Journal of Atmospheric Science Research

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.

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%.

In Defence of the Biotic Pump

Peter Paul Bunyard — 2025-01-25

The biotic pump theory of Anastassia Makarieva and Victor Gorshkov invited considerable controversy when published in 2007. Experiments carried out by Bunyard et al. on the relationship between airflow and water vapour condensation and employing the physics of ideal gases to determine absolute humidity and energy flows, indicate that the physical processes underpinning the biotic pump theory are correct and must play a significant role in determining regional and global weather patterns. Further evidence is given showing that the energies associated with condensation correlate with measured airflow. Given the role of the biotic pump in generating flying rivers over the Amazon Basin, deforestation can result in hydrological collapse. How close to that point in time can now be determined. An annual precipitation of 1800 mm is close to the threshold when rainfall is insufficient to sustain the forests. Experiments on different types of vegetation, measuring vapour emissions as latent heat, indicate the degree to which plants cool their environment by means of transpiration. By regulating the rate of transpiration plants respond to ambient temperature and prevent overheating. Forests in particular can help cool the Earth’s surface. In conclusion. the invention of the atmospheric heat engine in 1700 illustrates the power of condensation to drive atmospheric air flows and its functioning illustrates the physics underpinning the biotic pump.

Sub-Seasonal Variability of Summer Monsoon Rainfall in CMIP6 Simulation over the Gangetic Plain of India

Devendra Kumar Tiwari — 2025-01-25

This current research work is focused on the performance of the Coupled Model Intercomparison Project (CMIP6) models in replicating Indian Summer Monsoon (ISM) rainfall patterns, mainly focusing on the Gangatic Plain, spanning from 1979 to 2014. The evaluation employs rigorous validation against rainfall data from the Indian Meteorological Department (IMD) and includes models with a resolution of 100km or less. Results highlight three standout models CMCC-CM2-SR5, EC-Earth3-AerChem, and CMCC-ESM2—for their commendable accuracy in capturing rainfall distribution in the Gangatic Plain. Monthly assessments reveal that these models closely mimic observed rainfall, unlike other models such as CMCC-CM2-HR4, CNRM-CM6-1-HR, EC-Earth3-CC, and MPI-ESM1-2-HR, which fail to replicate observed rainfall patterns. The simulated seasonal cycle of rainfall in CMCC-CM2-SR5 aligns well with observed patterns, especially for July, August, and September. Although there are some amplitude differences, CMCC-CM2-SR5 accurately represents the range and median of observed rainfall during these months. Interannual fluctuations in mean rainfall during the JJAS period can also be derived from observed data. Furthermore, CMCC-CM2-SR5, EC-Earth3-AerChem, and CMCC-ESM2 successfully capture interannual variability in July, August, and September, indicating substantial rainfall variability on a sub-seasonal scale across the Indian subcontinent. However, the assessment emphasizes the need for improved accuracy in depicting rainfall variability in CMIP6 models to bridge existing gaps between simulated and observed rainfall. Nevertheless, the study emphasizes the ongoing necessity for enhancements to ensure more accurate simulations and a closer match to actual rainfall variability in the examined CMIP6 models.

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.

Comprehensive Studies on Atmospheric Sciences

Jianhui Bai — 2025-01-25