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Aerosol characteristics and particle production in the upper troposphere over the Amazon Basin

We made airborne measurements of aerosol particle concentrations and properties over the Amazon Basin. We found extremely high concentrations of very small particles in the region between 8 and 14 km altitude all across the basin, which had been recently formed by gas-to-particle conversion at these altitudes. This makes the upper troposphere a very important source region of atmospheric particles with significant implications for the Earth’s climate system.

Response to marine cloud brightening in a multi-model ensemble

Marine cloud brightening (MCB) has been proposed to help limit global warming. We present here the first multi-model assessment of idealized MCB simulations from the Geoengineering Model Intercomparison Project. While all models predict a global cooling as intended, there is considerable spread between the models both in terms of radiative forcing and the climate response, largely linked to the substantial differences in the models’ representation of clouds.

Agricultural ammonia emissions in China: reconciling bottom-up and top-down estimates

Substantial differences exist in current estimates of agricultural ammonia emissions in China, hindering understanding of their environmental consequences. This study applies both bottom-up and top-down methods to better quantify agricultural ammonia sources in China using observations from satellite and surface networks interpreted by a chemical transport model. Our estimate of annual Chinese anthropogenic ammonia emission is 11.7 tg (teragram) for 2008 with a strong seasonality peak in summer.

Temporal variability of tidal and gravity waves during a record long 10-day continuous lidar sounding

Gravity waves (GWs) as well as solar tides are a key driving mechanism for the circulation in the Earth’s atmosphere. The temporal variation of these waves is studied using a record long 10-day continuous Rayleigh–Mie–Raman lidar sounding at midlatitudes. This data set shows a large variability of these waves on timescales of a few days and therefore provides new insights into wave intermittency phenomena, which can help to improve model simulations.

First tomographic observations of gravity waves by the infrared limb imager GLORIA

Using the infrared limb imager GLORIA, the 3-D structure of mesoscale gravity waves in the lower stratosphere was measured for the first time, allowing for a complete 3-D characterization of the waves. This enables the precise determination of the sources of the waves in the mountain regions of Iceland with backward ray tracing. Forward ray tracing shows oblique propagation, an effect generally neglected in global atmospheric models.

GLORIA">Read more

The role of meteorological conditions and pollution control strategies in reducing air pollution in Beijing during APEC 2014 and Victory Parade 2015

The generalized linear regression model (GLM), even based only on meteorological parameters, could be satisfactory to estimate the contribution of meteorological conditions in reducing air pollution and hence the contribution of control strategies in reducing air pollution. Using the GLM, we found that the meteorological conditions and pollution control strategies contributed 30% and 28% to the reduction of the PM_2.5 concentration during APEC 2014 and 38% and 25% during Parade 2015.

APEC 2014 and Victory Parade 2015">Read more

A new diagnostic for tropospheric ozone production

Understanding tropospheric ozone chemistry has been at the centre of the field of atmospheric chemistry for the last 30 years. However, our conceptual approach to diagnosing ozone production in global models has not advanced in this time. Our work presents a new and powerful approach for diagnosing tropospheric ozone production, providing a significant enhancement in our ability to understand the processes controlling ozone and how we can validate our assessment of these processes.

Impact of agricultural emission reductions on fine-particulate matter and public health

This study shows that agricultural emissions are important for air quality and their reduction can effectively reduce the concentration of fine particles and their associated premature mortality. Therefore, emission control policies, especially in North America and Europe, should also involve strong ammonia emission decreases to optimally reduce fine-particle concentration.

A growing threat to the ozone layer from short-lived anthropogenic chlorocarbons

We have observed large amounts of man-made chlorine compounds in E and SE Asia and in the upper tropical troposphere. These relatively short-lived compounds are not controlled by the Montreal Protocol, but if significant quantities were able to reach the stratosphere, the long-term recovery of stratospheric ozone would be delayed. We have also identified an important atmospheric transport mechanism that can rapidly transport these chemicals from E Asia to the upper troposphere via the tropics.

An update on ozone profile trends for the period 2000 to 2016

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.

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