Scale of heat waves
The scale of heat waves is an indicator of the heat in the atmosphere. This indicator describes the average temperature trends during heat waves 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 scale of heat waves for the Basque Country as a whole, with the trend being almost non-existent and insignificant.
- The spatial variability in the scale of heat waves was practically non-existent throughout the region, being very close to zero.
Relationship of the indicator to climate change
Heat waves are periods characterised by several days of very hot temperatures compared to local average temperatures. Heat waves can have an impact on human health, infrastructure, energy demand and natural ecosystems.
Unusually hot days and heat waves are a natural part of the daily variability. However, as the Earth's climate warms, hotter than usual days and nights are becoming more common and heat waves are expected to become more intense. The increase in these extreme heat events may lead to more heat-related illnesses and deaths, especially if individuals and communities do not take measures to adapt. Even small increases in extreme heat can lead to more deaths and illnesses. This means that it is important to analyse the change in the scale of heat waves in the Basque Country.
Figure 1. Time series of the scale of heat waves in the period 1971-2016 for the Basque Country as a whole.
A time series analysis of the scale of heat waves shows a non-significant positive trend (p = 0.42) for the period 1971-2016, reflecting the variability of the series itself (Figure 1). The correlation coefficient near 0 shows that there is no linear relationship between the scale 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 scale of heat waves in the Basque Country, 1971-2016.
At a spatial level, the trends observed throughout the region since 1971 have been almost non-existent (close to zero), with no statistical significance, except in very specific areas, which cannot be ruled out as being due to the uncertainty introduced by the basic spatial interpolation model (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 scale of heat waves for each year, expressed in this case as the average temperature of all heat waves identified by the ‘number of heat waves’ indicator. These have been 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