Physics is the third discipline investigated in CloudRoots. As the figure of DISCIPLINES shows, clouds perturb and control the amount of direct and diffuse radiation reaching the surface. The available energy is then partitioned into sensible heat flux, which is the main driver of atmospheric convective turbulence, and evapotranspiration, which is the main source of moisture needed to form and intensify clouds. Key aspects in this land-atmosphere-cloud system are the conditions in the free troposphere. These conditions are the lapse rate of temperature and moisture, and subsidence motions as well as the influence of large-scale advection. The combined and integrated experiments designed in CloudRoots will enable us to obtain enough observational evidence which will be used to design, constrain and evaluate the numerical experiments carried out by DALES and CLASS.