Optical turbulence forecast: ready for an operational application

Abstract

One of the main goals of the feasibility study MOSE (MOdelling ESO Sites) is to evaluate the performances of a method conceived to forecast the optical turbulence above the ESO sites of the Very Large Telescope and the European-Extremely Large Telescope in Chile. The method implied the use of a dedicated code conceived for the optical turbulence (OT) called Astro-Meso-Nh. In this paper we present results we obtained at conclusion of this project concerning the performances of this method in forecasting the most relevant parameters related to the optical turbulence (C 2 N , seeing ε, isoplanatic angle θ 0 and wavefront coherence time τ 0 ). Numerical predictions related to a very rich statistical sample of nights uniformly distributed along a solar year and belonging to different years have been compared to observations and different statistical operators have been analyzed such as the classical bias, RMSE, σ and more sophisticated statistical operators derived by the contingency tables that are able to quantify the score of success of a predictive method such as the percentage of correct detection (PC) and the probability to detect a parameter within a specific range of values (POD). The main conclusions of the study tell us that the Astro-Meso-Nh model provides performances that are already very good to definitely guarantee a not negligible positive impact on the Service Mode of top-class telescopes and ELTs. A demonstrator for an automatic and operational version of the Astro-Meso-Nh model will be soon implemented on the sites of VLT and E-ELT.

Filtering techniques to enhance optical turbulence forecast performances at short time-scales

“…Fluid Mech., 7, 397 Turchi, A., Masciadri, E., Kerber, F., Martelloni, G., 2019, MN-RAS, 482, 206 Turchi, A., Martelloni, G., Masciadri, E., 2018 10703, id. 107036H Turchi, A., Masciadri, E., Fini, L., 2017, MNRAS, 466, 1925Veillet, C., Ashby, D.S., Christou, J., et al, 2016 9910, Observatory Operations: Stretegies, Processes and Systems VI, 99100S Ye, Q.Z., 2011, PASP, 123, 113 Table A1 summarises the effective number of nights used for the analysis for each parameter. For temperature and relative humidity we have 351 nights i.e.…”

“…The atmospherical mesoscale model Meso-Nh 4 (Lafore et al (1998); Lac et al (2018)) has been used in this study for the forecast of the atmospheric parameters (T, RH, WS and WD) while the Astro-Meso-Nh code (Masciadri et al (1999); Masciadri et al (2017)) has been used for the forecast of the optical turbulence i.e. the seeing.…”

“…Also accessible through lbto.org. 3 http://mkwc.ifa.hawaii.edu/ ing (Masciadri et al 2017). The technique we proposed and implemented in ALTA Center has a few important appealing characteristics:…”

Overview of the Meso-NH model version 5.4 and its applications

“…In addition to atmospheric studies, Meso-NH has been extensively used for various innovative applications in Earth system sciences, such as hydrology (e.g., Vincendon et al, 2009), oceanography (e.g., Lebeaupin Brossier et al, 2009), optical turbulence for astronomy (e.g., Masciadri et al, 2017), wildland fire (e.g., Filippi et al, 2011), and atmospheric electricity (e.g., Barthe et al, 2012b). Meso-NH is also an on-line atmospheric chemistry model, handling gas-phases (Tulet et al, 2003;Mari et al, 2004), aqueous chemistry (Leriche et al, 2013), aerosols and volcanic eruptions 5 Sivia et al, 2015).…”

“…The performance of Meso-NH has also been evaluated on sites offering long-term statistics, such as the optical turbulence applied to ground- based astronomy for a statistically rich sample of nights above the European Southern Observatory (ESO) sites (Lascaux et al, 2013;Masciadri et al, 2013Masciadri et al, , 2017, Arizona , and Antarctica (Lascaux et al, 2010(Lascaux et al, , 2011.…”