| Product description | (2008-06-25) |
| WHAT ? | PRODUCT-ID |
ARIVO-GLOBAL-ARRGL05-OBS
|
| PRODUCT TYPE |
In situ datasets
| OUTPUT TYPE |
Along track (observations)
|
| OVERVIEW |
General information
The mean seasonal cycle of the ocean temperature and salinity has been computed from a monthly analysis of in-situ data over the period 2002-2007. The statistical error is also provided (percent of variance).
Processing information / observing platforms :
The monthly field are taken from ARRAGL05 optimal analysis of the dataset provided by Coriolis datacenter. Each month of the cycle is thus the average of the corresponding month of the 6 years of analysis.
Temperature and salinity measurements are obtained from autonomous instruments, drifting or anchored or from instruments deployed from a ship. The data are transmitted in real time by satellite, or in delayed mode. The main instruments types are :
- Argo profiling floats: These drifting floats collect vertical profiles of temperature and salinity every 10 days between their maximum pressure (usually 2000 dbars) and the surface.
- XBT: eXpendable BathyThermograph are launched from a steaming ship and measure temperature (and salinity in the case of XCTD) most XBT reach 800 m.
- CTD: This high quality measurement is obtained from a research vessel in the context of a scientific cruise. Pressure and temperature sensors are carefully calibrated and water samples are taken to adjust the salinity measurement.
- Time series: Time series of pressure, temperature and salinity are recorded at high time resolution (hours) from sensors installed on fixed points (mooring) or drifting buoys.
The configuration is described in detail in (Charraudeau and Gaillard, 2007). The horizontal grid is ½ degree Mercator limited to 77S-77N. The resolution increases with latitude, from 0.5° at equator to 0.1125° at 77N. In the vertical, 151 levels between 0 and 2000m are analyzed.
Statistical information on the field and data noise are introduced through the covariance matrices. The covariances of the analyzed field are specified by a structure function modeled as the sum of two gaussians, the first term corresponding to the large scale field (LS), the second to the mesoscale (MS). The large scale lengths are taken isotropic and equal to 300km, the target Argo resolution, the corresponding time scale is set to 3 weeks. The meso-scale length is proportionnal to the Rossby Radius computed from the annual climatology. In the equatorial band, this value is bounded by the large scale length in the zonal direction, and by the length scale of the adjacent zones in the meridional direction. At high latitudes, it is bounded by the resolution of the estimation grid.
Description of method
The In Situ Analysis System (ISAS-V4) uses estimation theory for mapping of a scalar field on a regular grid from sparse and irregular data (Bretherton et al.,1976) it is described in Gaillard and Charraudeau, 2008). The interpolated field, represented by the state vector, is constructed as the departure from a reference field values at the grid points. This reference is derived from previous knowledge (her we use WOA05 monthly climatology).
Quality
The analysis method gives an estimate of error by providing the percentage of a priori variance.The mean of this percent variance is given in the files and gives a measure of the accuracy of the estimate.
Suitability:
This mean can be used as a reference to study interannual variability over this period. It can also be an interesting initial state for numerical models.
References:
Gaillard, F., E. Autret, V.Thierry, P. Galaup, C. Coatanoan, and T. Loubrieu , 2008 : An operational system for real time and delayed mode quality control of Argo profiles. In press JAOT.
Autret, E., F. Gaillard, 2004 : Les analyses Coriolis et le suivi climatologique : mise en oeuvre sur l'Atlantique Nord. La lettre Mercator, 11.
Gaillard, F. and E. Autret, 2005 : Coriolis real-time analysis system : validation over the North-Atlantic. Coriolis , newsletter 1.
Gaillard, F. and R. Charradeau: ISAS-V4.1b: Description of the method and user manual. Rapport LPO 08-03
Charraudeau, R. , Gaillard, F.: ISAS-V4, Mise en place de la configuration. Rapport LPO-07-09.
|
| PARAMETERS GROUP |
| (from BODC) |
|
| PARAMETERS
(parameter, unit, convention)
|
- sea_water_salinity,1e-3,CF
- sea_water_temperature,K,CF
|
| WHERE ? | GEOGRAPHICAL COVERAGE |
| GEOGRAPHICAL SCALE |
Global scale
|
| SPATIAL RESOLUTION |
0.5 deg. Merc
|
| VERTICAL COVERAGE |
from 2000 to 0 meters.
|
| WHEN ? | TEMPORAL COVERAGE | Since 2003-01-01 - 2007-01-01 | TEMPORAL RESOLUTION | |
| PROCESS/ UPDATE | UPDATED | annually |
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