Summer winds over the Iberian Peninsula related to thermal low conditions from COSMO-REA6 (1995-2018) high-resolution reanalysis

Thermal low pressure systems are typically generated over continental mid-latitudes and subtropical regions during summer, related to a strong heating over land caused by the long lasting solar radiation during this part of the year. They present a clear diurnal cycle, being more intense during the afternoon, and weakens at nighttime. In Europe, a thermal low forms frequently over the Iberian Peninsula. As strong pressure gradients are generated from the coastal regions to the interior of the Peninsula, wind characterization is a relevant feature to describe the Iberian thermal low. In particular, wind typically enters from the north (the Basque Country) and the east (the Mediterranean coast of Murcia and Valencia) through gaps between mountain ranges, and move respectively in a southwestward or westward direction. In the northern area, the wind flows into the regions of Burgos and Valladolid after channeling across the Duero valley, while in the southeast it reaches a large part of Castilla-La Mancha and even Extremadura. These winds are known in the Iberian Peninsula, for example, the regional wind from the Mediterranean to the Castilla-La Mancha plateau is typically named as Solano. Nevertheless, no systematic effort has been made to fully characterize and quantify its frequency or intensity, so no objective thresholds of wind speed, direction or spatial extension have been defined so far. A first effort to define such objective values is then proposed here. Hourly 10-m wind and 2-m specific humidity fields from COSMO-REA6 very high resolution (0.055º) reanalysis covering the 1995-2018 period are used. This high resolution, both temporal and spatial, will allow us to inspect the orographic aspects that seem to be relevant for these regional winds, together with its clear diurnal cycle and the moisture transport from coastal to inner regions. Humidity is a relevant variable for characterizing these flows, as there are marked differences between the moist air entering from the sea and the dry summer air characteristic of the inner regions of the Iberian Peninsula. The climatic perspective allows to study if interannual variability or trends are also relevant. First results indicate that these regional winds, with mean hourly speeds above 5 m/s for several hours per day, appear during most of the summer days, with important variations in spatial extension and strength. Strong moisture gradients are frequently observed during such episodes. Maximum speed and humidity jumps occur during the afternoon. This analysis is just a starting point, which will be followed by a deeper examination of these flows.