BITMAP was an Indo-UK-German project (NERC Grant award: NE/P006795/1) 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 had suggested that the pole-to-equator temperature difference is an essential ingredient driving variations in the monsoon.

BITMAP's initial focus was on the impact of the temperature difference between pole and equator on the establishment and variation of regional circulations. The project used 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.

The project then related the gradient to position of the strongest rainfall and strength and position of monsoon circulation. The project also examined the impact of different pole-to-equator temperatures on hydroclimates of the vulnerable Hindu Kush-Himalaya (HKH) region in High Asia.

Next the project tested 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. The project also helped evaluate and improve these models by determining the problems caused by typical monsoon errors (e.g. misplaced tropical rainfall) on simulation of polar climates; the project also explored how errors in model Arctic sea-ice distribution affect the monsoon. Finally the project analyzed effects of variations in climate.

The project measured and modelled 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, the project used observations and models to assess the role of the changing Arctic temperatures on the jet stream and on the regularity of heavy rainfall and flooding events that affect South Asia.

The objectives of the BITMAP project were as follows:
(1) Better understand the impact of the South Asian monsoon on temperature and circulation structure in the Arctic, including the role of changes in monsoon diabatic heating;

(2) Better understand the impact of the changing equator-to-pole temperature gradient on the establishment, maintenance and variation of regional circulations over the poles and monsoons;

(3) Analyze the impacts of the changing equator-to-pole temperature gradient in a warming climate on subseasonal-to-seasonal monsoon variability, with the express impact of improved scientific underpinning of forecasting at NCMRWF;

(4) Better understand how dynamical connections between high- and low-latitude regions influence moisture transports reaching high Asia from higher latitudes.