DADB - Seasonal Temperature, Salinity and Density Anomaly

15 depth levels

Observational Data

Two basic collections of temperature and salinity measurements, namely "Mediterranean Oceanic Data base" (MODB) and "Adriatic Sea Temperature, Oxygen and Salinity data set" (ATOS2), constitute the foundation for the "Dartmouth Adriatic Data Base", herein DADB.

The MODB comprises temperature and salinity observations for the entire Mediterranean Sea (no coastal data) and it was extracted from http://modb.oce.ulg.ac.be/modb/welcome.html for the Adriatic Sea.
The ATOS2 was assembled at IRPEM-CNR, Italy and extracted via ftp from ftp://bora.imga.bo.cnr.it and contains both open sea and coastal data for temperature and salinity at all depths.

SET	SPAN (years*)	SURFACE data	SUBSURFACE data
MODB - CTD	1974 - 1989	652	8855
MODB - BT	1950 - 1990	1640	3943
MODB - BOTTLE	1911 - 1979	2106	9848
ATOS2	1911 - 1986	5845	34,964
TOTAL number of observations:			57,610

DADB_raw Construction

The merging of "MODB" and "ATOS2" gave rise to two problems: redundancy and uneven space-time distribution of the data. To solve the former, duplicates were eliminated, and only those observations that were independent in space and time were retained. The seasonal grouping of the monthly files was done according to previous studies of the Adriatic Sea (Zore-Armanda 1969, Gacic at al. 1997): winter -- from January to March, spring -- from April to June, summer -- from July to September, and autumn -- from October to December. This seasonally aggregated set of data shows a more uniform distribution over the domain than the monthly data, both in space and in terms of the number of valid measurements for at least one parameter (T or S): 14349, 13523, 16168, 11726 locations for winter, spring, summer and autumn, respectively.

The uneven spatial coverage of the data required care in binning these four seasonal data sets. Most of the observations were made at 0, 5, 10, 20, 30, 50, 75, 100, 150, 200, 250, 300, 400, 500, 800, 1000 and 1200 m depth. The fact that the average depth of northern and middle Adriatic is less than 150 m and that 90% of the measurements are in those top 150 m forced the selection of the most meaningful depth levels for aggregation of the data. These levels are selected such that, after averaging temperature and salinity values with the same initial time/space location within each vertical bin, each interval is centered on the depth with the greatest number of measurements (levels listed above). In this way, the redundancy within each vertical bin is minimized by analyzing both the horizontal and vertical spread of the observations. Fifteen "slices" were cut over the whole depth after the data centered at 250 m were distributed to the adjacent layers, and the data for 1000 and 1200 m were grouped together since they are only in the South Adriatic Pit and the temperature/salinity range is the same. This preprocessing was meant to reflect the structure of the observational data, rather than to rely on some preconceived notions of what the vertical layers should be and how the horizontal gaps should be filled.

For more information on the DADB construction and climatological results you can order a copy of this M.S. Thesis from Prof. Benoit Cushman-Roisin at Dartmouth College.

Optimal Linear Estimation (OAX)

Climatological fields for each season were estimated using four-dimensional optimal linear interpolation on the DADB_raw temperature and salinity fields. The OAX5 package used to obtain the DADB seasonal T and S was developed at the Bedford Institute of Oceanography by Ian he, Ross Hendry and Gerry Boudreau. For a complete reference for the algorithm, see the "Technical Report on Objective Analysis Project" here.

DADB - Climatological Data

The following table contains the DADB compressed files for each season and depth level. They are named "DADB_season_depth.dat.gz", and the format is as follows:

bin center: 0 m
lat,lon,depth(m),T(C),S(psu),density anomaly(sgt units)
19.410 40.810 0.0000 14.7395 38.4443 28.6898
19.392 40.820 0.0000 14.7317 38.4618 28.7050
19.392 40.801 0.0000 14.8745 38.4631 28.6740
19.423 40.825 0.0000 14.6853 38.4295 28.6904
...
(9739 nodes in the horizontal for each depth level)

SEASON	DEPTH, in meters
Winter	0	5	10	20	30	50	75	100	150	200	300	400	500	800	1050
Spring	0	5	10	20	30	50	75	100	150	200	300	400	500	800	1050
Summer	0	5	10	20	30	50	75	100	150	200	300	400	500	800	1050
Autumn	0	5	10	20	30	50	75	100	150	200	300	400	500	800	1050

Climatological Fields - Temperature

The figures below present the temperature (T), salinity (S) and density anomaly (σ) fields at selected depth levels, obtained after the application of OAX with the preceding parameter values.

SEASON	T		S	σ
Winter	T all	T 4 levels	S 4 levels	σ 4 levels
Spring	T all	T 4 levels	S 4 levels	σ 4 levels
Summer	T all	T 4 levels	S 4 levels	σ 4 levels
Autumn	T all	T 4 levels	S 4 levels	σ 4 levels