Modeling of Indian monsoon extremes during 850-2000AD using the proxy-data from speleothems.

This work highlights the potential significance of palaeoclimate model outputs in explaining the physical processes and mechanisms to better understand the speleothem-based proxy records of the precipitation and temperature signals during the Indian northeast and southwest monsoon from 850 to 2000AD. Thus, discussion is mainly focused on this conception by providing insights for aligning modeling preferences with the proxy records. δ18O speleothem values show that precipitation over northeast India (NEI) remained constantly higher than that over the summer core monsoon zone (CMZ) from 850-2000AD. Based on the dynamical numerical coupled model (CSIRO-Mk3L-1–2) outputs, the data are in alignment with the presence of four proxy-based major extreme climatic events: Dry Century (DC), Medieval Climatic Anomaly (MCA), Extreme Dry Century (EDC) and Little Ice Age (LIA) during the last millennia. In these extremes a significant trend in diurnal temperature range (DTR), in particular, is correspondingly observed. These extremes and associated mechanisms are examined using surface energetics and corresponding atmospheric-oceanic coupled processes. The analysis of downward radiative (shortwave and longwave), latent and sensible heat fluxes provided better rationale and understanding of associated physical processes and mechanisms. It is found that the latent and sensible heat fluxes were balanced by downward radiative fluxes and the remaining part of energy was anomalously trapped inside the surface, thus reflecting anomalous climatic behavior during these extremes. [ABSTRACT FROM AUTHOR]