Normalized Annual Cereal Yields and Solar-Climate Time Series Data for Spain (1961–2021)

Description

This dataset contains normalized annual agricultural yield time series for major rainfed cereal crops in Spain (Oats, Barley, Rye, and Wheat), alongside multi-crop ensemble averages and solar-hydroclimatic indicator metrics spanning the 61-year period from 1961 to 2021. The raw crop production metrics were compiled from official FAOSTAT records and national agricultural statistics, subsequently normalized to isolate relative yield fluctuations and technological growth trends.

Steps to reproduce

Steps to Reproduce [1] Raw Data Compilation & Normalization Download or extract the annual crop yield series (Oats, Barley, Rye, and Wheat) for Spain (1961–2021) from FAOSTAT / national agricultural statistics databases.Normalize each individual crop series to a scale between 0 and 1 to allow multi-crop aggregation and standard scale comparisons. [2] Ensemble Aggregation & Deterministic Detrending Calculate the 4-cereal ensemble mean (Average 4 cereals) across the normalized crop yield series.Fit a quadratic polynomial regression model (y = a x^2 + b x + c) to the ensemble mean to isolate long-term technological progress trends (Quadratic trend).Subtract the fitted quadratic trend from the ensemble yield values to derive raw detrended residual yield series (Mean - trend (H)). [3] Low-Frequency Filtering & Stationarity Testing Apply a 5-year centered moving average window to the detrended yield residuals to isolate low-frequency, quasi-decadal fluctuations (NFsT).Run Augmented Dickey-Fuller (ADF) unit root tests on the filtered series (NFsT) to verify stationarity prior to spectral decomposition.Spectral & Cross-Correlation AnalysisExecute Fast Fourier Transform (FFT) power spectral density estimation and cross-correlation analyses between the detrended/filtered yield series (NFsT) and the solar activity index (e.g., Sunspot Numbers, WN) to identify quasi-decadal periodicity (~8–14 years) and intermittency patterns.

Institutions

• Universidad Nacional Autónoma de Nicaragua-León

  León Department, León
• Ministerio de Ciencia, Tecnología y Medio Ambiente

  Havana, Havana

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