Evaluation of a Dynamical Basis for Advance Forecasting of the Date of Onset of Monsoon Rainfall over India
IR@C-MMACS: CSIR-Centre for Mathematical Modelling and Computer Simulation, Bangalore
View Archive Info| Field | Value | |
| Title |
Evaluation of a Dynamical Basis for Advance Forecasting of the Date of Onset of
Monsoon Rainfall over India
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| Creator |
Goswami, P
Gouda, K C |
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| Subject |
Indian Monsoon
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| Description |
The onset of the Indian summer monsoon (ISM) represents one of the most dramatic transitions in the
regional circulation pattern. The onset also marks the beginning of the main rainy season for India; advanced
and accurate forecast of the date of the onset of monsoon (DOM) thus has application in many sectors.
Although the standard deviation (s) in DOM over the past hundred years is only 7 days, nearly 50% of the
cases show large (.1s) deviations; forecasting of DOM, especially for the extreme years is thus nontrivial and
is rarely attempted because of the poor skill of most GCMs in the long-range prediction of daily ISM rainfall.
Aprimary cause for the poor skill in forecasting parameters like rainfall appears to be the loss of predictability
due to noise introduced by local synoptic processes. However, sharp transitions in the regional circulation
pattern and associated rainfall, which are likely to be less affected by synoptic noise, may have higher predictability,
somewhat similar to the way that monthly mean parameters are more predictable. This premise is
explored for advanced forecasting of the onset of ISM over Kerala, India, and it is shown that significant skill is
possible in advanced forecasting of DOM.Ageneral circulation model (GCM) with a special feature, variable
resolution, and an objective debiasing of daily rainfall forecast, is used to meet the special requirements of
forecasting DOM. Based on a set of objective and validated criteria, hindcasts of DOM are generated in
a complete operational setting from a five-member ensemble for each year for the period 1980–2003. The
hindcasts are evaluated in terms of a number of parameters; as well as against a climatological forecast (null
hypothesis), for 70% of the forecasts, the mean absolute error is less than that of the climatological forecasts.
Furthermore, in contrast to the climate forecasts, these forecasts capture 7 out of 9 large (.1s in observation)
departures from the mean within the mean error, which implies high skill. Implications of the results for
predicting certain weather and climate processes are discussed.
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| Publisher |
American Meteorological Society
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| Date |
2010-08
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| Type |
Article
PeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://cir.cmmacs.ernet.in/231/1/2010MWR2978[1].pdf
Goswami, P and Gouda, K C (2010) Evaluation of a Dynamical Basis for Advance Forecasting of the Date of Onset of Monsoon Rainfall over India. Monthly Weather Review, 138 (8). pp. 3120-3141. ISSN Online ISSN: 1520-0493, Print ISSN: 0027-0644 |
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| Relation |
http://journals.ametsoc.org
http://cir.cmmacs.ernet.in/231/ |
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