10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Aerosol Characterization in Oujda (Morocco) for the Period 2011-2015
Ibtissam Marsli, MOHAMMED DIOURI, Abdelouahid Tahiri, Djamaleddine Chaabane, Atmospheric Physic, LME, University of Oujda, Morocco
Abstract Number: 813 Working Group: Remote/Regional Atmospheric Aerosol
Abstract This study focus on the data analysis of aerosol optical characteristics: aerosol optical depth, Angstrom coefficient, refraction index, single scattering albedo, radiative forçage and particle size distribution registered by the network AERONET/PHOTONS. Oujda (34.65 °N, 1.89° W) Northeastern of Morocco, 55Km from the Mediterranean Sea. It enjoys a dry climate with a mild winter to cold and rainy and a hot summer marked by the Mediterranean breeze and the influence of the desert air masses coming from the Sahara, called Chergui wind violent, very dry and hot which blows on North Africa and the South of the Mediterranean Sea. Maritime and continental air masses are the dominant daily changes depending on the general weather.
The seasonal cycle of optical thickness at 0.5μm has two periods: the first extends from October to February with low values and small deviations. The second from March to September with relatively high monthly averages which can reach 0.4 with large deviations. These largest values are associated with small values of the Angstrom coefficients characteristic of the presence of mineral dust in summer coming mainly from Southeast. High values of the Angstrom coefficients result mainly from combustion processes (industrial and domestic), road traffic (arrival of emigrants in summer), and construction sites. These results confirm the importance of desert aerosol in summer and less degree in the spring and are consistent with the measurement campaigns carried out early 2000s. The refractive index varies little with an average real part of the order of 1.475 and of the order of 12.3010-3 for the imaginary part. The monthly spectral averages of the single scattering albedo remain high varying between 0.70 and 0.98; the higher values registered in winter where in the absence of clouds the clarity of the sky is dominant. The radiative forcing observed at the top of the atmosphere varies between -20 and +7W/m2, the negative values corresponding to the increase of the reflected flux due to the diffusion of the radiation towards the larger space by the aerosols thus contributing to cooling of the Earth-Atmosphere system and positive values indicate less reflected radiative energy. At the surface, the observed values vary between -140 and -50W/m2 , and are representative of the importance of forward IR scattering of the coarse particle modes characteristic of desert aerosols which cause a decrease in the net flux.
The seasonal average of PSD for the five years seems identical and show larger amplitudes for the coarse mode around an average radius of 2.56µm and with a maximum recorded in summer for which the volume concentrations can reach 0.24μm3/μm2 and confirms the relative influence of Saharan and desert mineral dust advections. The fine mode present a constant at the general average, and remains less important than that of the coarse with an average radius of the order of 0.15µm.