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The impact of stochastic physics on tropical rainfall variability in global climate models on daily to weekly time scales
Author(s) -
Watson Peter A. G.,
Berner Judith,
Corti Susanna,
Davini Paolo,
Hardenberg Jost,
Sanchez Claudio,
Weisheimer Antje,
Palmer Tim N.
Publication year - 2017
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd026386
Subject(s) - precipitation , climatology , environmental science , tropics , climate model , tropical climate , stochastic modelling , climate change , atmospheric sciences , meteorology , mathematics , geography , statistics , physics , geology , ecology , biology , archaeology
Many global atmospheric models have too little precipitation variability in the tropics on daily to weekly time scales and also a poor representation of tropical precipitation extremes associated with intense convection. Stochastic parameterizations have the potential to mitigate this problem by representing unpredictable subgrid variability that is left out of deterministic models. We evaluate the impact on the statistics of tropical rainfall of two stochastic schemes: the stochastically perturbed parameterization tendency scheme (SPPT) and stochastic kinetic energy backscatter scheme (SKEBS), in three climate models: EC‐Earth, the Met Office Unified Model, and the Community Atmosphere Model, version 4. The schemes generally improve the statistics of simulated tropical rainfall variability, particularly by increasing the frequency of heavy rainfall events, reducing its persistence and increasing the high‐frequency component of its variability. There is a large range in the size of the impact between models, with EC‐Earth showing the largest improvements. The improvements are greater than those obtained by increasing horizontal resolution to ∼20 km. Stochastic physics also strongly affects projections of future changes in the frequency of extreme tropical rainfall in EC‐Earth. This indicates that small‐scale variability that is unresolved and unpredictable in these models has an important role in determining tropical climate variability statistics. Using these schemes, and improved schemes currently under development, is therefore likely to be important for producing good simulations of tropical variability and extremes in the present day and future.