There is growing evidence that “tropical widening” has occurred over the past ~40 years. However, there is an order of magnitude disagreement among published rates of tropical widening, which range from a few tenths up to several degrees latitude per decade. The interrelationships between the diverse array of tropical width metrics used in the literature need to be better understood in order to explain the discrepancy among past tropical widening estimates and to provide clarity regarding future projections. The ISSI Tropical Widening Diagnostics Intercomparison Project (TWDIP) team will fulfill this goal by conducting the first systematic intercomparison of tropical width diagnostics.

Contribution of IMK-ASF: satellite data of quantities that can be used as metrics, and development of methods to determine the width of the tropical pipe in the stratosphere.