Systematic Errors in the Simulation of Mean and Variability of the Asian Summer Monsoon in Climate ModelsPrimary Author: Annamalai, H.
Additional Authors: Markus Stowasse, J.P. McCreary and K.R. Sperber
Systematic Errors in the Simulation of Mean and Variability of the Asian Summer Monsoon in Climate Models
H. Annamalai*, Markus Stowasse*, J.P. McCreary* and K.R. Sperber+
*International Pacific Research Center (IPRC)/SOEST University of Hawaii,
+PCMDI, LLNL, CA
Email: hanna@hawaii.edu
More than 125 years ago, H. Blanford envisioned that the tropical Indian Ocean not only supplies the moisture for the Asian summer monsoon rains but that it is also vitally `linked to the intensity of the monsoon through coupled land-atmosphere-ocean phenomena. Despite sustained improvements in climate models, simulating the monsoon annual cycle and its variations at intraseasonal to interannual time scales remains one of the most difficult challenges for the modeling community. There are a number of reasons for the models' poor performance. First, and perhaps foremost, is the complexity of the monsoon, which involves the interaction of phenomena on a variety of time(intraseasonal to interannual and longer) and space(regional to global) scales. Secondly, key physical processes (e.g., the generation of clouds) are not adequately represented in the models. Thirdly, we lack the necessary observations that are needed to provide a more complete understanding of air-sea-land interaction processes that shape the mean monsoon and its variability.
In this study, the ability of the current state-of-the-art coupled models to simulate the summer season (June-September) climatology of key variables, such as precipitation, soil moisture, the vertical distribution of moisture, vertical velocity, sea surface temperature, and salinity will be presented. In particular, our diagnostics will focus on: (i) the sensitivity to the models' basic state in representing the spectrum of monsoon variability, including synoptic systems to the ENSO-monsoon association; and (ii) the role of air-sea interactions over the tropical Indian Ocean in ameliorating systematic errors in the simulation of the mean monsoon and its variability. In addition, results from sensitivity experiments with linear atmospheric models, and diagnostics from newly available satellite observations will be discussed.
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