CHLA-Z: Global Chlorophyll-a Vertical Distribution Dataset

Description

CHLA-Z is a global gridded dataset providing estimates of chlorophyll-a concentration as a function of depth (0–200 m) on a regular latitude/longitude grid, along with derived vertical-structure metrics. The product is generated using a boosted regression tree (BRT) model trained on PACE OCI Level-3 mapped remote-sensing reflectances (Rrs) and in-situ chlorophyll profile observations from Bio-Argo and OOI.

Core variable: CHLA (time, z, lat, lon) — chlorophyll-a concentration (mg m^-3)
Derived layers: CHLA_int_0_200 (mg m^-2), CHLA_peak (mg m^-3), CHLA_peak_depth (m), CHLA_depth_center_of_mass (m)
Vertical grid: 10 m bin centers with bounds z_start/z_end
Spatial grid: global regular lat/lon (~4 km nominal; 0.041666668° step)
Temporal resolution: daily
Format: Zarr v3 (cloud-optimized) and NetCDF (by day)

Note on “4 km”: This dataset is on a regular latitude/longitude grid (0.041666668°). North–south spacing is ~constant; east–west spacing decreases with latitude (cos(lat)).

Example notebook

View notebook on GitHub |

Python (stream Zarr)

import xarray as xr

zarr_url = "gcs://nmfs_odp_nwfsc/CB/fish-pace-datasets/chla-z/zarr"
ds = xr.open_zarr(zarr_url, consolidated=False, 
          storage_options={"token": "anon"})

# Example: time series at a point (nearest grid cell)
pt = ds["CHLA"].sel(lon=-155, lat=20, method="nearest")
pt = pt.isel(z=0) # surface
pt.sel(time=slice("2024-03-01", "2024-04-01")).plot()

Python (stream a NetCDF day)

import xarray as xr

url = "gcs://nmfs_odp_nwfsc/CB/fish-pace-datasets/chla-z/netcdf/chla_z_20240305_v2.nc"
ds = xr.open_dataset(url, engine="h5netcdf", 
          storage_options={"token": "anon"})

# Plot surface CHLA for that day
ds["CHLA"].isel(time=0, z=0).plot()

R (download NetCDF)

R typically does not stream NetCDF directly from gcs://. Download first using HTTPS.

library(terra)
url <- "https://storage.googleapis.com/nmfs_odp_nwfsc/CB/fish-pace-datasets/chla-z/netcdf/chla_z_20240305_v2.nc"
download.file(url, "chla_z_20240305_v2.nc", mode = "wb")
f <- "chla_z_20240305_v2.nc"
r <- rast(f, subds = "CHLA")   # SpatRaster with 20 layers (z levels)
# surface CHLA = first z layer
surf <- r[[1]]
plot(log10(surf), main = "log10 Surface CHLA (z=1)")

Resources

Google Cloud Bucket:
gs://nmfs_odp_nwfsc/CB/fish-pace-datasets/chla-z
https://console.cloud.google.com/storage/browser/nmfs_odp_nwfsc/CB/fish-pace-datasets/chla-z

Access: Public / no authentication required for reads

Browse resources:

GitHub Repo

Repo: https://github.com/fish-pace/chla-z

Suggested citation

Holmes, E. E. (2026). CHLA-Z: Global chlorophyll-a vertical distribution (0–200 m) derived from PACE OCI and Bio-Argo (draft) (0.1.0) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.18204005

Example chlorophyll-a vertical profiles from CHLA-Z — Example chlorophyll-a vertical profiles (0–200 m) from the CHLA-Z dataset.

Status: Research/draft product. Validation and uncertainty characterization are in progress; please consult the documentation and repository for updates.

CHLA-Z: Global Chlorophyll-a Vertical Distribution (0–200 m)