Investigation of weather anomalies in the low-latitude islands of the Indian Ocean in 1991

Abstract

International audienceTemperature, precipitation and sunshine duration measurements at meteorological stations across the southern Indian Ocean have been analysed to try to differentiate the possible influence of the Mount Pinatubo volcanic eruption in the Philippines in June 1991 and the normal weather forc- ings. During December 1991, precipitation on the tropical is- lands Glorieuses (11.6◦ S) and Mayotte (12.8◦ S) was 4 and 3 times greater, respectively, than the climatological mean (precipitation is greater by more than than twice the standard deviation (SD)). Mean sunshine duration (expressed in sun hours per day) was only 6 h on Mayotte, although the sun- shine duration is usually more than 7.5 ± 0.75 h, and on the Glorieuses it was only 5 h, although it is usually 8.5 ± 1 h. Mean and SD of sunshine duration are based on December (1964–2001 for Mayotte, 1966–1999 for the Glorieuses).The Madden–Julian Oscillation (MJO) is shown to corre- late best with precipitation in this area. Variability controlling the warm zone on these two islands can be increased by the Indian Ocean Dipole (IOD), El Niño, the quasi-biennial os- cillation (QBO) and/or solar activity (sunspot number, SSN). However, temperature records of these two islands show weak dependence on such forcings (temperatures are close to the climatological mean for December). This suggests that such weather forcings have an indirect effect on the precipi- tation.December 1991 was associated with unusually low val- ues of the MJO index, which favours high rainfall, as well as with El Niño, eastern QBO and high SSN, which favour high variability. It is therefore not clear whether the Mount Pinatubo volcanic eruption had an effect. Since the precipitation anomalies at the Glorieuses and Mayotte are more or less local (Global Precipitation Climatology Project (GPCP) data) and the effect of the Pinatubo volcanic cloud should be more widespread, it seems unlikely that Pinatubo was the cause.Islands at higher southern latitudes (south of Tromelin at 15.5◦ S) were not affected by the Pinatubo eruption in terms of sunshine duration, precipitation or temperature

Spatio‐temporal variability of rainfall in a high tropical island: Patterns and large‐scale drivers in Réunion Island

“…Rainfall data ( RR as the rain rate) at island scale were available for the period 1975–2015 thanks to a large network of 54 rain‐gauges covering most of the territory. The reader is referred to Réchou and Kirkwood () for more details about this rain‐gauge network. Moreover, it is worth noticing that the rain‐gauges are not uniformly located throughout the island.…”