Forecasting Cloud Cover and Atmospheric Seeing for Astronomical Observing: Application and Evaluation of the Global Forecast System - Astrophysics > Instrumentation and Methods for AstrophysicsReport as inadecuate




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Abstract: To explore the issue of performing a non-interactive numerical weatherforecast with an operational global model in assist of astronomical observing,we use the Xu-Randall cloud scheme and the Trinquet-Vernin AXP seeing modelwith the global numerical output from the Global Forecast System to generate3-72h forecasts for cloud coverage and atmospheric seeing, and compare themwith sequence observations from 9 sites from different regions of the worldwith different climatic background in the period of January 2008 to December2009. The evaluation shows that the proportion of prefect forecast of cloudcover forecast varies from ~50% to ~85%. The probability of cloud detection isestimated to be around ~30% to ~90%, while the false alarm rate is generallymoderate and is much lower than the probability of detection in most cases. Theseeing forecast has a moderate mean difference absolute mean difference <0.3-in most cases and root-mean-square-error or RMSE 0.2-0.4- in most casescomparing with the observation. The probability of forecast with <30% errorvaries between 40% to 60% for entire atmosphere forecast and 40% to 50% forfree atmosphere forecast for almost all sites, which being placed in the bettercluster among major seeing models. However, the forecast errors are quite largefor a few particular sites. Further analysis suggests that the error mightprimarily be caused by the poor capability of GFS-AXP model to simulate theeffect of turbulence near ground and on sub-kilometer scale. In all, althoughthe quality of the GFS model forecast may not be comparable with thehuman-participated forecast at this moment, our study has illustrated itssuitability for basic observing reference, and has proposed its potential togain better performance with additional efforts on model refinement.



Author: Q.-z Ye

Source: https://arxiv.org/







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