27Cities Analyzed
Beta 1.0
CLeNE is currently in beta. Your feedback helps us improve city-level NO₂ exposure intelligence.
Submit FeedbackWest Africa'sNO₂ Exposure IntelligencePlatform
Transforming Sentinel-5P TROPOMI observations and population data into city-level exposure insights for policymakers, researchers, and the public.
2019 - 2025TROPOMI Observations
365.6MUrban Pop Covered
40/100WA Avg NPWEI
INSIGHTS
Latest Analysis
Explore recent CLENE analysis generated from Sentinel-5P TROPOMI observations, population exposure layers, and city-level air quality intelligence.
METHODOLOGY
How We Compute the NPWEI
A four-step pipeline from raw satellite data to a normalised population exposure index.
Data Acquisition
Monthly TROPOMI NO2 L3 files (.nc4) downloaded from NASA GES DISC for Jan 2019-Dec 2025. NASA Gridded 2020 population raster clipped to West Africa at 0.1 degree resolution.
Urban Masking
Pixel density computed accounting for latitude-varying cell area. Only pixels >=50 people/km2 contribute, isolating genuine urban exposure from sparse rural areas.
PWE Computation
PWE = sum(population x NO2) / sum(population) per city and country. Seasonal means computed for DJF, JJA, and Annual using RegularGridInterpolator alignment.
Normalisation & Export
Raw PWE normalised 0-100 per season: NPWEI = (PWE - min)/(max - min) x 100. Exported as JSON and PNG overlay tiles for web rendering.
RISK CLASSIFICATION
Understanding the NPWEI Risk Scale
The Normalised Population-Weighted Exposure Index (NPWEI) is scored 0-100 across five tiers. Cities and countries are benchmarked relative to each other within each season, making the index a comparative measure of relative urban NO2 burden.
MinimalLowModerateHighVery High
Very High
80-100High
60-79Moderate
40-59Low
20-39Minimal
0-19