PALM-BIO 2.0: Introducing the modernised biometeorology module

The first version of the biometeorological module (BIO) in PALM was published in 2020. The module contained three widely used and well-validated indices: i) perceived temperature (PT), ii) universal thermal climate index (UTCI), and iii) physiologically equivalent temperature (PET). Supported indices were calculated directly in PALM and used as user-defined outputs. However, the current implementation had several important limitations. The most critical shortcoming was the necessity to re-run the entire simulation whenever the user changed any hardcoded parameters of the indices. Other limitations included unclear parameterisations of the mean radiant temperature (MRT) reference shape, missing documentation for some indices (primarily PET), and problematic parallelisation or temporal averaging. Those limitations often resulted in inconsistent outputs. To solve these issues, we developed a new version of the BIO module, PALM-BIO 2.0. Most essential updates are as follows: clean code structure following internal code standards, adoption of a unified naming convention, various parameterisations for MRT calculation (e.g., black-globe thermometer, ellipsoidal approximation of the human body), preparation of the indices for the physiological module updates, and index corrections and improvements following current research (especially PET). To eliminate the need to re-run PALM simulations when only biometeorological input parameters change, the code was extended to output the meteorological variables required to calculate biometeorological indices into an intermediate file, enabling their calculation in a postprocessing stage. A postprocessing utility was also developed as a part of this update. PALM-BIO 2.0 is prepared for easy extension; for example, two new indices are being implemented: wet-bulb globe temperature (WBGT) and humidity index (HUMIDEX). Finally, our plans also consider UTCI*, adjusted UTCI, and the Dynamic Mean thermal sensation Vote (DMV).