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Seasonal Teleconnections to the Indian Monsoon: Understanding the Large-scale Atmospheric Tropical Environment (STIMULATE)


STIMULATE is a collaborative project between the National Centre for Atmospheric Science (NCAS) / Department of Meteorology at University of Reading, the School of Earth and Environment at Univesity of Leeds, the School of Geosciences at University of Edinburgh and the Climatic Research Unit/School Environmental Sciences at University of East Anglia.

STIMULATE is led by Principal Investigator Dr Andy Turner at University of Reading, alongside Dr Nick Klingaman and Dr Kevin Hodges.

The team at Leeds is led by Dr Jennifer Fletcher, with Dr John Marsham.

Dr Massimo Bollasina will coordinate the work at Edinburgh.

The work at UEA is led by Dr Ben Webber with Prof. Manoj Joshi.

The new research at each institute is mainly carried out by PDRAs: Drs. Zhen Liu, James Mollard, Umakanth Uppara & Peter Willetts.

View picture of the STIMULATE team.

Funding information

STIMULATE is funded by the Weather and Climate Science for Services (WCSSP) India scheme administered by the Met Office on behalf of the Newton Fund. Projects funded under this programme aim to ...advanc[e] scientific understanding and modelling capabilities that can be translated into services, to protect lives and livelihoods across India

Project background

STIMULATE aims to address the following research objectives:

  1. Determine the underpinning coupled mechanisms of key teleconnections driving seasonal monsoon variability and the interactions between them;
  2. Determine the key relevant coupled model biases and their impact on seasonal monsoon prediction;
  3. Understand the nature of interactions down temporal and spatial scales, from decadal modes through seasonal variability, to enable enhanced prediction at regional scales in India.

Project meetings

Agenda of STIMULATE annual (virtual) project meeting held 14-15 May 2020.


Publications arising from STIMULATE are listed below and will be updated periodically. Team members are highlighted in bold. If you are not a subscriber to these journals, email me for an offprint.

  1. Dominant patterns of boreal summer interactions between tropics and mid-latitude: Causal relationships and the role of timescales. G. Di Capua, J. Runge, R. V. Donner, B. van den Hurk, A. G. Turner, R. Vellore, R. Krishnan and D. Coumou (2020). Weather and Climate Dynamics, submitted 17 April 2020, Discussions version published online 23 April 2020. |
    Tropical convective activity represents a source of predictability for mid-latitude weather in the Northern Hemisphere. In winter, the El Niño-Southern Oscillation (ENSO) is the dominant source of predictability in the tropics and extra-tropics, but its role in summer is much less pronounced and the exact teleconnection pathways are not well understood. Here, we assess how tropical convection interacts with mid-latitude summer circulation at different intraseasonal time-scales and how ENSO affects these interactions. First, we apply maximum covariance analysis (MCA) between tropical convective activity and mid-latitude geopotential height fields to identify the dominant modes of interaction. The first MCA mode connects the South Asian monsoon with the mid-latitude circumglobal teleconnection pattern. The second MCA mode connects the western North Pacific summer monsoon in the tropics with a wave-5 pattern centred over the North Pacific High in the mid-latitudes. We show that the MCA patterns are fairly insensitive to the selected intraseasonal time-scale from weekly to 4-weekly data. To study the potential causal interdependencies between these modes and with other atmospheric fields, we apply causal effect networks (CEN) at different time-scales. CENs extend standard correlation analysis by removing the confounding effects of autocorrelation, indirect links and common drivers. In general, there is a two-way causal interaction between the tropics and mid-latitudes but the strength and sometimes sign of the causal link are time-scale dependent. We introduce causal maps that plot the regionally specific causal effect from each MCA mode. Those maps confirm the dominant patterns of interaction and in addition, highlight specific mid-latitude regions that are most strongly connected to tropical convection. In general, the identified causal teleconnection patterns are only mildly affected by ENSO and the tropical-mid-latitude linkages remain similar. Still, La Niña strengthens the South Asian monsoon generating a stronger response in the mid-latitudes, while during El Niño years, the Pacific pattern is reinforced. This study paves the way for process-based validation of boreal summer teleconnections in (sub)seasonal forecast models and climate models and therefore helps to improve sub-seasonal and climate projections.

Page constructed by Dr Andy Turner; last updated May 2020.