Elham Rahmani [1] [1] Dr.Abdolmajid Liaghat [1] – Prof.Ali Khalili [1] [1] [1] Irr. & Reclam. Eng. Faculty, Agro meteorology Department, university of Tehran, Tehran, Iran 10th International Meeting on Statistical Climatology (10IMSC)

Introduction The main drought definition is the lack of gaining water in specific period of time and in a distinct region. Drought causes extensive damages to agricultural products. Rainfall has the major part in all definitions of drought indexes. The climatic parameters are usually used for estimating crop products and predicting agricultural droughts.

In this research, the attempt is to define different models that relate drought indexes and climatic parameters combinatory on crop yield, using classical (regression) methods.

Methodology  To develop regression models, different climatic parameters and drought indexes were used to relate them with crop yield.  Data were collected from north east of Iran, Tabriz and Miane synoptic stations.

Tabriz Miane

Climatic Parameters

Drought Indexes

Estimated Drought Indexes  The Percentage of Normal Precipitation Index (PNPI)  Standard Index of Annual Precipitation (SIAP)  Converted Selenianov Hydrothermal Index (HT)  Nguyen Index (k)  Rainfall Anomaly Index (RAI)  Standardized Precipitation Index (SPI)  Shashko Moisture Drought Index (MD)  Transeau Index (Ih)

Single and Multivariate Regression Models

single models

Multivariate models

Calling Regression Models

Rain fed barley yield Miane(17 years) Rain fed barley yield Tabriz(17 years) Rain fed barley yield Tabriz(30 years) Irrigated barley yield Tabriz(30 years) Developed Models R1-1-I Active temp. above 10° R1-2-I Rainfall R1-3-I Relative humidity R1-4-I Average wind speed R1-5-I Sunshine hours R1-6-I Average min. temperature R1-7-I Average max. temperature R1-8-I Average mean temperature R1-9-I Evaporation R1-10-I Vapor pressure R1-11-I Hydrothermal index (HT) R1-12-I Shashko moisture drought Index (Md) R1-13-I Nguyen Index (k) R1-14-I Transeau Index (Ih) R1-15-I Standard index of annual precipitation (SIAP) R1-16-I The Percentage of normal precipitation index (PNPI) R1-17-I Rainfall Anomaly Index (RAI) R1-18-I SPI R1-19-I SPI R1-20-I SPI R1-21-I SPI R1-22-I SPI R1-23-I Climatic parameters R1-24-I Drought indexes R1-25-I Climatic parameters and drought indexes

Evaluation of Model function indexes

The values of R, RMSE and MBE for models ModelsR (test)RMSE (test)MBE (test)MBE %(test) 1-25-I R R

Ranking Models

Conclusion  The best multivariate regression model includes P, wind, Sunshine, t>=10, K  Among the drought indexes studied in this research, RAI, Ih, SPI24, K are the most effective ones on the crop yield estimation.  The multiple models include the combination of climatic parameters & drought indexes together are better for crop yield prediction.  To predict the yield of products, multiple models are better than simple models.

Thanks for your kind attention