During the months of February–March (FM) of the 2020–2022 period, several intense dust intrusions from northern Africa affected Europe. The frequency of dust events was exceptional, considering that wintertime is the season with minimum dust activity in the Mediterranean, and some episodes displayed a duration and/or intensity never recorded before, affecting large areas of the western Euro-Mediterranean (WEM) region. The main objective of this work is to construct a catalogue of FM dust events over the WEM for the 2003–2022 period based on satellite aerosol retrievals and to analyse their atmospheric drivers at the synoptic and large scales, paying special attention to the recent 2020–2022 period of high dust activity. Overall, our results indicate large intraseasonal and interannual variability in the occurrence of wintertime dust events over the WEM. Dust events of FM 2020–2022 were characterized by enhanced dust concentration and high maximum altitudes in comparison with those of previous years (2003–2019). WEM dust events are associated with enhanced activity of high-pressure systems over the Euro-Atlantic sector, which favour the obstruction of the westerlies and the occurrence of cut-off lows at subtropical latitudes. However, these high-pressure systems can exhibit a large variety of configurations, including meridional dipole blocking patterns with poleward shifted jets or Mediterranean subtropical ridges with an intensified mid-latitude jet. The former is the dominant favourable pattern for WEM dust occurrence, but the latter was relatively common during the 2020–2022 period.

Every year, large-scale African dust outbreaks frequently pass over the Canary Islands (Spain). Here we describe the seasonal evolution of atmospheric aerosol extinction and meteorological vertical profiles on Tenerife over the period 2007–2018 using long-term micropulse lidar (MPL-3) and radiosonde observations. These measurements are used to categorise the different patterns of dust transport over the subtropical North Atlantic and, for the first time, to robustly describe the dust vertical distribution in the Saharan Air Layer (SAL) over this region. Three atmospheric scenarios dominate the aerosol climatology: dust-free (clean) conditions, the Saharan summer scenario (summer-SAL) and the Saharan winter scenario (winter-SAL). A relatively well-mixed marine boundary layer (MBL) was observed in the case of clean (dust-free) conditions; it was associated with rather constant lidar extinction coefficients (α) below 0.036 km⁻¹ with minimum α (< 0.022 km⁻¹) in the free troposphere (FT). The summer-SAL has been characterised as a dust-laden layer strongly affecting both the MBL (Δα = +48 % relative to clean conditions) and the FT. The summer-SAL appears as a well-stratified layer, relatively dry at lower levels ($\mathrm{\Delta }r\sim -\mathrm{44}$ % at the SAL’s base, where r is the water vapour mixing ratio) but more humid at higher levels compared with clean FT conditions ($\mathrm{\Delta }r\sim +\mathrm{332}$ % at 5.3 km), with a peak of α> 0.066 km⁻¹ at ∼ 2.5 km. Desert dust is present up to ∼ 6.0 km, the SAL top based on the altitude of SAL's temperature inversion. In the winter-SAL scenario, the dust layer is confined to lower levels below 2 km altitude. This layer is characterised by a dry anomaly at lower levels (Δr∼ −38 % in comparison to the clean scenario) and a dust peak at ∼ 1.3 km height. Clean FT conditions were found above 2.3 km. Our results reveal the important role that both dust and water vapour play in the radiative balance within the summer-SAL and winter-SAL. The dominant dust-induced shortwave (SW) radiative warming in summer (heating rates up to +0.7 K d⁻¹) is found slightly below the dust maximum. However, the dominant contribution of water vapour was observed as a net SW warming observed within the SAL (from 2.1 to 5.7 km) and as a strong cold anomaly near the SAL's top (−0.6 K d⁻¹). The higher water vapour content found to be carried on the summer-SAL, despite being very low, represents a high relative variation in comparison to the very dry clean free troposphere in the subtropics. This relevant aspect should be properly taken into account in atmospheric modelling processes. In the case of the winter-SAL, we observed a dust-induced radiative effect dominated by SW heating (maximum heating of +0.7 K d⁻¹ at 1.5 km, near the dust peak); both dust and atmospheric water vapour impact heating in the atmospheric column. This is the case of the SW heating within the SAL (maximum near the r peak), the dry anomaly at lower levels (Δr∼ −38 % at 1 km) and the thermal cooling (∼ 0.3 K d⁻¹) from the temperature inversion upwards. Finally, we hypothesise that the SAL can impact heterogeneous ice nucleation processes through the frequent occurrence of mid-level clouds observed near the SAL top at relatively warm temperatures. A dust event that affected Tenerife on August 2015 is simulated using the regional DREAM model to assess the role of dust and water vapour carried within SAL in the ice nucleation processes. The modelling results reproduce the arrival of the dust plume and its extension over the island and confirm the observed relationship between the summer-SAL conditions and the formation of mid- and high-level clouds.

This paper presents a comparative study of shortwave downward radiation (SDR) measurements and simulations, obtained with the radiative transfer model LibRadtran, at the Baseline Surface Radiation Network (BSRN) site of Izaña Atmospheric Observatory (IZA, Spain). The analysis is based on cloud‐free days between March 2009 and August 2012 (386 days), including aerosol‐free and Saharan mostly pure mineral dust conditions and comparing the day‐to‐day, annual, and interannual variability. The observed agreement between simulations and measurements is excellent: the variance of daily measurements overall agrees within 99% with the variance of daily simulations, and the mean bias (simulations−measurements) is −0.30±0.24 MJm⁻²(−1.1±0.9%) for global, −0.16±0.34 MJm⁻²(−0.4±0.9%) for direct, and +0.02±0.25 MJm⁻²(+0.9±9.2%) for diffuse SDR. Furthermore, the diurnally averaged aerosol radiative forcing (ΔDF) and radiative forcing efficiency (ΔDF^eff) due to Saharan mostly pure mineral dust events has been computed at Izaña Observatory. The mean ΔDF values are −7±1, −96±5, and 44±2 Wm⁻² for global, direct, and diffuse BSRN SDR, respectively (mean aerosol optical depth, AOD, at 500 nm of 0.18±0.01), whereas the mean ΔDF^effvalues are −59±6, −495±11, and 230±8 Wm⁻² per unit of AOD at 500 nm for global, direct, and diffuse BSRN SDR, respectively. These values highlight the importance of scattering processes for mineral dust aerosols: the ratio between ΔDF and the corresponding SDR without aerosols is ~2.5% for diffuse SDR versus 0.2% for direct SDR. This illustrates the significant potential of mineral dust particles to cool the Earth‐atmosphere system.

High-resolution Fourier transform infrared (FTIR) solar observations are particularly relevant for climate studies, as they allow atmospheric gaseous composition and multiple climate processes to be monitored in detail. In this context, the present paper provides an overview of 20 years of FTIR measurements taken in the framework of the NDACC (Network for the Detection of Atmospheric Composition Change) from 1999 to 2018 at the subtropical Izaña Observatory (IZO, Spain). Firstly, long-term instrumental performance is comprehensively assessed, corroborating the temporal stability and reliable instrumental characterization of the two FTIR spectrometers installed at IZO since 1999. Then, the time series of all trace gases contributing to NDACC at IZO are presented (i.e. C₂H₆, CH₄, ClONO₂, CO, HCl, HCN, H₂CO, HF, HNO₃, N₂O, NO₂, NO, O₃, carbonyl sulfide (OCS), and water vapour isotopologues H${}_{\mathrm{2}}^{\mathrm{16}}$ O, H${}_{\mathrm{2}}^{\mathrm{18}}$ O, and HD¹⁶O), reviewing the major accomplishments drawn from these observations. In order to examine the quality and long-term consistency of the IZO FTIR observations, a comparison of those NDACC products for which other high-quality measurement techniques are available at IZO has been performed (i.e. CH₄, CO, H₂O, NO₂, N₂O, and O₃). This quality assessment was carried out on different timescales to examine what temporal signals are captured by the FTIR records, and to what extent. After 20 years of operation, the IZO NDACC FTIR observations have been found to be very consistent and reliable over time, demonstrating great potential for climate research. Long-term NDACC FTIR data sets, such as IZO, are indispensable tools for the investigation of atmospheric composition trends, multi-year phenomena, and complex climate feedback processes, as well as for the validation of past and present space-based missions and chemistry climate models.