Atmospheric ammonia (NH) emanations from Lake Natron's saline mudflats.

In a recent global analysis of satellite-derived atmospheric NH data, a hotspot was observed in the vicinity of Lake Natron, Tanzania. The lake is in the centre of an endorheic (limited drainage) basin and has shallow, saline-alkaline waters. Its remote location and the absence of nearby large anthropogenic sources suggest that the observed NH is mainly of natural origin.

Industrial and agricultural ammonia point sources exposed.

Through its important role in the formation of particulate matter, atmospheric ammonia affects air quality and has implications for human health and life expectancy. Excess ammonia in the environment also contributes to the acidification and eutrophication of ecosystems and to climate change. Anthropogenic emissions dominate natural ones and mostly originate from agricultural, domestic and industrial activities.

Retrieving radius, concentration, optical depth, and mass of different types of aerosols from high-resolution infrared nadir spectra.

We present a sophisticated radiative transfer code for modeling outgoing IR radiation from planetary atmospheres and, conversely, for retrieving atmospheric properties from high-resolution nadir-observed spectra. The forward model is built around a doubling-adding routine and calculates, in a spherical refractive geometry, the outgoing radiation emitted by the Earth and the atmosphere containing one layer of aerosol. The inverse model uses an optimal estimation approach and can simultaneously retrieve atmospheric trace gases, aerosol effective radius, and concentration.

Development of a stabilized low temperature infrared absorption cell for use in low temperature and collisional cooling experiments.

We have constructed a stabilized low temperature infrared absorption cell cooled by an open cycle refrigerator, which can run with liquid nitrogen from 250 to 80K or with liquid helium from 80K to a few kelvin. Several CO infrared spectra were recorded at low temperature using a tunable diode laser spectrometer. These spectra were analyzed taking into account the detailed effects of collisions on the line profile when the pressure increases.

Concentration measurements of ozone in the 1200-300ppbv range: an intercomparison between the BNM ultraviolet standard and infrared methods.

Simultaneous ultraviolet (UV) and infrared (IR) measurements of ozone concentration in air in the 1200-300 ppbv range have been performed using the ultraviolet absorption in the Hartley band at 0.2537 microm and the infrared absorption of a doublet at 9.507 microm in the nu(3) vibration-rotation band.