pvtend: PV Tendency Decomposition

v|release| · Source on GitHub · README

PV tendency decomposition for atmospheric blocking, propagating anticyclones, and all synoptic-scale cyclonic event lifecycle analysis.

pvtend diagnoses the growth, propagation, and decay of mid-latitude weather events by decomposing potential vorticity (PV) tendencies from ERA5 pressure-level data onto physically meaningful components using an orthogonal basis framework. This is the Part I work of Yan et al. (in prep.) about blocking lifecycle analyses on onset, peak, decay stages.

Gallery

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Idealized four-basis reconstruction demo

Idealized validation: a Gaussian PV anomaly with prescribed propagation, intensification, and deformation is decomposed into four orthogonal bases and reconstructed with near-zero residual.

Real ERA5 blocking event (track 425) — animated lifecycle showing total PV on a cartopy map (left) and the four projected basis components (right) evolving from 13 h pre-onset to 12 h post-onset. The analysis is done on a weighted average surface across 300, 250, 200 hPa levels.

Geopotential-height lifecycle decomposition

Geopotential-height (Z500) variant of the four-basis decomposition (track 425) — animated lifecycle showing Z anomaly from the 1990–2020 hourly climatology, with adaptive prenorm and blockid contour overlay. See notebook 03z_four_basis_projection_geopotential.

Event catalogues

Blocking and PRP-high events are identified as persistent anticyclonic anomalies in 500 hPa geopotential height using TempestExtremes v2.1 to track contiguous Z500 anomaly features that exceed a fixed threshold for ≥5 days, producing CSV catalogues with columns for event ID, centre lat/lon, onset/peak/decay timestamps, and area.

Sample catalogue (ERA5, 1990–2020 blocking): ERA5_TempestExtremes_z500_anticyclone_blocking.csv (view on GitHub)

Features

PV tendency computation — zonal advection, baroclinic counter propagation, vertical advection, and approximated diabatic heating terms.
QG omega solver — Hoskins Q-vector formulation with FFT+Thomas (default) and 3-D direct/iterative (BiCGSTAB+ILU) backends.
Helmholtz decomposition — spherical-harmonic backend (default, via pyspharm) plus a legacy spherical-FFT solver, with a parity-mirror trick that lifts NH-only fields onto the global sphere for a near-zero harmonic residual.
Moist/dry omega splitting — decomposes vertical motion into moist and dry contributions.
Isentropic diagnostics — PV-tendency analysis on isentropic surfaces.
Orthogonal basis decomposition — projects PV tendency onto intensification (β), propagation (αx, αy), and deformation (γ) modes.
Composite explorer — plot_var for bootstrap-significant spatial maps with shared colorbars; plot_baroclinic_tilt for two-level v′ overlay.
RWB detection — anticyclonic/cyclonic Rossby wave breaking classification.
Composite lifecycle — multi-stage ensemble averaging with onset/peak/decay staging.
ω blowup detection — post-hoc CSV scan flagging ERA5 timestamps whose 300 hPa absolute ω exceeds a fixed Pa s⁻¹ hard cutoff (canonical ±5 Pa/s); replaces the silent in-solver clip used in pvtend ≤ 2.9.
CLI pipeline — end-to-end processing via pvtend-pipeline.

Contents

pvtend: PV Tendency Decomposition

Gallery

Event catalogues

Features

Indices and tables