Physical Meteorology

Like the other lecturers he had a relaxed, friendly manner and was a good teacher. His lectures related to the subjects of solar and terrestrial radiation, heat balance of the northern hemisphere, cloud physics, the precipitation process, and the upper atmosphere.

The 49 pages of the notes I made on Houghton's lectures remind me of the detail covered in his lectures which I found both interesting, informative and stimulating. Later studies I made of rainfall, rain-making and drought were the result of an interest kindled by Houghton's lectures.

His lectures on radiation included a discussion of the efforts of the Smithsonian Institute to measure the intensity of the solar beam (the so-called 'solar constant') and the scattering and absorption of solar and long-wave radiation. I had gathered a reasonable knowledge of these subjects from Humphrey's Physics of the Air but the discipline of note taking, completing assignments and tests, and a final examination in the competitive atmosphere of the classroom ensured that my knowledge of the subject was expanded.

The lectures of cloud physics were of special interest and this was obviously Houghton's special area of research. He provided much information on the processes of condensation and evaporation, sizes of cloud and rain drops, collision processes and condensation nuclei. His lectures also referred to the reflection of radar beams by water drops, which was at the time when the Bureau's 277 radars were being installed.

In referring to rain-making Houghton indicated that cloud seeding with dry-ice and silver iodide was likely to change the condensation process in clouds. He pointed out, however, that the water content of the droplets in an average cumulus would only amount to a few millimetres if precipitated so that sustained and vigorous condensation was required for significant rainfall. Presumably such sustained condensation would require significant upward motion in the cloud.

Bureau of Meteorology