atmospheric chemistry

Aura/HIRDLS reveals global characteristics of the double tropopause

Double tropopause example

Aura’s High Resolution Dynamics Limb Sounder (HIRDLS) reveals the global pattern of the double tropopause using the HIRDLS high vertical resolution profiles. Composition and structure near the tropopause are important for the Earth radiative balance and quantifying transport of ozone and other stratospheric species into the troposphere.

Progress in Understanding Climate-Relevant Processes in the Upper Troposphere and Lower Stratosphere

Schematic snapshot of the extratropical UTLS.

The extratropical upper troposphere and lower stratosphere (Ex‐UTLS) is a transition region between the stratosphere and the troposphere. In this region, dynamics, chemistry, clouds and radiation are strongly coupled, which makes this region important for chemistry-climate interactions. Significant progress has been made in understanding the climate-relevant processes in this region during the last decade, assisted by a suite of new observational studies.

Satellite-based estimates of reduced CO and CO2 emissions due to traffic restrictions during the Beijing 2008 Olympics

CO burden in the Beijing area.

The MOPITT multispectral CO product along with model simulations from WRF-Chem have recently been applied to analyze emissions of both CO and CO2 during the 2008 Beijing Summer Olympics. The results suggest that urban traffic controls instituted during the Olympics significantly reduced emissions of CO and CO2. A manuscript by H. Worden, et al., describing this pioneering work has recently been submitted to Geophysical Research Letters.

New ozonesonde climatology between 1995 and 2009

UTLS ozone in Western Europe

A new ozonesonde climatology for the period 1995-2009 was compiled for model evaluation and comparison to other observations [Tilmes et al., 2011]. This climatology allows evaluating the performance of ozone especially in the troposphere and lower stratosphere. Various models still show significant shortcomings to reproduce the structure and seasonality of ozone, one of the most important trace gases in the atmosphere.

Hunting for molecular species in newly formed biogenic nanoparticles

Dr. Paul Winkler with the TDCIMS instrument.

New particle formation, the spontaneous creation of new nanometer-sized particles in the atmosphere, is often the dominant source of particles in remote regions. A major part of newly formed aerosol consists of organic material that can be attributed to photo-chemically reacted volatile organic compounds emitted by vegetation. Understanding the mechanisms responsible for the growth of these biogenic nanoparticles into sizes where they may scatter radiation efficiently or change cloud properties is vitally important for assessing the impacts of new particle formation on climate.

MOPITT's 'Multispectral' View of Recent Russian Fires

Russian firefighter

During the summer of 2010, large areas of central Russia were devastated by extensive wildfires burning through forests and dry peat bogs. In addition to the threat from the actual fires, the smoke and pollutants generated by the fires created an air quality crisis for millions of Russians, including residents of Moscow. Figure 1 below shows imagery from the MODIS satellite instrument for Aug. 8; a vast smoke plume is clearly evident.

Cloud Tops and Tropopause

The tropopause

The tropopause is a fundamental boundary of the atmosphere, separating the turbulent mixing dominated troposphere from the much more stable and stratified stratosphere. To examine the role of the tropopause and the jet streams in constraining the cloud distributions, ACD scientists performed an analysis of cloud top and tropopause relationships using the Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) cloud data and National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) tropopause data.

Carbon Monoxide Variability over the United States

Surface concentrations of total CO.

Understanding the spatio-temporal distribution of air pollution is made easier if we are able to differentiate between the different processes driving pollutant variations. This involves understanding how the surface and tropospheric concentrations at a given time and location are governed by direct emissions of pollution, chemical processing and transport into the region from further afield.

Chemical Boundary Conditions for Regional Modeling

Plot of lateral boundary conditions in regional atmospheric transport models.

The importance of lateral boundary conditions (BC) in regional atmospheric transport models or numerical prediction models has been well established in the meteorological community. Much more recently, attention has also been drawn to the consideration of chemical lateral boundary conditions in regional chemical transport models (CTMs) and in air quality simulations, and the importance of the inflow of pollution on local air quality.

ENSO and WACCM

Altitude-time composite of anomalies in water vapor.

El Nino-Southern Oscillation (ENSO) is the largest source of interannual variability in the tropical troposphere. Some studies have documented the propagation of the ENSO signal to the stratosphere (Calvo Fernandez et al., 2004; Sassi et al., 2004; Garcia-Herrera et al. 2006) through the anomalous propagation and dissipation of ultralong Rossby waves at middle and high latitudes, which modify the stratospheric mean meridional circulation. A recent study using the Whole Atmosphere Community Climate Model (WACCM3.5), has also shown the intensification of the tropical upwelling in the lowermost part of the stratosphere, below 20km, during warm ENSO events and its weakening during the opposite phase (Calvo et al. 2010). This is mainly due to anomalous forcing by orographic gravity waves especially during the strongest warm ENSO episodes; as a result of anomalies in the location and intensity of the subtropical jets and in the meridional gradient of temperature observed during ENSO episodes.

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