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COmbining Multi-platform, Multi-tracer Atmospheric measurements with Atmospheric Modelling to better Estimate Sources and sinks of atmospheric constituents

Project summary

This project focuses on better understanding the causes of greenhouse gas variability in the atmosphere, using existing and ongoing measurements, and atmospheric models. Simultaneous, co-located measurements of various atmospheric constituents from different instruments will be used to improve knowledge of sources and sinks of greenhouse gases.

The global carbon cycle and the greenhouse gases CO2 and CH4 are important drivers of climate change. Understanding the fluxes of these gases to and from the atmosphere is crucial for understanding past, present and future climate variability. This project focuses on using simultaneous co-located measurements of greenhouse gas amounts together with modelling their atmospheric co-variability to better estimate these fluxes by individual processes and on better temporal and spatial scales. In particular, co-located solar remote-sensing and in situ measurements will be combined, and the ability of the remote-sensing instruments to measure numerous gases will be exploited to improve flux estimates and atmospheric modelling

Project aims

  1. to improve greenhouse gas flux estimates by combining long-term time series of in situ and column measurements in an inversion scheme
  2. to establish, using a model framework and the lengthening time series of surface and column data in the southern hemisphere, the interannual variability of tropical Australian biosphere fluxes and their relationship with climate variables, such as the Southern Oscillation Index and the timing of the onset of the Austral-Indo monsoon
  3. to develop and implement a novel and innovate method, based on the multiple-tracer approach, to use co-variations of these gases to further constrain greenhouse gas flux estimates
  4. to collect an additional independent dataset, and use this to analyse and assess the aforementioned results

Work packages

1. Combining in situ and column measurements of greenhouse gases to estimate GHG fluxes
To date, the Total Carbon Column Observing Network (TCCON - see more about TCCON here) data has been used predominantly to validate satellite retrievals of GHGs or to independently validate model simulations. One study (Chevallier et al, 2012) used TCCON data to estimate GHG fluxes, showing the potential, especially in Australasia, of these measurements to help constrain fluxes.

The majority of TCCON sites also have an instrument measuring surface in situ concentrations of at least CO2, if not more GHGs. The utility of co-located column and surface measurements has not been extensively explored. We will investigate the use of these co-located measurements in an inversion, and the effects on flux estimations.

The focus of this work package will be Australasia, using the TCCON sites and Darwin, Wollongong and Lauder. These sites are all equipped with FTIR in situ gas analysers, designed and developed by CAC at the University of Wollongong. These "Spectronus" analysers (for more info see here) measure 10-minutely concentrations of CO2, CH4, N2O and CO.

TCCON - The Total Carbon Column Observing Network


The Total Carbon Column Observing Network (TCCON) is a global network of high spectral resolution Fourier Transform InfraRed spectrometers, acquiring spectra in the near (or shortwave) infrared (NIR or SWIR). From these high quality spectra, precise and accurate column average dry-air mole fractions of CO2, CH4 and other gases can be retrieved. Consistent instrumentation and retrieval setup, and careful attention to instrument performance allow for very precise measurements to be made, with excellent inter-site consistency.

The absolute accuracy in comparison to other measurements is ensured via comparison to integrated, co-located measurements that are independently well-calibrated and characterised. This is typically via in situ monitors on aircraft overflights, but can also be achieved via balloon-borne soundings. Such a technique, such as via AirCore, is promising as a cost-effective means of ensuring the long-term stability of sites.

Establishment of AirCore measurements in Australia

As part of my DECRA fellowship, I am seeking a PhD student to work on organising, undertaking and analysing AirCore launches over Wollongong, Darwin, and a new site to be established at Alice Springs. The analysis would include comparison to ground-based spectra and to model simulations. The student would have the opportunity to collaborate with the developers of the AirCore system at NOAA, Boulder, Colorado.

In situ FTIR trace gas analyser - Spectronus

Section Under Construction

Available research projects

Column Greenhouse Gas Measurements in Australia and validation using AirCore

Currently there are two TCCON sites in Australia operated by the University of Wollongong. This student will be responsible for establishing a third site in Alice Springs, starting with a pilot study deploying a low resolution EM27-SUN. The student will also have the opportunity to make AirCore launches at Wollongong, Darwin, Alice Springs and potentially at other Australian sites to validate the ground-based total column measurements. This project will involve collaboration with Caltech, NASA, NOAA and CSIRO, and is funded by the Australian Research Council.

Establishing a regional scale modelling framework to use column greenhouse gas measurements to infer Australian and global CO2 fluxes

With nearly 10 years of TCCON data acquired at Darwin, and 7 years from Wollongong, there is now a significant time series of measurements of column-averaged CO2 and other gases in Australia. This project will seek to establish a model framework using GEOS-Chem and either a higher resolution, nested grid within GEOS-Chem, or WRF-Chem nested within GEOS-Chem, to use these measurements, as well as the surface measurements, to infer Australian and global CO2 fluxes. The student will also seek to use the fact that many different gases are measured by TCCON and the in situ networks to obtain additional information about the CO2 fluxes. The project is funded by the Australian Research Council.

Using OCS to partition biosphere CO2 fluxes between photosynthesis and respiration.

Determining CO2 fluxes using atmospheric concentration data can generally only yield net fluxes, and not differentiate between the different source/sink processes that are co-located. This project will seek to partition between biospheric photosynthesis and respiration by using atmospheric in situ and column amounts of carbonyl sulfide (OCS), which is taken up along with CO2 during photosynthesis, but not respired. This will be done via an expanding network of simultaneous OCS and CO2 column measurements, in conjunction with a chemical transport model. Derived photosynthetic fluxes will be compared to those derived from satellite-based measurements of plant fluorescence, and simulated fluxes from DGVMs. In particular, the student will seek to understand the dependence of photosynthesis and respiration on temperature and precipitation to improve predictions in carbon-climate modelling. Note: the student will also have the opportunity to work on improving the ground-based total column average retrievals of OCS, ethane and HCN from an expanded measurement range at TCCON sites, and ensuring inter-site consistency.

Improved HDO retrievals from ground-based NIR spectra and comparisons to satellite products

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© Nicholas Michael Deutscher, 2014