NNJA-AI

Warning

Under development.

NNJASource accesses the NNJA-AI cloud-hosted observation archive (NOAA/NASA Joint Archive) stored on GCS.

Install the extra dependency

pip install nnja-ai

Usage

import datetime
from dartobsgen import ObsGenConfig, NNJASource, generate_obs_sequences

config = ObsGenConfig(
    start=datetime.datetime(2021, 1, 1),
    end=datetime.datetime(2021, 1, 2),
    lat_min=-90, lat_max=90,
    lon_min=-180, lon_max=180,
    obs_types=[
        "METAR_TEMPERATURE_2_METER",
        "METAR_U_10_METER_WIND",
        "METAR_V_10_METER_WIND",
    ],
    assimilation_frequency=datetime.timedelta(hours=6),
    output_dir="./obs_output",
)

source = NNJASource(catalog_mirror="gcp_nodd")

if __name__ == "__main__":
    written = generate_obs_sequences(config, source)
    print(written)

Supported NNJA obs types

DART obs type	NNJA dataset	Variable
METAR_TEMPERATURE_2_METER	conv-adpsfc-NC000001	TMPSQ1.TMDB (K)
METAR_U_10_METER_WIND	conv-adpsfc-NC000001	derived from WNDSQ1.WSPD + WNDSQ1.WDIR
METAR_V_10_METER_WIND	conv-adpsfc-NC000001	derived from WNDSQ1.WSPD + WNDSQ1.WDIR
RADIOSONDE_TEMPERATURE	conv-adpupa-NC002001	TMDB_PRLC{n} mandatory levels
RADIOSONDE_U_WIND_COMPONENT	conv-adpupa-NC002001	derived from WDIR_PRLC{n} + WSPD_PRLC{n}
RADIOSONDE_V_WIND_COMPONENT	conv-adpupa-NC002001	derived from WDIR_PRLC{n} + WSPD_PRLC{n}

Radiosonde pressure suffix n: column TMDB_PRLC5000 → 500 hPa = 50 000 Pa (pressure_Pa = int(n) × 10).

Custom error variances

Override the default error variances (1.0 for all obs types) by passing a custom obs_type_map to NNJASource or to ObsGenConfig:

source = NNJASource(
    catalog_mirror="gcp_nodd",
    obs_type_map={
        "METAR_TEMPERATURE_2_METER": {
            "nnja_dataset": "conv-adpsfc-NC000001",
            "kind": "scalar",
            "nnja_col": "TMPSQ1.TMDB",
            "vert_unit": "surface (m)",
            "vert_col": "SELV",
            "default_err_var": 4.0,   # 2 K std dev → 4 K² variance
        },
    },
)

GCS mirror options

Mirror	Description
"gcp_nodd"	NOAA Open Data Dissemination (default, open access)
"gcp_brightband"	Brightband mirror