The Roles of Low-level Jets in “21·7” Henan Extremely Persistent Heavy Rainfall Event

Luo, Yuhan; Du, Yu

doi:10.1007/s00376-022-2026-1

Cited by 33 publications

(19 citation statements)

References 63 publications

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“…Based on the analysis of , the residual term in their horizontal momentum model comprises friction, vertical advection, and other uncertainties, and the friction force dominates this term, and Luo et al (2022) also used reanalysis data to calculate the friction term as the residual term. We use the data at 900 hPa and 950 hPa to obtain the vertical variation of ageostrophic wind in the last term at 925 hPa.…”

Section: Diagnostic Equation Of Ageostrophic Windsmentioning

confidence: 99%

“…The mean state of this term is calculated by the average of the heavy rainfall day. Its diurnal state is derived from the monthly mean during the whole of May to avoid the impacts of synoptic weather systems on diurnal variation (Luo et al, 2022). (2022), we define these two confluence patterns of the ageostrophic wind as confrontational confluence pattern and asymptotic confluence pattern, respectively.…”

Section: Two-dimensional Linear Horizontal Momentum Equationmentioning

confidence: 99%

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Mechanisms of Ageostrophic Wind Convergence in the Boundary Layer of Coastal Warm-Sector Extreme Heavy Rainfall

Xia

Huang

Fei

et al. 2023

Preprint

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The South China coast has a high incidence of warm-sector heavy rainfall (WSHR) events. The ageostrophic winds in the boundary layer in most of these events associated with the southwesterly boundary layer jets (BLJs) mainly exhibit strong convergence at rainfall area. In this paper, we analyze two cases of WSHR in May 2013 and May 2015, which occurred in similar synoptic environments but varied in intensity, extent, and duration of rainfall, where the ageostrophic winds are the confrontational confluence and asymptotic confluence pattern, respectively. ERA-5 reanalysis data and the diagnostic equation of ageostrophic wind are used to examine the factors affecting the ageostrophic winds in the northern land region and the southern offshore region of the rainfall. The results suggest that land-sea contrast leads to the convergence of ageostrophic winds in the rainfall area. Boundary layer friction dominates the northeasterly ageostrophic winds on land. The diurnal variation of BLJs dominates the ageostrophic winds and their diurnal variation at sea, contributing southwesterly or southeasterly ageostrophic winds, so the phase difference between the land and sea forms confrontational or asymptotic confluence, respectively. BLJs with different intensities, extents, and diurnal variations can lead to different ageostrophic wind patterns and their confluence modes. The land-sea thermal contrast can directly affect ageostrophic winds, and it can also affect the diurnal variation of BLJs, thus affecting the ageostrophic winds and their confluence mode. It is further verified that the BLJs and thermal forcing are important in warm-sector heavy rainfall processes in South China.

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Section: Diagnostic Equation Of Ageostrophic Windsmentioning

confidence: 99%

Section: Two-dimensional Linear Horizontal Momentum Equationmentioning

confidence: 99%

Mechanisms of Ageostrophic Wind Convergence in the Boundary Layer of Coastal Warm-Sector Extreme Heavy Rainfall

Xia

Huang

Fei

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…Slater et al (2015) proposed that the residual term of the horizontal momentum equation included errors arising from the time-interpolation and implicit horizontal diffusion of the model. Based on the analysis of , the residual term in their horizontal momentum model comprises friction, vertical advection, and other uncertainties, and the friction force dominates this term, and Luo and Du (2023) also used reanalysis data to calculate the friction term as the residual term. We use the data at 900 and 950 hPa to obtain the vertical variation of ageostrophic wind in the last term at 925 hPa.…”

Section: Diagnostic Equation Of Ageostrophic Windsmentioning

confidence: 99%

Mechanisms of Ageostrophic Wind Convergence in the Boundary Layer of Coastal Warm‐Sector Extreme Heavy Rainfall in South China

Xia,

Huang,

Fei

et al. 2023

JGR Atmospheres

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The South China coast has a high incidence of warm‐sector heavy rainfall (WSHR) events. The ageostrophic winds in the boundary layer in most of these events associated with the southwesterly boundary layer jets (BLJs) mainly exhibit strong convergence at rainfall area. In this paper, we analyze two case studies of WSHR in May 2013 and May 2015, which occurred in similar synoptic environments but varied in intensity, extent, and duration of rainfall, where the ageostrophic winds are the confrontational confluence and asymptotic confluence pattern, respectively. ERA‐5 reanalysis data and the diagnostic equation of ageostrophic wind are used to examine the factors affecting the ageostrophic winds in the northern land region and the southern offshore region of the rainfall. The results suggest that land‐sea contrast leads to the convergence of ageostrophic winds in the rainfall area. Boundary layer friction dominates the northeasterly ageostrophic winds on land. The diurnal variation of BLJs dominates the ageostrophic winds and their diurnal variation at sea. It can contribute southwesterly or southeasterly ageostrophic winds, so the phase difference between the land and sea forms confrontational or asymptotic confluence, respectively. BLJs with different intensities, extents, and diurnal variations can lead to different ageostrophic wind patterns and their confluence modes. The land‐sea thermal contrast can directly affect ageostrophic winds, and it can also affect the diurnal variation of BLJs, thus affecting the ageostrophic winds and their confluence mode. It is further verified that the BLJs and thermal forcing are important in WSHR processes in South China.

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“…Furthermore, favorable roles were played by an upper‐tropospheric trough and a lower‐tropospheric vortex in terms of the lower‐level convergence and upward motion in the region (Liang et al., 2022). Meanwhile, Luo and Du (2022) found that the south–north shifts of the heavy rainfall were related to the transitional directions of the boundary‐layer jets affected by the east–west shifts of the western Pacific subtropical high. Besides, this unprecedented event was not relevant to the back building and echo training of convective cells that are often found in warm‐sector rainfall events, but was instead induced by a single quasi‐stationary storm (Wei et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

Unprecedented July Rainfall in North China in 2021: Combined Effect of Atlantic Warming and Arctic Sea‐Ice Loss

Liu,

Zhu,

et al. 2023

JGR Atmospheres

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Record‐breaking July‐mean precipitation hit North China in 2021, resulting in huge economic losses and human casualties. The prevailing easterlies over the southern flank of a remarkable anomalous anticyclone centered over the Kuril Islands transported sufficient water vapor into North China, resulting in persistent downpours on the windward side of the North China Plain. The anomalous anticyclone was a portion of the Eurasian Rossby wave trains. The record‐high Atlantic sea surface temperature anomalies induced the Rossby wave trains, which ended with an anomalous anticyclone over the Kuril Islands; meanwhile, the record‐low sea‐ice concentration over the Laptev–East Siberian Seas reinforced the anomalous anticyclone. Therefore, the combined effect of Atlantic and Arctic thermal forcings caused the record‐breaking July‐mean rainfall in North China in 2021. Using these two boundary layer forcings as independent predictors to run a multiple regression model produced encouraging hindcasting skills.

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The Roles of Low-level Jets in “21·7” Henan Extremely Persistent Heavy Rainfall Event

Cited by 33 publications

References 63 publications

Mechanisms of Ageostrophic Wind Convergence in the Boundary Layer of Coastal Warm-Sector Extreme Heavy Rainfall

Mechanisms of Ageostrophic Wind Convergence in the Boundary Layer of Coastal Warm-Sector Extreme Heavy Rainfall

Mechanisms of Ageostrophic Wind Convergence in the Boundary Layer of Coastal Warm‐Sector Extreme Heavy Rainfall in South China

Unprecedented July Rainfall in North China in 2021: Combined Effect of Atlantic Warming and Arctic Sea‐Ice Loss

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