Pre-release: This software is under active development. APIs may change before v1.0.0 (first stable release at paper acceptance).

TEXAS — A proxy system model for TetraEther indeX of Ammonia oxidizerS

TEXAS-PSM (texas-psm) is a Python package implementing a Bayesian proxy system model for the TEX86 paleothermometer. TEXAS is its sensor model — the calibration linking temperature to the index — while TEXAS-PSM is the whole chain around it: sensor, archive, observation, and the inversion back to temperature. The distribution name and the import already carry that split (pip install texas-psm, import TEXAS). It fits hierarchical generalized-logistic Stan models to isoGDGT proxy data (Scaled RI) for thermal responses — with optional non-thermal corrections for AOA ecology (GDGT-2/3 ratio) and nutrient effects (NO₃) — and reconstructs paleotemperatures from new sediment records with full posterior uncertainty.

📦 Installation   📖 Documentation   🤝 Contributing   📄 License

What it does

TEXAS implements a two-stage workflow:

Optional non-thermal predictors — the GDGT-2/GDGT-3 (G23) and NO₃ — enter inside the logistic, as a shift of the curve's location parameter T₀:

T₀_eff = T₀ + γ_{G23}·G23 + γ_{NO₃}·log₁₀(NO₃)
Scaled RI = b + (1 − b) / (1 + exp(−k·(T − T₀_eff)))^(1/ν)

The γ coefficients are in °C per predictor unit, so a sample with a given G23 behaves like water that is γ·G23 °C colder. Because the predictors translate the curve rather than adding an offset to the response, the predicted Scaled RI stays inside (b, 1) for any finite predictor value — the bound a ratio has by definition is reproduced by construction, with no truncation or clipping. They are fitted through an Error-in-Variables (EIV) Stan model that separates analytical measurement error from oceanographic process noise. Inverse models use reduce_sum for within-chain parallelism.

T₀ is the curve's location, not its inflection point. The steepest response sits at T₀ − ln(ν)/k, roughly 4–5 °C below T₀ for the fitted ν. Because dRI/dT varies about sixfold across the calibrated range, there is no single thermal sensitivity to quote for this proxy.

Quick start

pip install texas-psm
# or, with uv:  uv add texas-psm

Inverse reconstruction runs Stan, so pip/uv users need CmdStan installed once — run TEXAS.install_cmdstan() (or the texas-install-cmdstan command), which installs the tested version and verifies the toolchain. Docker and conda-lock bundle it. The forward predict_proxy_from_T is pure Python and needs no CmdStan. See Installation.

import TEXAS

# Download pre-computed posteriors from Zenodo (~0.3 MB for univariate)
TEXAS.download_posteriors(["tx.GHPU.sst.sri03.p0"])   # univariate SST calibration
# Posterior names are CESM-style case ids (tx.<compset>.<temp>.<proxy>.<predictors>);
# legacy long names (gen_logi_fixed_...) are also accepted everywhere. See
# "How posterior files are named" in the docs quickstart.

# Forward: temperature → Scaled RI
result = TEXAS.predict_proxy_from_T(
    temperatures=[15, 20, 25, 30],
    posterior="tx.GHPU.sst.sri03.p0",
)

# Inverse: Scaled RI → temperature
result = TEXAS.predict_T_from_proxyObs(
    proxyObs=my_ri_array,
    prior_mu_t=15.0, prior_sigma_t=10.0,
    fwd_posterior="tx.GHPU.sst.sri03.p0",
    temptype="SST",
)
result["p50"]   # median temperature (°C)
result["p5"]    # 5th percentile
result["p95"]   # 95th percentile

For Docker, conda-lock, uv, and development installs, see Installation.

Data and posteriors

Pre-computed posteriors and training data are hosted on Zenodo: https://doi.org/10.5281/zenodo.19666744

import TEXAS

TEXAS.download_all()               # posteriors + training CSVs
TEXAS.download_posteriors()        # forward posteriors only (~158 MB total;
                                   # EIV multiv posteriors are ~78 MB each)
TEXAS.download_training_data()     # training CSVs + CMEMS NO₃ field

Pass names= to download only what you need:

# Univariate SST posterior — ~0.3 MB
TEXAS.download_posteriors(["tx.GHPU.sst.sri03.p0"])

Load a posterior directly from disk (no cache lookup):

import xarray as xr
ds = xr.load_dataset("/path/to/posterior.nc")
result = TEXAS.predict_T_from_proxyObs(..., fwd_posterior=ds)

Check what is cached:

TEXAS.list_posteriors()

Example usage

import numpy as np
import xarray as xr
from TEXAS import compute_scaledRI, predict_proxy_from_T, predict_T_from_proxyObs

# ── Compute Scaled Ring Index from raw GDGT abundances ────────────────────────
df["scaledRI_cren3"] = compute_scaledRI(
    df["GDGT-0"], df["GDGT-1"], df["GDGT-2"], df["GDGT-3"],
    df["cren"],   df["cren_prime"],          # cren_weight=3 by default (RI₀₋₃)
)

# ── Forward prediction (temperature → proxy) ──────────────────────────────────
result = predict_proxy_from_T(
    temperatures=np.linspace(5, 35, 100),
    posterior="tx.GHPU.sst.sri03.p0",
)
# result["p50"], result["p5"], result["p95"] — numpy arrays

# ── Inverse reconstruction (proxy → temperature) ──────────────────────────────
result = predict_T_from_proxyObs(
    proxyObs=df["scaledRI_cren3"].values,
    prior_mu_t=15.0, prior_sigma_t=10.0,
    fwd_posterior="tx.GHPU.sst.sri03.p0",
    temptype="SST",
    save_results=True,   # write quantile .nc + .npz to the invT cache dir
)

# ── Multivariate model with NO₃ and GDGT-2/3 correction ──────────────────────
# This is the default: omitting fwd_posterior selects the full multivariate
# T₀-shift calibration, which ships inside the package — no download needed.
# Pass temptype="thermoT" for the thermocline-integrated calibration.
result = predict_T_from_proxyObs(
    proxyObs=df["scaledRI_cren3"].values,
    prior_mu_t=15.0, prior_sigma_t=10.0,
    fwd_posterior="tx.GHEB.sst.sri03.G23-N1p0",   # the default; may be omitted
    temptype="SST",
    gdgt23ratio=df["gdgt23ratio"].values,
    no3=df["no3"].values,           # or: site_lat=, site_lon=, no3_dataset= for WOA23 lookup
)

# ── Pass a pre-loaded dataset (Colab / Google Drive) ──────────────────────────
# (downloads are named by case id; v0.2.0-era files keep their legacy name)
ds = xr.load_dataset("/content/drive/MyDrive/posteriors/tx.GHPU.sst.sri03.p0.fwd.nc")
result = predict_T_from_proxyObs(..., fwd_posterior=ds)

Repository layout

src/TEXAS/
  predict.py        High-level API: predict_proxy_from_T / predict_T_from_proxyObs
  stan/             Sampler, compiler, I/O, and invT orchestration
  stan_models/      Stan model files (.stan) — bundled in the pip package
  data/             Input data builders, filters, screening, ocean property lookups
  ensemble/         Posterior ensemble generation and model detection
  models/           Logistic curve functions and classical calibrations
  utils/            Path constants, system info, Zenodo download utilities
notebooks/
  quickstart_demo.ipynb     Minimal end-to-end path: GDGTs -> Scaled RI -> temperature
  quickstart_extended.ipynb Longer walkthrough: a published record, model comparison
  manuscripts/      Finalized SI notebooks behind the paper (SI_code00 .. SI_code03)
  reviewer_response/ Analyses answering review comments, not cited in the paper
  superseded/       Pre-revision (additive-formulation) versions, kept for provenance
streamlit_app/      Drag-and-drop web interface (Streamlit)
docker/             Dockerfile and compose configuration
docs/               Jupyter Book documentation source (guides, API, tutorial)
tests/              Unit tests

API at a glance

Full API reference: https://paleolipidRR.github.io/TEXAS

Citation

If you use TEXAS in your research, please cite:

Rattanasriampaipong, R. et al. (in prep). TEXAS: A proxy system model for TEX86 paleothermometry. AGU Paleoceanography and Paleoclimatology.

See CITATION.cff for machine-readable citation metadata.

License

MIT © Ronnakrit Rattanasriampaipong — see LICENSE for the full text.