Journal of Atmospheric Science Research

Convective Available Potential Energy and Convective Inhibition in ERA-Interim Reanalysis during the AMMA SOP Campaign

Cyrille Meukaleuni — 2025-04-03

A statistical analysis of Convective Inhibition (CIN) and Convective Available Potential Energy (CAPE) is conducted using a six-hourly ERA-Interim dataset for the summer of 2006 over West Africa as part of the African Monsoon Multidisciplinary Analyses (AMMA) SOP3 Campaign. This study analyses the trends and empirical orthogonal functions (EOF) of CAPE and CIN, along with the summer variability of CAPE and CIN with precipitation. CAPE exhibits its maximum over the continent around 14°N, while CIN peaks over the ocean. The variance of the main EOF is about 42% and its amplitude is low in the equatorial zone and slightly higher in the Sahelian regions. The variance of the second EOF is 16.4% and shows its maximum towards the south of Gambia. The significance of the trends of the pairs (first and second) of CAPE and CIN with rainfall is explored through the canonical correlation analysis (CCA) of these three parameters. The first and second pairs of CCA show a correlation of around 68% and 60%, respectively, with 12.2 and 10.8 degrees of freedom. The correlation coefficient at the 95% confidence level is 0.21 for the first CCA pairs and 0.65 for the second CCA pairs. In the Sahelian and Sudanese regions, the variance is approximately 78% and 73% respectively, primarily driven by the first CCA pair. The Guinea and wet equatorial areas are influenced by the second CCA pair, where the explained regional variance exceeds 60%.

Analysis of the Climatic Impacts of SO2 Injection into the Stratosphere on Precipitation Indices in the Sahel

Tji Souleymane Coulibaly — 2025-05-20

Stratospheric Aerosol Injection (SAI) emerges as a geoengineering strategy to mitigate global warming by reflecting sunlight back into space. However, this approach raises significant concerns, particularly regarding its impact on rainfall characteristics in the Sahel. This study investigates the effects of injecting sulfur dioxide (SO₂) into the stratosphere using the IPSL-CM5A-LR climate model, under two forcing scenarios: RCP4.5 (Representative Concentration Pathway of 4.5 W m^–²) and a combination of RCP4.5 with geoengineering forcing (G3). The analysis focuses on future climate conditions in the Sahel, based on 30-year averages over two distinct periods: 2020–2050 and 2050–2080. The results highlight notable differences between the “with injection” and “without injection” scenarios. The number of consecutive wet days (CWD) increases with SO₂ injection, indicating prolonged rainfall periods. Annual total precipitation on wet days (PRCPTOT) exhibits a slight upward trend with SO₂ injection, potentially mitigating drought effects. Conversely, maximum daily precipitation (Rx1day) and five-day precipitation (Rx5day) are slightly higher in the absence of injection, suggesting a reduction in extreme precipitation intensity when SO₂ is introduced. The Simple Daily Intensity Index (SDII) shows moderate variations between scenarios, with a slight decrease observed under SO₂ injection. These findings indicate that SO₂ injection could help stabilize precipitation regimes and reduce climate extremes in the Sahel. However, further research is crucial to gaining a deeper understanding of the long-term implications of this method and optimizing its application.

Spatiotemporal Variability of Tropospheric NO₂ and Aerosol Optical Depth in Lahore Division

Muhammad Zeeshan — 2025-04-23

This study examines the spatiotemporal variations of tropospheric Nitrogen dioxide (NO₂) and Aerosol Optical Depth (AOD) over the Lahore Division, utilizing satellite and ground-based data spanning from 2006 to 2023. The findings indicate consistently elevated NO₂ levels, attributed to the dense population, industrial activities, and crop residue burning, with mean values ranging from 3.87 to 6.34 × 10¹⁵ mole/cm². A seasonal analysis for the period 2021–2023 revealed heightened NO₂ concentrations during winter and autumn, with peaks observed in winter 2022 (4.86–8.09 × 10¹⁵ mole/cm²) and autumn 2021 (4.18–6.85 × 10¹⁵ mole/cm²), reflecting post-COVID-19 recovery trends. AOD variations demonstrated higher values in summer and fall (0.5–0.69), predominantly influenced by fine-mode aerosols, with an increasing trend post-COVID-19. The summers of 2021, 2022, and 2023 recorded peak AOD levels (0.68–1.10, 0.75–0.93, and 0.91–1.14, respectively). In 2023, a strong positive correlation (r = 0.02 to 0.19, R = 0.13) suggested an increase in anthropogenic emissions due to urbanization. The changes in NO₂ and AOD patterns from 2019 to 2023 underscore the impact of COVID-19-related restrictions on industrial, commercial, and transportation activities.