Geographical distribution of the Thuriferous juniper (Juniperus thurifera L.) and the influencing factors in the Atlas Mountains of Azilal (Central High Atlas, Morocco)

ABSTRACTThe present study describes the contribution of geomatic science in mapping and determining the factors influencing the spatial distribution of Juniperus thurifera in the high mountains of Azilal, Morocco. The methodology adopted is based on the use of a Landsat 8 OLI satellite image to determine the spatial distribution of J. thurifera and a WorldClim database to extract the climat conditions.The Digital Elevation Model (DEM) of 30 m resolution was used to derive the topographic parameters. The geological map was digitized and used to derive the different lithological classes. The results obtained show that the J. thurifera tree is distributed in four distinct biogeographic zones (Ait Bouguemez, Zaouit Ahansal, Anergui and Tifirt N'ait Hamza). It is mainly found on the North and/or West-facing aspect at altitudes ranging from 1600 to 3400 m, and on moderate-to-high slopes. It develops with a predominance of limestone, marl-limestone, and sandstone. It prefers areas withclimate types: cold to very cold semi-arid and cold to very cold subhumid. Well-preserved J. thuriferastands can only be observed in certain regions.. These results can be useful in selecting potential sites for reforestation of J.thurifera in similar terrain conditions to develop and manage this species in mountainous areas

Using sentinel-1A SAR wind retrievals for enhancing scatterometer and radiometer regional wind analyses

Scatterometer surface wind speed and direction observations in combination with radiometer wind speeds allow to generate surface wind analyses with high space and time resolutions over global as well as at regional scales. Regarding scatterometer sampling schemes and physics, the resulting surface wind analyses suffer from lack of accuracy in areas near coasts. The use of the synthetic aperture radar (SAR) onboard the Sentinel-1A satellite attempts to address the enhancement of surface wind analyses issues. In this study, SAR wind speeds and directions retrieved from backscatter coefficients acquired in interferometric wide (IW) swath mode are used. Their accuracy is determined through comprehensive comparisons with moored buoy wind measurements. SAR and buoy winds agree well at offshore and nearshore locations. The statistics characterizing the comparison of SAR and buoy wind speeds and directions are of the same order as those obtained from scatterometer (Advanced SCATterometer (ASCAT) and RapidScat) and buoy wind comparisons. The main discrepancy between SAR and buoy data are found for high wind speeds. SAR wind speeds exceeding 10 m s–1 tend to be underestimated. A similar conclusion is drawn from SAR and scatterometer wind speed comparisons. It is based on the underestimation of SAR backscatter coefficient (σ°) with respect to σ° estimated from scatterometer winds and the geophysical model function (GMF) named CMOD-IFR2 (Ifremer C band MODel). New SAR wind speeds are retrieved using CMOD-IFR2. The corrected SAR retrievals allow better determination of the spatial characteristics of surface wind speeds and of the related wind components in near-coast areas. They are used for enhancing the determination of the spatial structure function required for the estimation of wind fields gridded in space and time at the regional scale. The resulting wind fields are only determined from scatterometer wind observations in combination with radiometer retrievals. Their qualities are determined through comparisons with SAR wind speeds and directions, and through their application for determination of wind power off Brittany coasts