Large-scale climatic drivers for warm-season compound drought and heatwave frequency over North China

Based on multiple observational and reanalysis datasets, this study investigated the large-scale climatic drivers responsible for the warm season (April to September) compound drought and heatwave (CDHW) frequency over the North China (NC) domain, both locally and remotely. The warm-season NC CDHW frequency exhibited salient year-to-year variation. We identified that the extensive equivalent barotropic high-pressure anomaly centered around Lake Baikal could be the predominant local-scale driving factor. In addition, the low-pressure circulation anomaly to the southeast played a secondary dynamic amplification role. Such a dipole pattern can jointly cause more frequent occurrences of NC CDHWs by triggering anomalies in localized meteorological variables (e.g., surface warming and drying) and land surface variable (reduced soil moisture) that are favorable for CDHW formation during the warm season. Regarding remote driving factors, central eastern Maritime Continent (MC) convection centered over New Guinea could be an influential and direct atmospheric forcing factor. Meanwhile, the sea surface temperature (SST) anomaly pattern over the tropical eastern Pacific (TEP) was identified as a crucial oceanic forcing indirectly modulating the NC CDHW frequency through the critical me-dium of MC convection. Through a Hadley-like meridional overturning circulation pattern, the suppressed MC convection can remotely induce a dipolar pattern similar to that related to a higher NC CDHW frequency, exerting a so-called direct modulation effect. Furthermore, positive TEP SST anomalies act as anomalous Rossby wave sources via anomalous upper-tropospheric divergence, characterized by westward-propagating descending Rossby waves with notable wave energy advecting westward toward the central-eastern MC. In such a scenario, a reversed Walker-like circulation pattern can form to sustain the suppressed MC convection, playing an inter-mediate role in the maintenance of the high-pressure anomaly centered around Lake Baikal. Our findings may provide new insights into the synergistic roles of distant climatic driving factors in the modulation and main-tenance of interannual variations of warm-season NC CDHW.