The Impact of Anthropogenic Heat Effect on the Evolution of a Merge - Formation Bow Echo in the Greater Bay Area of China

The impacts of the anthropogenic heat (AH) effect on the evolution of a merger-formation bow echo over the Guangdong-Hong Kong-Macao Greater Bay Area are documented. The utilization of radar data assimilation greatly improves the simulated results comparing against observations, strengthening the robustness of analyses in this work. The simulation with AH effect produces the most accurate results compared to observations, exhibiting approximately 62% larger spatial extent of heavy rainfall (> 30 mm) and twice the area of strong winds (> 10.8 m s^-1) compared to the non-AH simulation. Additionally, the top 1% rain rates and surface winds from the AH-included simulation are about 25% stronger and 23% greater, respectively, relative to the non-AH counterpart. On the one hand, higher AH flux tends to enhance the values of CAPE and vertical wind shear within urban areas on average, providing favorable thermodynamic environmental conditions for convective development. On the other hand, greater AH effect triggers stronger convective cell, leading to more intense merged system. This cell plays a crucial role in the merger process and the formation of bow echo, but it does not persist sufficiently in the non-AH simulation. A third sensitivity simulation, excluding the urban land cover, produces results comparable to those of the non-AH simulation. This study quantifies the relative contribution of the AH effect to the evolution of convective systems and the associated weather-related hazards over the Greater Bay Area, underscoring the significant impacts of AH forcing on the regional flow patterns and the corresponding convection dynamics.