lwbgt

lwbgt is a stable, low-level C/FFI implementation of the Liljegren outdoor wet bulb globe temperature (WBGT) model. It preserves the original scalar binary ABI and legacy WBGT calculations while removing repeated and dead work; the current source corrects the scalar 2 m wind output. Dependency-free Python and R bindings use the same native kernel. SwiftPM exposes the stable C interface as CLWBGT.

Use lwbgt as an auditable numerical backend. It deliberately leaves weather data ingestion, unit conversion, missing-data policy, heat-risk classification, and application defaults to callers. For a higher-level Python workflow, consider pywbgt or thermofeel.

Version: v0.4.3. The 852-case comparison with the retained original C found bit-identical Tg, Tnwb, Tpsy, WBGT, and esat under matched build settings; this is not an all-input guarantee. Direct scalar estimated wind at 2 m is corrected, and the original 1950–2049 year range is retained. See the compatibility policy.

Python

python -m pip install lwbgt

from lwbgt import Input, calculate, calculate_batch, esat

weather = Input(
    year=2024, month=4, day=15, hour=14, minute=30,
    gmt_offset_hours=8, averaging_minutes=60, urban=1,
    latitude_deg_north=1.3521, longitude_deg_east=103.8198,
    solar_w_m2=742.0, pressure_hpa=1008.4,
    air_temperature_c=32.1, relative_humidity_percent=68.0,
    wind_speed_m_s=2.8, wind_height_m=10.0,
    vertical_temperature_difference_c=1,
)

result = calculate(weather)
assert result.status == 0
print(result.wbgt_c)

results = calculate_batch([weather, weather])
print(esat(273.15, phase=0))

Input and Result are immutable typed records. Field names, units, status codes, and failure behaviour are defined by the ABI contract. See the input assumptions before substituting unavailable observations.

R

Install from R-universe:

install.packages("lwbgt", repos = "https://zyf0717.r-universe.dev")

Or install the latest GitHub release from the r/ subdirectory:

install.packages("remotes", repos = "https://cloud.r-project.org")
remotes::install_github("zyf0717/lwbgt/r@*release", upgrade = "never")

The R API provides lwbgt_input(), calculate(), and esat(). It returns ordinary data frames, recycles scalar constructor arguments, and isolates invalid or non-convergent rows. See the R quick start.

SwiftPM

Add the package and its C-library product to a Swift target:

let package = Package(
    dependencies: [
        .package(url: "https://github.com/zyf0717/lwbgt.git", from: "0.4.3"),
    ],
    targets: [
        .target(
            name: "WeatherService",
            dependencies: [
                .product(name: "CLWBGT", package: "lwbgt"),
            ]
        ),
    ]
)

import CLWBGT

CLWBGT exposes lwbgt.h directly; it is not an idiomatic Swift wrapper. SwiftPM builds the canonical C sources without vendoring or generated copies. Linux and macOS downstream consumption are tested in release mode.

Native C

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build --parallel
ctest --test-dir build --output-on-failure
cmake --install build --prefix /desired/prefix

The install provides static and shared libraries, lwbgt.h, CMake package metadata, and pkg-config metadata. CMake consumers can select lwbgt::static or lwbgt::shared after find_package(lwbgt CONFIG REQUIRED). GCC, Clang/AppleClang, and MinGW GCC are supported. MSVC is unsupported; the numerical target is built in GNU89 mode.

Documentation

Licence and attribution

Project-authored files are Apache-2.0 licensed. The retained upstream source and modified derivative remain under the UChicago Argonne Liljegren WBGT v1.1 terms. See LICENSING.md and retain the acknowledgement in NOTICE when redistributing.

This project is not affiliated with or endorsed by the original authors, UChicago Argonne, or the U.S. Department of Energy.