STL decomposition by species#
This notebook shows the STL decomposition of each Sentinel-5P species over the West Bank and the Gaza Strip, on a weekly cadence.
Each species has a short note before its chart. The note gives the atmospheric lifetime and the main emission sources. Atmospheric lifetime helps interpret the chart: short-lived species are generally more sensitive to nearby, recent emissions, while long-lived species include a larger transported or global background. Meteorology, clouds, sampling, and retrieval quality also affect every weekly satellite column, so none of the series is a direct emissions measurement.
The dashed grey rule marks 7 October 2023. The dashed red rule marks the ceasefire that took effect on 10 October 2025. Orange circles identify weeks interpolated before STL fitting.
Nitrogen dioxide (NO₂)#
Lifetime. NOₓ persists for hours to days. Daytime lifetimes near large cities are often about four hours at low and middle latitudes and can be longer in winter.
Sources. Combustion at high temperature. Road traffic, power generation, diesel generators, industry, and shipping. Explosions and large fires can also release NOₓ, while soils and lightning contribute natural emissions.
Sources: IPCC AR6 WGI Chapter 6; Beirle et al. (2011); EPA NO₂ overview.
Carbon monoxide (CO)#
Lifetime. About one to four months, generally longer in winter and at higher latitudes.
Sources. Incomplete combustion. Traffic, heating, waste burning, biomass burning, and wildfires. Oxidation of methane and other hydrocarbons also makes CO in the atmosphere.
Sources: IPCC AR6 WGI Chapter 6; NASA AIRS CO overview; NOAA atmospheric-isotope overview.
Sulphur dioxide (SO₂)#
Lifetime. Usually less than one day to several days in the boundary layer, depending on oxidation, deposition, cloud water, season, and location.
Sources. Burning of sulphur-rich fuel. Heavy fuel oil, coal, diesel generators, refineries, cement plants, and shipping. Volcanoes are a major natural source.
Notes SO₂ over a small area is close to the detection limit of the instrument, and the weekly retrieval goes negative. The series is therefore asinh transformed, not log transformed.
Sources: IPCC AR6 WGI Chapter 6; EPA Sulfur Dioxide Basics; Bauduin et al. (2014).
plot_stl("so2")
Absorbing aerosol index (AAI)#
AAI is not a gas. It is an index of ultraviolet-absorbing particles in the column, mainly desert dust and smoke. The index has no unit. Negative values do not necessarily mean clean air: they can also reflect non-absorbing aerosol and retrieval or radiometric effects.
Lifetime. AAI is an optical index, not a particle species, so it has no single atmospheric lifetime. The absorbing particles it represents can remain airborne from minutes to weeks depending on size, composition, altitude, and weather. Wet deposition often shortens their residence time.
Sources. Sand and dust storms, smoke from fires and from burning buildings, and soot from combustion.
Sources: TROPOMI UV Aerosol Index ATBD; IPCC AR6 WGI Chapter 6; Bond et al. (2013); Ginoux et al. (2012).
References#
Atmospheric lifetimes and emission sources#
IPCC AR6 WGI Chapter 6: Short-lived Climate Forcers — assessed lifetimes and source sectors for NOₓ, CO, SO₂, aerosols, O₃, and CH₄.
Beirle et al. (2011), Science — satellite-derived urban NOₓ lifetimes.
EPA Basic Information about NO₂ — major combustion sources.
NASA AIRS carbon monoxide overview and NOAA atmospheric-isotope overview — CO lifetime, direct combustion, and secondary production.
EPA Sulfur Dioxide Basics and Bauduin et al. (2014) — SO₂ sources and lifetime variability.
TROPOMI UV Aerosol Index ATBD, Bond et al. (2013), and Ginoux et al. (2012) — AAI interpretation, carbonaceous aerosol, and mineral dust.
Palmer et al. (2003), TROPOMI formaldehyde description, and Liao et al. (2021) — HCHO lifetime, VOC oxidation, and fire plumes.
NASA Ozone Watch and EPA Ground-level Ozone Basics — stratospheric share and tropospheric formation.
Global Methane Budget and NOAA CarbonTracker-CH₄ — methane sources and global background.