Tune MATCH with CORe to Ed4, 2026 March

[davidfillmore]

Goal

Tune MATCH aerosol emissions driven by CORe reanalysis meteorology against the MODIS Ed4 assimilated AOD for March 2025, targeting the March 2026 CORe run.

Background

CORe reanalysis replaces CDAS as the meteorological driver for MATCH. Key differences affect aerosol emissions:

• Soil moisture (SOILW): CORe uses 18-bit packing (range 0.02–1.0) vs CDAS 9-bit (range 0.10–0.43). A single linear rescaling cannot match CDAS dust across months — e.g., Jan 2026 CORe dust is higher than CDAS, Feb 2026 is substantially lower.
• Wind speed: CORe winds differ from CDAS, producing a systematic sea salt AOD bias over oceans.

Rather than matching CDAS (which itself has biases), we tune directly against assimilated AOD.

Reference Data

March 2025 total extinction AOD (TOTEXTTAU) on the MATCH T62 grid (192×94), extracted from:

• MATCH_Terra-Aqua-MODIS_Ed4.TOTEXTTAU_L192x94.nc4 — MATCH + MODIS Ed4 assimilation
• MATCH_NOAA20-VIIRS_Ed1C.TOTEXTTAU_L192x94.nc4 — MATCH + VIIRS Ed1C (independent validation)

Tuning Parameters

Three namelist parameters control the tuning, all with identity defaults:

Parameter	Default	Location	Purpose
sslt_scale	1.0	src/getsslt.F	Sea salt emission flux multiplier
vwc_scale	1.0	dst/dstmbl.F	Dust soil moisture rescaling slope
vwc_offset	0.0	dst/dstmbl.F	Dust soil moisture rescaling offset

Approach

Step 1: Extract March 2025 reference field

Extract the March 2025 TOTEXTTAU from the Ed4 assimilation file.

Step 2: Tune sea salt (sslt_scale) over clean-ocean regions

Over remote ocean where total AOD is dominated by sea salt (Southern Ocean 50–65S, central South Pacific 30–50S/150W–90W, remote South Atlantic 30–50S/30W–10E), compare free-running MATCH AEROD against the Ed4 March 2025 field to fit sslt_scale.

Step 3: Tune dust (vwc_scale, vwc_offset) over dust-dominated regions

With sea salt scaling fixed, compare MATCH AEROD against the Ed4 March 2025 field in dust-dominated regions (Sahara/Sahel 10–30N/20W–30E, Atlantic dust corridor 5–25N/60W–20W, Arabian Peninsula 15–30N/35–60E, Gobi/Taklamakan 35–45N/75–110E) to fit vwc_scale and vwc_offset.

Step 4: Validate

• Cross-validate against VIIRS Ed1C March 2025
• Compare against CDAS baseline runs
• Check per-species fields when available

Deliverable

A set of tuning coefficients (vwc_scale, vwc_offset, sslt_scale) for March, applied to the March 2026 CORe run.

See AOD_TUNE.md for the broader tuning plan.