A document by Kenza Khomsi. Click on the document to view its contents.

More recurrent heatwaves and extreme ozone episodes are likely to occur during the next decades and a key question is about the concurrence of those hazards, the atmospheric patterns behind their appearance and their joint effect on human health. In this work, we use surface maximum temperature and O3 observations during extended summers in two cities from Morocco: Casablanca and Marrakech, between 2010 and 2019. We assess the connection between these data and climate indexes (North Atlantic Oscillation (NAO), Mediterranean Oscillation (MO) and Saharan Oscillation (SaOI)). We then identify concurrent heatwaves and ozone episodes, the weather type behind this concurrence and the combined health risks. Our findings show that the concurrence of heatwaves and O3 episodes depends both on the specific city and the large-scale atmospheric circulation. The likely identified synoptic pattern is when the country is under the combined influence of an anticyclonic area in the north and the Saharan trough extending the depression centered in the south. This pattern generates a warm flow and may foster photochemical pollution. Our study is the first step towards the establishment of an alert system. It will help to provide recommendations for coping with concurrent heatwaves and air pollution episodes.

On the 20th April 2020, the end of the first strict lockdown in Morocco, 2403410 cases of the corona Virus were confirmed globally. The number of Morocco confirmed cases attended 2990 and 143 deaths were recorded. Due to the pandemic, all avoidable activities in the country were prohibited since the kingdom announced the general lockdown on 20th March 2020. This study aims at comparing the air quality status in Casablanca and Marrakech from Morocco, before the pandemic and during the confinement to show whether COVID-19 compelled lockdown may have saved lives by restraining air pollution than by preventing infection. We used the difference-in-difference and the Theil and Sen non-parametric approaches for univariate time series. We defined the before quarantine period as between the 16th February and the 19th March and the during quarantine as between the 20th March and 20th April. We assessed changes in air quality during vs. before the quarantine period in 2020 and compared these with corresponding changes in the same lunar calendar periods in 2016-2019. Then we calculated the avoided cause-specific mortality attributable to the decreases in NO2 and PM2.5 based on the concentration-response functions from previous studies. We found that NO2 dropped by -12 μg/m³ in Casablanca and -7 μg/m³ in Marrakech. PM2·5 dropped by -18 μg/m³ in Casablanca and -14 μg/m³ in Marrakech. CO dropped by -0.04 mg/m³ in Casablanca and -0.12 mg/m³ in Marrakech. This air pollution reduction had created human health benefits and had reduced mortality and saved lives mainly from cardiovascular diseases. Our results are in complete agreement with the worldwide studies. Yet, they should be interpreted carefully because of the potential common impacts NO2 and PM2·5 may have on health. Further investigation may be undertaken to explore the reduction in the concentrations of industry-related pollutants.

PM10 has natural and anthropogenic sources, it is an urban air pollutant from desertic areas or emitted by industry and traffic activities, it reduces visibility and threatens human wellbeing mainly in big cities. Casablanca concentrates many industrial units and a large vehicle fleet. The rate of urbanization in the metropolis and the population density are the highest in Morocco. Marrakech is one of the most populated cities in the country where the motorization rate has increased during recent years. The present work is based on PM10 daily measurements between 2013 and 2016. The main objective is to assess the concentrations of PM10 in Casablanca and Marrakech and study their relationship with the atmospheric circulation. First, we assessed PM10 correlations with climate indexes (NAO and MO), then we characterized the contribution of large-scale atmospheric patterns related to PM10 extreme events. The novelty of this research is the creation of a new climate index to characterize the oscillation, in the country’s southern desert, between the Saharan depression and the Azores high. The time series of the new Saharan Oscillation Index (SaOI) were calculated. This study has demonstrated the relationship between MO and PM10 averages and has shown that particulate pollution in the study area is partly induced by continental northeasterly to southwesterly flow. This flow is triggered by the Saharan trough and managed by the high-pressure area in the north. The assessed correlations related to the SaOI confirm the relationship between this index, PM10 averages, and MO and NAO indexes mainly in winter. The Saharan Oscillation is the new relevant key to understand worldwide pollution by fine particles.