The impact of aerosols and land surface properties on the lifted temperature minimum in the nocturnal atmospheric boundary layer field and laboratory experiments

Abstract

The thesis focuses on the effect of radiation forcing by atmospheric aerosols on the nocturnal boundary layer close to ground. This study is on the anomalous temperature profile that develops after sun-set, under calm, clear-sky conditions, and which is characterized by the occurrence of minimum temperature a few decimeters above the ground. This phenomenon was first reported by Ramdas and Atmanathan in 1932, and is referred in the literature as „Lifted temperature minimum’ (LTM), or „The Ramdas effect’. In the thesis, we present results from both field observations and laboratory experiments on this phenomenon. Temperature profile close to ground, in the nocturnal boundary layer, influences the surface energy budget, and plays an important role in many micrometeorological processes including the formation of inversion layers, and radiation-fog. Research work on this topic, by our group, has shown that a homogeneous atmosphere does not cause the preferential cooling necessary for the development of an LTM-type profile [Mukund et. al. (2010); Ponnulakshmi et. al. (2012a), (2012b)].