, 74-85, doi: 10.1002/joc.2256.
Herrera, S., J. Fernández and J. M. Gutiérrez. 2016. Update of the Spain02 Gridded Observational Dataset for Euro-CORDEX evaluation: Assessing the Effect of the Interpolation Methodology. Int. J. Climatology, 36, 900-908, doi: 10.1002/joc.4391.
Klein Tank, A.M.G., Zwiers, F.W., Zhang, X. 2009. Guidelines on analysis of extremes in a changing climate in support of informed decisions for adaptation, climate data and monitoring WCDMP-No 72, WMO-TD No 1500, p 5.
Proyecto Klimatek 2016. Elaboración de escenarios regionales de cambio climático de alta resolución sobre el País Vasco. IHOBE. Gobierno Vasco.
The Basque Country
No changes appreciated
Since 1971