TITLE:
Influence of Sea Level Pressure on Inter-Annual Rainfall Variability in Northern Senegal in the Context of Climate Change
AUTHORS:
Aichetou Dia-Diop, Malick Wade, Sinclaire Zebaze, Abdoulaye Bouya Diop, Eric Efon, Andre Lenouo, Bouya Diop
KEYWORDS:
Global Precipitation Climatology Project (GPCP), West Africa monsoon, Inter-Tropical Convergence Zone, African Easterly Jet (AEJ), Tropical Easterly Jet (TEJ), Sea Level Pressure (SLP)
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.12 No.1,
January
7,
2022
ABSTRACT: This study examines the inter-annual
variability of rainfall and Mean Sea Level Pressure (MSLP) over west Africa based
on analysis of the Global Precipitation Climatology Project (GPCP) and National Center for Environmental
Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis
respectively. An interconnection is found in this region, between Mean Sea
Level Pressure (MSLP) anomaly (over Azores and St. Helena High) and monthly
mean precipitation during summer (June to September: JJAS). We also found that
over northern Senegal (15°N - 17°N; 17°W - 13°W)
the SLP to the north is strong; the wind converges at 200 hPa corresponding to the position of the African Easterly Jet (AEJ) the
rotational wind 700 hPa (corresponding to the position of the African
Easterly Jet (AEJ) coming from the north-east is negative. In this region, the
precipitation is related to the SLP to the north with the opposite sign. The
Empirical Orthogonal Functions (EOF) of SLP is also presented, including the
mean spectrum of precipitation and pressures to the north (15°N - 40°N and 50°W - 25°W) and south (40°S - 10°S and 40°W - 0°E). The dominant EOF of Sea Level Pressures north and south of the
Atlantic Ocean for GPCP represents about 62.2% and 69.4% of the variance,
respectively. The second and third EOFs of the pressure to the north account
for 24.0% and 6.5% respectively. The second and third EOFs of the pressure to
the south represent 12.5% and 8.9% respectively. Wet years in the north of
Senegal were associated with anomalous low-pressure areas over the north
Atlantic Ocean as opposed to the dry years which exhibited an anomalous high-pressure
area in the same region. On the other hand, over the South Atlantic, an
opposition is noted. The wavelet analysis method is applied to the SLP showings
to the north, south and precipitation in our study area. The indices prove to
be very consistent, especially during intervals of high variance.