Derived Meteorological Spring Indices and Analysis Data for Northern Hemisphere Land, 1961–2100

This dataset contains derived meteorological spring indices and supporting analysis data for the manuscript “Regional Spring Lengthening and Shortening Linked to Asymmetric Atmospheric Circulation Changes Across the Northern Hemisphere.” It includes historical spring onset, spring end, and spring length derived from ERA5-Land for 1961–2025; trend and contribution analyses; regional time series and Pettitt change points; atmospheric circulation diagnostics based on ERA5 500 hPa geopotential height and winds; CMIP6 historical evaluation data; and future multi-model ensemble projections under SSP5-8.5 for 2026–2100.