Dust- Droughts Relationship in CMIP6 Simulations

Abstract:

Both the atmospheric and land surface conditions affect the dust cycle in the climate system. In particular, the occurrence of drought can modulate emission of dust on interannual time scales. Studies have shown, however, that models generally do not represent dust variability, and that there is a large inter-model spread in the simulation of dust. In this study, we compare the relationship between drought and dust in 12 global circulation models (GCMs) participating in Phase Six of the Coupled Model Intercomparison Project (CMIP6) for historical (1950-2014) and future (2050-2100: SSP585) scenarios. The relationships between drought and dust are based on linear regression analysis. Our results show that the Standardized Soil Moisture Index (SMI) better explains the dust variability over most regions than the Standardized Precipitation Index (SPI), highlighting the importance of the condition of the land surface, and thus surface temperature on dust emission. We do not detect any systematic change in the drought-dust relationship in the future scenario compared to that in the historical simulations. Across models, the strength of the drought-dust relationship explains much of the spread in interannual variability of dust emission over South Africa, India, Australia, and North America, indicating models that capture this relationship generate greater variability. We also find that the strength of the dust-drought relationship does not explain the spread of the annual mean. Through similar analysis we investigate GCMs disagreement in dust seasonality, predictability, and deposition. Finally, we compare and contrast our results with satellite observations and reanalysis.