Multi-scale analysis of intense cold waves and atmospheric circulation mechanisms in northern Morocco

Due to its geographical location, the Mediterranean region is subject to increasingly frequent and intense climatic events.Within this region, northern Morocco is one of the areas most exposed to extreme temperature phenomena, which manifest themselves either as very large positive temperature anomalies, reflecting intense heat, or as negative anomalies, synonymous with cold spells.This study aims primarily to fill the gaps in the analysis of the frequency and evolution of cold spells in the north of the country, based on the design of an innovative statistical model that allows the use of absolute temperature thresholds.Secondly, it was essential to assess the applicability of this approach to regionally heterogeneous climatic conditions.To achieve these objectives, several climate indices were used.The calculations were developed on RClimdex using maximum daytime temperatures and minimum nighttime temperatures.The results reveal that an extremely severe cold wave was recorded at 70% of the coastal and continental stations studied between January 1 and 7, 2025, with a total weight varying between 11.3 °C and 37 °C and between 2.4 °C and 7.8 °C during the month of February.The calculation of thermal indices (TX10p, TN10p, FD, and CSDI) showed variable trends.The TX10p showed a drop of -0.13 days (10 yr) -1 in Tangier and Casablanca.A slight increase was observed for the TN10p index +0.04days (10 yr) -1 .Similar results were detected for the FD +0.024 days (10yr) -1 and the CSDI +0.012 days (10 yr) -1 .The use of weather maps (at 500 and 1015 hPa) enabled a more in-depth analysis and confirmed the results obtained.the research demonstrates the scientific relevance of coupling innovative statistical model with regionally heterogeneous climatic conditions for cold waves risk assessment in North African countries, offering insights that can guide both policy design and climate risk management strategies.