E4DRR/gik-ecmwf-par-v2

ECMWF IFS Ensemble — Grib-Index-Kerchunk reference parquets (v2)

Lightweight reference parquets ([url, offset, length] triplets into the public ECMWF GRIB archive on AWS S3) for streaming the 51-member IFS ensemble without downloading full GRIB files. Built by ICPAC for continuous climate-risk monitoring over East Africa (E4DRR / SEWAA).

This is v2: the per-level-keys-fixed catalog (v20260623), spanning all four ECMWF schema eras, superseding the collapsed-pressure-level E4DRR/gik-ecmwf-par.

Coverage

1256 dates, 00Z, 20230118 → 20260702, 51 members each (control + ens_01..ens_50), ~21 GB. Continuous except the 6 dates ECMWF never published at 0.4° (20230427, 20230428, 20230429, 20230430, 20230501, 20230502).

Era	Grid	pl levels	Control	Dates	# dates
0p4	451×900 (0.4°)	9	bundled enfo	2023-01-18 → 2024-02-28	401
49r1	721×1440 (0.25°)	9→13	bundled enfo	2024-02-29 → 2026-05-12	804
50r1	721×1440 (0.25°)	14	oper (dual-stream)	2026-05-13 → present	51

Layout

catalog.parquet / catalog.csv      # one row per date (era, grid, levels, path, source)
par/{YYYY}/{MM}/{YYYYMMDD}/00z/{date}00z-{control|ens_NN}.parquet
validation/herbie_intercomparison/ # GIK-vs-Herbie plots + stats per era

Usage (stream one member)

import pandas as pd, fsspec, json, gribberish, numpy as np
df = pd.read_parquet("hf://datasets/E4DRR/gik-ecmwf-par-v2/par/2026/07/20260701/00z/2026070100z-control.parquet")
z = {k: (json.loads(v) if isinstance(v, str) and v[:1] in "[{" else v) for k, v in zip(df.key, df.value)}
url, off, length = z["step_000/t/pl/500/control/0.0.0"]           # [s3_url, offset, length]
with fsspec.filesystem("s3", anon=True).open(url + ".grib2", "rb") as f:
    f.seek(off); raw = f.read(length)
arr = gribberish.parse_grib_array(raw, 0).reshape((721, 1440))    # 451x900 for 0p4

Validation

Every era is value-validated against Herbie ground truth (t @ 500/850 hPa): 0.25° eras are bit-exact (r=1.000000, RMSE ~1e-4 K); 0.4° r≥0.9997. See validation/herbie_intercomparison/ and its summary.md.

Provenance

Mirrored from gs://gik-ecmwf-aws-tf/v20260623_run_par_ecmwf/ (ICPAC). Reference dates: 0p4 20230601, 49r1 20250515 (13-level superset), 50r1 20260513. Templates: E4DRR/grib-index-kerchunk-templates.