Spatiotemporal Heterogeneity of Precipitable Water Diurnal Variation over the Tibetan Plateau Based on a Refined 2D Water Vapor Reconstruction

Atmospheric water vapor is a critical factor influencing rainfall, snowfall, and avalanche occurrences, with its diurnal variations providing key insights into such phenomena. However, in high-altitude mountainous areas, the spatial and temporal resolution of water vapor products is insufficient to depict their diurnal variation characteristics. This study aimed to refine the understanding of diurnal Precipitable Water Vapor (PWV) variations using the ANUSPLIN to obtain a two-dimensional water vapor field with a resolution of 0.1° × 0.1° during the monsoon period from 2007 to 2015, which was verified based on ground-based GPS water vapor observations. The findings reveal that incorporating China Meteorological Forcing Data (CMFD) greatly enhances the diurnal variation patterns of PWV, resulting in the appearance of extreme values of PWV daily variation about three hours later than the MERRA reanalysis. In the southern Tibetan Plateau (TP), the diurnal variation of PWV is closer to GPS PWV in terms of amplitude and phase. Spatially, PWV variations are weaker in the central TP but stronger in other regions, particularly during the mid-monsoon period (July–August). Temporally, the central TP experiences maximum PWV from nighttime to early morning (18:00–4:00 UTC), while the surrounding southern and northern areas peak from afternoon to evening (8:00–12:00 UTC), approximately three hours earlier than precipitation peaks. Temporally, the central Tibetan Plateau experiences maximum PWV from nighttime to early morning (18:00–4:00 UTC), while the surrounding southern and northern areas peak from afternoon to evening (8:00–12:00 UTC), approximately three hours earlier than precipitation peaks.