And Additional Contributions Abstracts




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AC-2A-07: CLIVAR Global Ocean Observation and Synthesis Activities
Caltabiano, Antonio
National Oceanography Centre, Southampton, UNITED KINGDOM
 

The overall mission of CLIVAR, the Climate Variability and Predictability Project of the World Climate Research Programme (WCRP) is to observe, simulate and predict the Earths climate system, with a focus on ocean-atmosphere interactions. CLIVAR has established its Global Synthesis and Observations Panel (GSOP) to develop, promote and seek to implement strategies for global ocean synthesis efforts, building on previous experiences and developments, eventually leading to a fully coupled reanalysis with atmosphere, ocean. land and cryosphere models. The panel is also responsible for the definition and (in collaboration with relevant bodies) fulfillment of CLIVAR's global needs for sustained observations. To do this it works closely with CLIVARs regional ocean basin panels on the one hand and international bodies such as Global Ocean Observing System, the Ocean Observations Panel for Climate and the Joint WMO-IOC Technical Commission on Oceanography and Marine Meteorology on the other.


One of the main contributions of GSOP to CLIVAR science is its evaluation of the current generation of ocean synthesis/reanalysis products providing guidance on their use for study of the global ocean circulation. This evaluation has led to several improvements in the products. Notably it has led to several papers comparing different ocean synthesis products and thus to first specifications of uncertainties in ocean syntheses. An Ocean Synthesis Directory provides community links to global ocean synthesis data.


GSOP is engaging through its ocean synthesis project in decadal forecast experiments. One key element is for ocean synthesis groups to provide updated datasets to be used for the decadal prediction experiments. GSOP is also currently in the process of providing all available ocean syntheses as initial conditions for decadal prediction experiments. First such experiments are ongoing and show some success. Possibilities of coupled data assimilation are also being explored. These efforts are currently only just spinning up and will grow over the coming years.


The panel co-sponsors (with the International ocean carbon Coordination project and the International Geosphere-Biosphere Programmes Surface-Ocean / Lower Atmosphere Study- Integrated Marine Biogeochemistry and Ecosystem Research Carbon Coordination Group) the Global Ocean Ship-based Hydrographic Investigations Panel (GO_SHIP). GO_SHIP brings together interests from physical hydrography, carbon, biogeochemistry, Argo, OceanSITES, and other users and collectors of hydrographic data to develop a strategy for ship-based repeat hydrographic observations post CLIVAR. This activity includes the review and an update of the WOCE hydrographic manual. More widely, GSOP is also seeking to organize the production of an update to the 2002 WOCE Global Data Set v3 to include observations made between the WOCE era and the end of 2010.


This poster will provide illustrations of the work of GSOP including the outputs from ocean synthesis intercomparisons, CLIVAR links to ocean carbon activities and GSOPs role, with others, in promoting the sustained global ocean observation network.


AC-2A-08: Deep ocean observing system over middle and long time scale: the E2M3A site in the Southern Adriatic
Cardin, V.R.; Bensi, M.; Gaèiæ , M.
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, ITALY
 

The open-ocean convection has been considered the engine of the global conveyor belt. It is a mechanism forming new dense and oxygenated waters, and it riggers the solubility and the biological pump. Among the few zones in the world interested by the open-ocean convection, the South Adriatic is a small but key area for the intermediate and deep thermohaline cell of the Eastern Mediterranean. There, the Adriatic Dense Water ADW formed prevailing by the open-ocean vertical convection , becomes the main component of the Eastern Mediterranean Deep Water (EMDW). This process takes place in the South Adriatic Pit (SAP) in the centre of the cyclonic gyre. The extension of the vertical mixing, varies on the interannual and decadal time-scales in function of the air-sea heat fluxes and the pre-conditioning vertical density structure.


The high spatio-temporal variability of the deep convection and its interaction with other processes makes difficult it study. Oceanographic cruises provide a good spatial coverage but lack in temporal resolution. The need of high temporal sampling to resolve events and rapid processes and the long sustained measurement of multiple interrelated variables from sea surface to seafloor can be solve by the use of moorings located in specific areas as the Southern Adriatic Pit.


In the framework of the Italian VECTOR project a deep-sea mooring (41°29.7N, 17°42.1E) containing CT sensors at five depths, an upward looking 150 kHz ADCP and an Aanderaa current meter RCM11 was located in the vertical convection area. Moreover, two sediment traps were positioned at 168 m and 1174 m on the mooring line. This mooring configuration permits to individuate water mass formation, measuring simultaneously physical and chemical parameters. The mooring is still in the water and new upgrades will be done in the framework of the European project EuroSITES during 2009. The deployment of pCO2 sensor together with a pH sensor within the mixed layer will allow to estimate the Carbon system at the site. The deployment of a surface buoy will allow the real data transfer from the platform to the land station.


Here, data recorded in the period between end-November 2006 and October 2008 covering two consecutive year with pre-conditioning and deep convection periods will be presented . Surface chlorophyll a obtained from the SeaWiFS data is a good indicator of the vertical mixing patch as demonstrated earlier, and here it has been used in determining the patch position with respect to the mooring location and its geometry.

 

AC-2A-09: WCRP CLIVAR and ocean observations
Cattle, Howard
National Oceanography Centre, Southampton, UNITED KINGDOM
 

The overall mission of CLIVAR, the Climate Variability and Predictability Project of the World Climate Research Programme (WCRP) is to observe, simulate and predict the Earths climate system, with a focus on ocean-atmosphere interactions. CLIVAR is a long-term, 15 year, programme which began its implementation phase in 1998. Its role is to provide international coordination in areas of science that progress our understanding of climate variability and change and climate prediction. Implementation of CLIVAR is carried out through the activities of its regional panels (one for each of the ocean basins, and one each for the American and Asian-Australian monsoon and African climate systems) and through its global modelling, observational and synthesis groups. Modelling activities within CLIVAR are focussed on coupled numerical model experiments on seasonal, decadal and centennial timescales, including prediction of the response to both natural and anthropogenic forcing. Special attention is given to assessing and improving predictions and facilitating their applications to society. A key question is how anthropogenic climate change will both be influenced by and modulate climate variability and what are the implications for prediction out to decades and longer.


CLIVAR has overall responsibility for the role of the oceans in climate within WCRP. Sustained ocean observations (as well as ocean process studies) provide key inputs to CLIVAR activities and CLIVAR seeks to stimulate the continued development of the Ocean Observing System in collaboration with the Global Ocean Observing System, the Ocean Observations Panel for Climate and the Scientific Committee on Antarctic Research. It does this through the activities of its Atlantic, Pacific, Indian and Southern Ocean Basin Panels and its Global Synthesis and Observation Panel (GSOP). CLIVAR was an early co-sponsor (with the Global Ocean Data Assimilation Experiment) of Argo and is, for example, co-sponsor of OceanSITES, the PIRATA array and the developing Indian Ocean sustained ocean observing network.


Ocean modelling is an integral part of the work of CLIVARs coupled modelling and seasonal prediction working groups for which ocean observations are needed both for model initialization and validation. A key activity within CLIVAR, carried out by GSOP is the coordinated application of data assimilation systems to provide and intercompare integrated ocean syntheses. These have the potential to provide initial conditions for climate predictions on seasonal to decadal timescales (coordinated by CLIVARs seasonal and coupled modelling working groups) and for validation and comparison of coordinated ocean-ice reference experiments by CLIVARs group on ocean model development. Ocean observations also have a role in CLIVARs wider activities in monsoon and African climate prediction.

This poster will summarize the key ocean-related activities of CLIVAR from the perspective of the role of sustained ocean observations in research on climate variability and change. It will provide a backdrop to posters describing the ocean-observation-related work of CLIVARs ocean basin panels and GSOP in more detail.


AC-2A-10: Observed Freshening and Warming of the Western Pacific Warm Pool
CRAVATTE, Sophie1; Delcroix, Thierry1; Zhang, Dongxiao2; McPhaden, Michael3; Leloup, Julie4
1IRD-LEGOS, FRANCE;
2PMEL/NOAA, UNITED STATES;
3NOAA-PMEL, UNITED STATES;
4RSMAS, UNITED STATES
 

Trends in observed sea surface salinity (SSS) and temperature are analyzed for the tropical Pacific during 19552003. Since 1955, the western Pacific Warm Pool has significantly warmed and freshened, whereas SSS has been increasing in the western Coral Sea and part of the subtropical ocean. Waters warmer than 28.5°C warmed on average by 0.29°C, and freshened by 0.34 pss per 50 years. Our study also indicates a significant horizontal extension of the warm and fresh surface waters, an expansion of the warm waters volume, and a notable eastward extension of the SSS fronts located on the equator and under the South Pacific Convergence Zone. Mixed layer depth changes examined along 137°E and 165°E are complex but suggest an increase in the equatorial barrier layer thickness. Our study also reveals consistency between observed SSS trends and a mean hydrological cycle increase inferred from Clausius-Clapeyron scaling, as predicted under global warming scenarios. Possible implications of these changes for ocean-atmosphere interactions and El Niño events are discussed.


AC-2A-11: Developing global long-term altimeter datasets and climatologies of ocean wave measurements
Cromwell, David; Gommenginger, Christine P.
National Oceanography Centre, UNITED KINGDOM
 

The prime objective of this work is to build long-term climatologies of ocean significant wave height and wave period based on multi-mission satellite altimeter datasets. The development of such global climatologies is driven by the need to validate present day operational wave forecasting systems as well as improve our understanding of the role of waves in atmosphere-ocean dynamics, ocean surface transport and mixing, and facilitate the detection and measurement of global climate change as revealed in ocean wave parameters. Typical applications also include better estimation of ocean-based renewable energy resources and improved estimation of extreme sea states.

The basic methodology is first to calibrate altimeter-derived significant wave height (SWH) and wave period estimates against a network of in situ buoy measurements. In this study, we use primarily buoy data extracted from the National Data Buoy Center (NDBC) database, made available freely online by the US National Oceanic and Atmospheric Administration (http://www.ndbc.noaa.gov).

Altimeter SWH and radar backscatter, sigma-0, are extracted for the whole duration of the TOPEX, ENVISAT and JASON-1 altimeter missions, thus spanning a period of over 15 years. Collocation of altimeter and buoy data is performed here using a maximum time separation of 30 minutes (buoy data are collected hourly) and a range of maximum spatial separations of (a) 50 km; (b) 100 km; and (c) closest collocation up to a maximum of 500 km. The altimeter data are all obtained via the Radar Altimeter Database System (RADS) hosted at Delft University of Technology (http://rads.tudelft.nl/rads/rads.shtml). The SWH is measured directly by the altimeters while the wave period is calculated using the algorithm of Mackay et al. (2008).

An important consideration when dealing with long-term datasets is the development of a robust technique to perform the calibration in time: how do the best-fit parameters change in time, and what is the dependence on both the specified collocation distance and the duration of the collocated dataset for the ODR results? Our initial investigations suggest that 10 days of data provide too few measurements for a reliable calibration. Conversely, although performing the calibration over a year (or longer) typically provides tens of thousands of altimeter-buoy data pairs, leading to a high-precision calibration, it may smooth over potentially significant intra-annual variability.

Next, the calibration is applied to each dataset of along-track altimeter measurements, yielding along-track global estimates of SWH and wave period for each altimeter mission. These along-track data are then gridded using optimal interpolation to a regular temporal and spatial grid (typically monthly and 2x2 deg, respectively) over the global ocean (within the latitude range covered by each satellite altimeter).

Continuation of the work will include the investigation of other collocation techniques, such as the triple collocation between three independent datasets, which leads to estimate of errors on all data sources (Caires & Sterl, 2003). Additional altimeter datasets, from past and emerging missions, will also be incorporated in the study, including data from ERS-2, GFO, JASON-2 and Cryosat-2.


AC-2A-12: COriolis Re-Analysis (CORA) : a new comprehensive and qualified ocean in-situ dataset from 1990 to 2008
de Boyer Montegut, C.1; Cabanes, C.2; Coatanoan, C.1; Pertuisot, C.1; Petit de la Villeon, L.1; Carval, T.1; Pouliquen, S.1; Le Traon, P.-Y.1
1IFREMER, FRANCE;
2INSU/CNRS, FRANCE
 

Coriolis is a french programme basically aimed to contribute to the ocean in situ measurements part of the french operationnal system. It has been especially involved in gathering all global ocean in-situ observation data in real time, and developing continuous, automatic, and permanent observation networks. Coriolis data center now produces by the end of 2009 a comprehensive ocean in-situ dataset of temperature/salinity profiles on the global scale and ranging from year 1990 to 2008. This dataset is meant to be used for general oceanographic research purposes, for ocean model validation, and also for initialisation or assimilation of ocean models. Here we first present the observations types and distribution used to build this dataset (argo, gts data, vos ships, nodc historical data...). Then we will review the processing and quality controls that have been applied to the data (e.g. objective analysis to remove outliers and/or some visual checks). In a last part, we show some basic characteristics of the temperature and salinity fields constructed from this dataset.

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