OSVAS

Albedo Estimation - Quick Reference

TL;DR - Enable Albedo Estimation

1. Configure Your Station

Edit your station YAML (e.g., config_files/Stations/Cabauw/Cabauw.yml):

Station_metadata:
  ...
  estimate_albedo: true

2. Run OSVAS Workflow

export STATION_NAME=Cabauw
export OSVAS=$HOME/OSVASgh
export HARPSCRIPTS=$OSVAS/HARPSCRIPTS

python3 scripts/python_scripts/surfex_OSVAS_run_linux.py

The workflow automatically:

1. Downloads validation data (Step 2)
2. Estimates albedos from SW_OUT/SW_IN (Step 2b) ✨
3. Updates namelists with estimated values
4. Runs SURFEX simulations with new albedos (Step 3)

What Gets Computed?

• Midday SZA: SW_OUT/SW_IN between 11:00-13:00 UTC (high solar elevation)
• Daily averages: Mean albedo for each day
• Monthly values: Average of daily values per calendar month
• Six parameters:
  • XUNIF_ALBNIR_VEG - Vegetation NIR — estimated from data
  • XUNIF_ALBVIS_VEG - Vegetation VIS — estimated from data
  • XUNIF_ALBUV_VEG - Vegetation UV — fixed at 0.015 (not estimated)
  • XUNIF_ALBNIR_SOIL - Soil NIR (same as vegetation initially) — estimated from data
  • XUNIF_ALBVIS_SOIL - Soil VIS (same as vegetation initially) — estimated from data
  • XUNIF_ALBUV_SOIL - Soil UV — fixed at 0.06 (not estimated)

Output Files

File	Purpose
namelists/{station}/albedo_estimates.nam	Raw NIR/VIS albedo namelist blocks (UV is not included here — see below)
namelists/{station}/OPTIONS.nam_{expname}.backup_alb	Backup of original namelist
namelists/{station}/OPTIONS.nam_{expname}	Updated with new albedos

Note: if a namelist doesn’t already contain albedo blocks, update_namelist_albedos.py automatically inserts all six blocks into the &NAM_DATA_ISBA group — the four estimated NIR/VIS blocks plus fixed UV blocks (XUNIF_ALBUV_VEG = 0.015, XUNIF_ALBUV_SOIL = 0.06). If the namelist already has UV blocks, those are left as-is.

Disable Albedo Estimation

Set estimate_albedo: false in Station_metadata to skip this step.

Key Parameters

Parameter	Value	Notes
Time window	11:00-13:00 UTC	High solar angle, minimal geometric effects
Minimum SW_IN	0	Only daylight conditions
Albedo range	[0.0, 1.0]	Remove unphysical values
Monthly method	Mean of daily	Simple average

Troubleshooting

Problem	Solution
“No SW_OUT/SW_IN data”	Check Validation_data config includes SW_OUT/SW_IN
“No midday data”	Check UTC time zone of OBSTABLEs; adjust time window if needed
“Albedo values unrealistic”	Check measurement quality; likely sensor issues or calibration drift
No existing albedo blocks in namelist	Handled automatically — blocks are inserted into &NAM_DATA_ISBA. Only fails if that group is missing from the namelist
Namelist update fails	Verify vegtype matches in namelist and YAML config; confirm &NAM_DATA_ISBA exists

Full Documentation

See docs/step2b_albedo_estimation.md for detailed information.