Moist Baroclinic Instability along the Subtropical Mei-Yu Front

Yang, Guang‐Fu; Li, Tim

doi:10.1175/jcli-d-22-0140.1

Cited by 3 publications

(5 citation statements)

References 21 publications

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“…A 2.5-layer QG theoretical model is constructed, following Adames (2021) [48] and Yang and Li (2023) [54]. The model was an extension of a conventional 2-level QG model [41] by including a prognostic lower-tropospheric moisture tendency equation and a well-mixed PBL that interacts with the free-atmospheric circulation [51].…”

Section: Data and Modelmentioning

confidence: 99%

“…The model was an extension of a conventional 2-level QG model [41] by including a prognostic lower-tropospheric moisture tendency equation and a well-mixed PBL that interacts with the free-atmospheric circulation [51]. In the current model, the reference latitude is set to be 16 • N. For a detailed derivation of the model equations and methodology to solve the equations, readers are referred to Yang and Li (2023) [54] as well as Section 4.…”

Section: Data and Modelmentioning

confidence: 99%

“…In the current model, the reference latitude is set to be 16°N. For a detailed derivation of the model equations and methodology to solve the equations, readers are referred to Yang and Li (2023) [54] as well as Section 4.…”

Section: Background Field Featuresmentioning

confidence: 99%

“…Given the unique feature of the South Asian monsoon with pronounced easterly vertical shear and northward meridional temperature and moisture gradients, we constructed a 2.5-layer model in a way similar to Yang and Li (2023) [54]. This model involves both the QG dynamics [41] and moistening and condensational heating processes.…”

Section: Construction Of a 25-layer Model And Eigenvalue Solutionsmentioning

confidence: 99%

“…We speculate it might be attributed to simplifications and assumptions made during the derivation of the dispersion equation. In the current framework, the dispersion equation is derived directly from the three prognostic equations and solved with Newton's iteration method (Yang and Li 2023) [54].…”

Section: Dependence Of the Growth Rate On Convective Adjustment Timementioning

confidence: 99%

See 4 more Smart Citations

The Reexamination of the Moisture–Vortex and Baroclinic Instabilities in the South Asian Monsoon

Chen,

Li,

Cui

2024

Atmosphere

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Observational analyses reveal that a dominant mode in the South Asian Monsoon region in boreal summer is a westward-propagating synoptic-scale disturbance with a typical wavelength of 4000 km that is coupled with moistening and precipitation processes. The disturbances exhibit an eastward tilt during their development before reaching their maximum activity center. A 2.5-layer model that extends a classic 2-level quasi-geostrophic model by including a prognostic lower-tropospheric moisture tendency equation and an interactive planetary boundary layer was constructed. The eigenvalue analysis of this model shows that the most unstable mode has a preferred zonal wavelength of 4000 km, a westward phase speed of 6 m s−1, an eastward tilt vertical structure, and a westward shift of maximum moisture/precipitation center relative to the lower-tropospheric vorticity center, all of which agree with the observations. Sensitivity experiments show that the moisture–vortex instability determines, to a large extent, the growth rate, while the baroclinic instability helps set up the preferred zonal scale. Ekman-pumping-induced vertical moisture advection prompts an in-phase component of perturbation moisture relative to the low-level cyclonic center, allowing the generation of available potential energy and perturbation growth, regardless of whether or not a low-level mean westerly is presented. In contrast to a previous study, the growth rate is reversely proportional to the convective adjustment time. The current work sheds light on understanding the moisture–vortex and the baroclinic instability in a monsoonal environment with a pronounced easterly vertical shear.

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Section: Data and Modelmentioning

confidence: 99%

Section: Data and Modelmentioning

confidence: 99%

Section: Background Field Featuresmentioning

confidence: 99%

Section: Construction Of a 25-layer Model And Eigenvalue Solutionsmentioning

confidence: 99%

Section: Dependence Of the Growth Rate On Convective Adjustment Timementioning

confidence: 99%

See 3 more Smart Citations

The Reexamination of the Moisture–Vortex and Baroclinic Instabilities in the South Asian Monsoon

Chen,

Li,

Cui

2024

Atmosphere

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Increased synoptic variability along the subtropical Meiyu front under global warming

Yang

2022

Clim Dyn

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Southern Hemisphere baroclinic activity in seasonal forecasts

Trentini,

Calmanti,

Dell’Aquila

et al. 2024

Bull. of Atmos. Sci.& Technol.

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Accurate prediction of mid-latitude baroclinic activity is extremely relevant for understanding global climate dynamics and improving long-term weather forecasts. However, current seasonal forecast models struggle to accurately represent the variability of baroclinic activity in the Southern Hemisphere, which may affect their reliability and usefulness. Baroclinic instability in the mid-latitudes is a significant component of the climate system, as it is associated with the meridional transport of a large amount of energy and momentum. Therefore, the ability of the models to correctly predict the properties of the atmospheric circulation in this latitudinal region is a very important requirement. The aim of this study is to estimate the energy of atmospheric phenomena typical of the mid-latitudes, such as baroclinic perturbations, and to understand how seasonal forecasts can be practically used to assess the energy transfer in the atmosphere. We compare the Southern Hemisphere mid-latitude winter variability of the seasonal forecasts of the ECMWF, DWD and Météo France forecasting systems with the ERA5 reanalysis. The analysis is performed by computing the Hayashi spectra of the 500-hPa geopotential height field. Both the reanalysis and the seasonal forecast show a series of peaks in the spectral region of eastward-travelling waves, which corresponds to the high frequency and high wavenumber domain. We quantify the amount of energy released from the atmosphere by calculating the Baroclinic Amplitude Index. The results suggest that seasonal forecasts may not accurately capture the variability of geopotential height power spectra in the Southern Hemisphere, which poses a challenge in correctly distributing the energy over spatial and temporal dimensions. This study will show that this problem is particularly pronounced for wavenumber 4 over a period of 8 days. This misrepresentation likely contributes to the uncertainties in precipitation forecasting, with discrepancies exacerbated by a suboptimal description of baroclinic instability and dynamical components in the models. Our findings highlight the need for an improved representation of baroclinic processes in seasonal forecast models, which could lead to substantial advancements in long-term weather prediction capabilities and in a more complete understanding of climate dynamics.

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Moist Baroclinic Instability along the Subtropical Mei-Yu Front

Cited by 3 publications

References 21 publications

The Reexamination of the Moisture–Vortex and Baroclinic Instabilities in the South Asian Monsoon

The Reexamination of the Moisture–Vortex and Baroclinic Instabilities in the South Asian Monsoon

Increased synoptic variability along the subtropical Meiyu front under global warming

Southern Hemisphere baroclinic activity in seasonal forecasts

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