Climate variability

Lesotho, being in the subtropics, has a highly variable climate. The climate fluctuates significantly at seasonal, annual, and longer timescales. This is clearly depicted in the annual rainfall series for Mejametalana. There are years, such as 1981, 1992, and 2003, that received well below average rainfall, as well as years like 1976 and 2000 that registered above average rains.  

The question is: what drives the observed variability? A relationship between the El-Nino Southern Oscillation (ENSO) phenomenon and Lesotho’s rainfall has been established. The link is such that during El-Nino (warm ENSO event) below average rainfall is received while La-Nina (cold-ENSO event) is accompanied by above-normal rainfall over the country. However, some El-Nino (La-Nina) years are not accompanied by dry (wet) conditions. Also, either dry or wet conditions can occur during the so-called non-ENSO or neutral years suggesting the existence of other drivers of climate variability in Lesotho.

Some of the research questions that are being dealt with include:

·        What is the influence of ENSO on the rainfall season onset and cessation, and the frequency and intensity of dry spells in Lesotho?

·        What are the local drivers of climate variability over the country?

·        Can these local factors be incorporated as predictors in our climate models to improve prediction skill?