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The study evaluated the ECMWF model ability in forecasting lightning in Portugal during four fire seasons (2019–2022). The evaluation was made based on lightning data from the national lightning detector network, which was aggregated into resolutions of 0.5° and 1° over 3 h periods and analyzed from statistical indices using two contingency tables. The results showed that the model overestimates the lightning occurrence, with a BIAS greater than 1, with a success rate of 57.7% (49%) for a horizontal resolution of 1° (0.5°). The objective analysis was complemented by the spatial lightning distribution analysis, which indicated a time lag between the two data, i.e., the model started predicting lightning before its occurrence and finished the prediction earlier. Furthermore, such analysis revealed the lightning distribution being consistent with some weather patterns. The findings of this study provide insights into the applicability of the ECMWF lightning forecast data in the context of forecasting natural forest fires in Portugal. [ABSTRACT FROM AUTHOR]

An intense and long-lasting Saharan dust outbreak over the Iberian Peninsula (IP) in springtime 2021 is studied in this work with the aim of investigating the optical and mass contribution of both the fine and coarse dust particles along their transport by crossing the IP from the south-west to the north-east. Five Iberian lidar stations (El Arenosillo/Huelva, Granada, Torrejón/Madrid and Barcelona in Spain and Évora in Portugal) were monitoring the transport and evolution of the Saharan dust particles across the Iberian Peninsula from 25 March until 7 April 2021. Particular meteorological conditions determined the aerosol scenario along the overall dust event, differing the first part of the event (25–31 March), with the strongest dust incidence on 29–31 March at the south and central stations, and 1 April at Barcelona, from the second one (1–7 April). Both the fine dust (Df) and coarse dust (Dc) components of the total particle backscatter coefficient (total dust, DD = Dc + Df) were separately derived. The dust plume was well-mixed and no significant differences were found in the vertical structure of both the Dc and Df particle backscatter coefficients. The vertical total dust mass concentration, and its Df / DD ratio, were estimated from the extinction profiles using the well-defined conversion factors for North African dust. From the beginning of the dust outbreak until 1 April, the vertical Df / DD mass ratio was nearly constant in time at each station and also almost constant in altitude with values ~ 10 %. Regarding the columnar properties, the dust optical depth at 532 nm (DOD532), the relative mass loading and the centre-of-mass height were calculated, distinguishing the corresponding fine- and coarse-dust contributions. Firstly, the dust outbreak crossed the Iberian Peninsula from South-West to North-East and the mean DOD532 was decreasing along that dust pathway, reporting values from SW to NE stations of 0.34 at El Arenosillo/Huelva, 0.28 at Granada, 0.20 at Évora, 0.28 at Torrejón/Madrid and 0.14 at Barcelona, although its Df / DD ratio kept almost constant (28–30 %). On the other hand, a similar pattern was found for the total dust mass loading and its Df / DD ratio, i.e. mostly decreasing mean mass values were reported: 586 mg m-2 (El Arenosillo/Huelva), 483 mg m-2 (Granada), 332 mg m-2 (Évora), 464 mg m-2 (Torrejón/Madrid) and 248 mg m-2 (Barcelona), being constant its Df / DD ratio (~ 10 %) along the SW-NE dust pathway In addition, the episode-mean centre-of-mass height increased with latitude in overall, showing a high variability, i.e. being greater than 0.5 km at the southern sites (El Arenosillo/Huelva, Granada, Évora) and ~1.0 km at Torrejón/Madrid and Barcelona. However, despite the relatively high intensity of the dust intrusion, the expected ageing of the dust particles was barely observed. This is on the basis that the Iberian Peninsula is relatively close to the Saharan dust sources and then, under certain dust transport conditions, any potential ageing processes in the dust particles remain unappreciated. It must be highlighted the different relative contribution of the fine dust particles to the total dust found for their optical properties (~ 30 %), associated to the radiative effect of dust, with respect to the mass features (~ 10 %), linked to air quality issues, along the overall dust event by crossing the IP. Finally, the methodology introduced, which is mainly based on the two-step POLIPHON algorithm, shows the relevance of the use of the polarized lidar measurements, mainly with elastic systems, for separating the aerosol properties for the dust fine and coarse particles as an added value to the simple one-step approach used for simple dust/non-dust separation. [ABSTRACT FROM AUTHOR]

In order to advance the knowledge about precipitation development over Madeira island, four rainfall patterns are investigated based on high-resolution numerical simulations performed with the MESO-NH model. The main environmental conditions during these precipitation periods are examined, and important factors leading to significant accumulated precipitation in Madeira are shown. We found that the combination of orographic effect and atmospheric conditions is essential for the establishment of each situation. Under a moist and conditionally unstable atmosphere, convection over the island is triggered, and its location was determined mainly by variations of the ambient flow, which was also associated with different moist Froude numbers. Interestingly, our results showed some similarities with situations discussed in idealized studies. However, the real variations of the atmospheric configuration confirm the complexity of significant precipitation development in mountainous regions. In addition, precipitating systems initially formed over the ocean were simulated reaching the island. The four periods were characterised by different time durations, and the local terrain interacting with the mesoscale circulation was decisive in producing a large part of the precipitation, which concentrated in distinct regions of the island induced by the airflow dynamic. [ABSTRACT FROM AUTHOR]

Vegetation plays a key role in partitioning energy at the surface. Meteorological and Climate Models, both global and regional, implement vegetation using two parameters, the vegetation fraction and the leaf area index, obtained from satellite data. In most cases, models use average values for a given period. However, the vegetation is subject to strong inter-annual variability. In this work, the sensitivity of the near surface air temperature to changes in the vegetation is analyzed using a regional climate model (RCM) over the Iberian Peninsula. The experiments have been designed in a way that facilitates the physical interpretation of the results. Results show that the temperature sensitivity to vegetation depends on the time of year and the time of day. Minimum temperatures are always lower when vegetation is increased; this is due to the lower availability of heat in the ground due to the reduction of thermal conductivity. Regarding maximum temperatures, the role of increasing vegetation depends on the available moisture in the soil. In the case of hydric stress, the maximum temperatures increase, and otherwise decrease. In general, increasing vegetation will lead to a higher daily temperature range, since the decrease in minimum temperature is always greater than the decrease for maximum temperature. These results show the importance of having a good estimate of the vegetation parameters as well as the implications that vegetation changes due to natural or anthropogenic causes might have in regional climate for present and climate change projections. [ABSTRACT FROM AUTHOR]