Atmospheric Refraction Predictions Based on Actual Atmospheric Pressure and Temperature Data

Calculations of atmospheric refraction are generally based on a simplified model of atmospheric density in the troposphere that assumes the temperature decreases at a constant lapse rate L from sea level up to a height h 11 km t », and that afterward it remains constant.In this model, the ratio T o /L, where T o is the temperature at the observer's location, determines the length scale in the calculations for altitudes h h t  .But daily balloon measurements across the USA show that in some cases there is an inversion so that the air temperature actually increases from sea level up to a height h 1 km p », and only after reaching a plateau with temperature T o ¢ at this height, it decreases at an approximately constant lapse rate.Hence, in such cases the relevant length scale for atmospheric refraction calculations in the range h h h p t  < is T L o ¢ , and the contribution for h h p  has to be calculated from actual measurements of air density in this range.Moreover,in three examples considered here, the temperature does not remain constant for h h t  , but continues to decreases to a minimum at h 16 km m » , and then increases at higher altitudes at a lower rate.Calculations of atmospheric refraction based on this actual atmospheric data are compared with the results of current simplified models.