Wavelet-based analysis of hydro-climatic and vegetation dynamics in heterogeneous agro-climatic zones of East Africa

Abstract

ABSTRACT Natural and human-induced factors profoundly affect agricultural crop production in East Africa, sparking ongoing debates about their relative significance. This study investigates the impact of localized hydro-climatic variables like precipitation, temperature, vapor pressure deficit, and water deficit on crop production. Additionally, it examines climate oscillations such as El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), North Atlantic Oscillation (NAO), and Pacific Decadal Oscillation (PDO). Employing the Normalized Difference Vegetation Index (NDVI) metric, analysis focuses on four climatic zones, ranging from arid to humid. Results suggest that the dominant periodicities for NDVI and hydro-climatic factors are annual (8-16 months) and intra-annual (4-8 months), while circulation indices exhibit inter-annual and inter-decadal periodicity. The study reveals that vegetation dynamics are more sensitive to annual and intra-annual fluctuations in hydro-climatic factors compared to inter-annual and inter-decadal oscillations in circulation indices. The bi-variate wavelet coherence (WTC) analysis reveals that precipitation and ENSO are the most significant factors explaining vegetation variability, while multiple wavelet coherence (MWC) analysis demonstrates that all variables contribute significantly to NDVI variability. This research underscores the importance of wavelet techniques in deciphering complex relationships between hydro-climatic factors and crop production, with implications for agricultural management and policy in East Africa.