Introduction
The Icelandic Meteorological Office (IMO) conducted measurements in
the central Iceland Sea in the time period 2007–2009, specifically
in the northern Dreki area on the southern segment of the Jan Mayen
Ridge. The deployment was a part of a governmental preparation
project for the potential exploration for oil and gas on the
Icelandic continental shelf and the purpose of the measurements was
to obtain information on the local weather. The measurements were
conducted with a meteorological buoy making basic in situ
meteorological measurements as well as some oceanographic
measurements. After the end of the deployment the government phased
out the project and the data remained untouched and unused for
several years.
Lately the data have become of interest to the scientific
community. One reason is the discovery of the North Icelandic Jet
, a deep-reaching ocean
current hypothesized to originate in the Iceland Sea
, although the exact source and related
water mass transformation processes are not known. The Iceland Sea
is a local heat flux minimum and thus the oceanic deep convection
is not driven by the average large-scale atmospheric
circulation . However,
used the buoy data presented here to examine the surface
meteorological condition in the central Iceland Sea and concluded
that although on average the heat flux was low, on shorter timescales the Iceland Sea frequently experienced high heat flux events
in the wintertime.
The buoy measurements are unique due to the sparsity of in situ
observations over the ocean, especially in this region, and
used it in an evaluation of ocean
surface winds from reanalysis data sets and scatterometer-derived
gridded products.
Although measurements from the data set have been used in both
and they
have not been made publicly available earlier. However, now the
data set has been quality-checked, suspect data removed and made
publicly available from the PANGAEA Data Publisher.
The purpose of this article is to give a full description of the
buoy, deployment and measurements for any future users of the data
set.
In the following section there is a description of the buoy,
parameters measured and the deployment. Section
contains information on the measurements, the availability of data
and, where possible, reasons for periods of missing data. Lastly,
final remarks are in Sect. .
The instrumentation of the buoy: parameters measured, instrument, range and accuracy according to manufacturers.
Parameter
Instrument
Range
Accuracy
Air pressure
Vaisala PTB 220A
500–1100 hPa
±0.15 hPa
Air temperature
OCEANOR/Omega 300006
-40–+75∘C
±0.1∘C
Relative humidity
Vaisala HMP 45A
0.8–100 %
±2–3 %
Wind speed
Gill WindSonic
0–60 ms-1
±2%
Wind direction
Gill WindSonic
0–359∘
±3%
Wave height
Fugro OCEANOR Wavesense
0–20 m
±0.05 m
Wave period
Fugro OCEANOR Wavesense
1–30 s
±0.15 s
Wave direction
Fugro OCEANOR Wavesense
0–360∘
±1∘
Current speed
Aanderaa DCS 4100R
0–300 cms-1
±1%
Current direction
Aanderaa DCS 4100R
0–360∘ magnetic
±5–7.5 %
Water temperature
Aanderaa DCS 4100R
-10–+43∘C
±0.16∘C
Location
OCEANOR Jupiter 12 GPS receiver
n/a
±5 m
Orientation
Precision Navigation TCM 2.5 electronic compass
n/a
±1∘
The meteorological buoy on board the Icelandic Marine Research Institute's vessel Bjarni Sæmundsson on 22 November 2007, the day before deployment. Photo: Sighvatur K. Pálsson.
The buoy and the deployment
The buoy was a SEAWATCH Wavescan wave buoy from Fugro OCEANOR that
measured wave, current and meteorological parameters
. The hull was discus-shaped with a keel mounted
at the bottom to prevent capsizing of the buoy. The meteorological
sensors and the antennae were mounted on a mast (see
Fig. ). The hull had
a diameter of 2.8 m and total height (mast to keel) of
6.75 m. It had solar panels and sealed lead acid backup
batteries. Due to the low sun radiation condition during winter at
the measurement site the buoy was also supplied with lithium
batteries. Table lists the instrumentation of
the buoy and, for each parameter, range and accuracy according to
the manufacturers .
The location of the buoy, November 2007–April 2009. The retrieval location on 21 August 2009 is marked with a star.
Buoy measurements, units, resolution and short names used in the hourly data set.
Name
Parameter
Units
Resolution
Short name in data set
Location
Latitude
lat
degrees
0.01
Latitude
Longitude
lon
degrees
0.01
Longitude
Meteorological
Sea level pressure
P
hPa
0.1
PPPP
Air temperature at 3.5 m height
T
∘C
0.001
TTT
Relative humidity at 3.5 m height
RH
%
0.01
RH
Wind direction at 4 m height
Wdir
degrees
0.01
dd
Wind speed at 4 m height
WSP
m s-1
0.001
ff
Wind gust at 4 m height
WGS
m s-1
0.001
ff gust
Oceanographic
Water temperature at 1.5 m depth
Tw
∘C
0.01
Temp
Current direction at 1.5 m depth
Cdir
degrees
0.1
DIR
Current speed at 1.5 m depth
CSP
cm s-1
0.001
V
Height of highest wave
Hs
m
0.001
Wave h max
Period of the highest wave
s
THs
0.001
PwPw
Heave parameters computed from spectral analysis
Significant wave height (Hs), estimate
Hs
m
0.001
Wave h
Significant wave height (Hs), estimate lower frequency band
Hsa
m
0.001
Wave h
Significant wave height (Hs), estimate mid-frequency band
Hsb
m
0.001
Wave h
Mean wave period (Tz), estimate 1
Tz1
s
0.001
PwPw
Mean wave period (Tz), estimate 2
Tz2
s
0.001
PwPw
Mean wave period (Tz), estimate 2, lower frequency band
Tz2a
s
0.01
PwPw
Mean wave period (Tz), estimate 2, mid-frequency band
Tz2b
s
0.001
PwPw
Period of spectral peak
Tp
s
0.001
Time
Directional wave parameters computed from spectral analysis
Mean spectra wave direction
Mdir
degrees
0.01
Wave dir spr
Mean spectra wave direction, lower frequency band
Mdira
degrees
0.01
Wave dir spr
Mean spectra wave direction, mid-frequency band
Mdirb
degrees
0.01
Wave dir spr
Directional wave parameters
High-frequency mean wave period
Thhf
s
0.01
Time
Wave spreading at spectral peak period
SPSTp
degrees
0.001
Wave dir spr
List of periods where measurements are missing or clearly erroneous, parameters affected and reasons.
Time
Parameter
Reason
31 Dec 2007 00:00 UTC–6 Jun 2008 18:00 UTC
Location
Errors in location records
6 Jun 2008 19:00 UTC–7 Jun 2008 12:00 UTC
All data
The buoy was serviced
28 Oct 2008 01:00 UTC–1 Feb 20:09 UTC
P
The pressure measurements were too high*
27 Nov 2008 12:00 UTC–27 Nov 2008 16:00 UTC
Relative humidity
Relative humidity >100%
3 Dec 2008 09:00 UTC–11 Dec 2008 10:00 UTC
Relative humidity
Relative humidity >100%
12 Dec 2008 18:00 UTC
Location
Errors in location records
2 Feb 2009 08:00 UTC–1 Mar 2009 02:00 UTC
Relative humidity
Relative humidity >100%
20 Feb 2009 12:00 UTC–24 Feb 2009 09:00 UTC
All data
Measurements were missing
17 Apr 2009 09:00 UTC–end of deployment
Location and current parameters
GPS sensor failed
17 Apr 2009 09:00 UTC–end of deployment
Water temperature
Temperature sensor failed
* Pressure measurements were compared to ECMWF operational forecasts.
The buoy was deployed in the northern Dreki area
on the southern segment of the Jan Mayen Ridge, anchored at
68.47∘ N, 9.27∘ W from 23 November 2007 to
21 August 2009 (see Fig. ), drifting inside a circle
with a diameter of approximately 2 km. It was serviced
once during the deployment, on 7 June 2008. The internal compass
and the GPS sensor failed on 17 April 2009 between 08:00 and
09:00 UTC. Thus after that time the exact location of the
buoy is not known and there are no measurements of current speed
and direction. After the failure the buoy broke free. Using the
locations of the satellites retrieving information from the buoy
it can be seen that this happened in May and the buoy then started
drifting northward. It was rescued by the Marine Research
Institute on 21 August 2009 at 69.40∘ N,
9.62∘ W, having drifted about 104 km to the north
from the mooring location; see location in Fig. .
Monthly average values, as well as maximum and minimum values where appropriate, for most of the
meteorological parameters. The dew point, Td, and the vapour pressure,
Pv, are calculated using an equation from . Insufficient data is represented with –.
T‾
Tmax‾
Tmax
Tmin‾
Tmin
Td‾
Pv‾
P‾
Pmax
Pmin
WSP‾
WSPmax
WGSmax
∘C
∘C
∘C
∘C
∘C
∘C
hPa
hPa
hPa
hPa
m s-1
m s-1
m s-1
Dec 2007
1.3
2.7
5.1
-0.3
-6.4
-1.0
5.8
999.7
1024.4
966.2
8.7
16.3
25.8
Jan 2008
-0.2
1.1
3.9
-1.3
-7.7
-2.7
5.2
997.3
1019.3
971.1
8.5
16.1
22.9
Feb 2008
-0.6
0.7
3.6
-2.1
-9.5
-3.1
5.1
998.9
1047.4
949.5
9.6
18.3
27.0
Mar 2008
-2.1
-0.8
2.5
-3.4
-7.3
-5.2
4.4
1007.5
1020.4
977.8
8.7
16.4
25.6
Apr 2008
-0.4
0.4
2.4
-1.4
-4.6
-2.4
5.3
1016.7
1035.2
999.8
7.0
14.5
22.1
May 2008
1.6
2.4
4.6
0.8
-3.4
0.3
6.4
1024.2
1039.2
1007.8
5.1
14.0
17.7
Jun 2008
4.3
5.0
6.9
3.5
1.3
2.7
7.5
1016.0
1024.5
1007.4
6.1
11.5
15.5
Jul 2008
6.9
7.6
10.7
6.1
2.7
6.2
9.6
1012.9
1028.5
987.9
5.7
11.2
16.4
Aug 2008
8.7
9.2
10.9
8.0
5.7
6.8
10.0
1009.2
1028.9
984.0
5.9
14.6
20.8
Sep 2008
7.6
8.4
10.7
6.7
2.0
5.5
9.3
1007.6
1021.6
975.3
7.6
16.3
27.7
Oct 2008
2.9
4.3
7.1
1.4
-4.8
0.3
6.6
992.3
1014.1
940.6
9.0
17.8
29.8
Nov 2008
-0.3
1.4
6.1
-2.1
-8.0
-3.2
–
–
–
–
8.8
16.9
25.8
Dec 2008
0.7
1.8
4.0
-0.6
-6.1
-1.7
–
–
–
–
8.2
16.1
25.1
Jan 2009
0.0
1.3
3.6
-1.6
-8.0
-1.9
–
–
–
–
7.6
17.2
24.4
Feb 2009
-2.0
-0.6
2.6
-3.3
-8.5
-2.3
5.3
1026.6
1033.0
994.7
7.9
17.0
23.4
Mar 2009
-0.5
0.8
2.5
-1.8
-5.7
-2.1
5.3
1004.5
1019.9
980.5
8.5
19.3
25.3
Apr 2009
0.7
1.7
3.4
-0.4
-5.2
-0.9
5.9
1010.2
1027.9
993.3
7.4
14.7
21.9
May 2009
2.9
3.6
4.8
1.9
-1.3
2.0
7.1
1010.1
1034.1
983.4
6.6
14.1
20.5
Jun 2009
3.7
4.5
8.4
2.9
0.0
1.6
7.1
1019.7
1030.6
994.9
4.3
14.8
18.7
Jul 2009
7.1
7.9
9.6
6.2
3.6
5.8
9.3
1015.3
1025.2
996.2
5.3
11.6
16.0
Aug 2009*
8.6
9.2
10.0
7.8
6.1
7.3
10.4
1010.4
1021.3
978.0
5.7
14.1
25.6
* Only 21 days as the buoy was retrieved on 21 August at 20:00 UTC.
Monthly average values for a few of the oceanographic parameters: water temperature, current speed, mean wave period, height of highest wave, significant wave height and period of spectral peak. The parameter Δ(Tw-T)‾ is the monthly averaged difference between the water temperature and the air temperature. Insufficient data is represented with -.
TWater‾
Δ(Tw-T)‾
CSP‾
TZ‾
Hmax‾
Hs‾
Tp‾
∘C
∘C
cm s-1
s
m
m
s
Dec 2007
3.0
1.7
14.7
8.3
5.7
3.9
11.0
Jan 2008
2.2
2.3
14.5
8.0
5.2
3.5
10.8
Feb 2008
1.4
2.0
17.2
8.1
5.9
4.0
10.7
Mar 2008
1.2
3.3
14.7
7.4
4.9
3.3
9.6
Apr 2008
0.8
1.2
11.7
6.7
3.3
2.2
9.0
May 2008
2.2
0.5
8.8
6.1
2.2
1.5
8.2
Jun 2008
5.1
0.8
11.2
5.9
2.3
1.6
7.8
Jul 2008
7.4
0.5
12.0
5.6
2.1
1.5
7.3
Aug 2008
9.5
0.8
13.2
5.8
2.3
1.6
7.6
Sep 2008
8.5
0.9
14.6
6.7
3.8
2.6
8.8
Oct 2008
5.2
2.3
15.8
7.9
5.6
3.9
10.3
Nov 2008
3.0
3.3
15.1
7.6
5.2
3.5
10.3
Dec 2008
2.1
1.4
13.1
7.8
5.0
3.4
10.5
Jan 2009
1.6
1.6
11.2
8.2
5.1
3.5
10.8
Feb 2009
1.3
3.3
10.7
7.8
4.6
3.1
10.5
Mar 2009
1.1
1.6
11.4
7.3
4.5
3.1
9.7
Apr 2009
1.7
1.3
11.1
6.8
3.7
2.5
8.9
May 2009
–
–
–
6.4
3.0
2.0
8.4
Jun 2009
–
–
–
5.6
1.7
1.2
7.1
Jul 2009
–
–
–
5.7
2.0
1.3
7.6
Aug 2009*
–
–
–
6.2
2.5
1.7
8.2
* Only 21 days as the buoy was retrieved on 21 August at 20:00 UTC.
Measurements of mean sea level pressure (hPa). The gap from 28 October 2008 to 1 February 2009 is due to measurement errors. A histogram of measurements is inset.
Measurements of air temperature (∘C) at 3.5 m height. A histogram of measurements is inset.
Measurements of wind speed and wind gust (m s-1) at 4 m height: time series (a) and histograms of wind speed measurements (b) and of wind gust measurements (c).
The measurements
A list of measurements conducted, units, resolution and short names
in the data set can be found in Table . The data were
recorded every hour. The measurement time period was 23 November
2007 03:00 UTC–21 August 2009 20:00 UTC and
Table contains a list of times when some or all of the
measurements were missing and the reason when known. In addition
other obvious errors were removed, such as spurious
longitude =0∘.
A wind rose, showing the frequency (%) and wind speed (m s-1) for different wind directions at 4 m height (22.5∘ bins).
Measurements of relative humidity (%) at 3.5 m height. A histogram of measurements is inset.
Measurements of water temperature (∘C) at 1.5 m depth. Air temperature is shown in the background. A histogram of water temperature measurements is inset.
Table contains averages for most of the
meteorological parameters measured, and maxima and minima where
appropriate, while Table contains averages for the main oceanic
parameters. The daily values and average, maximum and minimum values
are calculated and then the monthly averages of the daily values. In
addition to measured values the dew point, Td, the vapour
pressure, Pv, and the difference between the water temperature
and the air temperature are calculated and the mean values included
in the table.
Air pressure
Air pressure was measured with a Vaisala PTB220A digital barometer
designed to operate over a wide pressure and temperature range
. A comparison of the pressure data to ECMWF
operational analysis confirmed the suspicion that the measurements
were off for months after the passing of the deepest low, on
24 October 2008, possibly due to water in the sensor inlet. The
error was not just a bias error; in addition, during the first half
the pressure was too high, while during the second half the
magnitudes of extreme were too small and the extrema were not all
accounted for. From 1 February 2009 the measurements were in
agreement with ECMWF analysis (not shown). To avoid any confusion
the pressure data from 24 October 2008 to 1 February 2009 are removed
from the data set. The buoy measurements of mean sea level
pressure are shown in Fig. , with the exception of the
erroneous data. During the deployment, the average pressure was
1009 hPa, varying from a minimum of 941 hPa to
a maximum of 1047 hPa. Note that the maximum was measured
on 13 February 2008 and a local minimum of 950 hPa a week
later, on 21 February 2008, emphasizing the variability of the
synoptic situation in the region.
Measurements of current speed (cm s-1) at 1.5 m depth. A histogram of measurements is inset.
A frequency rose, showing the frequency (%) and current speed (cm s-1) for different current directions (22.5∘ bins) at 4 m height. Note that current direction is defined as the direction the current is streaming toward, which is opposite to the convention of wind direction.
A frequency rose, showing the frequency (%) and height of highest wave (m) for different wave directions (22.5∘ bins), with wave directions defined in the same way as wind directions.
Air temperature
Air temperature was measured at 3.5 m height with
a OCEANOR/Omega temperature sensor, a robust and compact
sensor. The thermistor element was protected by a sun radiation
screen . The lowest temperature measurement was
-9.5 ∘C and the highest 10.9 ∘C,
a span of about 20 ∘C (see
Fig. ). During late autumn, winter and spring the
temperature variations were much greater than during the summer and
early autumn. The temperature variations during the cool seasons
are related to the variation in weather regimes, from northerly
cold air outbreaks to warm air advection by synoptic cyclones
moving into the area from the south . The
highest temperatures were measured in late summer, mainly in August
and September 2008, while temperatures below
-5 ∘C were measured most frequently in February,
followed closely by January and March.
Wind speed and wind direction
The wind speed, wind gust and wind direction were measured at
4 m height with a Gill WindSonic wind sensor
. It has been shown that during rough seas, due
to sheltering effects and elevation changes, wind measurement by
buoys can be negatively biased
e.g.. Here, no attempt is
made to compensate for a potential bias in the data set; that is
left to the user.
The maximum measured wind was 19.3 ms-1 and the
maximum gust 29.8 ms-1. The gust factor was in general
below 1.5. There was a significant lower wind speed during the
summer months than the winter months (see Fig. ). The
monthly mean wind speed was the highest in February 2008 and lowest
in June 2009 (see Table ).
The wind rose in Fig. shows that the most common
wind directions were northerly to northeasterly, approximately
30 % of the time, and the least common wind directions
were westerly to northwesterly. This is in accordance with wind
directional frequency in Iceland (not shown).
Measurements of significant wave height (m) and the spectral peak period (s). (a) Time series and (b) histograms.
Measurements of the highest wave height (m) and the mean wave period (s). (a) Time series and (b) histograms.
Relative humidity
The relative humidity was measured at 3.5 m height with
a Vaisala HMP 45A relative humidity sensor based on the capacitive
thin film polymer HUMICAP 180 . As the
measurements were made over the sea the relative humidity was in
general high with the lowest measurement at 50 % (see
Fig. ). In all cases of relative humidity below
55 % the air temperature was below freezing and in most
cases winds were light. The mean relative humidity was
87 %.
Water temperature
Water temperature was measured at 1.5 m depth with the
Aanderaa DCS 4100R current speed and water temperature sensor. The
temperature was measured using a temperature-dependent
crystal-oscillator circuit . After 17 April 2009
all measurements from the current sensor were invalid. The water
temperature measurements were thus made over 16 consecutive
months. The lowest temperature was measured in spring and the
highest from the end of July until mid-September. The rise in
temperature during late spring and early summer was slower than the
fall in the autumn (see Fig. ). The lowest and highest
monthly means were in April and August 2008. The air temperature is
also shown in the figure. The amplitude of the water temperature
variations is much less than that of the air temperature. The
differences between the water temperature and the air temperature,
Tw-T, were calculated, and on a monthly basis the difference
varied between 0.5 and 3.3 ∘C, with the least
difference during summer months but large variation during the
winter months, related to different air mass impacting the area.
Current speed and direction
Current speed and direction were measured at 1.5 m
depth with the Aanderaa DCS 4100R current speed and water
temperature sensor. The sensor used the Doppler shift principle and
together with orientation from the internal compass determined
current speed and direction . As mentioned
earlier, after the compass and the GPS sensor broke down on
17 April 2009 all current measurements are missing. As stated in
Sect. the buoy was anchored at 68.47∘ N,
9.27∘ W and drifted inside a circle with a diameter of
approximately 2 km. Here, no adjustments are made to the
measured ocean currents, but a user of the ocean data may want to
consider doing corrections. The mean current speed was
13 cms-1 and the maximum 52 cms-1. The
monthly mean current speed varied from 8.8 cms-1 in
May 2008 to 17.2 cms-1 in February 2008. By
convention, current directions are defined opposite to wind
directions; northerly current moves toward north while northerly
wind is coming from north. The most common current directions were
southwesterly (toward southwest) and easterly directions (toward
east) least common (see Fig. ).
Wave parameters
The wave parameters are measured with Fugro OCEANOR Wavesense,
a robust integrated wave sensor and data logger. Accelerometers,
rate gyros and magnetometers were mounted orthogonally to provide
the basic data. These data were then used as input to algorithms,
which calculated heave, roll, pitch, surge, sway and compass time
series. Significant wave height, wave direction, wave period and
a number of other statistical parameters were then found from these
time series . Figure shows the
frequency of wave directions. By convention, wave directions are
defined in the same way as wind directions. The most common
directions were northeasterly to east-northeasterly, a slight
clockwise rotation from the most common wind directions (see
Fig. ). The least common wave direction was
northwesterly. Figure shows the significant wave
height (the mean height of the highest one-third of the waves) and
the spectral peak period (the wave period with the highest energy)
and Fig. the highest wave height and the mean wave
period (the mean of all wave periods). Both wave height and wave
periods have an annual variation with minimum during summer and
maximum during winter, as well as more variability during winter.
The monthly mean significant wave height varied from
1.2 to 3.9 m and the monthly mean maximum wave height from
1.7 to 5.9 m.