The Indo-Gangetic Low-Level Jet

The Indo-Asian Monsoon (IAM) plays an integral role in transporting water vapor across the Indo-Gangetic Plains (IGP) and the Himalayan Mountains (HM). We use various reanalysis products to highlight an easterly low-level jet across the IGP, which we identify as the primary moisture transport mechanism for the northeastern branch of the IAM. We find that this easterly flow is responsible for the bulk of the precipitation at the east-central margin of the HM, and yet modeling and theory have largely ignored this important feature. Thus, we analyze various atmospheric general circulation models found in the CMIP5 archive and illustrate that more than half the models fail to reproduce the easterly low-level jet. As a result, the biased models simulate an excessive westerly moisture transport and tend to misrepresent precipitation rates along the east-central HM, the IGP, and the Ganges Basin. Our study highlights the long-standing model-data biases across the region and has implications for future projections of the IAM.