The mesoscale model Meso-NH is used to simulate the optical turbulence at Mt Graham (Arizona, USA), site of the Large Binocular Telescope. Measurements of the CN2-profiles obtained with a generalized scidar from 41 nights are used to calibrate and quantify the model's ability to reconstruct the optical turbulence. The measurements are distributed over different periods of the year, permitting us to study the model's performance in different seasons. A statistical analysis of the simulations is performed for all the most important astroclimatic parameters: the CN2-profiles, the seeing ε, the isoplanatic angle θ0 and the wavefront coherence time τ0. The model shows a general good ability in reconstructing the morphology of the optical turbulence (the shape of the vertical distribution of CN2) as well as the strength of all the integrated astroclimatic parameters. The relative error (with respect to measurements) of the averaged seeing on the whole atmosphere for the whole sample of 41 nights is within 9.0 %. The median value of the relative error night by night is equal to 18.7 %, so that the model still maintains very good performances. Comparable percentages are observed in partial vertical slabs (free atmosphere and boundary layer) and in different seasons (summer and winter). We prove that the most urgent problem, at present, is to increase the ability of the model in reconstructing very weak and very strong turbulence conditions in the high atmosphere. This mainly affects the model's performances for the isoplanatic angle predictions, for which the median value of the relative error night by night is equal to 35.1 %. No major problems are observed for the other astroclimatic parameters. A variant to the standard calibration method is tested but we find that it does not provide better results, confirming the solid base of the standard method.
MOSE: a feasibility study for optical turbulence forecasts with the Meso-Nh mesoscale model to support AO facilities at ESO sites (Paranal and Armazones)
Forecast of the atmospheric parameters and optical turbulence applied to the ground-based astronomy is very crucial mainly for the queue scheduling. So far, most efforts have been addressed by our group in developing algorithms for the optical turbulence (CN2) and annexed integrated astroclimatic parameters and quantifying the performances of the Astro-Meso-Nh package in reconstructing such parameters. Besides, intensive analyses on the Meso-Nh performances= in reconstructing atmospheric parameters relevant for the ground-based astronomy has been carried out. Our studies referred always to the…
In this contribution, we present the most recent progresses we obtained in the context of a long-term program we undertook since a few years towards the implementation of operational forecast systems (a) on top-class ground-based telescopes assisted by AO systems to support the flexible scheduling of observational scientific programs in night as well in day time and (b) on ground-stations to support free space optical communication. Two topics have been treated and presented in the Conference AO4ELT6: 1. ALTA is an operational forecast system for the OT and all the critical atmospheric paramet…
MOSE: optical turbulence and atmospherical parameters operational forecast at ESO ground-based sites. I: Overview and atmospherical parameters vertical stratification on [0-20] km
MOSE: optical turbulence and atmospherical parameters operational forecast at ESO ground-based sites. II: atmospherical parameters in the surface layer [0-30] m
这篇文章是一系列文章的第二篇,旨在证明所有最相关的经典大气参数(风速和风向,温度,相对湿度)和光学湍流(Cn 2和衍生的天文气候参数,如视宁度,等晕角,波前相干时间.)的预测在天文应用中的可行性。这项研究是在MOSE项目的框架内进行的,重点放在两个ESO地面基地Cerro Paranal和Cerro Armazones的上方。本文介绍了Meso-Nh模式重建近地层大气参数(风速、风向和绝对温度,[0-30] m a.g.l.)的能力。对近地层大气各参数的模式重建结果令人满意。对于温度,在所有水平下,RMSE(均方根误差)低于1°C。对于风速,其为~2 m/s,并且对于风向,其在所有水平处处于[38-46°]的范围内,其对应于范围[21-26°]内的RMSE_relative。如果对风向应用滤波器(从计算中丢弃小于3 m/s的风),则风向RMSE在范围[30-41°]内,即RMSE_relative在范围[17-23°]内。对表层大气参数的模式业务预报适用于不同的应用,其中包括:利用提前数小时重建的夜晚开始时的温度对圆顶进行热化;提前知道夜间强风的主要方向,可以使天文学家预测夜间能见度好/差的情况,并相应地规划观测;防止自适应次镜因风速而产生的抖动。