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Information in this document has been derived from documentation files on NSIDC's CD-ROM titled Eastern Arctic Ice, Ocean and Atmosphere Data, Volume 1: CEAREX-1, version 1.0, 8/91.
Platform movement was vector subtracted from the measured wind velocity (relative wind) to give the true wind speed and direction. The velocities of the ship platforms were determined from bridge heading and speed instruments.
Surface Measurements:
The surface data represent averages from consecutive ten-minute periods. The instruments were located on a bow mast, 16 meters above sea level. The relative wind speed and direction were measured with a cup anemometer and a vane. Temperature was obtained from an aspirated, radiation-shielded, platinum-resistance thermometer (PRT). Humidity was obtained from a cooled-mirror hygrometer. Pressure was not measured.
The temperature was accurate to within 0.5 degrees C and the humidity to within 3 percent relative humidity. Wind speed and direction were usually accurate to 0.3 m/s and 10 degrees respectively. There were some brief periods when the wind measurements were less accurate because of ship-induced air flow distortion.
Upper-air Measurements
Rawinsonde measurements were obtained and are summarized in Lindsay (1984) but are not included on the CEAREX CD-ROM. Please contact NSIDC User Services for current availability of these data.
POLAR QUEEN Surface Measurements
During most of MIZEX-84, the POLAR QUEEN was moored to a large ice floe. Near-surface wind speed and air temperature were measured at four levels from a 6.7 meter profile mast located on the floe 60 meters from the ship. The profile enabled the wind speed to be measured with an accuracy of 0.1 m/s. Temperature was accurate to 0.1 degree C.
When the profile mast was not deployed, during transit periods, or when the profile mast had an upwind obstruction, the wind and temperature was measured at 16 meters elevation from a bow mast on the ship. During these times, the accuracies for wind speed and temperature were estimated to be 0.3 m/s and 0.5 degree C. In all cases, the wind speed was adjusted to the 10 meter value using standard flux-profile relationships. Both the ice tower and bow mast locations had cup anemometers and radiation-shielded aspirated platinum-resistance thermometers.
Wind direction was measured with a vane on the bow mast with an accuracy of 5 degrees. The wind vane was not operational before June 11, therefore wind direction and wind speed were not available when the ship was moving. Humidity was measured with a cooled-mirror hygrometer on the bow mast and was accurate to 3 percent relative humidity. Pressure was measured in the ship's laboratory with an accuracy of 2 mb. All values are ten-minute averages.
Data described in section II.B of Lindsay (1985) contains extra variables that flag suspect values of wind speed, wind direction, temperature and humidity. These data are not included on the CEAREX CD-ROM. Please contact NSIDC User Services for information about its availability.
POLAR QUEEN Upper-air Measurements
Rawinsondes were launched from the ship at least twice a day using a Vaisala Upper Air Sounding system. The rawinsondes and initial processing of the data were provided by the Alfred Wegener Institute for Polar Research (AWI).
The accuracy of the temperature and dewpoint temperature was 0.2 degree C and 1.0 degree C respectively, while height was accurate to 30 meters. Vector wind was accurate to 2.0 m/s. Because rawinsonde measurements are instantaneous, they do not necessarily represent average conditions, particularly if strong secondary circulations are present.
HAAKON MOSBY Measurements
The surface data from the HAAKON MOSBY were obtained using instruments similar to those on the POLAR QUEEN. The wind, air temperature and humidity probes were mounted on a platform extending forward of the HAAKON MOSBY's main mast at a height of 15 meters above sea level. Pressure was measured in the ship's laboratory. The accuracies were: wind speed, 0.3 m/s; wind direction, 10 degrees; air temperature, 0.5 degree C; relative humidity, 3 percent; pressure, 2 mb. All observations were averaged over ten-minute intervals. The accuracy of the wind measurements was worse when the winds were directly from the stern. Rawinsondes were launched four times a day or more. The accuracies were identical to those for the POLAR QUEEN measurements.
POLARSTERN Measurements
The POLARSTERN had two anemometers, wind vanes, and temperature sensors. The set of sensors on the side of the ship from which the wind was blowing was used. If the two wind vanes could not agree on which side that was, the side with the higher wind speed was used. The humidity was calculated from an Li-Cl sensor. The values represent ten-minute averages. The accuracies are similar to those indicated above for the HAAKON MOSBY data.
The rawinsondes were usually launched every three hours. The estimated accuracies were identical to the POLAR QUEEN data.
VALDIVIA Measurements
The data were based on manually recorded observations of the permanent ship instruments. The observations were usually made every three hours and are based on averages over a few seconds. Sometimes the wind speed was estimated from sea state. Pressure was obtained from a barometer on the bridge. Humidity was not measured. The accuracies were: wind speed, 2.0 m/s; wind direction, 15 degrees; air temperature, 1.0 degree C; pressure, 2 mb.
The rawinsondes were usually launched every six hours. The processing of the data and the estimated accuracies were identical to the POLAR QUEEN data.
The POLAR CIRCLE collected data from March 22 through April 11. A Coastal Climate WeatherPak meteorological station (met station) was located on a platform extending forward of the POLAR CIRCLE's bow mast at a height of 16 meters above sea level. This instrument measured wind speed and direction, temperature, and relative humidity. There was a bug in the WeatherPak software in the wind speed calculation when the wind speed was greater than 9 m/s. During these periods, wind speed was measured from sonic anemometers at the same location. There was excellent agreement (within 0.3 m/s) between these sensors at lower wind speeds; therefore reported speeds should be accurate to at least this amount. The errors associated with distortion of airflow by the ship were believed to be less than 5 percent because the anemometer locations were well away from blocking structures. An exception was when the wind was directly from the stern, when errors may have been as great as 20 percent. The temperature was accurate to 1.0 degree C and the relative humidity to within 5 percent.
All the wind speed and direction values for all the ships were corrected for ship motion based on the ship's speed and heading. On the POLAR CIRCLE, the ship's heading was obtained from a compass on the WeatherPak and was routinely checked against the ship's gyroscope. Unfortunately, the ship caused extreme magnetic distortion for certain headings so that there were occasionally considerable errors in the true wind directions between the times when the gyroscope heading was recorded. When the POLAR CIRCLE was near the HAAKON MOSBY, the wind direction from the latter should be used. Most of the time the wind directions from the POLAR CIRCLE were accurate to within 20 degrees. This problem did not affect the true wind speed calculations. The data were averaged over ten-minute periods.
Vertical profiles of temperature, humidity and winds were obtained nominally every six hours using a rawinsonde system manufactured by the VIZ Corporation. The vector winds were determined from an Omega navigation system on the rawinsondes and were usually accurate to 1.0 m/s. In regions of strong vertical shear, errors may increase to 2.0 m/s. The temperature and dewpoint temperature were accurate to 0.2 degree C and 1.0 degree C respectively, while the heights were accurate to 30 meters. Because rawinsonde measurements are instantaneous, they do not necessarily represent the average conditions, particularly when strong secondary circulations are present.
HAAKON MOSBY Measurements
The HAAKON MOSBY had a Coastal Climate WeatherPak meteorological station at 18 meters elevation with the same instruments and similar accuracies as the POLAR CIRCLE for all parameters except wind direction. Because the WeatherPak software had a bug in the calculation of these wind speeds, a miniature cup anemometer was used to measure wind speeds above 11 m/s. Unlike the POLAR CIRCLE, there was no magnetic distortion of the compass; therefore wind directions were usually accurate to 5 degrees. During a few periods when air flow was from the stern of the ship, flow distortion may have caused 20 percent errors in wind speed and direction. Ten-minute averages were recorded.
The rawinsondes launched from the HAAKON MOSBY were manufactured by the Vaisala Corporation using a system developed by R. Helvey of the Pacific Missile Test Center. The rawinsondes were usually launched every six hours. The temperature data obtained from these rawinsondes have an accuracy of 0.2 degree C and the dewpoint temperatures are accurate to within 1.5 degrees C. Wind data were obtained using an Omega navigation tracking system on each rawinsonde. The vector wind speeds were usually accurate to 2 m/s. Winds in the lower 500 meters of the rawinsonde flights had to be interpolated from surface and upper-level measurements and therefore are likely to have larger errors. The heights are accurate to within 30 meters.
VALDIVIA Measurements
Instruments on the VALDIVIA measured all the basic parameters except humidity. Because of a problem recording the correct time, only data collected only during standard observation periods (when the time was known) are included on the CEAREX CD-ROM. This was usually every three hours. The accuracies of the values were the same as those from the HAAKON MOSBY.
The rawinsonde system on the VALDIVIA was virtually identical to the POLAR CIRCLE system and had the same accuracies. Launches were usually performed every six hours.
A Coastal Climate WeatherPak meteorological station was located on a platform extending forward of the POLARBJORN's bow mast at a height of 14 meters above sea level. This instrument measured wind speed and direction, temperature, and relative humidity. Temperature data are accurate to within 1.0 degree C and humidity to within 5 percent. Accuracy of wind speed and direction depended on wind direction relative to the ship; a "sheltering" effect was observed with winds directly from the stern. This situation seldom occurred during the drift phase because of the ship's slowly varying heading and persistent northerly winds. Wind speeds are accurate to within 0.3 m/s and direction to within 10 degrees, although during periods of unfavorable wind direction, errors may have been larger.
All winds were corrected for ship motion based on ship speed and heading. Throughout most of the drift, ship and ice relative winds were within 0.5 m/s. However, after November 15 when the POLARBJORN was mobile, this correction was important.
POLARBJORN Upper-air Measurements
Vertical profiles of temperature, humidity, and wind speed and direction were obtained twice daily throughout the experiment, with additional launches during periods of extreme or unusual weather. The system used rawinsondes and software developed by the VIZ Corporation. The rawinsondes were equipped with thermistors that measured temperatures to within 0.2 degree C. The humidity sensor consisted of a specially coated glass plate, the resistance across which varies with humidity. Humidity measurements generally agreed quite well with Coastal Climate WeatherPak readings, although some overestimation was evident. Winds were measured using Omega tracking and were therefore unavailable during periods of high solar flare activity.
A systematic underestimation of low-level winds occurred because of the necessary three-minute averaging of all wind data. Underestimation resulted from inclusion of lighter inversion-layer winds in the average. Rawinsonde wind directions were generally accurate to within 20 degrees. This data set includes virtually all rawinsonde data with very little editing. Spurious wind data take the form of shallow (100 meter) jets; data users should be skeptical of any soundings exhibiting large vertical shear in the absence of a temperature inversion.
Altitude was measured with a baroswitch, occasionally yielding spurious contacts, particularly at low levels. An effort was made to remove spurious contacts, but success in this difficult task is a function of operator experience, therefore inaccuracies may exist in some soundings. Errors of this type are always largest at higher levels because of the cumulative effect of erroneous contacts during the rawinsonde's ascent.
HAAKON MOSBY Surface Measurements
A Coastal Climate WeatherPak meteorological station was used on board the HAAKON MOSBY to measure air temperature, relative humidity, atmospheric pressure, and wind speed and direction. This station was mounted on a platform extending forward of the HAAKON MOSBY's bow mast at a height of 15 meters above sea level. All observations were averaged over ten-minute intervals. The temperature data obtained from this instrument were accurate to within 1.0 degree C and the relative humidity data to within 5 percent.
The accuracy of the wind measurements depended on the wind direction relative to the ship; a "sheltering" effect was observed with winds blowing directly from the stern. Wind speeds are accurate to within 0.3 m/s and direction to within 10 degrees, although when winds were from the stern the errors are likely to be larger. All wind data have been corrected for ship motion based on ship speed and heading. The measurements of atmospheric pressure are accurate to within 2 millibars.
HAAKON MOSBY Upper-air Measurements
Vertical soundings of the atmosphere were routinely obtained roughly every six hours, with rawinsonde flights at approximately 0000, 0600, 1200 and 1800 UTC every day, depending upon equipment or environmental difficulties. During periods of unusual or exceptional weather conditions soundings were made more frequently. The number of soundings made in a single day varied from zero to as many as nine.
The vertical profiles of temperature, dew point temperature and wind speed and direction were measured using rawinsondes manufactured by the Vaisala Corporation and software developed by Roger Helvey. The temperature data obtained from these rawinsondes have an accuracy of 0.2 degree C and the dewpoint temperatures are accurate to within 1.5 degrees C. Wind data were obtained using an Omega navigation tracking system on each rawinsonde. The vector wind speeds are considered to be accurate to within 1 m/s. Winds in the lower 500 meters of the rawinsonde flights had to be interpolated from surface and upper-level measurements and therefore are likely to have larger errors. The heights are accurate to within 30 meters. Obvious errors in the profile data were removed but the data are otherwise unedited.
Oceanography Camp (O-Camp) Surface Measurements
Wind speed, wind direction, temperature, humidity and pressure were obtained from a Coastal Climate WeatherPak meteorological station and recorded on Hewlett-Packard 200 series computers. The data were averaged over ten-minute periods. The winds were measured at a height of 2.82 m above the ice surface. Temperature, humidity and pressure were measured at 2.24 m. The temperature was accurate to 0.5 degree C; relative humidity, 8.0 percent; wind speed, 0.2 m/s; wind direction, 5.0 degrees; and pressure, 2.0 mb. The pressure data show some high frequency fluctuations that are not believed to be real.
Computer and met station malfunctions created periods when data were missing or obtained from other instruments. Considerable post-experiment editing was required to provide the best estimates of the basic meteorological parameters. The periods and substitution measurements made when problems occurred are described in the following paragraphs.
Computer malfunction between March 27 and March 30 required that the met station data be manually recorded. For some parts of these days, the values of all parameters are based on ten-second average measurements with irregular intervals ranging from 4 to 90 minutes between recorded measurements. For other periods of time, no data were recorded.
On March 30, a sonic anemometer was deployed at a height of 3.33 m. It measured average wind speed and direction, with an accuracy of 0.3 m/s and 10 degrees, respectively, every ten minutes. Twice on March 30, air temperature was recorded manually using an unshielded alcohol thermometer located beside the hut 0.7 m above the surface. From March 31 through April 1, the alcohol thermometer was located in a homemade box shield located 1.7 m above the surface. During this period, the temperature was manually recorded hourly during waking hours, and was accurate to within 1.5 degrees C.
Beginning March 31, pressure from an altimeter in the camp manager's hut was recorded two or three times a day. Starting April 2, the sonic anemometer was used to determine ten-minute average temperature.
The pressure and temperature sensors described in the previous two paragraphs were calibrated later in the experiment when a replacement met station was available for comparison. After adjusting for bias, the above sensors compared very well with the met station and the accuracies were estimated to be at least as good as the met station accuracies, (2.0 mb and 0.5 degree C, respectively). Although temperature as measured by a sonic anemometer is affected by humidity, the effect in the Arctic is too small to alter the accuracy stated above.
On April 9, a replacement met station was deployed and recorded average pressure, temperature, humidity and winds every ten minutes. The heights and accuracies were the same as described earlier for the met station. The values recorded by this instrument were used for presentation in the atlas for the rest of the experiment, although the other sensors were still operational and provided intercomparisons for the post-calibrations described above.
Therefore, with the exception of the gap from March 28 to 30, all basic meteorological parameters were obtained by at least one sensor throughout the experiment at the O-Camp. Humidity was the one exception; it was available only when the met station was operational.
O-Camp Upper-air Measurements
Upper-air measurements of the basic meteorological parameters were obtained from rawinsondes launched from the O-Camp. The rawinsondes were launched two or more times each day. This system was manufactured by the VIZ Corporation. The winds were measured by an Omega navigation tracking system on each rawinsonde.
The accuracy of the temperature and dewpoint temperature was 0.2 degree C and 1.0 degree C respectively, while height was accurate to 30 m. Vector wind speed was usually accurate to 1.0 m/s, although in shear regions and near the surface errors may increase to 2.0 m/s. Sometimes, the Omega tracking system had problems and errors were extreme. These bad periods have not been removed from the data and can be identified by spikes or false jets in the sounding data. A comparison of data obtained from two profiles made within an hour confirmed the above accuracy estimates. Because rawinsonde measurements are instantaneous, they do not necessarily represent the average conditions, particularly if strong secondary circulations are present.
Acoustics Camp (A-Camp) Surface Measurements
Wind speed, wind direction, temperature, humidity and pressure were obtained from a Coastal Climate WeatherPak meteorological station (met station) and recorded on Hewlett-Packard 200 series computers. The data were averaged over ten-minute periods. The winds were measured at a height of 2.82 m above the ice surface. Temperature, humidity, and pressure were measured at 2.24 m. The temperature was accurate to 0.5 degree C; relative humidity, 8.0 percent; wind speed, 0.2 m/s; wind direction, 5.0 degrees; and pressure, 2.0 mb. The pressure data show some high frequency fluctuations that are not believed to be real.
The A-Camp data were obtained entirely from the met station and contain no gaps larger than one-half hour. No editing of the data was needed and the above accuracies and heights apply throughout the measurement period.
A-Camp Upper-air Measurements
There were no upper-air measurements taken at A-Camp.
The header record contains:
1. LOC platform label , e.g. MIZEX84HM, CEAREXPB, etc.
2. XLAT latitude (degrees north)
3. XLON longitude (degrees east are positive, degrees west are negative)
4. IDATE date (YYMMDD; i.e. year, month of year, day of month)
5. ITIME time at start of sounding (HHMM); i.e. hour, minute
6. IMAX number of records in the sounding
The profile data records contain:
1. RCOUNT record counter for sounding = 1.0 to IMAX
2. TA air temperature (degrees C)
3. TD dewpoint temperature (degrees C)
4. RH relative humidity ( percent)
5. PR pressure (mb)
6. WD wind direction (azimuthal)
7. WS wind speed (m/s)
8. Z height (m)
If one of the above variables has a value of -999.0, the value of that quantity was not available or was invalid. A FORTRAN program presented in the CD-ROM documentation file will read any of the upper-air files.
Additional information and graphical plots of the data are contained in hard-copy meteorological atlases (Lindsay 1984, 1985, 1986; Guest and Davidson 1988; Lackmann et al. 1989; Guest and Davidson 1989). In some cases, maps of sea level pressure analyses, maps of platform and ice edge positions, and radiation information are not presented on the CEAREX CD-ROM but are contained in the atlases.
All times in the data set and documentation are Universal Time Convention (UTC).
For a complete list of all CEAREX investigators, please refer to the CEAREX Investigator Address List.
Guest, P. S., and K. L. Davidson. 1989. CEAREX "O" and "A" Camp Meteorology Atlas. Naval Postgraduate School, NPS-63-89-007, 64 p.
Guest, P. S., and K. L. Davidson. 1988. MIZEX 87 Meteorology Atlas. Naval Postgraduate School, NPS-63-88-004, 140 p.
Lackmann, G. M., P. S. Guest, K. L. Davidson, R. J. Lind and J. Gonzales. 1989. CEAREX/POLARBJOERN Meteorology Atlas. Naval Postgraduate School, NPS-63-89-005, 545 p.
Lindsay, R. W. 1986. MIZEX 84 Six Hourly Radiosondes: POLAR QUEEN, POLARSTERN, HAAKON MOSBY, VALDIVIA. Polar Science Center, University of Washington, Technical Report, 240 p.
Lindsay, R. W. 1985. MIZEX 84 Integrated Surface Meteorological Data Set and Meteorological Atlas, 2nd ed. Polar Science Center, University of Washington, Technical Report, 240 p.