A Simplified Model for Free-atmosphere Seeing Estimation Using NCEP/NCAR Data at the ORM

Abstract We present and validate a simplified physical model for estimating free-atmosphere seeing ( ε free ) using NCEP/NCAR reanalysis data at the Roque de los Muchachos site. We compare the computed values to MASS-DIMM measurements across 235 common nights from 2008 May to 2009 September, and for a well-sampled night (2008 November 18). The seasonal comparison gives root mean square error (RMSE) = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0</mml:mn> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> <mml:mn>67</mml:mn> </mml:math> and r = 0.56. On the selected night, applying smoothing and bias correction lowers the RMSE to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0</mml:mn> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> <mml:mn>07</mml:mn> </mml:math> and raises r to 0.85. These findings support the use of this lightweight model for astroclimatology and preliminary site evaluation in areas lacking field measurements. A dual-panel figure summarizes both results.