Collocated NSCAT and Research Vessel Winds
General Description
High temporal resolution winds from automated weather systems were vector averaged, quality controlled, and collocated with NSCAT winds. This validation was first performed on the 50 km resolution data from the NSCAT-1 algorithm (Bourassa et al., 1997).
Cruises
|
Research Vessels |
Cruise Dates |
Cruise Locations |
Temporal Resolution |
Meta-Data |
|
RSVAurora Australis |
1196/9/30 - 1996/11/23 |
Southern Ocean |
12 sec |
|
|
R/V Knorr |
1996/10/24 - 1996/11/15 |
North Atlantic |
1 min |
|
|
1996/12/13 - 1997/3/17 |
storm chasing and Laborador Sea |
|||
|
R/V Thompson |
1996/7/8 - 1997/1/31 |
North Pacific crossing |
1 min |
|
|
1997/1/31 - 1997/3/3 |
Japan to Equatorial Pacific |
Collocation Criteria
For each collocation, the ship and NSCAT observations are coincident within 25km and 30 minutes.
Quality Control
Sometimes these data sets are stored in formats well described as cryptic. We must convert the data files to a usable form. The data then passes through a two level quality control process. The first level is automated, designed to catch physical impossibilities and flag unlikely values. The second stage is a visual examination, designed to spot systematic errors and evaluate the data flagged as questionable. A paper detailing this quality control, and demonstrating its value (Smith et al., 1999), is in press.
Averaging of Research Vessel Observations
The temporal resolution of the wind records range from 12 seconds to ten minutes. When possible these are averaged for a period preceding the NSCAT observation. Furthermore, in many cases, the observations that went into the records we receive are averages. When known, these averaging techniques will also be described.
Data Set Content
The data sets will be restricted to the closest collocation in space within 30 minutes of the satellite observation. The data sets will contain scatterometer wind speed and direction, cell location information, ship winds adjusted to equivalent neutral 10 m winds, the original true winds (i.e., earth relative, with directions referenced to true North) calculated from the ship observations, and the data used in the conversion to equivalent neutral winds.
Data Format
Detailed descriptions of the data content and format, units, and variable declarations for each data file.
Meta-Data
Key information such as the height of the instruments.
Read Programs
The collocated data files are stored in a NetCDF format. NetCDF libraries are required to access the data, and can be obtained from UNIDATA.
Bourassa, M. A., M. H. Freilich, D. M. Legler, W. T. Liu, and J. J. O'Brien, 1997: Wind observations from new satellite and research vessels agree. EOS Trans. of Amer. Geophys. Union, 597 & 602.
Smith, R. S, M. A. Bourassa, and R. J. Sharp, 1998: Establishing more truth in true winds. J. Atmos. Oceanic Technol., in press.
