Influence of moisture source dynamics and weather patterns on stable isotopes ratios of precipitation in Central-Eastern Africa

Key Factors of Precipitation Stable Isotope Fractionation in Central-Eastern Africa and Central Mediterranean

“…The significant variations in altitudes in Virunga, often abrupt, are recorded in the noticed difference between the mean annual precipitation in the Virunga lowlands (found below 2000 m a.s.l. ; 1300-1700 mm yr -1 ) and highlands (> 2000 m; up to 2300 mm yr -1 ) [29,30]. Virunga has a bimodal precipitation regime: a dry season (July to August) and a wet season (September to June); with a short dry-like period observed from mid-January to late-February.…”

“…; evaporation rates~1500 mm yr -1 ), Lake Edward (912 m a.s.l. ), several springs, and middle to large rivers (see compilation in [22,30]). At the regional scale, Virunga is located at the border between the Central and Eastern Africa regions, where a humid rainforest tropical climate predominates.…”

“…The Virunga mountains influence the regional wind circulation, particularly those of the lower atmosphere. Virunga is part of the African Great Lake Region (Figure 1), where Lake Victoria, Lake Tanganyika, Lake Malawi, Lake Albert, etc., large rivers, and wetlands impact the East African regional climate and moisture production [30]. These lakes, large rivers and wetlands are subject to important evaporation.…”

“…After collecting the required aliquot for laboratory analysis and measuring the monthly precipitation amounts, the containers were washed with distilled water, and changed every 2-3 months during the study period. Water samples were filtered in the field through 0.45-mm-pore-size polysulfone syringe filters and stored at room temperature in 30 [32,33,41,42].…”

“…Samples were first run in duplicate on a different day and instrument. Samples for which repeatability of the two runs was not within 2 times the typical uncertainty were repeated on a dual-inlet isotope ratio mass spectrometer (Isoprime DI 100) following equilibration with H 2 or CO 2 gases respectively [44] [30]. The majority of the samples from the Mediterranean was analyzed at the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Palermo.…”