Dr. Stella M L Melo
CURRENT PROJECTS
v Solar variability and climate
v Measurement of minor constituents at the stratosphere
v Planetary Atmospheres
v Laboratory Spectroscopy
RESEARCH INTERESTS
Climate and its changes
The impacts
of climate variability and the threat of future changes are issues brought to
our attention on an almost daily basis. As natural disasters like heavy rain,
tornados, heavy snowfall, hurricanes, etc, are likely to increase in occurrence
bringing severe economic and social consequences, governments are urged to
devise mitigation policies. Climate is a global issue and demands international
effort and from the international debate brought about by the
It is recognized that climate is affected by the presence of humans. The problem is to understand and be able to model exactly how. One of the most critical aspects of the climate system, and also one of the least understood, is that it varies naturally on a large range of time scales. As a consequence, perturbations to climate caused by anthropogenic processes may be masked within the climate system, making their detection difficult. We first need to identify the natural climate variability and describe its forcing mechanisms, and then properly isolate the anthropogenic effects and forecast future scenarios at the appropriate level of reliability.
Among the sources of natural variability in the Earth's climate, and maybe one of the most puzzling so far, is the change in the solar energy output. We know that the solar radiation changes on a variety of time scales. What we do not know is how those changes could affect the Earth's climate and at what level of importance. Indeed, the present knowledge of this subject is rather thin. While a considerable part of the scientific community recognizes that changes in the Sun have indeed the potential to force changes in climate, still there is no consensus on its degree of importance.
One intrinsic difficulty in the evaluation of solar variability forcing in climate models in the present state of our knowledge is that it is based on proxies or empirical models that describe the solar variability only partially. Model experiments being performed for the IPCC (Intergovernmental Panel on Climate Change) studies need TSI (Total Solar Irradiance) reconstructions back to 1850. However, irradiance has been measured only from late 1978. Unfortunately, these constructions of irradiance time series and spectral irradiance variability used in climate models are now considered obsolete. Adding to the difficulties is the fact that recent results for solar cycle 23 show the first clear breakdown in the relation between solar activity and solar variability: the irradiance representing variability is higher at the maximum of cycle 23 than activity indices such as sunspot number, 10.7 cm radio flux, Be10 cosmogenic isotope, etc. While these activity indices appeared to be reasonable proxies for long-term irradiance variability before cycle 23, the latest research indicates that we now cannot really say for which cycles (prior to cycle 21) these indicators are reliable for climate studies. Another important point is that the solar variability is different at different spectral regions and forces climate differently. Therefore, spectral information is desired for model simulations but the available datasets here are reduced and difficult to combine in a consistent way.
This research project is composed of two parts: the implementation of solar and particle forcing on the Canadian Middle Atmospheric Model and the IGCM-FASTOC model, and the development of the coupling of a solar and a climate models including the development of an interface to transform solar activity in solar irradiance (or radiance, depending on the needs). Climate and atmospheric model data will be compared to existing observational data. We work in close collaboration with the science team of the PICARD satellite mission lead by the French space agency. PICARD is a satellite mission to measure simultaneously the absolute total and spectral solar irradiance, the diameter and solar shape, and to probe the Sun's interior by helioseismology. These measurements obtained all along the mission will allow study the variation of the measured parameters as a function of the solar activity.
With a team that combines expertise in Earth atmospheric environment and in solar physics, we address both sides of the problem: to understand the processes governing the variability in the solar irradiance and the processes governing the associated responses of the Earth atmosphere to such changes.
Laboratory spectroscopy
This project has two main objectives:
1 - To measure, in the laboratory, ultraviolet (UV), visible, and infrared (IR) absorption parameters of gases of atmospheric importance at high resolution and a range of temperatures and pressures, for use in atmospheric sciences.
2 - To
establish an association between the Canadian Space Agency (CSA) and the
Spectroscopy is one of the most used tools for remote sensing/sounding of planetary atmospheres. Either absorption or emission spectroscopic measurements are largely used to determine atmospheric temperature, composition and dynamics. Most satellite missions supported by the CSA for atmospheric studies include spectroscopic instruments: WINDII on UARS, SWIFT on Chinook (interferometers), OSIRIS on Odin, ACE-FTS and MAESTRO on SCISAT-1 (spectrometers) and MOPITT on TERRA (radiometer). Laboratory characterization of spectroscopic parameters is fundamentally necessary for extracting the desired quantity, normally temperature, composition or winds, from the measurements needed. The accuracy of the atmospheric parameters measured using spectroscopic techniques and calculations of the atmospheric properties depends on the accuracy of the line positions, intensities, assignments, broadening coefficients, pressure-induced shifts, line-mixing parameters, and the possible temperature dependences of most of these parameters. The need for laboratory measurements remains a critical problem. For example, trace gas retrievals from the ACE-FTS (Atmospheric Chemistry Experiment - Fourier Transform Spectrometer) instrument on board the CSA SCISAT-1 mission have revealed significant deficiencies in some of the laboratory data that are currently available, for example, in the infrared cross sections of CFC-113 and HCFC-142b, for which “a major limitation for our retrievals is the lack of cross section measurements”.
Planetary atmospheres
Airglow is a powerful tool to remote sensing atmospheric parameters as temperature and composition. It has been shown useful also to determine dynamic characteristics of the atmosphere such as propagation of gravity waves and tides. However, much still remain to be understood in terms of airglow chemistry in itself. Comparative atmospheres taken both at the model and measurement levels are very powerful technique to address not only this aspect but also for climate studies and detection of natural variabilities in a climate system.
The focus of this research project is the Martian atmosphere. However, the tools (models/simulations) are developed in a way they could be adapted to other planets that have atmosphere, such as Venus or Jupiter for example. The objective is to investigate the feasibility of using airglow measurements to determine the temperature of the Martian atmosphere at critical altitudes for satellite aerobreaking (50 to 80 km altitude). SPICAM instrument demonstrated in early 2005 that nightglow emissions are present and measurable in the Martian atmosphere. However, the use of airglow to sound the Martian atmosphere temperature has not been explored yet.
Recent Publications
- S. M. L. Melo, R. Blatherwick, J. Davies, P. Fogal, J. de Grandpre, J. McConnell, C. T. McElroy, C. McLandress, F. J. Murcray, J. R. Olson, K. Semeniuk, T. G. Shepherd, K. Strong, D. Tarasick, and B. J. Williams-Rioux, Summertime stratospheric processes at northern mid-latitudes: comparisons between MANTRA balloon measurements and the Canadian Middle Atmosphere Model, Atmos. Chem. Phys., 8, 2057-2071, 2008 - special issue on MANTRA. (http://www.atmos-chem-phys.net/8/2057/2008/acp-8-2057-2008.html)
- A. Fraser, F. Goutail, C. A. McLinden, S. M. L. Melo, and K. Strong, Lightning-produced NO2 observed by two ground-based UV-visible spectrometers at Vanscoy, Saskatchewan in August 2004, Atmos. Chem. Phys., 7, Number 6, 1683-1692, 2007. (www.atmos-chem-phys.net/7/1683/2007/)
- K. Le Bris, K. Strong, S. M. L. Melo, and Jason C. Ng, Structure and conformational analysis of CFC-113 by density functional theory calculations and FTIR spectroscopy, Journal of Molecular Spectroscopy, 243, 178-183, 2007. (doi:10.1016/j.jms.2007.02.003)
- Melo, S. M. L., O. Chiu, A. Garcia Munoz, K. Strong, J. C. McConnell, T. G. Slanger, M. J. Taylor, R. P. Lowe, I. C. McDade, and D. Huestis, Using airglow measurements to observe gravity waves in the Martian atmosphere, Adv. Space Res. 8, 730-732, 2006. (doi:10.1016/j.asr.2005.08.041)
- Garcia-Munoz, A., J. C. McConnell, I. C. McDade, S. M. L. Melo, Airglow on Mars: Some model spectations for the OH Mainel band and the O2 IR atmospheric band, Icarus, Volume 176, Issue 1, Pages 75-95 2005. (http://www.sciencedirect.com/science/journal/00191035)
- K. Strong, G. Bailak, D. Barton, M. R. Bassford, R. D. Blatherwick, S. Brown, D. Chartrand, J. Davies, James R. Drummond, P. F. Fogal, E. Forsberg, R. Hall, A. Jofre, J. Kaminski, J. Kosters, C. Laurin, J. C. McConnell, C. T. McElroy, C. A. McLinden, S. M. L. Melo, K. Menzies, C. Midwinter, F. J. Murcray, C. Nowlan, R. J. Olson, B. M. Quine, Y. Rochon, V. Savastiouk, B. Solheim, D. Sommerfeldt, A. Ullberg, S. Werchohlad, H. Wu and D. Wunch, A Balloon Mission to Study the Odd-Nitrogen Budget of the Stratosphere, Atmosphere-Ocean, 43(4), 283-299, 2005. (http://www.cmos.ca/Ao/Abstracts/chrono.html)
- Melo, S. M. L., K. Strong; M. R. Bassford, K. E. Preston, C. T. McElroy, E. V. Rozanov, and T. Egorova, Retrieval of stratospheric NO2 vertical profiles from ground-based measurements: results for the MANTRA 1998 field campaign, Atmosphere-Ocean, 43(4), 339-350, 2005. (http://www.cmos.ca/Ao/Abstracts/chrono.html)
- R.L. Waterland, M.D. Hurley, J.A. Misner, T.J. Wallingtonb
, S. M. L. Melo, K. Strong, R. Dumoulin, L. Castera, N.L. Stockd