On the secular variation of rainfall at Rothamsted

A detailed study of the rainfall at Rothamsted over the 76 harvest years, 1854-1929, has revealed the fact that not only have there been sensible changes in the average yearly rainfall of a similar character to those observed at other stations in England and Wales, but the distribution of rainfall throughout the year has changed. The maximum in autumn (and equally the minimum in spring) occurs significantly later to-day than was the case 76 years ago, but there is some sign that this movement is now reversing its direction, as appeared to have happened towards the end of the eighteenth and again in the middle of the nineteenth centuries, as judged from early records at a number of other stations. It would be interesting to have similar detailed analyses of the rainfall data at other places. The British Rainfall Organization is responsible for collecting the records of a very large number of stations, and a useful supplement to the monthly values now recorded would be a statement of the numerical constants specifying the distribution of rainfall throughout each year, taking as a unit a period of six days, or some other agreed number. The calculations for each year can be made on a single sheet of foolscap, and might form a routine operation at each station at the close of the year. If done for a large number of stations this analysis would furnish valuable climatological information on the general character of the incidence of rainfall over the whole country. Given information of an equal precision as to crop yield or other data of agricultural importance, the value of such rainfall distribution constants would be very great for the purposes of agricultural meteorology.