A semi‐implicit deep‐atmosphere spectral dynamical kernel using a hydrostatic‐pressure coordinate

Quart J Royal Meteoro Soc

et al. 2019

Self Cite

Most global models employ a vertical coordinate based on the moist hydrostatic pressure, and therefore do not conserve dry air mass. Such an issue should be taken seriously into account, especially in developing global high-resolution atmospheric models to address nonhydrostatic motions explicitly. In this article, we present a modified nonhydrostatic moist global spectral dynamical core using a dry-mass vertical coordinate, which conserves the mass of dry air naturally. In addition to the vertical coordinate, the modified dynamical core differs from the original Aladin-NH like dynamical kernel in the state variables employed. Specifically, a new temperature variable is introduced to formulate the governing equations and the mass continuity equation is expressed in terms of the dry air density. To assess its performance, an idealized splitting supercell test is conducted. Simulation results from both the modified and original dynamical cores are presented and compared. The results indicate that only the modified dynamic core is able to simulate the splitting supercell with good accuracy comparable to reference solutions from the Model for Prediction Across Scales (MPAS). K E Y W O R D SAladin-NH, dry-mass vertical coordinate, idealized supercell simulation, nonhydrostatic moist atmosphere, spectral dynamical core

“…Actually, the present modified moist dynamical core is an extension of our previous works (Wu et al, ; Yang et al, , ). Following Bénard et al .…”

Section: Solver Formulationsupporting

confidence: 58%

Section: Solver Formulationmentioning

confidence: 99%

A modified nonhydrostatic moist global spectral dynamical core using a dry‐mass vertical coordinate

Peng

Quart J Royal Meteoro Soc

et al. 2019

Self Cite

“…The time discretization adopts the semi-implicit semi-Lagrangian scheme, and the spatial discretization adopts the spherical harmonic functions expansion (horizontal) and the finite-element method (vertical). For details, see Wu, et al [25], Yang, et al [26,27], and Yin, et al [28,29].…”

Section: Assimilation System and Forecast Modelmentioning

confidence: 99%

Effect of Flow-Dependent Unbalanced Background Error Variances on Tropical Cyclone Forecasting

Liu

et al. 2022

JMSE

The background error variance in variational data assimilation can significantly affect a model’s initial field. Around extreme weather events, the variance of the unbalanced control variables have contributed highly to the total variance. This study investigates the effect of flow-dependent unbalanced variance on tropical cyclone (TC) forecasts using the ensemble of data assimilation (EDA) method. The analysis of TC Saudel (October 2020) shows that flow-dependent unbalanced variances can better represent the uncertainty in the background error, which is investigated in terms of magnitude and distribution. The vertical distribution of the temperature-explained variance ratio also shows that the contribution of the vorticity-balanced variance around Saudel is lower than the global average (in the troposphere). Single-observation experiments reveal that the structured flow-dependent errors of unbalanced control variables can also introduce corresponding structural information in analysis increments. As expected, the experiments in which the variances of all variables are flow-dependent in the one-month TC forecast performed better overall. Compared with the reference, these forecasts reduce the average absolute track and intensity errors by approximately 31% and 9%, respectively. The results demonstrate that EDA-based unbalanced variances can indeed improve the mean forecast skills of TC tracks and intensities despite instability at some lead times by improving the forecast of the circulation situation and providing a more appropriate balance relationship between variables.

Quart J Royal Meteoro Soc

“…Further details about YHGSM are available in Wu et al . (2011), Yang et al ., (2015; 2017), Yin et al . (2018) and Peng et al .…”

Section: Single‐precision Fast Spherical Harmonic Transform Set‐up In Yhgsmmentioning

confidence: 99%

An implementation of single‐precision fast spherical harmonic transform in Yin–He global spectral model

Yin

Song

et al. 2021

Self Cite

In this article, we describe an implementation of single‐precision fast spherical harmonic transform (SHT) in the Yin–He global spectral model (YHGSM). The potential of single‐precision arithmetic is explored for accelerating fast SHT. In particular, we assess the impact of using single‐precision fast SHT on the meteorological skill of YHGSM. Compared to double‐precision SHT, single‐precision fast SHT against is accelerated by about 59.83%, whereas the run‐time reduction achieved 25.28% in model integration for TL2047L137. The simulation results indicate that single‐precision fast SHT can improve computational efficiency without a noticeable impact on the forecast skill.