Quantifying S2S Rainfall Characteristics

Subseasonal-to-Seasonal (S2S) rainfall characteristics such as onset, demise, and strength and duration of intermittent dry periods, or relative dry periods between rainfall seasons, provide important insight for the agriculture, health, disaster, and energy industries. These characteristics are classified as S2S because they exhibit S2S variation in their interannual variability, or the characteristic is within a rainfall season that spans a few weeks to a few months. These characteristics are examples of what are known as “weather within climate”, or characteristics of weather that lead to climate anomalies such as floods and agricultural droughts.

Several methods have attempted to calculate temporal characteristics of rainfall and few have worked with intermittent dry periods and calculate intermittent dry period characteristics. Issues arise when applying these methods for complex rainfall regimes, or regions that have one or more of the following: (1) multiple rainfall seasons in a given year, (2) a relatively wet dry season, (3) unclear transitions between wet and dry seasons. This research develops a new and comprehensive method for calculating S2S rainfall characteristics, especially for regions that have complex annual rainfall cycles.