Spatiotemporal Climate Variability over Senegal and its Relationships with Global Climate

• Main Author: Fall, Souleymane
• Other Authors: Hugh Devine, Committee Member, Dev Dutta S. Niyogi, Committee Co-Chair, Fredrick Semazzi, Committee Co-Chair, Sethu Raman, Committee Member
• Language: unknown
• Published: 2004
• Subjects: ArcGIS Spatial Analyst; Climate variability in West Africa; tropical Atlantic SST; EOF Analysis; step change detection; predictability of Sahel rainfall; Pacific; North Atlantic
• Online Access: http://www.lib.ncsu.edu/resolver/1840.16/1304

Climate variability over Senegal and its relationships with global climate is examined for the period 1971-1998. Monthly observed rainfall for 20 stations over Senegal, monthly mean temperature for 12 stations and monthly average CMAP data were averaged for the months of June July, August and September, to generate seasonal rainfall totals for the wet season and climate indices averaged over the study period. The monthly SST data is the NOAA Extended Reconstructed SST data (ERSST) provided by the NOAA-CIRES Climate Diagnostics Center in Boulder, Colorado. The monthly, seasonal and annual temperature and precipitation distributions are mapped analyzed using ArcGIS Spatial Analyst. Rainfall distribution over Senegal is dominated by a N-S gradient, and temperature distribution by an E-W gradient. The mapping of the coefficient of variation for all stations reveals that for both rainfall and the number of rainy days, June is the month that exhibits the greater variability, especially in the West and North of the country. As regard to temperatures, the months from January to April are accountable for most of the variability, especially in the sub-arid areas of the North and Northwest. Trends in precipitation and temperature are estimated using a linear regression analysis and interpolation maps for the slopes. Areas of positive slopes are limited for rainfall (Northeast and Southwest of Senegal), but important and statistically significant for temperature throughout the country. To investigate the climate variability over Senegal two EOF analyses are performed: for 1971-1998 using observations, and for 1979-7998 using additional CMAP data. The first analysis reveals a strong domination of the first EOF mode for rainfall over Senegal. The corresponding time series mostly fluctuates on a high frequency mode. Its correlations with Atlantic and Pacific SST don't show a strong relationship leading to predictability. However, the second mode for September is well correlated with North Atlantic SST. Despite modest ...