91̽��

The realization that the response of the Earth’s climate system to a climate forcing depends on the magnitude but also critically on the nature of the forcing mechanism is over three decades old. By “nature” of a forcing mechanism we refer to its geographical and temporal distribution, but also notably its altitude variation. As an introductory framework, I will describe our group’s work, ranging from early efforts with airborne observations to constrain the vertical distribution of aerosol radiative properties to more recent work on processes that determine the vertical distribution of aerosol and cloud properties in the Earth’s atmosphere. I will describe airborne instrument development work and more recent efforts in various airborne and satellite projects. I will outline the range of tools used in this research, from simple look-up table retrievals of aerosol refractive indices to machine-learning (ML)-based estimates of aerosol absorption and cloud condensation nuclei using only lidar observations and reanalysis data as predictors. I will conclude by describing my personal vision for how this observational work must be dedicated to aiding the development and validation of Earth System Models at all scales.