It is rainy season in Hong Kong. Recently, there have been a series of rainstorm. The number of black rainstorm warnings and rainfall have broken the historical records, causing widespread concern. The frequent occurrence of extreme weather tests the resilience of urban disaster prevention and also raises questions about the underlying causes. From July 29 to August 5, rainstorm was triggered by the intertwined monsoon and upper air disturbance. The Hong Kong Observatory issued four black rainstorm warning signals, breaking the record of the most "black rain" in a year. Especially from the late night of August 4th to the early morning of August 5th, the Observatory issued two "black rain" warnings, with a gap of only about 6 hours, breaking the record for the shortest interval since 1999. From early morning to 5 pm on August 5th, the rainfall in many districts of Hong Kong surged, with most areas accumulating over 200 millimeters, and some areas in the urban area and eastern New Territories even exceeding 300 millimeters. Among them, the headquarters of the Hong Kong Observatory recorded 358.8 millimeters, breaking the record for the highest daily rainfall in August. The Hong Kong Observatory recently pointed out that the rainstorm was related to the simultaneous action of various atmospheric conditions. With the gradual strengthening of the southwest monsoon on August 2nd, a continuous supply of water vapor is being transported to the coast of southern China. In addition, recent high-altitude disturbances and good high-altitude divergence make it easier for low-level air to climb up to the top of the atmosphere, which is very favorable for the development of heavy rain. The scientific director of the Hong Kong Observatory, Mai Peiti, stated that the prevailing wind direction in Hong Kong changes from easterly to southwesterly every May and June. Due to the abundant water vapor brought by the southwest monsoon, the atmosphere will become unstable, which is conducive to the development of convective activity. If it is combined with other favorable atmospheric systems such as high-altitude disturbances, rainstorm may occur. The continuous rainstorm from August 4 to 5 was caused by the combined action of the southwest monsoon and upper air disturbance. Is this weather combination a rare phenomenon or is it gradually becoming the norm in Hong Kong's summer? Will the atmospheric conditions involved and the mechanism of triggering rainstorm occur more frequently in the future? Regarding this, McPetty stated that favorable atmospheric conditions and triggering mechanisms for heavy rain may not necessarily occur and cooperate simultaneously. In addition, the location, time and rainfall of rainstorm development are also random, so the location where the southwest monsoon brings heavy rain will be different each time. The record breaking "black rain" of flooding and landslides is not only a natural disaster, but also a test of Hong Kong's ability to respond. During the effective period of the "black rain" warning on August 5th, multiple areas in Hong Kong experienced flooding and landslides. A citizen captured footage of a hillside flood near the University of Hong Kong, with mud and sand pouring down towards the pedestrian bridge. There is also water accumulation on Pokfulam Road and Smithfield Road, and cars need to slow down to pass. In the face of the sudden rainstorm, various departments of the SAR government responded quickly. The Emergency Monitoring and Support Centre has been operating continuously during the rainstorm, and the Home Affairs Department has opened several temporary shelters for residents in need. The Drainage Services Department has dispatched over 180 emergency response teams to handle flooding cases, inspecting and clearing approximately 240 locations in Hong Kong that are prone to flooding due to siltation. District councilors and care teams went to visit affected citizens, understand their needs, and deliver supplies. On the second day after the end of the 'black rain', reporters visited multiple locations affected by flooding, including Hong Kong Island, and saw that the accumulated water, collapsed trees, and sediment had been treated, and vehicle traffic had returned to normal. During the rainstorm, Hong Kong received 20 reports of landslides. Zhang Weiwen, Director of the Geotechnical Engineering Department of the Special Administrative Region Government, stated that in order to quickly respond to emergencies, the department immediately arranged for engineers to inspect the landslide site and provide technical advice to relevant maintenance departments. Multiple temporary measures have also been taken at the site, including clearing the accumulated mountain mud on the road, reinforcing the slope structure, and laying temporary drainage systems, to ensure smooth road traffic and public safety. At present, most cases have completed temporary reinforcement works. Next, we will further evaluate the risks of these slopes and carry out permanent consolidation works according to the 'Landslide Prevention and Control Plan', in order to minimize the chance of landslides happening again. ”Zhang Weiwen said. Some experts predict that extreme weather may become more frequent in the future, and Hong Kong needs to strengthen its climate risk assessment and infrastructure disaster resistance capabilities with the assistance of artificial intelligence in disaster prevention work. In addition to infrastructure and contingency mechanisms, technology is gradually intervening in forecasting work. The Hong Kong Observatory pointed out that the long and narrow rain belt formed during the rainstorm was closely related to the southwest monsoon, and the artificial intelligence computer model "Fengwu" had captured that the east-west rain belt would cover the coast of Guangdong about a week ago, and predicted the highest daily rainfall close to the actual situation. Although the distribution may not be entirely accurate, it can provide a basis for early prediction of heavy rainfall. Rainstorm is one of the main factors causing landslide. In terms of slope safety, Hong Kong has recently introduced technologies such as artificial intelligence to improve monitoring efficiency. Zhang Weiwen stated that in the past, the Geotechnical Engineering Department mainly relied on the rainfall in the past 24 hours as the basis for prediction, while the artificial intelligence system comprehensively considered multiple factors, including geological structure, slope inclination, etc., to more comprehensively assess the risk of landslides. In this' black rain ', they have seen initial results and will continue to optimize the system in the future. In addition to the government response, Zhang Weiwen also appealed that although the rainstorm had passed, the risk of landslides still existed and we should not take it lightly. He suggested that citizens should suspend mountaineering or enter areas affected by landslides after rainstorm to ensure their own safety. (New Society)