Abstract

This paper presents the improvement of the fuzzy inference model primarily developed for predicting rainfall with data from United States Department of Agriculture (USDA) Soil Climate Analysis Network (SCAN) Station at the Alabama Agricultural and Mechanical University (AAMU) Campus for the year 2004. The primary model was developed with Fuzzy variables selected based on the degree of association of different factors with various combinations causing rainfall. An increase in wind speed (WS) and a decrease in temperature (TP) when compared between the ith and (i-1)th day were found to have a positive relation with rainfall. Results of the model showed better performance after introducing the threshold values of 1) relative humidity (RH) of the ith day; 2) humidity increase (HI) when compared between the ith and (i-1)th day; and 3) product (P) of increase in wind speed (WS) and decrease in temperature (TP) when compared between the ith and (i-1)th day. In case of the improved model, errors between actual and calculated amount of rainfall (RF) were 1.20%, 2.19%, and 9.60% when using USDA-SCAN data from AAMU campus for years 2003, 2004 and 2005, respectively. The improved model was tested at William A. Thomas Agricultural Research Station (WTARS) and Bragg farm in Alabama to check the applicability of the model. The errors between the actual and calculated amount of rainfall (RF) were 3.20%, 5.90%, and 1.66% using USDA-SCAN data from WATARS for years 2003, 2004, and 2005, respectively. Similarly, errors were 10.37%, 11.69%, and 25.52% when using SCAN data from Bragg farm for years 2004, 2005, and 2006, respectively. The primary model yielded the value of error equals 12.35% using USDA- SCAN data from AAMU campus for 2004. The present model performance was proven to be better than the primary model.

Highlights

  • Application of fuzzy set theory has rapidly increased with establishing its utility in numerous areas of the scientific world

  • This paper presents the improvement of the fuzzy inference model primarily developed for predicting rainfall with data from United States Department of Agriculture (USDA) Soil Climate Analysis Network (SCAN) Station at the Alabama Agricultural and Mechanical University (AAMU) Campus for the year 2004

  • Fuzzy inference models are involved with the variables which are perceived by the experts who are responsible for inferring the consequence part of the production rule

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Summary

Introduction

Application of fuzzy set theory has rapidly increased with establishing its utility in numerous areas of the scientific world. The fuzzy logic possibility and its degree of effect due to the ambiguous input variables are considered by some as being generated in the human mind and is often referred to as expert knowledge. Based on the generated idea that the possibility and degree of effect from vague and ambiguous inputs exists, the knowledge based rules can be expressed in the form of statements, called fuzzy statements or production rules. These statements consist of antecedent (conditional part) and consequent (inference or effect due to the vague and ambiguous conditional variables) part. Improvement of the primary model was necessary to enhance its performance in the sense of preciseness and to improve the match between actual and calculated values of rainfall, hereafter termed RF

Fuzzy Systems and Rules
Min-Max Composition
Defuzzification
Primary Model
Improvement of the Primary Model
Assumptions on RH
Selection of Variables in the Primary Model
Maximum Amount of RF
Selection of Other Variables and Threshold
Conclusions
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