Optical Turbulence Measurements and Models for Mount John

Site measurements were collected at Mount John University Observatory in 2005 and 2007 using a purpose-built scintillation detection and ranging system. C 2 N (h) proling indicates a weak layer located at 12 { 14 km above sea level and strong low altitude turbulence extending up to 5 km. During calm weather conditions, an additional layer was detected at 6 { 8 km above sea level. V (h) proling suggests that tropopause layer velocities are nominally 12 { 30 ms 1 , and near-ground velocities range between 2 { 20 ms 1 , dependent on weather. Little seasonal variation was detected in either C 2 N (h) and V (h) proles. The average coherence length, r0, was found to be 7 1 cm for the full prole at a wavelength of 589 nm. The average isoplanatic angle, 0, was 1:0 0:1 arcsec. The mean turbulence altitude, h0, was found to be 2:0 0:7 km above sea level. No average in the Greenwood frequency, fG, could be established due to the gaps present in the V (h) proles obtained. A modied Hufnagel-Valley model was developed to describe the C 2 N (h) proles at Mount John, which estimates0 at 6 cm and 0 at 0.9 arcsec. A series of V (h) models were developed, based on the Greenwood wind model with an additional peak located at low altitudes. Using the C 2 (h) model and the suggested V (h) model for moderate ground wind speeds, fG is estimated at 79 Hz.