Thanks to the 1987 Montreal Protocol and its amendments, ozone-depleting chlorine (and bromine) in the stratosphere has declined slowly since the late 1990s. Improved and extended long-term ozone profile observations from satellites and ground-based stations confirm that ozone is responding as expected and has increased by about 2 % per decade since 2000 in the upper stratosphere, around 40 km altitude. At lower altitudes, however, ozone has not changed significantly since 2000.

This study reports the distinct effects of street canyons on new particle formation (NPF) under warm or cold ambient temperature conditions because of on-road vehicle emissions; i.e., stronger condensation sinks are responsible for the reduced NPF in the springtime, but efficient nucleation and partitioning of gaseous species contribute to the enhanced NPF in the wintertime. The oxidization of biogenic organics is suggested to play an important role in growing new particles.

We assess NO_x emission trends over Chinese cities based on satellite NO₂ observations using a method independent of chemical transport models. NO_x emissions over 48 Chinese cities have decreased significantly since 2011. Cities with different dominant emission sources (i.e. power, industrial, and transportation sectors) showed variable emission decline timelines that corresponded to the schedules for emission control in different sectors.

We introduce a novel 3-D method of measuring atmospheric gravity waves, based around a 3-D Stockwell transform. Our method lets us measure new properties, including wave intrinsic frequencies and phase and group velocities. We apply it to data from the AIRS satellite instrument over the Southern Andes for two consecutive winters. Our results show clear evidence that the waves measured are primarily orographic in origin, and that their group velocity vectors are focused into the polar night jet.

Atmospheric methane simulations in the Arctic have been made for 2012 and compared to continuous observations at six measurement sites. All methane sources significantly affect the measurements at all stations, at least at the synoptic scale, except for biomass burning. An appropriate modelling framework combined with continuous observations of atmospheric methane enables us to gain knowledge on regional methane sources, including those which are usually poorly represented, such as freshwater.