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Abstract

Knowledge of and the ability to predict lifting condensation levels (LCL) is important ingredient in weather predictions, cloud formation, planetary albedo and Earth’s energy balance. It is also essential topic in aviation safety and flight operations. In this article, we derive a new model of LCL and compare it to some older commonly-used models. This includes also the recently published Romps’ (2017) model. The new model presented here includes dependence, however weak, of the surface atmospheric pressure and the specific humidity on the LCL height and temperature. Such is not the case with widely used models and expressions by Espy and FAA among others, which neglect the effect of atmospheric pressure and specific humidity. We also present an iterative successive-approximations numerical method on computations of the LCL temperature and compare it with closed-form Bolton’s model. All these LCL models assume constant atmospheric lapse rate, which is the result of isentropic lifting including adiabatic cooling of moist air. Air pressure at LCL height is computed using Poisson’s equation. Our model predictions come close to the exact solution of LCL parameters in terms of Lambert’s special functions by Romps’, but more efforts are required to understand all the differences.

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