Beni Mellal isoplanatic angle as determined by ERA5

Abstract

In this publication, we continue a series of investigations carried out in the High Atlas, in particular at Oukaïmdan and Aklim, by identifying a new astronomical site in the Beni Mellal mountains, notably at Tassemit. At present, we rely on satellites to gather meteorological and geophysical data. The analysis of atmospheric turbulence and wind speed distribution is of crucial importance in the evaluation of astronomical sites and the implementation of adaptive optics systems. This study examines optical turbulence using a general model, as well as wind characteristics at Tassemit. The data used come from reanalyses (ERA5) of the European Centre for Meteorological Forecasting, covering a 10-year period. We study vertical variations and seasonal trends in wind speed and atmospheric turbulence. At a pressure level of 200 hPa, wind speeds \(V_{200}\) show lower levels in summer and autumn, with the exception of November, while they are higher in winter and spring. At Tassemit, extreme values of \(V_{200}\) are observed in April, reaching 26.87 \(\mathrm {ms^{-1}}\), and in August, with a minimum of 12.32 \(\mathrm {ms^{-1}}\). Furthermore, the locations of the peaks in the \(C_{n}^2\) profiles correspond to the tropopause and jet stream regions at the Tassemit site. In addition, the aim of this work is to calculate the astroclimatic parameters for the qualification of the astronomical sites (\(r_{\textrm{0}}\), and \(\theta _{\textrm{0}}\)). The initial data come from the Tassemit site. The medians of the \(r_{\textrm{0}}\) and \(\theta _{\textrm{0}}\) values are 11.19 cm and 1.65 arcsec accordingly, offering a possible point of reference for astronomical uses.