Impact of Parameterized Topographic Drag on a Simulated Northeast China Cold Vortex

Northeast China cold vortex (NECV) is the major influencing weather system in northern China. Yet the impacts of complex terrain on the evolution of NECV remains poorly understood. This work studies the influence of subgrid orographic drag (SOD) on a heavy‐rain‐producing NECV occurred in July 2011 using the Weather Research and Forecasting model. A series of numerical experiments are conducted with different parameterizations of SOD including turbulent orographic form drag (TOFD), flow blocking drag (FBD), and mountain wave drag (MWD). Results show that the NECV intensity is overestimated in the absence of SOD parameterization, accompanied with too‐low geopotential height (GPH) and too‐strong horizontal winds. The parameterization of TOFD can significantly decelerate the 10‐m winds, whereas the FBD and MWD play a minor role. However, the influence of TOFD is overwhelmed by FBD and MWD in the troposphere, especially the latter. This implies that the breaking of mountain waves play a more important role in weakening the NECV than the low‐level flow blocking. The lower‐tropospheric MWD directly weakens the convergence and ascent motion of the NECV, producing an anti‐cyclonic circulation that uplifts the GPH under the constraint of quasi‐geostrophic vertical vorticity. This MWD‐induced circulation indirectly weakens the NECV in the mid‐upper troposphere by producing a warm advection that counters the low‐level cold advection to the southwest of the NECV. The findings provide useful insights into the impacts of complex terrain on the NECV and highlight the importance of topographic drag parameterization in the simulation and short‐range forecast of NECV. Plain Language Summary Northeast China cold vortex (NECV) is a major influencing weather system in northern China which often promotes severe convective weather like heavy rainfall, hail, and tornado. Past studies have revealed the importance of atmospheric circulations (e.g., Rossby waves associated with Eurasian blocking), sea surface temperature anomalies over North Pacific, and large‐scale orography in East Asia on the evolution of NECV. However, the underlying terrain in East Asia is much complex. It is still unclear how the NECV is affected by complex terrain. This work studies a NECV case using the Weather Research and Forecasting model, focusing on the impacts of different topographic drags including turbulent orographic form drag (TOFD), mountain wave drag (MWD), and flow blocking drag (FBD) produced b