Interannual teleconnections in the Sahara temperatures associated with the North Atlantic Oscillation (NAO) during boreal winter

. The North Atlantic Oscillation (NAO) is the most recognized and leading mode of 32 atmospheric variability observed over the Atlantic sector of the Northern Hemisphere, and its 33 impacts on weather and climate over the North Atlantic and Eurasia via large-scale teleconnections 34 have been extensively studied. Here we use a multidata synthesis approach to analyze surface and 35 tropospheric variables from multiple long-term observational and reanalysis datasets to identify 36 the NAO’s footprint on interannual temperature variability over the vast but least-studied Sahara 37 Desert during December – January – February – March for the satellite era (1979-2022) and century-38 long periods. Our results present evidence for a solid teleconnection pattern in surface and 39 tropospheric temperatures associated with the NAO over the Sahara and document some major 40 spatial – temporal and vertical characteristics of this pattern. It is found that the Saharan temperature 41 anomalies are negatively correlated with the NAO index and this correlation is very strong, 42 consistent, and statistically significant between different periods and across different datasets. The 43 teleconnection is closely linked to large-scale circulation anomalies throughout the troposphere 44 over the North Atlantic – Sahara sector, where the anomalous horizontal wind components and 45 geopotential height exhibit opposite changes in sign with altitude from the lower to upper 46 troposphere. During the negative NAO − (positive NAO+) phase, above-normal (below-normal) 47 temperatures over the Sahara could be mainly explained by three major processes: (1) advection 48 of climatological warm and moist (cold and dry) air over the North Atlantic (northern higher 49 latitudes) by the anomalous southwesterly (northeasterly) flow in the lower troposphere; (2) 50 advection of anomalous North Atlantic warm (cold) air by the climatological strong westerlies in 51 the middle and upper troposphere; and (3) strengthened (weakened) vertical mixing in the 52 atmospheric boundary layer. These results suggest that the NAO plays an important role in 53 modulating the interannual temperature variability over the Sahara, and that this NAO footprint is 54 mostly realized through horizontal temperature advection and vertical heat transfer by turbulent 55