Fundamental problems and limitations of the application of the sonic anemometer-thermometer to the study of the eddy transport of physical entities in the atmospheric boundary layer are discussed. The sonic anemometer-thermometer is most promising equipment for this purpose, but its character and limitation should be borne in mind on the way of application. The main points are line-averaged character of the sensor and humidity dependence of the temperature indications. Applications to the measurement of vertical eddy transport of particular physical entities are discussed respectively
