Figures and Tables for
Mesoscale Correlation Length Scales from NSCAT and Minimet
Surface Wind Retrievals in the Labrador Sea
submitted to
Journal of Atmospheric and Oceanic Technology
R.F. Milliff, P.P. Niiler, J. Morzel, A.E. Sybrandy, D. Nychka, and W.G. Large
December, 2001
Figures for LabSea Paper (Fig. 1 - 11)
(click on figure to view larger image)
Fig. 1 : Satellite and drifter observations in the Labrador Sea.
a) AVHRR infrared satellite image of the Labrador Sea region from
NOAA-12 on 30 January 1997, 21:03 UTC. Cold cloud tops and ice surfaces
appear in lighter shades, while the relatively warm sea surface is dark.
The coastlines for Labrador in the southwest and Greenland in the northeast
are overlain in black (image provided by Dr. Ian Renfrew).
b) NSCAT wind vectors on 31 January 1997, 0:52 UTC (revolution no. 2382)
from the Ku-2000 GMF retrievals with six MINIMET observations from within
18 to 53 minutes of the satellite image. Solid arrows are MINIMET drifter
data with observed wind directions and speeds, and open arrows are observed
MINIMET drifter directions and colocated NSCAT speeds. Rain-flagged retrievals
in the NSCAT surface wind vectors have been removed from the snapshot in
panel b . Nonetheless, vector wind retrievals north of 60° N,
and between 55° W and 60° W exhibit rain-contaminated behaviors such
as cross-swath orientation and discontinuities in the implied flow field
that do not make meteorological sense.
Fig. 2 : MINIMET Drifter Components.
Schematics depicting:
the fully deployed MINIMET drifter configuration including surface
and sub-surface floatation, the hydrophone cage, and a holey sock
drogue; an expanded view of the WOTAN instrument configuration; and
an expanded diagram of the surface floatation components.
Fig. 3 : Tracks of all MINIMET drifters
in a) the first deployment (22 October 1996 through 3 March 1997),
and b) the second deployment (19 February 1997 through 28 May 1997).
Open circles mark the deployment locations for each MINIMET drifter, and the filled
circles mark MINIMET drifter positions at the end of the observational
record for each drifter.
Fig. 4 : Sample wind direction calibration diagram for MINIMET
drifter 16895.
Wind direction difference (NSCAT-MINIMET Drifter) vs.
MINIMET Drifter wind direction is plotted for all colocations within
60min and 50km. Colocation symbols correspond to refinements
in the colocation dataset used for MINIMET calibration with NSCAT as
described in the text. A-priori refinements are depicted
according to separation distance (squares), wind speed regime (triangles),
and possible upwind-downwind ambiguity removal errors (diamonds).
Numerals inside each symbol represent temporal separations in the
NSCAT and MINIMET colocations (multiply numerals by 10 minutes). The
dashed line represents a uniform offset and the curve is the result of
a fit of sine and cosine terms derived independently for each drifter
(and reported in Table 2).
Fig. 5 : MINIMET wind speed calibration scatterplot comparisons
with NSCAT wind speeds derived from the NSCAT Ku-2000 GMF.
The lefthand panels depict comparisons for MINIMET drifter 16895 in the sound
frequency bands 1-2 kH (top) and 6-8kHz. Righthand panels
are the combined scatterplots for all MINIMET drifters in the
Labrador Sea deployments.
Fig. 6 : Surface vector wind retrievals
from consecutive NSCAT
descending orbits and coincident MINIMET drifters in the Labrador Sea
on 3 December 1996 ( a) at 1422 UTC for revolution 1548, and
b) at 1603 UTC for revolution 1549). In both panels the satellite
moves from North to South. During rev 1548 the 600km-wide right side
of the swath (24 across-track WVC) covers most of the Labrador Sea.
In the next rev the left half of the swath overlaps with the previous
swath. All 11 MINIMETs of the
first Labrador Sea deployment are depicted in each panel. The MINIMET
observations all occurred within 37 minutes (before or after) of the first
overpass, and again within 32 minutes of the second overpass.
Filled vectors are data with drifter observed wind direction and speed,
and unfilled vectors are observed drifter direction but colocated
NSCAT speed.
Fig. 7 : Time series for drifter 16895
of a) air pressure, b) wind speed, and c) wind direction for
110 days spanning much of the first Labrador Sea deployment. Open circles in wind speed
and direction time series are for colocated NSCAT data as derived from
the Ku-2000 GMF.
Fig. 8 : RMS differences vs. spatial lag
for a) wind speed and b) wind direction from coincident
fields of MINIMET (closed circles) and NSCAT (open circles) observations.
An estimate of the uncertainty (ranges indicated by vertical lines, and
1 standard deviations indicated by boxes) of the RMS differences is provided
for wind direction as described in the text. Rms bin weights in c)
are provided for MINIMET direction (closed circles) and speed (crosses over
circles), and for NSCAT (open circles), where direction and speed are
always sampled together.
Fig. 9 : Record comparisons for nearby MINIMET drifters 16896 and 16886.
Panels depict time series for: a) separation distance;
b) wind speed from MINIMET 16896 (no data for 16886);
c) wind direction (16896 filled circles, and 16886 open circles); and
d) wind direction difference over more than 4 days. Smooth solid
(for 16896) and dashed (for 16886) lines in panel c depict 12hr
running mean wind direction time series. The wind direction differences
in panel d are computed after removing the respective 12hr running means.
Fig. 10 : Spatial correlation model fits
for a) zonal and b) meridional wind component terms
(e.g. u* and v* terms as described in the text).
Plus signs indicate the scatter in each component as a function
of spatial lag bin, and the curve is described by the spatial correlation
model (4) in the text. Parameters and their standard deviations
for the spatial correlation model are listed in each panel.
Fig. 11 : Pre-deployment tests of two engineering MINIMET drifters
off California, when within 100-300m of each other. The top panel compares
time series of wind direction when wind speeds ranged from 6-7ms-1
and the bottom panel is for wind speeds 1-3ms-1. In each panel the
drifter wind direction time series as well as time series from two ship
anemometers are shown. The raw direction time series correspond
to the vertical axes on the lefthand margins. In addition, the MINIMET
wind direction differences are plotted with respect to the righthand
axes. In the top panel the RMS of wind direction differences is 6°,
and 8° in the bottom panel.
Tables for LabSea Paper (1 - 3)
(click on figure to view larger image)
Table 1. MINIMET Wind Direction and Speed Data
MINIMET wind direction and speed data in first and second
deployments. Listed are the dates of the entire wind direction data period,
the number of days with direction data, the number of direction data, the
number of days with speed data, and the number of speed data.
Table 2. MINIMET Calibration Coefficients for Wind Direction and Speed
MINIMET Calibration Coefficients for Wind Direction and Speed. Listed are the
number of co-located drifter and NSCAT data for each drifter, the number of
co-located data used to fit the calibration function, the mean distance
and the mean time difference of co-located data, and the resulting calibration
coefficients. The wind speed calibration coefficients are based on the
1-2kHz band.
Table 3. Root-mean-square wind direction differences of nearby drifters
during steady wind conditions
For each drifter pair the average distance, the average time difference,
the average speed, the number of data, and the rms wind direction differences
are listed. There are five separate events. The direction differences are
based on drifter directions that are adjusted by the half-day running mean of
each drifter (see Fig. 10d).
last modified on September 14, 2001
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