Better understanding of Interregional Teleconnections for prediction in the Monsoon and Poles

BITMAP is an Indo-UK-German project to develop better understanding of processes linking the Arctic and Asian monsoon, leading to better prospects for prediction on short, seasonal and decadal scales in both regions. Recent work has suggested that the pole-to-equator temperature difference is an essential ingredient driving variations in the monsoon. BITMAP's initial focus will be on the impact of the temperature difference between pole and equator on the establishment and variation of regional circulations. We will use existing databases of multiple climate models to unpack the impact of different forcing agents (e.g. greenhouse gases and polluting aerosols) on the relative warming of the northern and southern hemispheres and pole-to-equator temperature gradients. Next we will relate the gradient to position of the strongest rainfall and strength and position of monsoon circulation. We will also examine the impact of different pole-to-equator temperatures on hydroclimates of the vulnerable Hindu Kush-Himalaya (HKH) region in High Asia. Next we will test the impact on Arctic circulation patterns of "diabatic" heating arising from the monsoon rainfall (via waves in the atmosphere) by conducting novel experiments with climate models. This will also help us evaluate and improve these models by determining the problems caused by typical monsoon errors (e.g. misplaced tropical rainfall) on simulation of polar climates; we will also explore how errors in model Arctic sea-ice distribution affect the monsoon. Finally we will analyze effects of variations in climate. We will measure and model the impact of typical strong and weak Asian monsoon summers on atmospheric waves that travel to the poles and thereby develop a better understanding of the pathways to Arctic circulation, with implications for predicting sea-ice extent. In the other direction, we will use observations and models to assess the role of the changing Arctic temperatures on the jetstream and on the regularity of heavy rainfall and flooding events that affect South Asia.

The main user benefits of this work will be felt through the national meteorological services (chiefly NCMRWF, our funded partner) via increased understanding of the drivers of extreme rainfall events in northern India. Existing collaborators external to the project, such as the UK Met Office, will also feel such benefits since they provide the background modelling architecture used by NCMRWF and will thus be keen to hear of the model performance, particularly in the rarely studied phenomena of western disturbances.

Secondly, national and state government ministries in South Asia will benefit through better-informed decision-making on the effects of changing climate on the mean monsoon and extreme events, particularly in the north. These events are particularly relevant for flooding (e.g. Pakistan 2010 and Uttarakhand 2013 floods) and thus infrastructure management or design, disaster preparedness (including evacuation procedures) and climate resilience. India has made great strides over the last decade in their preparedness for coastal disasters due to tropical cyclones, so if the same benefits could be extended to westerly systems - improved forecasting, and relevant emergency planning for the region - many losses could be saved. Improvements will have been achieved by this project if the value of forecasts made and of the changing statistics of extreme events can be better communicated to society.

Thirdly, the improved projections to be made in this project of the impact of climate warming, and tropical monsoon variability, on sea-ice extent, and of the impact of tropical biases in forecast and climate models on the simulation of sea ice, may have benefits in shipping and mining industries in the North Atlantic, North Pacific and North Sea.

Finally, the general public in UK, India and Germany will benefit from being given an understanding of the impacts of climate warming on the monsoon and Arctic regions, including on the merits and limitations of forecasts and of the process of modern atmospheric science, potentially encouraging career choice and interest.