PWV and coherence time for Tassemit by ERA5

Abstract

In this publication, we follow up our work in the High Atlas, in particular at of Tassemit in the Beni Mellal mountains. Our database is drawn from reanalyses ERA5 by the European Centre for Weather Forecasting, covering a period of 10 years, evaluating new parameters: precipitation water vapor (PWV), cloud cover, wind speed, geopotential, total precipitation, evaporation, coherence time ${\tau }_{OA}$, and scintillation rate ${\sigma }_I^2$. The latter are key astroclimatic parameters for qualifying of new astronomical sites.

The results highlight favorable atmospheric conditions, with a mean and median PWV of 3.68 and 3.35 mm, respectively. The site also features low cloud cover, moderate wind speeds, and low total precipitation, ensuring climatic stability suitable for advanced astronomical projects. We compared the measurements made by MASS-DIMM and calculated by ERA5 for coherence time ${\tau }_{OA}$ and scintillation rate ${\sigma }_I^2$ at the Observatorio del Roque de Los Muchachos ORM: The results were encouraging, as the recalculated values of ${\tau }_{OA}$ and ${\sigma }_I^2$ for the Tassemit site showed improved precision and consistency with expected atmospheric conditions. We have also recalculated ${\tau }_{OA}$ and ${\sigma }_I^2$ for the Tassemit site, and we have the medians of the values of ${\tau }_{OA}$ and ${\sigma }_I^2$ which are 5.93 ms and 0.00307 arcsec, respectively. This is used as a reference in astronomy.