ABSTRACT The vertical distributions of atmospheric turbulence ($C_n^2$) are key factors in determining the performance of ground-based telescopes and interferometers. As site-testing campaigns are extremely expensive, atmospheric modelling may represent the estimated results of astronomical sites. We propose a new outer-scale model to estimate refractive index structure constant ($C_n^2$) profiles containing potential temperature and wind shear. The integrated astroclimatic parameters (Fried parameter r0, seeing ε, isoplanatic angle θ0, and coherence time τ0) can also be calculated using this outer-scale model. Radiosonde measurements from a filed campaign at Tibet (Lhasa) and Rongcheng (Shandong) are utilized to quantify the performance of this model. Compared with the Dewan model, HMNSP99 model and Thorpe model, the new model gives better results as a profile and an astroclimatic parameter estimator. Compared with the measured median profile, the correlation coefficient reaches 0.88 in Lhasa and 0.87 in Rongcheng.