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# The Characteristics of Flood-Drought Abrupt Alternation in North China During Midsummer and Its Response to Atlantic Sea Surface Temperature

## Details

**Authors** Haoyu Li, Lijuan Wang, Zhihong Jiang

**Year** 2026

**Publisher** International Journal of Climatology

**Kind of work** article

**Discipline** Climatology

[Read it at the publisher](https://doi.org/10.1002/joc.70587) 
10.1002/joc.70587

## In authors' words

### Abstract

Based on the ERA5 reanalysis data, precipitation data provided by the China Meteorological Administration, and the Met Office Hadley Center Sea Ice and SST dataset, this study investigates the characteristics of midsummer flood‐drought abrupt alternation (FDAA) in North China and its correlation with Atlantic sea surface temperature (SST) by using the water vapour budget equation and the moist static energy (MSE) budget equation. The results indicate that FDAA, primarily driven by the anomalous vertical advection of moisture, occurs frequently in North China during midsummer, with dynamic processes playing a dominant role. In drought‐to‐flood years, the blocking high on the eastern side of the Ural Mountains guides cold air southward, while the western Pacific subtropical high (WPSH) is anomalously extended northward, leading to the convergence of cold and warm air over North China. Concurrently, North China is located on the northwest side of an anomalous anticyclone that extends from the Korean Peninsula to Japan over the northwest Pacific in the lower troposphere. This configuration induces southerly winds that transport high moist enthalpy air, especially warm air, into North China, favouring the transition from drought to flood. The opposite pattern is observed in flood‐to‐drought years. Quantitative analysis using the dynamic adjustment method reveals that the circulation component exhibits spatial correlations of 0.72 and 0.59 with the wind anomalies in DTFs and FTDs, respectively. Thus, the anomalous anticyclone (cyclone) in the northwest Pacific plays an important role in influencing FDAA in North China during midsummer. FDAA in North China is closely related to the tropical Atlantic SST anomaly (SSTA). In positive SSTA years, the tropical Atlantic SST warming in July can enhance convective activity in the Atlantic basin, which alters the Walker circulation and produces a sinking motion in the central Pacific. An anticyclonic circulation is generated over the northwest Pacific and centered around 20° N. Under the influence of prevailing northerly winds, precipitation decreases, resulting in a dry period in North China. The positive SSTA in the tropical Atlantic, which persists from July into August, promotes a northward shift of the anticyclonic circulation towards the southeast of North China in August. At this time, southerly winds prevail in North China, leading to anomalous upward motion and resulting in a transition from drought to flood. In negative SSTA years, the opposite pattern occurs.

### What they set out to do (purpose)

To characterize midsummer flood-drought abrupt alternation events in North China and determine their relationship to Atlantic sea surface temperature anomalies.

### Who or what was studied (sample)

ERA5 reanalysis data, China Meteorological Administration precipitation records, and Met Office Hadley Centre sea ice and SST data for North China during midsummer.

### How they did it (methods)

Water vapor budget and moist static energy budget equations combined with a dynamic adjustment method to quantify atmospheric circulation contributions and their correlation with Atlantic SST anomalies.

### What they found (results)

Drought-to-flood and flood-to-drought transitions in North China were driven by opposing atmospheric circulation configurations linked to tropical Atlantic sea surface temperature anomalies, with the northwest Pacific circulation component showing spatial correlations of 0.72 and 0.59 with wind anomalies in the two transition types respectively.

## Commentary

### In short

The finding shows a distinctions (D) structure, in which flood and drought form two abruptly alternating, mutually exclusive categorical states, coupled with a relationships (R) structure linking Atlantic sea surface temperature anomalies and atmospheric circulation to the direction of that alternation.

**Patterns it shows** D, R

**Added** 2026-09-17

**How to cite this** Haoyu Li, Lijuan Wang, Zhihong Jiang (2026). The Characteristics of Flood-Drought Abrupt Alternation in North China During Midsummer and Its Response to Atlantic Sea Surface Temperature. International Journal of Climatology.