Document Type : Research Paper


1 PhD Graduate in Watershed Management, Faculty of Natural Resources, University of Tehran, Karaj, Iran

2 Professor, Faculty of Natural Resources, University of Tehran, Karaj, Iran

3 Professor of Soil conservation and watershed management Research Institute, Tehran, Iran

4 Associate Professor, Faculty of Natural Resources, University of Tehran, Karaj, Iran



Precipitation plays an important role in climatic, water, energy and biogeochemical cycles. Several global and regional data sets currently provide historical estimates of this variable over Iran, including the MWEP and WFDEI forcing datasets and production of some institutions such as MOHC, SMHI and IITM. All these datasets provide data with different resolutions based on gage stations, satellite Images and models output. In this study, we do an inter comparison between these data sets during 1990- 2008. We also validate all ten data sets against independent ground station observations over 30 second-order basins of Iran. MSWEP and WFDEI have an acceptable compatibility with observational data on different spatial and temporal resolutions. RMSE and Bias are 5.68, 6.34 and 0.58, 2.75 for these two datasets during 228 months, respectively. However, it is needed that MSWEP improves in the western and northwestern parts of the country and WFDEI in June and September months. Our findings in this research provide valuable guidance for a variety of stakeholders, including rainfall- runoff and land-surface modelers, watershed management studies and data providers.


  • Boegh, E., Thorsen, M., Butts, M. B., Hansen, S., Christiansen, J. S., Abrahamsen, P., Hasager, C. B., Jensen, N. O., van der Keur, P., Refsgaard, J. C., Schelde, K., Soegaard, H., and Thomsen, A. (2004). Incorporating remote sensing data in physically based distributed agro-hydrological modelling, J. Hydrol., 287, 279–299.
  • Beck, H. E., Vergopolan, N., Pan, M., Levizzani, V., Albert I.J.M. van Dijk., Weedon, G. P., Brocca, L., Pappenberger, F., Huffman, G. J and Wood, E. F. (2017). Global-scale evaluation of 22 precipitation datasets using gauge observations and hydrological modeling, Hydrol. Earth Syst. Sci., 21, 6201–6217.
  • Cosgrove, B. A., Lohmann, D., Mitchell, K. E., Houser, P. R., Wood, E. F., Schaake, J. C., Robock, A., Marshall, C., Sheffield, J., Duan, Q. Y., Luo, L. F., Higgins, R. W., Pinker, R. T., Tarpley, J. D., and Meng, J. (2003). Real-time and retrospective forcing in the North American Land Data Assimilation System (NLDAS) project, J. Geophys. Res.-Atmos., 108, 1887–1902,, 2003.
  • Duan, Z., Bastiaanssen, W. G. M., and Liu, J. (2012). Monthly and annual validation of TRMM Muliti satellite Precipitation Analysis (TMPA) products in the Caspian Sea Region for the period 1999– 2003, Geoscience and Remote Sensing Symposium, 3696–3699,
  • Dee, D. P., Uppala, S. M., Simmons, A. J., Berrisford, P., Poli, P., Kobayashi, S., Andrae, U., Balmaseda, M. A., Balsamo, G., Bauer, P., Bechtold, P., Beljaars, A. C. M., van de Berg, L., Bidlot, J., Bormann, N., Delsol, C., Dragani, R., Fuentes, M., Geer, A. J., Haimberger, L., Healy, S. B., Hersbach, H., Holm, E. V., Isaksen, L., Kallberg, P., Kohler, M., Matricardi, M., McNally, A. P., Monge-Sanz, B. M., Morcrette, J. J., Park, B. K., Peubey, C.,de Rosnay,P.,Tavolato,C.,Thepaut,J.N.,andVitart,F. (2011). The ERA-Interim reanalysis: configuration and performance of the data assimilation system, Q. J. Roy. Meteor. Soc., 137, 553–597,
  • Huang, J. P., Yu, H. P., Guan, X. D., Wang, G. Y., and Guo, R. X. (2016). Accelerated dryland expansion under climate change, Nature Climate Change, 6, 166–172,
  • Hylke E. Beck., Albert I. J. M. van Dijk., Levizzani. V, Schellekens J., Miralles. D. G., Martens. B., and Roo A. (2017). MSWEP: 3-hourly 0.25◦ global gridded precipitation (1979–2015) by merging gauge, satellite, and reanalysis data. Hydrol. Earth Syst. Sci., 21, 589-615.
  • Luo, L. F., Robock, A., Mitchell, K. E., Houser, P. R., Wood, E. F., Schaake, J. C., Lohmann, D., Cosgrove, B., Wen, F. H., and Sheffield, J.(2003). Validation of the North American Land Data Assimilation System (NLDAS) retrospective forcing over the southern Great Plains, J. Geophys. Res.-Atmos., 108, 8843,
  • Kobayashi, S., Ota, Y., Harada, Y., Ebita, A., Moriya, M., Onoda, H., Onogi, K., Kamahori, H., Kobayashi, C., Endo,H., Miyaoka, K., and Takahashi, K.(2015). The JRA-55 Reanalysis: General Specifications and Basic Characteristics, J. Meteorol. Soc. Jpn., 93, 5-48,
  • Kamyar, A., Yazdanpanah, H. and Movahedi, S. (2017). Accuracy Evaluation of the Outputs of Regional Climate Models in Iran, Physical Geography Research Journal.
  • Kang, L. T., Huang, J. P., Chen, S. Y., and Wang, X. (2016). Long-term trends of dust events over Tibetan Plateau during 1961–2010, Atmos. Environ., 125, 188–198,
  • Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D., Gandin, L., Iredell, M., Saha, S., White, G., Woollen, J., Zhu, Y., Chelliah, M., Ebisuzaki, W., Higgins, W., Janowiak, J., Mo, K. C., Ropelewski, C., Wang, J., Leetmaa, A., Reynolds, R., Jenne, R., and Joseph, D.(1996). The NCEP/NCAR 40-year reanalysis project, B. Am. Meteorol. Soc., 77, 437–471, (1996)077<0437:Tnyrp>2.0.Co;2.
  • Pan, X. D., Li, X., Yang, K., He, J., Zhang, Y. L., and Han, X. J.(2014). Comparison of Downscaled Precipitation Data over a Mountainous Watershed: A Case Study in the Heihe River Basin, J. Hydrometeorol., 15, 1560 1574,
  • Qian, T., Dai, A., Trenberth, K. E., and Oleson, K. W. (2006). Simulation of Global Land Surface Conditions from 1948 to 2004. Part I: Forcing Data and Evaluations, J. Hydrometeorol., 7, 953–975,
  • Rodell, M., Houser, P. R., Jambor, U., Gottschalck, J., Mitchell, K., Meng, C. J., Arsenault, K., Cosgrove, B., Radakovich, J., Bosilovich, M., Entin, J. K., Walker, J. P., Lohmann, D., and Toll,D. (2004). The global land data assimilation system, B.Am. Meteorol. Soc.,85,381–394,
  • Taylor, K. E. (2001). Summarizing multiple aspects of model performance in a single diagram, J. Geophys. Res.-Atmos., 106, 7183–7192,
  • Weedon, G. P., Gomes, S., Viterbo, P., Shuttleworth, W. J., Blyth, E., Osterle, H., Adam, J. C., Bellouin, N., Boucher, O., and Best, M. (2011). Creation of the WATCH Forcing Data and Its Use to Assess Global and Regional Reference Crop Evaporation over Land during the Twentieth Century, J. Hydrometeorol., 12, 823–848, doi:10.1175/2011jhm1369.1.
  • Wang, W.,Cui, W.,Wang, J.,andChen,X. (2016a). Evaluation of GLDAS1 and GLDAS-2 forcing data and Noah model simulations over China at monthly scale, J. Hydrometeorol., 17, 2815–2833,
  • Xie, X., He, J.-H., and Qi, L. (2011). A review on applicability evaluation of four reanalysis datasets in China, Journal of Meteorology & Environment, 27, 58–65.
  • Zhao, T. B., Fu, C. B., Ke, Z. J., and Guo, W. (2010). Global Atmosphere Reanalysis Datasets: Current Status and Recent Advances, Adv. Earth Sci., 25, 242–254.
  • Zhao, F. and Zhu, J. (2015). Assessing Quality of Grid Daily Precipitation Datasets in China in Recent 50 Years, Plateau Meteorology, 34,50 58, 1000-0534.2013.00141.
  • Zhang, L., Liu, H., Ye, Y., and Huang, C. (2010). Distributed modeling of shortwave solar radiation distribution over the Tibetan Plateau, J. Natural Resources, 25, 811–821,