ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Characteristics and Possible Causes of the Extreme Precipitation over Heilongjiang Province in November 2024
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Abstract:
In November 2024, the precipitation in Heilongjiang Province reached 31.5 mm, ranking as the 4th highest in the same period since 1961. An extreme precipitation event during 25–29 November contributed 73% of the total monthly precipitation, with its 5-day accumulated precipitation being 13.5 times the climatological average for the same period. Analysis of the circulation evolution revealed a clear two-phase variation in the mid- to high-latitude circulation over Eurasia. In the early phase (1–24 November), precipitation was suppressed by a "negative in the west, positive in the east" geopotential height anomaly pattern, corresponding to below-normal precipitation. During the late phase ((25–29 November), the circulation adjusted to an "inverted Ω" pattern, characterized by the establishment of dual blocking highs over the Ural Mountains and the Sea of Okhotsk, which formed a stable configuration with the northeast cold vortex (NECV). This configuration guided the southward intrusion of polar cold air, which intensely converged with the warm and moist air transported by a low-level jet over Heilongjiang, enhancing moisture convergence and dynamic lifting. Influenced by the locked phase of the dual blocking highs, this weather system remained stagnant over the region, ultimately triggering a persistent, widespread heavy precipitation event. Statistics show that 4 of the 10 wettest Novembers in Heilongjiang since 1961 were dominated by single extreme precipitation events, revealing the critical role of synoptic-scale system adjustments in causing November precipitation anomalies. These results enhance our understanding of the causes of extreme precipitation in November in Heilongjiang Province and provide important references for its prediction.
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