ENSO AND PDO CLIMATE VARIABILITY IMPACTS ON REGIONAL MISSOURI CROP YIELDS A Thesis Presented to the Faculty of the Graduate School at the University of Missouri In Partial Fulfillment of the Requirements for the Degree Master of Science by CHASITY B. HENSON Dr. Patrick Market, Thesis Advisor MAY 2016 The undersigned, appointed by the dean of the Graduate School, have examined the thesis entitled ENSO AND PDO CLIMATE VARIABILITY IMPACTS ON REGIONAL MISSOURI CROP YIELDS presented by Chasity B. Henson, a candidate for the degree of master of science, and hereby certify that, in their opinion, it is worthy of acceptance. ________________________________________________ Professor Patrick Market ________________________________________________ Professor Anthony Lupo ________________________________________________ Professor Mark Palmer ACKNOWLEDGEMENTS My deepest gratitude is expressed to Dr. Patrick Market for being my advisor and motivator. I would also like to thank Dr. Anthony Lupo for being my co-advisor and for his help with the methodologies used in this study. Dr. Patrick Guinan also deserves a thank you for his contributions to this research. I recognize my thesis committee members, especially Dr. Mark Palmer, for taking the time to assess my performance as a graduate student. Suggestions and explanations from all four of these professors have greatly improved my education and the quality of this thesis. Lastly, I acknowledge Ryan Difani, my fellow graduate student, for his support and advice, specifically on the creation of Fig. 5.1. This work would not have been possible without support from Missouri EPSCoR (Experimental Program to Stimulate Competitive Research). Being a chapter of the National Science Foundation, the official disclaimer is as follows: This material is based upon work supported by the National Science Foundation under Award IIA-1355406. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. ii TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................................................................ ii LIST OF FIGURES .............................................................................................................v LIST OF TABLES ........................................................................................................... viii ABSTRACT .........................................................................................................................x CHAPTER 1. INTRODUCTION ........................................................................................1 1.1 Objectives ...............................................................................................3 1.2 Statement of Thesis .................................................................................4 CHAPTER 2. LITERATURE REVIEW .............................................................................5 2.1 Definitions...............................................................................................5 2.2 ENSO ......................................................................................................8 2.2.1 ENSO Characteristics .........................................................8 2.2.2 ENSO Impacts ..................................................................13 2.3 PDO Characteristics and Impacts .........................................................16 2.4 ENSO and PDO Relationships ..............................................................21 2.4.1 PDO Dependence on ENSO .............................................22 2.4.2 ENSO Modulated by PDO ...............................................23 2.4.3 PDO Modulated ENSO in the Midwest ...........................27 2.5 Climate Impacts on Crops .....................................................................30 iii CHAPTER 3. DATA AND METHODOLOGY ...............................................................34 3.1 Data Sources .........................................................................................34 3.2 Methods.................................................................................................36 3.2.1 Power Spectrum Analysis ................................................39 3.2.2 PDO Influence on ENSO .................................................41 CHAPTER 4. RESULTS ...................................................................................................43 4.1 Climatological Analysis ........................................................................43 4.2 ENSO and PDO Phase Interactions ......................................................47 CHAPTER 5. DISCUSSION .............................................................................................52 CHAPTER 6. CONCLUSIONS ........................................................................................58 APPENDIX A ....................................................................................................................60 APPENDIX B ....................................................................................................................84 REFERENCES ..................................................................................................................88 iv LIST OF FIGURES Figure 3.1. A map of Missouri outlining the six climate regions, determined by the National Oceanic and Atmospheric Administration (NOAA) using the Climate Divisional Dataset. NOAA defines these regions as Climate Divisions of Missouri. ..........................................................................................................35 Figure 3.2. Annual corn yields for region 1 in Missouri from 1919 to 2013, with a) the linear trend in yields shown and b) the trend removed. Data provided by the United States Department of Agriculture (USDA), graphed as yield (bushels per acre) versus time (year). .............................................................................37 Figure 4.1. Power spectrum resulting from the Fourier transform of a) detrended corn yields for region 1 in Missouri, found in Fig. 3.2b, b) average temperature (°F) for region 1 over the corn growing season of April through September, c) average precipitation (in.) for region 1 from April through September, and d) the convolution of the corn yield spectrum (Fig. 4.1a) with the spectra of seasonal temperature (Fig. 4.1b) and seasonal precipitation data (Fig. 4.1c). Average temperature and precipitation data were downloaded from the Midwestern Regional Climate Center (MRCC) for the years of 1919 to 2013. The ordinate displays wave power, which is the magnitude of the Fourier coefficients, while the abscissa displays wave number. The dashed (dotted) line represents the 95% confidence level against the red (white) noise background continuum (Wilks 2006). .............................................................44 Figure 4.2. As in Fig. 4.1, except involving the convolution of a) the annual SOI spectrum with b) the spectrum of annual mean values for the PDO index. Annual SOI data were obtained from the Bureau of Meteorology (2005) for the time period of 1901 to 2004 (www.environment.gov.au/node/22307). Annual mean values for the PDO index were obtained from the Japan Meteorological Agency (JMA) for the same time period of 1901 to 2004 (ds.data.jma.go.jp/tcc/tcc/products/elnino/decadal/pdo.html). ........................48 Figure 4.3. A map of Missouri outlining the six climate regions, defined by NOAA, including the statistically significant results found for both crops. El Niño/La Niña refers to the statistically significant difference in yields between El Niño years and La Niña years, found in Table 4.2. PDO/El Niño refers to the significant difference in yields between El Niño/Positive PDO years and El Niño/Negative PDO years, found in Table 4.3. ...............................................51 Figure 5.1. Timeline representing the crop growing season of 2012 (yellow), which runs from April 2012 to September 2012, and the JMA defined ENSO year of 2012 (red), which begins in October 2012 and ends in September 2013. ................54 v Figure A.1. As in Fig. 4.1d, except involving average July temperature (T) and average July precipitation (P) data for region 1. ...........................................................61 Figure A.2. As in Fig. 3.2, except annual corn yields for region 2 in Missouri from 1919 to 2013, with a) the linear trend in yields shown and b) the trend removed. ...62 Figure A.3. As in Fig. 4.1, except power spectrum resulting from the Fourier transform of a) detrended corn yields for region 2 in Missouri, found in Fig. A.2b, b) the convolution of the corn yield spectrum (Fig. A.3a) with the spectra of seasonal temperature (not shown) and seasonal precipitation data (not shown), and c) the convolution of the corn yield spectrum (Fig. A.3a) with the spectra of average July temperature (not shown) and average July precipitation data (not shown). .............................................................................................................63 Figure A.4. As in Fig. 3.2, except annual corn yields for region 3 in Missouri from 1919 to 2013, with a) the linear trend in yields shown and b) the trend removed. ...64 Figure A.5. As in Fig. A.3, except involving detrended corn yields for region 3 in Missouri, found in Fig. A.4b. ...........................................................................65 Figure