Periodic Reporting for period 2 - AWACA (Atmospheric WAter Cycle over Antarctica: Past, Present and Future)
Période du rapport: 2023-03-01 au 2024-08-31
Climate models predict that precipitation will increase in Antarctica, which will moderate global sea-level rise. Meanwhile, the isotopic composition of snowfall records climate parameters which can be recovered in ice cores. However, there are still major gaps in our understanding of the atmospheric water cycle over Antarctica. For the first time, the AWACA project will provide a consistent and comprehensive combined observation and modeling framework to understand and predict the fate of atmospheric water all along the tropospheric column. Specifically adapted/designed instruments will be combined to form observation platforms deployed at 5 sites along a 1100 km coast-to-plateau transect aligned with the typical moisture-carrying air mass trajectories. The challenges of working in full autonomy in Antarctica, never addressed to such an extent before, will be tackled by collaborating with experts in polar technology and logistics. The resulting data set will make possible the study of the processes driving the water fluxes and composition to an unprecedented level, and the gained insights will be a strong basis to develop new physics parameterizations for regional and climate models. Once validated along the transect but also in other regions of Antarctica thanks to satellite observations and past campaigns, those models will enable us to decipher the past and future variability of the atmospheric water cycle over Antarctica.
To reach the objectives listed above, the project must proceed along several lines in parallel. There has been work done on the design and construction of the automatic autonomous Observation Platform Units (OPU) which will be deployed along the 1100 km AWACA observation transect in Antarctica. Four shelters have been constructed to host the various in situ and remote sensing instruments necessary for the project. This was achieved in time to be shipped to Antarctica by the end of 2023 summer, so that it can reach Dumont d’Urville (DDU) station during the next austral (2023-24) summer, then be passed to the ice sheet proper on winter sea-ice when it forms and becomes strong enough. This will then be ready on site for the deployment during the 2024-25 austral summer.
At the same time, work has proceeded on radars, lidars and other instruments to be hosted by the OPUs which are designed and assembled by project teams in some cases or ordered to commercial providers generally with improved specifications to better handle the Antarctic conditions compared to the standard models. Most instruments still need work for full validation but they are not needed in the field before the main deployment season in 2024-25. A pilot meteorological station including turbulence measurements was already deployed at the coastal planned AWACA observation site (D17) during the 2022-23 Antarctic summer season. This includes a turbulence measurement sensor which had been previously evaluated at a blowing snow test site in the French Alps during the 2022-23 boreal winter. During the same Antarctic season, the first laser instrument specifically developed for the AWACA project by AP2E company to meet very low humidity requirements has been installed at Dumont d’Urville station for a one-year-long test in the field, along with a Picarro instrument for intercomparison. First tests of the snowflake capture device were performed in the Alps (February 2022) and in Antarctica (January 2023). Another early-delivered instrument has been shipped to be deployed already in the next (2023-24) season at DDU: a wind profiling radar which will report 3D wind speed and direction within the lowest 5 km above the surface. Before shipment, work was done to test the instrument at SIRTA test site near Paris during summer 2023.
On the model development side, we have worked along two main directions : equip the DYNAMICO dynamical core with limited-area configurations and water isotopes, and interface MAR and DYNAMICO. The limited-area capability of DYNAMICO has been ready since autumn 2022 and a few realistic limited-area configurations with LMDZ physics have been validated since. At the same time, the DYNAMICO transport scheme has been extended for an accurate treatment of isotopic ratios. Interfacing with LMDZ-iso physics remains to be done. Progress on interfacing DYNAMICO with MAR has been slow due to the internal structure of MAR which entangles dynamics and physics. Together with the wider MAR development team we have defined an incremental roadmap to disentangle dynamics from physics. To safely implement this roadmap we have developed a robust continuous integration infrastructure that will help avoid technical and scientific regressions along the way.
Data from 3 weeks of turbulence observation with the sensor deployed in the 2022-23 austral summer as described above, have been compared with LMDZ model and the agreement is quite good: the turbulence parametrizations in the model are reasonably successful in the conditions of this particular period. The agreement remains to be confirmed in other cases of wind and other surface meteorology conditions as more data become available with time.
At the same time, work has proceeded on radars, lidars and other instruments to be hosted by the OPUs which are designed and assembled by project teams in some cases or ordered to commercial providers generally with improved specifications to better handle the Antarctic conditions compared to the standard models. Most instruments still need work for full validation but they are not needed in the field before the main deployment season in 2024-25. A pilot meteorological station including turbulence measurements was already deployed at the coastal planned AWACA observation site (D17) during the 2022-23 Antarctic summer season. This includes a turbulence measurement sensor which had been previously evaluated at a blowing snow test site in the French Alps during the 2022-23 boreal winter. During the same Antarctic season, the first laser instrument specifically developed for the AWACA project by AP2E company to meet very low humidity requirements has been installed at Dumont d’Urville station for a one-year-long test in the field, along with a Picarro instrument for intercomparison. First tests of the snowflake capture device were performed in the Alps (February 2022) and in Antarctica (January 2023). Another early-delivered instrument has been shipped to be deployed already in the next (2023-24) season at DDU: a wind profiling radar which will report 3D wind speed and direction within the lowest 5 km above the surface. Before shipment, work was done to test the instrument at SIRTA test site near Paris during summer 2023.
On the model development side, we have worked along two main directions : equip the DYNAMICO dynamical core with limited-area configurations and water isotopes, and interface MAR and DYNAMICO. The limited-area capability of DYNAMICO has been ready since autumn 2022 and a few realistic limited-area configurations with LMDZ physics have been validated since. At the same time, the DYNAMICO transport scheme has been extended for an accurate treatment of isotopic ratios. Interfacing with LMDZ-iso physics remains to be done. Progress on interfacing DYNAMICO with MAR has been slow due to the internal structure of MAR which entangles dynamics and physics. Together with the wider MAR development team we have defined an incremental roadmap to disentangle dynamics from physics. To safely implement this roadmap we have developed a robust continuous integration infrastructure that will help avoid technical and scientific regressions along the way.
Data from 3 weeks of turbulence observation with the sensor deployed in the 2022-23 austral summer as described above, have been compared with LMDZ model and the agreement is quite good: the turbulence parametrizations in the model are reasonably successful in the conditions of this particular period. The agreement remains to be confirmed in other cases of wind and other surface meteorology conditions as more data become available with time.
Technology: the OPUs (with both the instrumental and energy sides) developed in the framework of AWACA will demonstrate the possibility to deploy complex instruments in very remote regions of Antarctica in a completely autonomous way. This will open new opportunities for all geoscience fields.
Observation: the unique combination of surface meteorology, isotopic composition and remote sensing of clouds and precipitation from coast to high plateau in Antarctica, over several years, will bring new insights into the relevant processes and mechanisms controlling the atmospheric branch of the water cycle.
Observations and modelling combined: insights coming from new observations will be implemented into the model suite, that will in turn be used to revisit past climate reconstruction from shallow ice cores as well as provide prediction of future precipitation over Antarctica with a reduced uncertainty.
Observation: the unique combination of surface meteorology, isotopic composition and remote sensing of clouds and precipitation from coast to high plateau in Antarctica, over several years, will bring new insights into the relevant processes and mechanisms controlling the atmospheric branch of the water cycle.
Observations and modelling combined: insights coming from new observations will be implemented into the model suite, that will in turn be used to revisit past climate reconstruction from shallow ice cores as well as provide prediction of future precipitation over Antarctica with a reduced uncertainty.