Contribution of phenology and soil moisture to atmospheric variability in ECHAM5/JSBACH model

Abstract

Soil moisture and phenology are seasonally varying modes of the land system. Due to their seasonal persistence, they have the ability to predictably influence seasonal weather. Hence, their use in seasonal forecasts can potentially improve the skill of the forecasts. However a complete measure of their influence in geographical locations and in different seasons is not known. As a result, modern seasonal forecasting techniques have not been able to fully exploit their persistence in improving skill of seasonal forecasts. By measuring similarity between model ensemble members that are forced by soil moisture and phenology respectively, in this study, we identify global hot spots where soil moisture and phenology impact key atmospheric variables in spring and summer seasons. Results indicate that over South East Asia (SEA) and the Sahel the phenology and soil moisture impact precipitation to an equal extent. Results show that 5–7 % of the variance in Indian summer monsoon precipitation is caused by soil moisture and phenology anomalies. Prior to the monsoon they influence predictors of the SEA monsoon. Hence, their persistence can be used to improve skill of seasonal forecasts, particularly of mesoscale systems like the SEA monsoon.