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Assessments of CMIP5-Derived Aerosol Distributions over India

Paper Reviewed
Sanap, S.D., Ayantika, D.C., Pandithurai, G. and Niranjan, K. 2014. Assessment of the aerosol distribution over Indian subcontinent in CMIP5 models. Atmospheric Environment 87: 123-137.

Citing 15 different studies in an introduction of their work, Sanap et al. (2014) state that "aerosols can have significant impact on regional climate through changes in radiative budget and modifications in precipitation processes, cloud properties and dynamical state of the atmosphere." And, therefore, they go on to examine aerosol distributions over the Indian subcontinent "as represented in 21 models from Coupled Model Inter-comparison Project Phase 5 (CMIP5) simulations, wherein model-simulated aerosol optical depth (AOD) is compared with Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite observations," with the overall objective of determining the models' abilities to capture the spatial and temporal distributions of different aerosol species over the Indian subcontinent.

In reporting their findings, the four Indian researchers say their study revealed that "most of the CMIP5 models were unable to simulate the aerosol distribution correctly over the Indian subcontinent." More specifically, they write that (1) the "majority of the CMIP5 models seriously underestimates the spatio-temporal variability of aerosol species over the Indian subcontinent," that (2) the magnitude of dust loading "is underestimated in [the] majority of the models," that (3) the "majority of the models show huge negative bias (underestimation) in AOD simulation over [the] Indo-Gangetic Plain," that (4) "biases in winds at 850 hPa (which play an important role in aerosol transport) are significantly large in most of the CMIP5 models)," that (5) "the aerosol concentration is found to be overestimated during monsoon season in some models," while (6) "it is underestimated in [the] majority of the models."

In light of these several disturbing discoveries, Sanap et al. conclude -- and rightly so -- that "aerosol sources/sinks, seasonal variation and associated aerosol chemistry need to be improved in those [CMIP5] models for better representation of the aerosol distribution over the Indian subcontinent," and, we would add, for better assessments of their associated climatic impacts."

Posted 28 April 2015