TEMPO (Tropospheric Emissions Monitoring of Pollution)

The first geostationary air-quality instrument over North America — hourly daytime measurements of tropospheric NO₂, HCHO, ozone, and aerosols across the continent. A genuine new capability layer; not an evolution of an existing sensor.

What it sees

• UV-Visible spectrometer measuring tropospheric column abundances of:
  • NO₂ (combustion + lightning + soil emissions) — the workhorse product
  • HCHO (formaldehyde) — biogenic VOC oxidation proxy + wildfire smoke
  • Tropospheric + total O₃
  • Aerosols (UV aerosol index)
• ~2 km × 4.5 km nadir pixel; ~5 km × 5 km at scan edges
• Hourly daytime cadence (sunlit hours only — UV-Visible technique)
• Coverage: North America roughly Mexico City through southern Canadian oil sands

Why it matters

• First-of-its-kind sub-daily air-quality data at neighborhood scales — previously only daily snapshots from polar orbiters (OMI / TROPOMI).
• Captures diurnal cycles of pollution that drive public-health outcomes (morning rush hour, midday photochemistry).
• Part of an emerging geostationary air-quality constellation: Korea’s GEMS (over Asia) + ESA’s Sentinel-4 (over Europe, launching 2026) = global coverage.
• The 800-user / 2-PB asymmetry (per FY2025 stats) shows extreme adoption concentration — a few research groups download enormous volumes; the broader user base hasn’t yet emerged. Major tooling gap at the broad-user layer.

Where to get the data

• earthaccess Python: short names TEMPO_NO2_L2, TEMPO_HCHO_L2, TEMPO_O3TOT_L2, etc.
• ASDC DAAC portal: asdc.larc.nasa.gov/project/TEMPO
• NRT (Near-Real-Time) products available since Sep 2025 for operational air-quality forecasting

What it enables

• Hourly NO₂ over your city, every daytime hour — pollution maps for environmental justice, transportation policy, electric-vehicle impact studies
• Wildfire smoke transport (HCHO tracer + aerosol index)
• Power-plant + industrial-source attribution (TEMPO’s spatial resolution can resolve point sources of NO₂)
• Diurnal cycles of pollution — morning vs evening rush patterns
• Cross-validation of ground-based monitors (EPA AirNow network)

Gotchas

• Daytime only. UV-Visible spectroscopy requires sunlight. No nighttime data.
• Cloud screening is essential. Clouds block the column retrieval entirely; downstream pipelines need solid cloud-fraction filtering.
• North America only. Asia is covered by GEMS; Europe by Sentinel-4 starting 2026. Don’t try to use TEMPO for global analyses.
• The 2 PB / 800 users stat suggests downstream tooling is sparse — be prepared to write more code than you’d expect.
• V04 (Sept 2025) is the current production version. Earlier versions (V01–V03) had known biases; reprocess if you’re using older data.
• L2 swath products use NASA standard “irregular” netCDF — not gridded; you have to regrid yourself or use the L3 daily gridded products.

Related missions

• GEMS (KARI / NIER): Korean geostationary equivalent over Asia (launched 2020).
• Sentinel-4 (ESA): European geostationary equivalent, launching 2026.
• TROPOMI on Sentinel-5P: polar-orbiting daily air-quality (the predecessor data layer; TEMPO captures the hourly variability TROPOMI misses).
• OMI on Aura: TEMPO’s spiritual ancestor in NASA’s atmospheric portfolio (2004–present).

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