Assessment of static stability indices and related thermodynamic parameters for predictions of atmospheric convective potential and precipitation over Nigeria

Three static stability indices (K-index, KI; Lifted-index, LI; and Total Totals index, TTI) and three related thermodynamic parameters (First and second Adedokun indices; ADED1 and ADED2 as well as the available potential energy; CAPE) were estimated to predict instability condition and precipitation over Nigeria. ERA5 reanalysis datasets of daily air temperature and specific humidity at multiple pressure levels from 1979 to 2018 were used for the prediction while the computed seasonal averages of the static stability indices (SSIs) and thermodynamic parameters (TPs) were validated with the precipitation data. It was revealed that SSIs and TPs produced ranges of values that were fairly good predictive of atmospheric convection and instability conditions over different climatic zones. They adequately captured seasonal variations in atmospheric instability conditions and migration and pulsation of the south-westerly and the north-easterly wind systems. Significant decreasing trends in annual SSIs, PTs, and precipitation were obtained over Sahel. Furthermore, fairly strong and significant positive correlations (0.66 ≤ r ≤ 0.87) were obtained between precipitation and SSIs in the north i.e. Sahel and Savannah. Fluctuation in precipitation was explained by 26–70% variations in LI, 13–19% in ADED1, and 27–36% variations in KI, particularly in the north. In conclusion, diminishing trends of the LI, KI, and ADED1 during the 40-year study period were adduced to reduced precipitation. The study has application in improved weather forecast of convection systems and precipitation in West Africa at large.