Refined characteristics of summer extreme humid-heat events in the Beijing-Tianjin-Hebei region based on multi-source datasets

As China's political center and the economic hub of northern China, the Beijing-Tianjin-Hebei (BTH) region is characterized by a high population density and a complex industrial structure. Driven by global warming, summer extreme humid-heat events in this region have become increasingly frequent. These events severely disrupt daily life and economic activities, attracting widespread public concern. This study evaluates the capability of various datasets to capture the fine-scale spatiotemporal characteristics of daytime and nighttime extreme humid-heat events. The analysis is based on data collected between 2016 and 2023 from national meteorological stations, regional automatic weather stations, and the China Meteorological Administration Land Data Assimilation System (CLDAS).

The results reveal a high degree of consistency among the three datasets in representing the annual climatic cycles of temperature and relative humidity, confirming their overall reliability for the region. However, discrepancies exist in the estimated frequency, intensity, and intraseasonal occurrence probability of extreme humid-heat events.

Further analysis reveals that these differences are closely associated with underlying terrain and land-surface features. For daytime events, regional stations in urban and plain areas record notably higher frequencies and intensities than both national stations and CLDAS, whereas the differences are relatively small in mountainous regions. For nighttime events, discrepancies among the datasets are more pronounced in urban and mountainous areas (with CLDAS exhibiting the most significant underestimation), whereas data consistency is relatively better in plain areas. Given that most national stations are located in urban areas, these discrepancies may indirectly reflect the climatic impact of urbanization on regional extreme humid-heat events.