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- Title
The Dichotomy of Wet and Dry Trends Over India by Aerosol Indirect Effects in CMIP5 Models.
- Authors
Rai, Pradeep Kumar; Sarangi, Chandan; Arun, N.; Kuiry, S. N.; Leung, L. Ruby
- Abstract
Aerosol‐cloud interactions, also known as aerosol indirect effect (AIE), substantially impact rainfall frequency and intensity. Here, we analyze NEX‐GDDP, a multimodel ensemble of high‐resolution (0.25°) historical simulations and future projections statistically downscaled from 21 CMIP5 models, to quantify the importance of AIE on extreme climate indices, specifically consecutive dry days (CDD), consecutive wet days (CWD), and simple daily intensity index (SDII). The 21 NEX‐GDDP CMIP5 models are classified into models with reliable (REM) and unreliable (UREM) monsoon climate simulated over India based on their simulations of the climate indices. The REM group is further decomposed based on whether the models represent only the direct (REMADE) or the direct and indirect (REMALL) aerosol effects. Compared to REMADE, including all aerosol effects significantly improves the model skills in simulating the observed historical trends of all three climate indices over India. Specifically, AIE enhances dry days and reduces wet days in India in the historical period, consistent with the observed changes. However, by the middle and end of the 21st century, there is a relative decrease in dry days and an increase in wet days and precipitation intensity. Moreover, the REMALL simulated future CWD and CDD changes are mostly opposite to those in REMADE, indicating the substantial role of AIE in the future projection of dry and wet climates. These findings underscore the crucial role of AIE in future projections of the Indian hydroclimate and motivate efforts to accurately represent AIE in climate models. Plain Language Summary: We investigate the impacts of aerosol on India's wet and dry climate. High‐resolution downscaled CMIP5 models were used to calculate extreme indices like CDD (consecutive dry days), CWD (consecutive wet days), SDII (precipitation intensity). From the group of 22 models, 12 reliable models were chosen based on their fidelity to the observations. Amongst the reliable models, certain models incorporate only aerosol‐radiation interaction (REMADE), while others have both aerosol‐radiation and aerosol‐cloud interaction (REMALL). We found that the simulated trends in the REMAll were similar to the observed trends. In the current period (1975–2005), the aerosol‐cloud interactions led to the reduction in rainfall (both frequency and intensity wise) and enhanced the dry days, however in the future projections, the reduction in aerosol emissions leads to a wetter climate (increase in wet days and rainfall intensity) over India. Key Points: Using statistical metrics downscaled CMIP5 models are classified into reliable models for better simulating the wet and dry indices over IndiaDownscaled reliable models that included all aerosol effects (AIE + ADE) improved the simulated trends in the historical period than the models with only ADEThere is a general drying‐up (frequency‐wise and intensity‐wise) in the historical period. In the future projections, the reduction in aerosols lead to a wetter climate (frequency‐wise and intensity‐wise)
- Subjects
INDIA; AEROSOLS; RAINFALL frequencies; CLIMATE extremes; ATMOSPHERIC models; RAINFALL; TWENTY-first century
- Publication
Earth's Future, 2023, Vol 11, Issue 8, p1
- ISSN
2328-4277
- Publication type
Article
- DOI
10.1029/2022EF003266