On the dust load and rainfall relationship in South Asia: an analysis from CMIP5
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This study is aimed at examining the consistency of the relationship between load of dust and rainfall simulated by different climate models and its implication for the Indian summer monsoon system. Monthly mean outputs of 12 climate models, obtained from the archive of the Coupled Model Intercomparison Project phase 5 (CMIP5) for the period 1951–2004, are analyzed to investigate the relationship between dust and rainfall. Comparative analysis of the model simulated precipitation with the India Meteorological Department (IMD) gridded rainfall, CRU TS3.21 and GPCP version 2.2 data sets show significant differences between the spatial patterns of JJAS rainfall as well as annual cycle of rainfall simulated by various models and observations. Similarly, significant inter-model differences are also noted in the simulation of load of dust, nevertheless it is further noted that most of the CMIP5 models are able to capture the major dust sources across the study region. Although the scatter plot analysis and the lead–lag pattern correlation between the dust load and the rainfall show strong relationship between the dust load over distant sources and the rainfall in the South Asian region in individual models, the temporal scale of this association indicates large differences amongst the models. Our results caution that it would be pre-mature to draw any robust conclusions on the time scale of the relationship between dust and the rainfall in the South Asian region based on either CMIP5 results or limited number of previous studies. Hence, we would like to emphasize upon the fact that any conclusions drawn on the relationship between the dust load and the South Asian rainfall using model simulation is highly dependent on the degree of complexity incorporated in those models such as the representation of aerosol life cycle, their interaction with clouds, precipitation and other components of the climate system.
KeywordsLoad of dust CMIP5 Lead–lag Annual cycle Aerosol life cycle
First author is thankful to Head MASD, Group Director ER&SSG and Director IIRS for providing the support to carry out the present research. We acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups for producing and making available their model output (listed in Table 1). We also acknowledged Giovanni TRMM Online Visualization and Analysis System (TOVAS) for making available the monthly global precipitation GPCP version 2.2 data set for the research purpose. We thank IMD for preparing the quality controlled daily rainfall data set and making it available for research purpose. The CRU TS3.21 data set has been procured from http://badc.nerc.ac.uk. TOMS aerosol index and GOCART dust optical depth have been obtained from http://disc.sci.gsfc.nasa.gov/data-hldings/PIP/aerosol_index.html and http://acd-ext.gsfc.nasa.gov/People/Chin/gocartinfo.html respectively. We thank editor and anonymous reviewers for the comments on an earlier version of this manuscript which have helped us to bring out the manuscript in the present form.
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