Mechanism of Coupled Upper Troposphere and Boundary Layer Induces Two Types of Short‐Term Heavy Rainfall Along the Eastern Foothills of the Taihang Mountains.

Using 11 years of hourly merged rainfall records and ERA reanalysis data, this paper reveals two major circulation modes leading to two types of short‐term heavy rainfall (STHR) along the Taihang Mountains' eastern foothills, and further explains their mechanisms. One circulation mode has a distinct warm anomaly at 300 hPa covering most areas of North China, together with the boundary‐layer westerly anomaly occurring in North China and its southern region (UTWA‐BLWA). UTWA‐BLWA effectively contributes to the reinforcement of the upper‐level divergence and the low‐level moisture convergence by promoting the strengthening of upper anticyclonic and low‐level southwesterly anomalies. The combined effects of low‐level jet (LLJ) and topographic uplift form the central‐northern STHR pattern. The other circulation structure has a 300‐hPa warm anomaly located to the southeastern Russia and a prominent 300‐hPa cold anomaly covering the south, together with the boundary‐layer easterly anomaly occurring over the whole region of eastern China (UTCA‐BLEA). The southern STHR pattern is attributed to the exit of the boundary‐layer jet (BLJ) over lower elevations due to moist transport and dynamic uplift associated with the easterly anomaly. The results indicate that the locations of STHR are related to the direction, intensity, and height of the LLJ. The findings highlight that the upper‐tropospheric temperature anomalies (UTTA) and boundary‐layer easterly flow jointly modulate heavy rainfall. Analysis of the coupled upper troposphere and boundary layer could help understand and forecast heavy rainfall. Plain Language Summary: Short‐term heavy rainfall (STHR) frequently occurs along the eastern foothills of the Taihang Mountains, which is difficult to forecast accurately and causes significant damage. Operational weather analysis and previous studies have suggested that the atmospheric conditions at the middle‐ and lower troposphere are the most important for STHR. Our findings highlight that the upper‐tropospheric temperature anomalies (UTTA) could represent the evolution of atmospheric structures favorable for heavy rainfall, and the boundary‐layer flow can refine the intensity and locations of orographic rain. The coupled UTTA and boundary‐layer easterly flow can jointly represent the major patterns of STHR over the eastern slope of Mt. Taihang. The results may provide helpful information for weather forecasts and warning issuing and give a better understanding of heavy rainfall in North China. Key Points: Upper‐tropospheric temperature anomalies (UTTA) can contribute to the favorable atmospheric conditions for short‐term heavy rainfall (STHR)The locations of STHR correspond to the direction, intensity, and height of the low‐level jetCoupling UTTA and boundary‐layer jet provides the two major patterns of STHR [ABSTRACT FROM AUTHOR]