A189-0021
Using Causal Effect Networking to determine the pathway of the ENSO-Indian Summer Monsoon teleconnection
Using Causal Effect Networking to determine the pathway of the ENSO-Indian Summer Monsoon teleconnection
Tuesday, 15 December 2020
Poster
Abstract:
The strength and timing of the Indian Summer Monsoon (ISM) is heavily influenced by a variety of factors. One of the key factors influencing monsoon precipitation is the El Nino Southern Oscillation (ENSO), with drought years in India usually accompanied with a warm ENSO anomaly or El Niño. This teleconnection, despite previous studies, is still not fully understood.
In this work, we use a causal effect networking (CEN) technique as a method of highlighting the pathway that leads from changes in ENSO sea surface temperatures to change in the ISM. CEN's are able to differentiate between correlations that are due to independent relationships and those which show correlation due to other influences. In previous literature, these algorithms have been used to show both the links and timescales of global influences on a variety of atmospheric variables, including the ISM. Using these CEN technique that have been applied to other atmospheric connections with ERA20C reanalysis data at a shorter timestep of 3 days, we can create a robust template of the teleconnection pathway, both spatially and temporally. Our results suggest that the pathway occurs through changes to the Walker circulation over the Pacific Ocean, and the follow-on impact in the Hadley circulation over the Western Indian Ocean, taking approximately 18 days.
We go on to use this template to determine differences in the teleconnection in a variety of models, including UK Met Office CMIP6 simulations, and reanalysis datasets. The technique and template are also applied and used as a method of highlighting the time-varying changes in the ENSO-ISM teleconnection, both through the effect of climate change, and through the influences of other long term phenomenon, such as the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation.
In this work, we use a causal effect networking (CEN) technique as a method of highlighting the pathway that leads from changes in ENSO sea surface temperatures to change in the ISM. CEN's are able to differentiate between correlations that are due to independent relationships and those which show correlation due to other influences. In previous literature, these algorithms have been used to show both the links and timescales of global influences on a variety of atmospheric variables, including the ISM. Using these CEN technique that have been applied to other atmospheric connections with ERA20C reanalysis data at a shorter timestep of 3 days, we can create a robust template of the teleconnection pathway, both spatially and temporally. Our results suggest that the pathway occurs through changes to the Walker circulation over the Pacific Ocean, and the follow-on impact in the Hadley circulation over the Western Indian Ocean, taking approximately 18 days.
We go on to use this template to determine differences in the teleconnection in a variety of models, including UK Met Office CMIP6 simulations, and reanalysis datasets. The technique and template are also applied and used as a method of highlighting the time-varying changes in the ENSO-ISM teleconnection, both through the effect of climate change, and through the influences of other long term phenomenon, such as the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation.