Boreal summer intraseasonal oscillations and seasonal Indian monsoon prediction in DEMETER coupled models |
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| Authors: | Susmitha Joseph A K Sahai B N Goswami |
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| Institution: | (1) Climate and Global Modeling Division, Indian Institute of Tropical Meteorology, Pune, India |
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| Abstract: | Even though multi-model prediction systems may have better skill in predicting the interannual variability (IAV) of Indian
summer monsoon (ISM), the overall performance of the system is limited by the skill of individual models (single model ensembles).
The DEMETER project aimed at seasonal-to-interannual prediction is not an exception to this case. The reasons for the poor
skill of the DEMETER individual models in predicting the IAV of monsoon is examined in the context of the influence of external
and internal components and the interaction between intraseasonal variability (ISV) and IAV. Recently it has been shown that
the ISV influences the IAV through very long breaks (VLBs; breaks with duration of more than 10 days) by generating droughts.
Further, all VLBs are associated with an eastward propagating Madden–Julian Oscillation (MJO) in the equatorial region, facilitated
by air–sea interaction on intraseasonal timescales. This VLB-drought–MJO relationship is analyzed here in detail in the DEMETER
models. Analyses indicate that the VLB-drought relationship is poorly captured by almost all the models. VLBs in observations
are generated through air–sea interaction on intraseasonal time scale and the models’ inability to simulate VLB-drought relationship
is shown to be linked to the models’ inability to represent the air–sea interaction on intraseasonal time scale. Identification
of this particular deficiency of the models provides a direction for improvement of the model for monsoon prediction. |
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