North Pole Environmental Observatory (NPEO) Oceanographic Mooring Data, 2001-2002Entry ID: ARCSS156
Abstract: This data set, acquired with an oceanographic bottom-anchored mooring, includes sea-ice draft and depth data, conductivity, temperature, pressure, salinity, and ocean current measurements such as speed and direction. Each mooring contains vertically distributed instruments, which measure ocean properties at fixed depths and record data internally. These data are retrieved annually when the mooring ... is recovered. Located on the Pole Abyssal Plain about 50 kilometers from the North Pole, the 2001 mooring was chosen because it provided a suitable landing site for the supporting aircraft. Ocean depth was approximately 4300 m. Data were recorded half-hourly to hourly from 1 April 2001 through 27 April 2002. The North Pole Environmental Observatory (NPEO) is a year-round, automated scientific observatory, deploying various instruments each April in order to learn how the world's northernmost sea helps regulate global climate. It consists of a set of unmanned scientific platforms that record oceanographic, cryospheric, and atmospheric data throughout the year. More information about the project is available at the project Web site, (http://psc.apl.washington.edu/northpole/) North Pole Environmental Observatory. Data are in ASCII text format and are available via FTP.
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Data Set Citation
Dataset Originator/Creator: Morison, J., K. Aagaard, R. Moritz, M. McPhee, A. Heiberg, M. Steele, and R. Andersen
Dataset Title: North Pole Environmental Observatory (NPEO) oceanographic mooring data, 2001-2002
Dataset Series Name: NPEO
Dataset Release Date: 2005-11-21
Dataset Release Place: Boulder, CO
Dataset Publisher: National Snow and Ice Data Center (NSIDC)Online Resource: http://nsidc.org/data/arcss156.html
Start Date: 2001-04-01Stop Date: 2002-04-27
CRYOSPHERE > SEA ICE > SEA ICE MOTION
OCEANS > OCEAN CIRCULATION > OCEAN CURRENTS
OCEANS > OCEAN PRESSURE > SEA LEVEL PRESSURE
OCEANS > OCEAN PRESSURE > WATER PRESSURE
OCEANS > OCEAN TEMPERATURE > WATER TEMPERATURE
OCEANS > SALINITY/DENSITY > CONDUCTIVITY
OCEANS > SALINITY/DENSITY > SALINITY
OCEANS > SEA ICE > SEA ICE MOTION
OCEANS > SEA ICE > SALINITY
ISO Topic Category
Quality Pressure is readily checked for consistency between different instruments, noting. However, investigators noted that precise ocean depth is difficult to determine and that line length errors are possible. The 2001-2002 mooring was well positioned with respect to depth. Four pressure sensors near the top of the mooring report instrument depths within 2 m of design depths. One sensor on RCM-7, ... serial number 11455, the only current meter recording pressure, reported itself some 7 m deeper than designed. The investigators accept as correct those four pressure measurements, located both above and below the suspect RCM, suggesting an erroneous offset in the one RCM pressure sensor. Consequently, a constant pressure was assigned to the 84 m design depth and used in the salinity calculation for that RCM. However, for completeness the pressure as measured is reported in the data file, and those measurements provide information on pull-down of the RCM. The deep Sea-Bird instruments, SBE-37s with serial numbers 1772, 1773, and 1774, unfortunately suffered from the failure of a new pressure sensor, which was subsequently confirmed by the manufacturer as flawed. These three instruments do report temperature and conductivity with good accuracy, and constant pressures inferred from the design depths are used in the calculation of salinity at those levels. Note that no pressure correction has been made for pull-down of these instruments, as is also the case for RCM serial number 11455. A stuck vane or malfunctioning compass afflicted RCM serial number 6545 at 600 m, constraining the direction to one-third of its full arc, while current speed appears reasonable. Both speed and direction are reported as measured. General information about the North Pole Environmental Observatory, the NPEO mooring, and various data extracts and summaries may be viewed on the NPEO website. See Bottom-Anchored Mooring (http://psc.apl.washington.edu/northpole/Mooring.html). Potentially important sources of error in the sea-ice draft computed as described above include the following: *Systematic and random errors in density rhow *Systematic and random errors in sound speed cbar *Random errors in sea-level air pressure Ps *Errors in the local value of earth's gravitational acceleration g *Timing variations in the sonar hardware/software system *Target identification errors for first-return echoes from targets not directly above the ULS, or from targets intervening between the ULS and the intended target (ice bottom or sea surface) *Non-hydrostatic (short) waves during open water intervals Extensive analysis, as reported in Moritz (2005) yields a net systematic error of approximately +0.3 meters, a standard deviation of random errors of approximately 0.05 meters during the summer, and an annual variation of systematic error on the order of 0.10 meters for ULS 22 at NPEO 2001-2002. The summertime random errors show some persistence over intervals of at least several hours. An offset correction was applied to both the 5-minute and 10-second time series, by identifying occurrence of open water based on a combined analysis of the ULS and ADCP data. The offset correction eliminates most of the net systematic error, and greatly reduces the random errors in summer. The offset has been applied to the data set provided here. Once the offsets are applied, summer (June-August) sea-ice drafts between -0.10 m and +0.10 m are reset to 0 m, consistent with the range of error variability for open water episodes and with the model that ice thinner than 10 cm is rare during these months. For all other months, sea-ice drafts between -0.05m and 0 m are reset to zero. Sea-ice drafts outside the range -0.05 m < draft < 20 m are replaced by the bad data value -999. This results in data with all sea-ice drafts in the interval 0 m to 20 m. The ULS is programmed to look for sea-ice drafts in a window that opens approximately 20 meters below sea level.
Data Set Progress
Role: DIF AUTHOR
Email: asad.ullah at sigmaspace.com
Hyer, E. J., J. S. Reid, and J. Zhang (2011), An over-land aerosol optical depth data set for data assimilation by filtering, correction, and aggregation of MODIS Collection 5 optical depth retrievals, Atmospheric Measurement Techniques, 4, 379-408, doi: 10.5194/amt-4-379-2011.
Levy, R. C., L. A. Remer, S. Mattoo, E. F. Vermote, and Y. J. Kaufman (2007), Second-generation operational algorithm: ... Retrieval of aerosol properties over land from inversion of Moderate Resolution Imaging Spectroradiometer spectral reflectance, J. Geophys. Res.-Atmos., 112(D13), D13211.
Remer, L. A., et al. (2005), The MODIS aerosol algorithm, products, and validation, J. Atmos. Sci., 62(4), 947-973.
Shi, Y., Zhang, J., Reid, J. S., Holben, B., Hyer, E. J., and Curtis, C.: An analysis of the collection 5 modis over-ocean aerosol optical depth product for its implication in aerosol assimilation, Atmos. Chem. Phys., 11, 557-565, 10.5194/acp-11-557-2011, 2011.
Zhang, J. L., and Reid, J. S.: MODIS aerosol product analysis for data assimilation: Assessment of over-ocean level 2 aerosol optical thickness retrievals, J. Geophys. Res.-Atmos., 111, 2006.
Zhang, J. L., Reid, J. S., Westphal, D. L., Baker, N., and Hyer, E. J.: A System for Operational Aerosol Optical Depth Data Assimilation over Global Oceans, Journal of Geophysical Research, 113, doi:10.1029/2007JD009065, 2008.
Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 2013-01-07
Last DIF Revision Date: 2013-01-16