Research On The Forecast Of Atmospheric Optical Turbulence And Analysis Of Potential Astronomical Sites In The Antarctic Continent

Antarctica may be the optimal location for the installation of a large-aperture astronomical telescope on Earth.Antarctic site testing for astronomy has increasingly become the focus of research conducted by scientific and technological powerhouses.Atmospheric optical turbulence is a crucial factor that impacts the imaging quality of ground-based optical astronomical telescopes.To fully exploit the exceptional astronomical observation conditions in Antarctica,this study employs the Polar-optimized version of the Weather Research and Forecasting model(Polar WRF)to predict and analyze atmospheric optical turbulence over Antarctica.Astronomical seeing above Dome A in Antarctica was first forecasted by Polar WRF,which is of great guiding significance for planning observations with large-aperture telescopes.Based on the Polar WRF forecasts provided by the Antarctic Mesoscale Prediction System(AMPS),the annual atmospheric optical turbulence conditions across the entire Antarctic continent were first evaluated,and some potential excellent astronomical observatory sites that have not been previously reported were identified.The main contributions of this paper are summarized as follows:1.The detailed procedures for installing,debugging,operating,and processing forecast results of the Polar WRF model on a PC are presented.2.Based on the Monin-Obukhov similarity theory,the Polar WRF model was used to predict the near-surface refractive index structure constant(Cn2)at the Antarctic Taishan Station.The correlation coefficient(Rxy)of log10(Cn2)was about 0.67 when compared with measurements from a micro-thermometer.The Polar WRF forecasts were extended to the entire Antarctic continent.It was found that near-surface Cn2 reached a minimum value under neutral stability while the sun elevation was about 20°.3.Based on the Tatarskii formula,a model for estimating near-surface Cn2 in Antarctica was established.This model can estimate Cn2 using automatic weather station measurements.The Rxy between estimated log10(Cn2)and observations reached 0.72.Additionally,a new estimation model based on Tatarskii’s formula for total atmospheric seeing was proposed.This estimation model can be used in conjunction with the Polar WRF model to forecast seeing.A sensitivity analysis of input parameters for this estimation model was conducted to study how different grid-level meteorological data and calculated values of boundary layer thickness affect prediction performance.The results showed that all Rxy between forecasted seeing and observations exceeded 0.62,where the observations are measured by DIMM from Dome A during the polar day and polar night.4.A strong correlation was found between the measured seeing and the Richardson number(Ri)predicted by the Polar WRF model.The Antarctic atmospheric Ri was estimated using AMPS-forecasted meteorological data,The Rxy of log10(Cn2)at McMurdo,South Pole,and Dome C were 0.72,0.59,and 0.53 respectively when compared with estimations from radiosonde measurements.Atmospheric activities such as polar vortexes,katabatic winds,and gravity waves that may trigger Antarctic optical turbulence were analyzed.5.An indicator for evaluating total atmospheric seeing was proposed based on the AMPS-forecasted boundary layer height and Ri.Compared with scattered statistical values from several sites above the Antarctic continent in recent～20 years,the Rxy reached 0.68.According to this indicator,the seeing in the Antarctic was predicted and sorted from best to worst as follows:Ric1,Ridge A(close to Ric2),Dome B(close to Ric3),Ric4,Dome A,Ridge B,Dome F,Dome C,and South Pole.Ric1 and Ric4 are local potential best astronomical sites.These two sites were first predicted in this paper and are located in the Transantarctic Mountains and high interior respectively.In summary,based on the Polar WRF forecasts and the proposed optical turbulence estimation model,the estimated optical turbulence is consistent with observations.This indicates that the proposed method for forecasting Antarctic optical turbulence is feasible.According to model forecasts,factors affecting optical turbulence in Antarctica were analyzed,the change rules of Antarctic optical turbulence were revealed,and some potential sites better than existing observatories were found,which has important guiding significance for future astronomical site selection in Antarctica.