Skip to main content

Daily precipitation forecast of ECMWF verified over Iran


In this paper, the performance of the Centre for Medium Range Weather Forecast (ECMWF) model (t + 27 h to t + 51 h) in predicting precipitation is discussed. This model is the first, which has been verified over Iran. The spatial resolution of the model is 0.351° and the 24-h forecasts are compared with daily observations. The study concentrates on year 2001 and the precipitation measurements were collected from the data of 2,048 rain gauges in Iran. The accuracy of four different interpolation methods (nearest neighborhood, inverse distance, kriging, and upscaling) was investigated. Using cross-validation, the inverse distance method (IDM) with minimum mean error was applied. Verification results are given in terms of difference fields (mean error = 0.46 mm/day), rank–order correlation coefficients (0.70), as well as accuracy scores (false alarm ratio = 0.50 and probability of detection = 0.60) and skill scores (true skill statistics [TSS] = 0.45) in year 2001. The position of the rain band was only partly captured by the ECMWF model; however, the position of maximum precipitations agrees with the observations well. The results show that the high values of TSS are associated with the large amounts of precipitation (over 25 mm). Slight to moderate precipitation events have been underforecasted by the model (bias < 1) and it leads to a small value of TSS for these thresholds (5–25 mm/day). The ECMWF model has better performance in high and mountainous regions than over flat terrain and in deserts. Comparing TSS over the Alborz and the Zagros Mountains, it is obvious that the ability of the model to predict the convective precipitation events needs some improvement. The amount of daily precipitation has been also slightly overestimated over Iran. From the beginning of January up to 21 March 2001, the ECMWF time series indicates an obvious phase shift of 1 day, although in other months, no phase shift is noticed.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11


  • Anderson Sh (2002) An evaluation of spatial interpolation methods on air temperature in Phoenix, AZ. Available at Accessed 10 June 2005

  • Cherubini T, Ghelli A, Lalaurette F (2002) Verification of precipitation forecasts over the alpine region using a high density observing network. Weather Forecast 17(2):238–249

    Article  Google Scholar 

  • Ebert EE, McBride JL (1997) Methods for verifying quantitative precipitation forecasts: application to the BMRC LAPS model 24-hour precipitation forecast. Technique development. Report No. 2, BMRC, Melbourne, Australia

  • Faraji E (1982) An investigation on the movement of low pressure, which cause precipitation over Iran. M.S. Thesis, Geophysics Institute of Tehran University

  • Gandin LS, Murphy AH (1992) Equitable skill scores for categorical forecasts. Mon Weather Rev 120:361–370

    Article  Google Scholar 

  • Khalili A, Hadjam S, Irannejad P (1991) Total precipitation analysis in Iran. Jamab Report, pp 1–4

  • Murphy AH, Daan H (1985) Forecast evaluation. Probability, statistics and decision making in the atmospheric sciences. Westview, Boulder, CO, pp 379–437

    Google Scholar 

  • Murphy AH, Epstein ES (1967) A note on probability forecast and “hedging”. J Appl Meteorol 6:1002–1004

    Article  Google Scholar 

  • Murphy AH, Winkler RL (1984) Probability forecasting in meteorology. J Am Stat Assoc 79:489–500

    Article  Google Scholar 

  • Murphy AH, Winkler RL (1987) A general framework for forecast verification. Mon Weather Rev 115:1330–1338

    Article  Google Scholar 

  • Olfat A (1969) The moving direction of cyclones over Iran. M.S. Thesis, Geophysics Institute of Tehran University

  • Raziei T, Saghafian B (2004) Drought tendency in southeast of Iran. Proceedings of the 1st National Water Resources Management Conference, University of Tehran, Tehran, Iran

  • Sanders F (1963) On subjective probability forecasting. J Appl Meteorol 2:191–201

    Article  Google Scholar 

  • Schwartz BE, Benjamin SG (1998) Verification of RUC-2 and Eta model prediction forecasts. Proceedings of the 12th Conference of Numerical Weather Prediction, Phoenix, AZ

  • Shepard D (1968) A two-dimensional interpolation function for irregularly-spaced data. Proceedings of the 23rd National Conference ACM, ACM 517–524

  • Stanski HR, Wilson LJ, Burrows WR (1989) Survey of common verification methods in meteorology. World Meteorological Organization: World Weather Watch Report No. 8 (TD No. 358), Geneva, Switzerland, 114 pp

Download references


This research was supported by the Islamic Republic of Iran Meteorological Organization and the Meteorological Department of the Free University of Berlin. The data used in this study have been provided by the European Centre for Medium range Weather Forecast (ECMWF) and the Iran Meteorological Organization (IRIMO).

Author information

Authors and Affiliations


Corresponding author

Correspondence to Sahar Sodoudi.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Sodoudi, S., Noorian, A., Geb, M. et al. Daily precipitation forecast of ECMWF verified over Iran. Theor Appl Climatol 99, 39–51 (2010).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


  • Root Mean Square Error
  • Kriging
  • Precipitation Amount
  • Skill Score
  • Mean Absolute Error