|From||"Roger Brugge" <email@example.com>|
|Date||Tue, 27 Nov 2012 09:19:12 +0000|
Forwarded from CLIMLIST... L-IPSL post-doctoral fellow offer in volcanism and climate : volcanism during the last millenium The excellence laboratory L-IPSL of the Institut Pierre-Simon Laplace offers a post-doctoral position of 2 years to address impacts of volcanism on climate in the last millenium. Context: It is now generally recognised that volcanic eruptions have an important effect on climate variability from inter-annual to decadal timescales. Using comprehensive Earth system models, much progress in understanding volcanic climate effects have been achieved in recent years, including the impacts on atmospheric chemistry and dynamics, on ocean dynamics, marine and terrestrial biochemistry and on the hydrological cycle. These results are however hampered by many assumptions on the reconstructed past volcanic activity, but also on the choice on sulphate aerosol size distribution and their implementation in the radiation scheme of models themselves. Several outstanding questions remain and concern the behaviour of huge SO_2 cloud injected into the stratosphere after super eruptions such as those that did occur during the last centuries. Description of work: All in all, these results call for more process-oriented sensitivity experiments. The challenging task for the hired post-doctoral fellow would be to improve the actual volcanic forcing reconstructions and its implementation in the IPSL models. As a first step, the focus will be on the calculation of the temporal evolution of volcanic aerosol size distribution, global fields, and optical characteristics, for the two biggest volcanic eruptions of the last millennium, i.e. the 1258 AD and the Tambora (1815). Such calculations will be done with a global 2-D stratospheric climate model including detailed microphysical and chemical processes for stratospheric volcanic aerosols. This model has been developed at the LATMOS laboratory (IPSL). New estimates of SO_2 release are now available for these two eruptions and will be used to constrain the SO_2 loading in the 2-D model. This will allow the calculation of (1) consistent evolution of the global distribution and size of stratospheric sulphate aerosols after each eruption and (2) deduce the related optical properties (AOD, single scattering albedo and parameters of asymmetry) for both v/isible/ and /infrared /spectral bands. In a second step and in collaboration with LMD laboratory (IPSL), the deduced new size distribution and optical parameters will be implemented into the LMDz radiation scheme for both spectral bands (visible and infrared). Sensitivity experiments with chemistry-climate models (CCM), LMDz-REPROBUS and/or LMDz-INCA, coupled to NEMO, including the new stratospheric aerosol radiation schemes will then be used to run sensitivity experiments and evaluate the impact of competing non-linear radiative and chemical processes on the simulated climates for volcanic eruptions. We will start by a test case, simulating the Mont Pinatubo eruption in the CCM model. The results will be validated against the large datasets of observations (satellite, balloon, reanalysis,…) and serve as a reference control run. Then we will tackle the two biggest volcanic eruptions for the last millennium (i.e. 1815, 1258 AD). In the last step, cross validations of the sensitivity experiments for the mega eruptions with proxy data will be essential to better evaluate the realism of the new volcanic forcing parameterisation for the largest eruptions. More proxy reconstructions are now available at IPSL (LSCE, LOCEAN, etc.) and in other national and international laboratories. They will help constrain the climate sensitivity. In interaction with the LOCEAN laboratory (IPSL), further tests will be required on the influence of the initial state (including the ocean) on the simulated climatic response following these volcanic eruptions before extending our approach to the whole millennium. Supervision team : The work will be conducted under the main supervision of M. Khodri (LOCEAN), in close connection with other researchers : M. Marchand (LATMOS), S. Bekki (LATMOS), O. Boucher (LMD), J. Mignot (LOCEAN), D. Swingedouw (LSCE). The work will be mainly conducted at LOCEAN, but in other IPSL sites also. Duration and salary:The post-doctorate will be recruited for 24 months with a net monthly salary around 2000 euros, commensurate with experience. This includes social services and health insurance. Contact for applications:Applications should include a vita, a statement of research interests and the names of at least two references including e-mail addresses and telephone numbers. Applications should be submitted by e-mail to Myriam Khodri (<Myriam.Khodri@ird.fr>).
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