`The normal condition of mankind," according to the poet A.E. Housman, "is one of just tolerable discomfort." So, climatically, it is with Mozambique in normal circumstances; the country enjoys, if that is the word, a sub-tropical climate with usually adequate but not excessive rainfall.
Superimposed on the orderly seasonal norms, however, as in the case of many places in the lower latitudes, are the erratic vagaries of those troublesome siblings, El Nino and La Nina.
The term El Nino is used to describe a general warming of the surface waters of the tropical Pacific Ocean, which occurs at irregular intervals of between three and seven years.
In normal times, steady easterly trade winds over the equatorial Pacific drag the warm surface water with them, causing a rise in sea level in the western part of that ocean. At the same time, cold water from below wells up near the coast of South America. Periodically, however, the trade winds relax for a time, and the warm surface waters in the western Pacific slosh back eastwards and raise the average temperature of a broad tropical swathe of ocean. The extra energy provided to the atmosphere by this "hotplate" engenders an El Nino.
El Nino reverberates globally around the lower latitudes. Arid areas of western South America are drenched with rain, and other areas in which rain is normally abundant experience droughts. This was the case in Mozambique following the 1992 El Nino, when the country experienced "wet" seasons that were among the driest this century. However, following the 1997/98 El Nino, there was adequate rainfall and the expected drought did not take place.
Now all is changed. La Nina is the name given to episodes which are almost a mirror image of El Nino: simplistically, the easterly trade winds are stronger than usual and push the warmer Pacific waters further west through the southern Indian Ocean. This relocated "hotplate", as it were, results in higher air temperatures than usual in the vicinity of southern Africa, and fuels a greater potential for very heavy rain.
The present La Nina has been running for two seasons and this is the second year that the rainy season in Mozambique, from December to March, has been wetter than usual.
In 1999 the rainfall was 50 per cent above normal; February 2000, as we have seen, has been particularly wet, with some places having almost three times the monthly average. The higher sea surface temperatures in the vicinity also provide energy for more active and more frequent tropical cyclones, an unwelcome extra ingredient in the disastrous mixture we have seen of late.