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Long-Lead Streamflow Forecasting Using Ensemble Streamflow Prediction Technique (ESP) and Large-Scale Climate Signals

Ashouri Talouki, Hamed | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39000 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Abrishamchi, Ahmad; Moradkhani, Hamid
  7. Abstract:
  8. In this research, two of the most prominent known sources of interannual and interdecadal climate variability in the form of El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) are analyzed to assess the influences of these large-scale climate phenomena on water supply in the Zayandeh-rood River Basin. For this purpose, any shifts in the mean and variance of the inflow volume of the Zayandeh-Rood Dam in different climate conditions (resulted by different combination of ENSO and PDO phases) has been analyzed and compared with similar statistics in neutral condition to find out if the differences are statistically significant. Correlation analysis indicates that the inflow volume has a direct relation with Pacific Decadal Oscillation Index (PDO Index) and an inverse relation with Southern Oscillation Index (SOI). Also, it was found that any significant shift in the April through September inflow volume to Zayandeh-Rood Dam arises only when El Niño and La Niña events occurs respectively in the positive and negative phase of the PDO. To give some physical justification to the results, precipitation and temperature patterns in the above basin of Zayandeh-rood Dam are analyzed. Furthermore, the information of these large-scale climate signals are incorporated in to a well-known advance hydrologic forecasting technique named Ensemble Streamflow Prediction (ESP). In order to consider the mixed effects of ENSO and PDO, four climate conditions are defined. Two forecast ensembles are then created, one of which consists of meteorological information of all the historical years prior to the forecast year, and the other consists of the information of the years of the climate group to which the forecast year belongs. The initialized hydrologic model is then driven for each forecast ensemble in each climate condition to produce the streamflow traces. Correlation coefficients of the median of the two ensemble forecasts and the observed value, as well as the RMSE of the forecasts indicate the superiority of the categorical ensemble forecast, particularly for El Nino/+PDO forecast years
  9. Keywords:
  10. Elnino-Southern Oscillation (ENSO) ; Long-Lead Streamflow Forecasting ; Ensemble Streamflow Prediction (ESP) ; Large-Scale Climate Signals ; Pacific Decadal Oscillation (PDO)

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