Penman, H L
Howard Latimer Penman, FRS, OBE 1909 (County Durham, UK) - 1984
Penman was educated at Blaydon Grammar School and at the Armstrong College of the University of Durham whence he graduated in physics in 1930. Penman's early postgraduate work was on the physics of sound, and later, at the Shirley Institute, on the physical properties of cotton.
Appointed in 1937 to the Physics Department of the Rothamsted Experimental Station, he studied gaseous diffusion through porous materials and evaporation from fallow soils. When war broke out he was recruited by the Admiralty and worked on the sound output of ships and submarines in connection with the development of acoustic mines. In 1944 he was recalled to Rothamsted to work on the physics of wet soil in preparation for the land campaign, where the "traffic ability" of soils would be vital to the progress of military vehicles.
Penman's researches into the evaporation process culminated in his 1948 Proceedings of the Royal Society paper "Natural evaporation from open water, bare soil and grass". Thereafter Penman travelled worldwide studying water use of crops and evaporation from open water surfaces, notably in the USA, in Australia on a Nuffield Foundation Fellowship, and in East and West Africa. In 1954 he was appointed head of the Physics Department at Rothamsted in succession to Dr R.K.Schofield, a post which he held until his retirement in 1974. Under his supervision and stimulation the Physics Department at Rothamsted produced a number of outstanding scientists in the field of soil physics and agricultural meteorology.
President of the Royal Meteorological Society from 1961 to 1963, he was elected to Fellowship of the Royal Society and awarded the OBE in 1963.
Although Penman himself was not a hydrologist and spent his working life in agricultural research, the importance of Penman's work was so acknowledged by the hydrological community that from 1964 to 1969 he was chosen to head the UK delegations to the Coordinating Council of the International Hydrological decade, at UNESCO in Paris. Likewise in the UK his guidance was sought in the discussions and negotiations which preceded the establishment at Wallingford of the DSIR Hydrological Research Unit, the precursor of the present NERC Institute of Hydrology.
Penman's study of the physics of evaporation was unique in that he solved the energy budget and vapour exchange equations by eliminating the dominant but not routinely measured soil surface temperature. His resulting combination equation converted the meteorological variables of air temperature and humidity, solar radiation or hours of bright sunshine and wind run at 2 m high, into "potential" evaporation or "potential" transpiration; "potential" implied an open water surface or a well-watered short grass surface of zero heat capacity and of infinite extent. The technique was applied by Penman and others, with considerable success, worldwide; it facilitated "normalization" of estimates of evaporation particularly in more extreme climatic regions and where substantial ranges in altitude occurred.
Valuable as was the application of Penman's estimate of evaporation in agricultural situations, it was invaluable to the hydrologist and water resources engineer: it provided for the first time a truly physical basis for estimating the most intractable (and at the time unmeasurable) component of the water balance of basin areas even over relatively short time periods.
Penman was successful in applying his techniques in agricultural irrigation practice at Woburn, UK, using grass and rotation crops; his results were reported in two series of three papers in the Journal of Agricultural Science in 1962 and 1970.
McCulloch, J. S. G. "HOWARD LATIMER PENMAN." Hydrological Sciences Journal 30, no. 3 (1985): 431-432.
Howard Penman: Wikipedia https://en.wikipedia.org/wiki/Howard_Penman