Atmospheric ammonia (NH 3 ) is a precursor to fine particulate matter formation and contributes to nitrogen deposition, with potential implications for the health of humans and ecosystems. Agricultural soils and animal excreta are the primary source of atmospheric NH 3 , but natural soils can also be an important emittor. In regions with distinct dry and wet seasons such as the Sahel, the start of the rainy season triggers a pulse of biogeochemical activity in surface soils known as the Birch effect, which is often accompanied by emissions of microbially-produced gases such as carbon dioxide and nitric oxide. Field and lab studies have sometimes, but not always, observed pulses of NH 3 after the wetting of dry soils; however, the potential regional importance of these emissions remains poorly constrained. Here we use satellite retrievals of atmospheric NH 3 using the Infrared Atmospheric Sounding Interferometer (IASI) regridded at 0.25° resolution, in combination with satellite-based observations of precipitation, surface soil moisture, and nitric dioxide concentrations, to present evidence of substantial precipitation-induced pulses of NH 3 across the Sahel at the onset of the rainy season in 2008. The highest concentrations of NH 3 occur in pulses during March and April, when biomass burning emissions estimated for the region by the Global Fire Emissions Database database are low. For the region of the Sahel spanning 10° to 16° N and 0° to 30° E, changes in NH 3 concentrations are weakly but significantly correlated with changes in soil moisture during the period from mid-March through April, when the peak NH 3 concentrations occur (r = 0.28, p = 0.02). The correlation is also present when evaluated on an individual pixel-basis during April (r = 0.16, p < 0.001). Using a simple box model, average emissions for the entire Sahel are between 2 and 6 mg NH 3 m −2 day −1 during peaks of the observed pulses, depending on the assumed effective lifetime. These early season pulses are consistent with surface observations of monthly deposition, which show an uptick in NH 3 deposition at the start of the rainy season for sites in the Sahel. The NH 3 concentrations in April are also correlated with increasing tropospheric NO2 concentrations observed by the Ozone Monitoring Instrument (r = 0.78, p < 0.0001), which have previously been attributed to the Birch effect. Box model results suggest that pulses occurring over a 35-day period in March and April are responsible for roughly one fifth of annual NH 3 emissions from the Sahel. We conclude that precipitation early in the rainy season is responsible for substantial NH 3 emissions in the Sahel, likely representing the largest instantaneous fluxes of nitrogen gas from the region during the year.