CroMonthlyGrids - monthly air temperature grids for climate monitoring and climate change detection

The focus of this work is to create homogenised mean monthly air temperature series, produce monthly temperature grids and derive climate monitoring products to assess the state of air temperature and the observed temperature change in Croatia. Having that in mind, monthly mean temperatures from 122 Croatian stations are homogenised and high resolution monthly gridded data are developed for the 1981-2018 period. The hierarchical clustering is introduced to define climate regions in Croatia needed for homogenisation. The breaks of homogeneity are detected by the standard normal homogeneity test. Further on, the regression kriging is applied to produce 1 km x 1 km monthly grids for each month in the analysed period. The quality of the interpolation was assessed by leave-one-out cross-validation and the root mean square error of 0.7°C. The quality of spatial interpolation is estimated with normalised error maps. Climate normals and trends are derived from homogenised station data and monthly grids. After 2000, average annual anomalies from the 30-years climate normal 1981-2010 were positive and up to 1.4°C warmer than the average, and just occasionally negative. The significant strong warming is observed and mapped over the entire Croatian territory in April, June, July, August and November, being stronger inland than on the coast. Annual trends were significant and in the range from 0.3°C/decade to 0.7°C/decade. That suggests that our region could face consequences such as devastating heatwaves, water shortages, loss of biodiversity and risks to food production, especially as being part of the Mediterranean where it seems that the observed trends are 2-2.5 times stronger than the global mean. We can hope that some of the presented climate monitoring products can help in assessing the vulnerability and the risk from climate change and help with the mitigation of the potentially affected sectors like forestry, agronomy, tourism, water management, energy production or consumption, health or others.