Modelling of monsoon rainfall for a mesoscale catchment in North-West India I: assessment of objective circulation patterns

Abstract

Abstract.Within the present study we shed light on the question whether objective circulation patterns (CP) classified from either the 500 HPa or the 700 HPa level may serve as predictors to explain the spatio-temporal variability of monsoon rainfall in the Anas catchment in North West India. To this end we employ a fuzzy ruled based classification approach in combination with a novel objective function as originally proposed by (Stehlik and Brdossy, 2002). After the optimisation we compare the obtained circulation classification schemes for the two pressure levels with respect to their conditional rainfall probabilities and amounts. The classification scheme for the 500 HPa level turns out to be much more suitable to separate dry from wet meteorological conditions during the monsoon season. As is shown during a bootstrap test, the CP conditional rainfall probabilities for the wet and the dry CPs for both pressure levels are highly significant at levels ranging from 95 to 99%. Furthermore, the monthly CP frequencies of the wettest CPs show a significant positive correlation with the variation of the total number of rainy days at the monthly scale. Consistently, the monthly frequencies of the dry CPs exhibit a negative correlation with the number of rainy days at the monthly scale. The present results give clear evidence that the circulation patterns from the 500 HPa level are suitable predictors for explaining spatio-temporal Monsoon variability. A companion paper shows that the CP time series obtained within this study are suitable input into a stochastical rainfall model.

Modelling of monsoon rainfall for a mesoscale catchment in North-West India II: stochastic rainfall simulations

“…The link between daily rainfall and the CP is established by conditional rainfall probabilities and amounts respectively. In a companion study (Zehe et al, 2006) we already showed that pressure patterns are, despite the fact that the Coriolis parameter is half as large as compared to the middle latitudes, suitable and parsimoneous predictors for explaining precipitation variability in the Anas catchment. Within the present study we will shed light on the question of whether the two different CP classification schemes, one for the 500 HPa level and the other for the 700 Hpa level, yield suitable inputs to the multivariate stochastic rainfall model that shall reproduce the precipitation behaviour observed in the Anas catchment.…”

“…With robust we mean that the method is computationally efficient and based on data that are globally freely available. As re-analysis data of atmospheric and oceanic state variables and fluxes but also climate model runs are globally available on resolutions ranging from 2.5 • to 1 • , downscaling methods (Wilby and Wilks, 1997) can help within this context (for a review of downscaling methods please refer to the companion paper Zehe et al, 2006). A major problem in the context of daily precipitation modelling is the spatial and temporal intermittency of precipitation i.e.…”

“…The study closes with discussion and conclusions in section 4. For details on the Anas catchment and the precipitation data base the reader might refer to the companion paper of Zehe et al (2006).…”

Precipitation downscaling under climate change: Recent developments to bridge the gap between dynamical models and the end user

“…Depending on the particular end user, in some regions it may therefore be important to provide reliable precipitation characteristics for a particular season. In monsoonal climates, such as the Indian subcontinent [ Zehe et al , 2006] and West Africa [ Laux et al , 2008], the prediction of the onset and strength of monsoon rainfall is critical for management of water resources and agriculture. In temperate climates there is much less of a seasonal pattern in rainfall, though seasonal evaporation can significantly impact the water cycle.…”

Sensitivity analysis of Takagi-Sugeno-Kang rainfall-runoff fuzzy models

“…Demicco and Klir, 2004). Applications of fuzzy methods in the hydrological context include modelling groundwater flow phenomena (Bárdossy and Disse, 1993;Bárdossy et al, 1995;Dou et al, 1999), and the interdependence between global circulation and precipitation (Özelkan et al, 1998;Pongracz et al, 2001;Zehe et al, 2006), for example. In the narrower context of river flow forecasting, fuzzy methods have been used for parameter estimation (Seibert, 1999;Yu and Yang, 2000), uncertainty analysis (Özelkan and Duckstein, 2001;Jacquin and Shamseldin, 2007) and the development of rainfall-runoff models (Hundecha and Bárdossy, 2001;Vernieuwe et al, 2005), among other applications.…”