[Manure] Possible transcription error in bedded pack MCF temperature bins

[tomhuhh]

Possible Transcription Error in Bedded Pack MCF Temperature Bins

Expected Behavior

The Methane Conversion Factor (MCF) lookup for bedded pack storage should be based on IPCC climate zones (e.g., Cool Temperate Moist, Warm Temperate Dry, etc.), as documented in the 2024 USDA GHG Inventory Methods Table 4-9. Each climate zone should have correctly defined temperature ranges.

Current Behavior

File: RUFAS/biophysical/manure/storage/bedded_pack.py
Reference: 2024 USDA GHG Inventory Methods, Table 4-9

The current implementation uses five temperature bins with boundaries at 4.6, 5.8, 13.9, and 25.1 °C to look up MCF values. According to IPCC (2019), these values are not climate zone boundaries — they are the average annual temperatures of named IPCC climate zones:

IPCC Climate Zone	Avg Temp (°C)
Cool Temperate Moist	4.6
Cool Temperate Dry	5.8
Warm Temperate Moist	13.9
Warm Temperate Dry	14.0
Tropical Montane	21.5
Tropical Wet	25.9
Tropical Moist	25.2
Tropical Dry	25.6

The representative means appear to have been lifted from the source table's zone descriptions and mistakenly used as bin edges — a misinterpretation of how Table 4-9 is structured. The source table maps MCF to named climate zones, not to temperature ranges derived from zone averages.

This produces two observable symptoms:

• The 4.6–5.8 °C bin is only 1.2 °C wide and carries the same mixed MCF (0.5%) as the bin below it, making it redundant.
• The 13.9–25.1 °C bin carries the same mixed MCF (1.0%) as the bin above it, suggesting another collapsed zone boundary.

A farm with an annual mean of, say, 6 °C would be placed in the Warm Temperate bin under this scheme — a clear misclassification.

Possible Solution

Replace the temperature-range bins with a climate-zone–based lookup that maps IPCC-defined climate zones directly to MCF values, consistent with how Table 4-9 is structured. Annual mean temperature should be used only to assign a farm to its correct IPCC climate zone using proper zone boundaries, not the zone representative means as cutoffs.

IPCC (2019) defines:

• Tropical Dry: has > 18°C mean annual temperature and mean annual precipitation < 1000mm;
• Tropical Moist: has > 18°C mean annual temperature and mean annual precipitation > 1000mm;
• Warm temperate moist: has > 10°C mean annual temperature and a ratio of potential evapotranspiration to
  precipitation > 1;
• Warm temperate dry: has > 10°C mean annual temperature and a ratio of potential evapotranspiration to
  precipitation < 1;
• Cool temperate moist: has > 0°C mean annual temperature and a ratio of potential evapotranspiration to
  precipitation > 1;
• Cool temperate dry: has > 0°C mean annual temperature and a ratio of potential evapotranspiration to precipitation < 1;

This classification should also be based on annual ambient temperature, not annual barn temperature.

Steps to Reproduce

1. Open RUFAS/biophysical/manure/storage/bedded_pack.py and locate BEDDED_PACK_MCF_TABLE.
2. Note the bin boundaries: 4.6, 5.8, 13.9, and 25.1 °C.
3. Cross-reference IPCC (2019): Cool Temperate Moist avg = 4.6 °C, Cool Temperate Dry avg = 5.8 °C, Warm Temperate Moist avg = 13.9 °C, Tropical Moist avg = 25.2 °C.
4. Observe that the bin boundaries exactly match zone representative means, not zone range boundaries.
5. Note that the two lowest bins produce identical MCF for mixed packs, confirming the split adds no information.

Context (Environment)

This affects all RUFAS simulations using bedded pack storage. Farms near the bin boundaries — particularly in the 4.6–5.8 °C range — may be assigned to the wrong MCF, leading to systematic over- or under-estimation of methane emissions.

Detailed Description

The USDA Table 4-9 defines MCF values keyed to IPCC climate zones. During implementation, the representative average temperatures for each zone appear to have been used as bin boundaries rather than as zone identifiers, producing a temperature-range lookup that does not correspond to any defined IPCC zone boundary. This is a transcription/interpretation error introduced at the point of code authorship.

Possible Implementation

1. Define an enumeration or mapping of IPCC climate zones (e.g., Cool Temperate Moist, Warm Temperate Dry, Tropical Wet, etc.).
2. Implement a climate zone classifier that maps annual mean temperature (and possibly moisture regime) to the correct IPCC zone.
3. Replace the temperature-range table with a zone-keyed MCF lookup.
4. Update calculate_bedded_pack_methane_conversion_factor to accept a climate zone instead of a raw temperature value.
5. Add docstring citations linking directly to IPCC (2019) and USDA Table 4-9 for traceability.

Target Deadline

[matthew7838]

@elle-andreen, could you weigh in on the issue?