Atmospheric Science in the Deep South National Science Challenge Adrian McDonald University of Canterbury, Christchurch, New Zealand
The Deep South The Deep South National Science Challenge is one of ten key areas for research that the New Zealand Government identified last year. These challenges are planned to be the foci for New Zealand research over the next 10 years. Objective: To understand the role of the Antarctic and southern ocean in determining our climate and our future environment.
The Deep South : Aims Increase the knowledge and reduce uncertainty of how the Antarctic influences the oceanic climate interfaces in the southern ocean, atmosphere, and biosphere. This will support the building of models that predict potential changes to our climate and ocean system and the risks and impacts on our resources Understand the critical role of the Antarctic and the southern ocean on our social, cultural, and economic wellbeing, and active kaitiakitanga. This will enable New Zealanders to effectively respond and adapt to change (refer Glossary for definition of change ) that impacts New Zealand, and sustainably manage New Zealand s natural resources accordingly Allow New Zealand to take advantage of its unique geographic location to develop a global hub for Antarctic and southern ocean research, to build international scientific collaborations that contribute to addressing climate change issues for research in Antarctic and the southern ocean, and to leverage benefits from this for New Zealand. Make a New Zealand contribution to national and international decisionmaking on global change.
Atmospheric Science in the Deep South Polar influences on the westerlies: The Southern Hemisphere westerly winds play a critical role in the climate of New Zealand and in Southern Ocean circulation. The strength and latitudinal position of these winds largely determine temperature and precipitation patterns in many parts of the country. The westerlies are primarily driven by the north south temperature gradient between the tropics and Antarctica. This dependence ensures that the westerlies both contribute to, and respond to circulation in the Southern Ocean, changes in the ozone hole and variations in cloud and precipitation patterns. Four main areas of activity: Climate modelling Manned research base on Auckland Island Research Cruise focussed on aerosol and air sea interactions (Mike Harvey just discussed in Session 3 so will skip this one) Atmospheric Remote Sensing above the Southern Ocean
Climate Modelling (Olaf Morgenstern, Sam Dean, Greg Bodeker, Peyman Zawar-Reza) A hierarchy of models with differing complexity, geographical coverage, and computational cost will be utilised. This will allow for different modelling approaches to be used to investigate different aspects of the climate system and potentially reduces uncertainty. NIWA UKCA: The most comprehensive, and most computationally demanding, model is a state of the art atmosphere ocean chemistry climate model, NIWA UKCA. This model simulates changes in the atmosphere ocean climate system, including the ozone layer, under increasing greenhouse gas concentrations and decreasing ozone depleting substance concentrations. Potential studies include an examination of the representation of interactions between aerosols and clouds in NIWA UKCA. HadGEM3: Due to its complexity, NIWA UKCA, is limited to relatively small ensemble sizes. NIWA also operates HadGEM3 A and this model will be used to run larger ensemble experiments. For the NSC we will construct a large ensemble of HadGEM3 A simulations that are based on the sea surface temperatures and ozone forcing predicted by NIWA UKCA. ISCM: ISCM is an interactive simple climate model that extends the MAGICC model used in the IPCC 5 th assessment report. This model expands on the MAGICC model by including the two way interaction between Antarctic stratospheric ozone and the southern high latitude climate system. We will use energy balance models in combination with ISCM to examine the interaction between cloud feedbacks and the sea ice albedo effect to examine how clouds may moderate polar amplification. WRF: The Weather Research and Forecasting (WRF) model is used at NIWA and University of Canterbury to undertake high resolution process studies and by the Meteorological Service of New Zealand Ltd. (MetService) to dynamically downscale forecasts from global modelling centres.
Initial Plans: Auckland Island Sub-Antarctic Base Macquarie Island Auckland Island Auckland Island is South of New Zealand and almost on a direct line from Christchurch to Macquarie Island. The Auckland Islands are an archipelago of the New Zealand sub-antarctic islands with a combined area of roughly 625 square kilometres (240 sq mi). They lie 465 kilometres (290 mi) from the South Island port of Bluff. Latitudes 50 30' and 50 55' S and longitudes 165 50' and 166 20' E.
Auckland Island Base Planned instrumentation on Auckland Island: Ceilometer (Adrian McDonald, UC) X-band vertically pointing weather radar (Geoff Austin, Auckland University) Radiosonde sounding system (Greg Bodeker, Bodeker Scientific and NZ MetService) UAV and Flux tower (Peyman Zawar-Reza, UC) Distributed wireless sensor network - SNOW WEB (Adrian McDonald, UC)
SNOW WEB: Future deployment to Auckland Island? SNOW WEB is a smart distributed wireless sensor network designed at UC. It has been designed for easy deployment and provides the ability to vastly increase the density of atmospheric (wind velocity, temperature, pressure and humidity) measurements in a region on a campaign basis. The Figure above shows a previous deployment around Ross Island in Antarctica and corresponding WRF output.
Atmospheric Remote Sensing above the Southern Ocean Remote sensing is seen as critical in providing large scale constraints for modelling. Three sets of systems will be used extensively: CloudSat/CALIPSO WindSat MISR Discuss only the latter two here.
WindSat Introduction (Adrian McDonald, UC) WindSat is a polarimetric microwave radiometer satellite. It operates at the following frequencies : 10.7, 18.7 and 37.0 GHz with polarizations vertical, horizontal, +45, 45, left hand and right hand circular 6.8 and 23.8 GHz with polarizations vertical and horizontal WindSat uses these measurements to derive the following quantities: sea surface wind speed and direction sea surface temperature Total column water vapour cloud liquid water rain rate
SAM regression analysis Initial study has focussed on using data from the WindSat instrument to develop an integrated viewpoint of variations linked to the Southern Annular Mode (SAM). This also provides analysis which can be compared with previous work to test WindSat output. Later analysis will aim to combine WindSat with other instruments to gain synergies (CloudSat/CALIPSO and MISR). To examine the impact of SAM on the WindSat variables we form anomalies by detrending and deseasonalising the daily WindSat data and then regressing these anomalies onto a daily SAM index. The patterns shown next indicate the change from the mean that would result from a one standard deviation positive SAM anomaly.
WindSat analysis : SAM regression (one sigma anomaly) Zonal wind (m/s) Meridional wind (m/s) SST(K) TCWV (%) Cloud Liquid water (%) Rain rate (%)
WindSat and ERA-interim analysis Initial comparison of the SAM positive anomaly in meridional wind from WindSat and ERA-interim shows clear relationships. Given this initial analysis uses different data periods the relationship is rather good. WindSat ERA-interim
WindSat and NVAP-M analysis Initial comparison of the Total column water vapour SAM positive anomaly from WindSat and NVAP-M shows clear relationships. Given this initial analysis uses different data periods the relationship is rather good. WindSat NVAP-M
WindSat cyclone detection (Adrian McDonald and Alex Schuddeboom, UC) A positive SAM phase is characterised by anomalously high pressure in the midlatitudes and anomalously low pressures in the latitudes closer to the South Pole. Initial analysis of the relative vorticity field, derived from WindSat wind speed and direction data, can be used to identify the position of cyclonic centres for different SAM phases.
MISR analysis (Roger Davies, Auckland University) Planned to examine the MISR wind product derived from cloud-tracked winds. Possible synergies with WindSat analysis, that gives surface winds, with MISR which gives height-resolved winds. Already known that the reanalysis data that does not ingest MISR winds has biases mainly over the Southern Ocean.
Conclusions The Deep South NSC aim is to understand the role of the Antarctic and southern ocean in determining New Zealand climate and New Zealand future environment. Four main areas of activity: Climate modelling Manned research base on Auckland Island Research cruise focussed on aerosol and air-sea interactions Atmospheric Remote Sensing above the Southern Ocean Initial remote sensing study described has focussed on using data from the WindSat instrument to develop an integrated viewpoint of variations linked to the Southern Annular Mode (SAM) and cyclone distributions. Potentially useful for identifying synoptic context for cloud regimes.
Acknowledgements Thanks to the New Zealand Antarctic Research Institute for partial funding for my attendance at this meeting.