Prediction of Monsoon Rainfall and River Discharge on 15–30-Day Time Scales

Webster, Peter J.; Hoyos, Carlos D.

doi:10.1175/bams-85-11-1745

Cited by 176 publications

(162 citation statements)

References 57 publications

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“…Thus, intraseasonal variability, possibly a phenomenon independent of ENSO, may dilute the overall impact of ENSO on the predictability of the monsoon. Intraseasonal variability strongly influences regional rainfall and is a source of extended range predictability of monsoon weather (Lawrence and Webster 2001;Webster and Hoyos 2004;Wang et al 2005a, Hoyos andWebster 2007). Therefore, it is important to assess the prediction skill of the monsoon intraseasonal variability in state-of-the-art ocean-atmosphere coupled forecasting system.…”

Section: Discussionmentioning

confidence: 99%

Asian summer monsoon prediction in ECMWF System 4 and NCEP CFSv2 retrospective seasonal forecasts

et al. 2012

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The seasonal prediction skill of the Asian summer monsoon is assessed using retrospective predictions ) from the ECMWF System 4 (SYS4) and NCEP CFS version 2 (CFSv2) seasonal prediction systems. In both SYS4 and CFSv2, a cold bias of sea-surface temperature (SST) is found over the equatorial Pacific, North Atlantic, Indian Oceans and over a broad region in the Southern Hemisphere relative to observations. In contrast, a warm bias is found over the northern part of North Pacific and North Atlantic. Excessive precipitation is found along the ITCZ, equatorial Atlantic, equatorial Indian Ocean and the maritime continent. The southwest monsoon flow and the Somali Jet are stronger in SYS4, while the southeasterly trade winds over the tropical Indian Ocean, the Somali Jet and the subtropical northwestern Pacific high are weaker in CFSv2 relative to the reanalysis. In both systems, the prediction of SST, precipitation and low-level zonal wind has greatest skill in the tropical belt, especially over the central and eastern Pacific where the influence of El Nino-Southern Oscillation (ENSO) is dominant. Both modeling systems capture the global monsoon and the large-scale monsoon wind variability well, while at the same time performing poorly in simulating monsoon precipitation. The Asian monsoon prediction skill increases with the ENSO amplitude, although the models simulate an overly strong impact of ENSO on the monsoon. Overall, the monsoon predictive skill is lower than the ENSO skill in both modeling systems but both systems show greater predictive skill compared to persistence.

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Section: Discussionmentioning

confidence: 99%

Asian summer monsoon prediction in ECMWF System 4 and NCEP CFSv2 retrospective seasonal forecasts

et al. 2012

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“…High potential usefulness of intraseasonal forecasts for agriculture, society and economy has triggered a number of research activities to develop empirical as well as dynamical models for extended range prediction of monsoon ISV. During the past few years, several studies (Waliser et al 1999;Mo 2001;Webster and Hoyos 2004;Jones et al 2004) have demonstrated the feasibility of predicting the active-break spells of ISM 20-25 days in advance. These models, however, could not be effectively used for real time operational forecasting due to nature of time filters involved in constructing the empirical models.…”

Section: Introductionmentioning

confidence: 99%

Absorbing aerosols facilitate transition of Indian monsoon breaks to active spells

et al. 2010

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While some long breaks of monsoon intraseasonal oscillations (MISOs) are followed by active spells (BFA), some others are not (BNFA). The circulation during BFA (BNFA) cases helps (prevents) accumulation of absorbing aerosols over central India (CI) resulting in almost three times larger Aerosol Index (AI) over CI, during BFA cases compared to BNFA cases. A seminal role played by the absorbing aerosols in the transition from break to active spells is unraveled through modification of the north-south temperature gradient at lower levels. The meridional gradient of temperature at low level (DT) between aerosol-rich CI and pristine equatorial Indian Ocean is large ([6°C) and sustains for long time ([10 days) during BFA leading to significant moisture convergence to CI. The stability effect arising from surface cooling by the aerosols is overcome by the enhanced moisture convergence creating a moist static unstable atmosphere conducive for the large-scale organized convection over the CI region leading to the resurgence of active spells. The moisture convergence induced by DT was also able to overcome possible aerosol indirect effect (Twomey effect) and initiate deep convection and transition to active condition. During BNFA cases, however the maximum DT, which was weaker than the BFA cases by more than 1.5°C, could not sustain required moisture convergence and failed to lead to a sustained active spell. Using data from MODIS (MODerate resolution Imaging Spectroradiometer) onboard Terra and several other input parameters from various satellites for the period 2000-2009, the aerosol induced radiative forcing representative of two regions-the CI to the north and the pristine ocean to the south-were estimated and support the differences in observed DT during the two cases. Our results highlight the need for proper inclusion of absorbing aerosols in dynamical models for simulation of the observed variability of MISOs and their extended range prediction.

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“…With 2/3 of the Indian population depending on agriculture for employment and 2/3 of the cultivated land relying on rainfed farming, water and food security closely follow climate variability and extremes. Thus, seasonal predictions of the onset and strength of monsoon rainfall are crucial for water resources as well as agricultural management and planning in India (Webster and Hoyos, 2004;Siddiq, 1999). During the monsoon season, usually from June to September, the Indian subcontinent receives 80-90% of the total annual rainfall in a sequence of rainy periods (monsoon bursts) and dry periods (monsoon breaks) of 10-20 days duration which stem, although they appear at first sight to be quite random, from intra seasonal oscillations (Webster and Hoyos, 2004).…”

Section: Introductionmentioning

confidence: 99%

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

Zehe

Singh

Bàrdossy

2006

Hydrol. Earth Syst. Sci.

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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.

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Prediction of Monsoon Rainfall and River Discharge on 15–30-Day Time Scales

Abstract: A new physically based prediction scheme for 20-30-day variability shows promise in monsoon regions for agricultural planning, disaster mitigation, and flood forecasting.

Cited by 176 publications

References 57 publications

Asian summer monsoon prediction in ECMWF System 4 and NCEP CFSv2 retrospective seasonal forecasts

Asian summer monsoon prediction in ECMWF System 4 and NCEP CFSv2 retrospective seasonal forecasts

Absorbing aerosols facilitate transition of Indian monsoon breaks to active spells

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

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