A convective plume formed above some burning forest materials was investigated experimentally. The conditions of moderate and strong ground fire were modeled. Variances and spectra of intensity fluctuations and angles of incidence of a laser beam passing through the convective plume, as well as the altitude temperature distribution inside the plume were measured. The values of the structure characteristic of the refractive index inside the plume obtained from optical measurements and from measurements of the temperature gradient were compared.