Fig. 2: Consistent spatial patterns in historical extreme precipitation trends.
From: Contrasting historical trends of atmospheric rivers in the Northern Hemisphere
a Linear trends of winter extreme precipitation (EP) frequency from 1950 to 2022 based on ERA5 reanalysis data (shading), alongside AR frequency trends (contours). b and c the same as a but based on CPC precipitation dataset over the contiguous U.S. (CONUS) and E-OBS precipitation dataset over Europe, respectively. Grid cells with significant trends at the 99% confidence level (p-value < 0.01) are marked by black scatters. d–i 73-year time series of winter EP days (black dashed lines) in each target region (polygons in panel (a)-(c)), along with the seven-year running averages (black solid lines) and its linear trend (black straight lines). Red and blue lines denote AR-related (EP days coinciding with ARs) and AR-unrelated EP days, respectively. Regional EP days are defined as days when regional mean precipitation exceeds the 85th percentile threshold. Observational precipitation data are used to define regional EP days for CONUS and Europe, whereas ERA5 data are used for the Hawaiian Islands and British Columbia. Solid lines denote trends significant at the 95% confidence level (p-value < 0.05), while dashed lines indicate insignificant trends. The increasing/decreasing rates (slopes) are provided in the panel legends.
