This chapter aims to characterise turbulent airflow in the surface boundary layer, following qualitative and quantitative approaches. The former is based on a generalisation of Navier–Stokes differential equations, applied to flow mean and fluctuation components for obtaining budgets of vectorial and scalar quantities. The latter is based on similarity relationships dependent on atmospheric stability for evaluation of the components of kinetic energy budget equations. Spectral and co-spectral frequency characterisation of the turbulent flow, aiming to analyse the spectral structure of production, transport, inertial and dissipative scales, was performed, grounded on a brief introduction to the fundamentals of FourierFourier or frequency analysis analysis. Comparison of measured and calculated spectra following empirical similarity principles, particularly in slopes of curves in the inertial region, is fundamental for quality control assessment of atmospheric measurements and evaluating turbulent dynamics under distinct atmospheric stability conditions. The assessment of the power spectrum, autocorrelationAutocorrelation and cross-correlationCross correlation functions enhances the potential of frequency analysis of predominant turbulent eddies. Finally, a discussion is presented about eddy covariance methodology to obtain vertical fluxes, with measurements of fluctuations of scalar and vectorial quantities. The methodology is applied under turbulent transport frequencies, considering quality control proceedings and applications on local carbon budgets.