Normalised DTR and Minimum Relative Humidity Across Köppen Climate Zones: Analysing Responses in Plant Phenology

Understanding global plant phenology dynamics is essential for predicting ecosystem responses to climate variability. This study introduces a novel approach to analyse plant phenology dynamics across Köppen climate zones using the Normalised Daily Temperature Range (DTRT) and minimum daily relative humidity (R1) indices. By coupling these selected indices with phenology-related satellite data, we investigate the seasonality of plant development worldwide. We use global conventional temperature and humidity reports to explore how environmental factors influence phenological patterns across diverse ecosystems, from tropical rainforests to polar regions. The Köppen climate classification system serves as a framework for categorising climatic regions based on temperature, precipitation, and vegetation characteristics, facilitating a comprehensive analysis of regional climate variations and their impact on plant phenology. Integrating observed meteorological data and satellite imagery, we explore complex interactions between climate indices and vegetation dynamics. Satellite-derived metrics, such as the normalised difference vegetation index (NDVI), provide valuable insights into vegetation greenness and growth stages, complementing the meteorological data used to calculate DTRT and R1 indices. Our study, conducted on a global scale, focuses on identifying the start and end of the vegetation season and examining changes in seasonality across different Köppen climate zones. We hypothesise that DTRT and R1 indices can serve as standalone tools for determining these key phenological events and fill the gaps in satellite-derived data. By comparing DTRT and R1 indices with satellite NDVI data, we aim to assess their accuracy in capturing vegetation phenology dynamics globally. The comparative analysis of indices and satellite data allows a comprehensive understanding of how climate variability influences the timing and duration of the vegetation season. This research enhances our ability to predict ecosystem responses to climate change and offers valuable insights for ecosystem management and conservation efforts on a global scale. 

Funding: This work is supported by contract for the Implementation and Financing of Scientific Research Project NIO in 2024 No. 451-03-66/2024-03/200117 dated February 5, 2024, COST Action CA20108 - FAIR NEtwork of micrometeorological measurements (FAIRNESS) and Centre of Excellence One Health, Ministry of Science, Technological Development and Innovations 451-03-1524/2023-04/16 

Acknowledgements: Serbian micrometeorological measurements and phenological observations by Forecasting and Reporting Service for Plant Protection of the Republic of Serbia (PIS) are financed by the Ministry of Agriculture, Forestry and Water Management of the Republic of Serbia and Provincial Secretariat for Agriculture, Water management and Forestry of the Vojvodina province, Republic of Serbia. FAIRNESS FMP 2.0 portal is used as one of the sources of micrometeorological data.