Evaluation of a Dynamical Basis for Advance Forecasting of 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 Date of Onset of
Monsoon Rainfall over India
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| Creator |
Goswami, P
Gouda, K C |
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| Subject |
Climate Modelling
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| Description |
The onset of 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; advance and
accurate forecast of the day of the onset of monsoon (DOM) thus has application in many sectors. Although
the standard deviation (s) in DOM over past hundred years is only 7 days, nearly 50% of the cases show
large (>1 s) deviations; forecasting of DOM, especially for the extreme years is thus a non-trivial and is
rarely attempted due to the poor skill of most GCM in predicting daily ISM rainfall at long range. A primary
cause for 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. We explore this premise
for advance forecasting of onset of ISM over Kerala and show that significant skill is possible in advance
forecasting of DOM. We use a global circulation model (GCM) with a special feature, variable resolution and
an objective debiasing of daily rainfall forecast, to meet the special requirements of forecasting DOM.
Based on a set of objective and validated criteria, hindcasts of DOM are generated in complete operational
setting from a 5-member ensemble for each year for the period 1980 to 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. Further, the forecasts
in contrast to the climate forecasts capture 7 out of 9 large (>1s in observation) departures from mean
within mean error, which implies high skill. Implications of the results for predicting certain weather and
climate processes are discussed.
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| Publisher |
CSIR Centre for Mathematical Modelling and Computer Simulation
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| Date |
2007-10
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| Type |
Monograph
NonPeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://cir.cmmacs.ernet.in/189/1/rrcm0716.pdf
Goswami, P and Gouda, K C (2007) Evaluation of a Dynamical Basis for Advance Forecasting of Date of Onset of Monsoon Rainfall over India. Technical Report. CSIR Centre for Mathematical Modelling and Computer Simulation, C-MMACS,Bangalore 560037,India. (Unpublished) |
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| Relation |
http://cir.cmmacs.ernet.in/189/
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