Archive for June, 2010

LIQUID MECCANO 2

Monday, June 28th, 2010

JUST A NEW UPDATE TODAY...

Fig 1.- SSHa field 27 jun 2010. 8 supergears...

Liquid Meccano 1

Sunday, June 27th, 2010

Buen dia  !!

Enclosed find this post with an update for 26th june 2010.
Figure 1 confirm that the last current disagreement stint has finished and Cook (ground true) is flying in a strong surface currents field flowing west, like these observed by the Global models.

Fig 1.- Current fields. 26th June 2010 (Geostrophic field, up and Total field, down).

The Figure 2 (SSHa field) confirms that Cook flies on the south border of a N warm eddy, a similar landscape to this observed the last segments (strong currents flowing west) BUT well reported (since 54 W) by the surface fields output of the global model forecasts..

Fig 2.- SSHa fields. 25th June 2010. Red colour represents currents >0.6 knots.

However, there is another (fascinant !) remark in the SSHa field. I have called it “LIQUID MECCANO”. Anticyclons and cyclone gires observed on the SSHa (figure 3), seems to “engage” like gears gyring in the same direction when contact of an immense clock. A cyclonic eddy located SW Cook is the centre of this successive circles of 4 warm anticyclonic, 6 cold cyclonic and 8 warm anticyclonics rings (figure 3).

Fig 3.- SSHa fields. 25th June 2010. Liquid MECCANO of gyre gears.

This meccano was also observed the last year during the RU27 mission. Scarlet founded some “flower-like” structure of cyclonic and anticyclonic eddies that engaged (cold-warm) or separated (warm-warm, cold–cold). The most fanny is the 4 months after (april 2010), the same “flower – like” features standed in the NE Atlantic. This meccano would avoid lost in the gyring momentum of each particular eddy.

But we can deduce a new and useful finding !! That would also mean that future Atlantic crossing gliders could fly CONSERVATIVE ROUTES (in spite of submesoescalar oscillations).
It looks like the first rutes founded by ancient sailors like Antonio de ALAMINOS, pilot of Juan PONCE DE LEON. Not only were the first European of whom we are certain he visited the territory of what is now the United States 1493-1505, but also he had found the Bahama Channel, which gave a shorter route between Cuba and Europe. Alaminos, who had noticed the unusually strong contrary current at Florida's south coast, is now considered the first sailor who reported a “warm highway” to come back Europe..It was called The Gulf Stream some centuries later.

enjoy !
Force, wind, sea and honour to all of you

Antonio G. Ramos

Luckily, We Aren’t in Antarctica

Friday, June 25th, 2010

We compared the glider and HYCOM from 6/24/2010.

The left graph shows the temperature profile from the glider and compares it to the right temperature profile from the HYCOM model. The temperature was very accurate and so it will contribute minimal error to the heat transport.

These are plots of the U and V components of the current. The glider only takes on measurement for depth average velocity. The glider reported a U velocity of .058 m/s, and a V velocity of -.16  m/s.

East/West Transport

This plot shows the transport predicted by the HyCOM model for the East/West direction. The surface shows a transport of 5 C*m/s West. The maximum eastern transport of about 2.5 C*m/s occurs at about 500 m.

North/South Transport

This plot shows the transport predicted by the HyCOM model for the North/South directions. The surface shows a transport of about 1.5 C*m/s in the South direction. The maximum transport in the North direction of about 0.75 C*m/s occurs at about 500 m depth.

update 23 june 2010

Thursday, June 24th, 2010

Hola a todos ¡

Firstable, let me thanks you Scott, Josh, Oscar and all the Cook team for this great blog present.

I would like to introduce this post with an update for 24th june 2010, NCOM and Hycom current fields (blogged by you) show that the last current disagreement stint apparently has finished (58-55 W).

Fig 1.- Current fields. 23th June 2010 (Geostrophic field, up and Total field, down).

igure 1 show that surface Hycom and NCOM data show a new agreement segment with strong surface currents flowing west at > 0.7 knots (red colour) in some windows.
The Figure 2 (SSHa field) shows that Cook flies on the south border of a N warm eddy or, in other words, in the north border of a S cold eddy. This borderline with a strong SSHa front seems very active. That would mean ahead COOK and in the26.3 N line a similar landscape to these observed the last segments (strong currents flowing west).

Fig 2.- SSHa fields. 23th June 2010. Red colour represents currents >0.7 knots.
Finally an interesting remark observed in the thermocline depth field (Fig. 3). Cooks flied a very active area with strong thermocline depth variations with deep blues anticyclonic gyres and white shallow cyclonic ones. It could affect the disagreement observed behind COOK.
Now Cooks is flying (apparently) a “remanse of peace” reading the thermocline depth update (not strong differences around).

Fig 3.- Thermocline depth fields. 23th June 2010.

Thanks again for this great blog present.

Force wind, sea and honour to all of you
Antonio G. Ramos

Cook’s Flight Characteristics

Thursday, June 24th, 2010

While analyzing Cook's flight characteristics, we have noticed that the glider is experiencing a drastic heading error at the start of each dive and climb.  In the figures below, the blue lines represent downcasts, and the red lines represent upcasts.  At the start of each dive, Cook veers 100 degrees or more to the left, and at the start of each upcast veers about 50 to 60 degrees to the right.  The glider seems to experience a larger range of heading error on downcasts than on upcasts as well.  The first plot shows typical heading error, and the second plot shows a more drastic error in which the glider actually rotated a full 360 degrees.

Taking a closer look at the previous plot (shown below),   the yellow points show that Cook's heading error went from about -2 radians (-120 degrees) to +3 radians (+170 degrees) in less than 10 meters.  From this data, we conclude that the glider rotated a full 360 degrees before heading in the correct direction.  Typically, the fin should be able to steer the glider in the desired direction.

The fin responded to Cook's heading error, but was not able to correct the deviation.  Once the glider was facing more than 180 in the wrong direction, the fin quickly changed position so that Cook would continue spinning in the same direction back to its correct heading.  The figure below shows the position of the fin in radians.

The pitch and roll do not seem to be affected by Cook's heading error and fin position.  The roll, however, does see a slight difference during upcasts and downcasts.  The roll never reaches more than 5 degrees in either direction, but is always slightly to the right and larger during upcasts.

Cook and HYCOM match up

Tuesday, June 22nd, 2010

The glider's data and the HYCOM surface model both show the currents going in the same direction. Despite a head current Cook is still managing about .24 m/s.

Where are the Currents Going?

Monday, June 21st, 2010

So today our task was to calculate and plot the heat transport using both the North/South velocity values and the East/West velocity values for the HyCOM data. We started with quick lesson of how to use simple math functions in MATLAB and were then able to take these values and learn to plot them.

East/West Transport

This is a plot of the East and West heat transport of the HyCOM model versus depth. East is in the positive direction and West is in the negative direction. The upper 1000 meters shows mostly transport west with a maximum value of about 0.75 degrees C meters per second. The depths below 1000 meters show little to no transport.

North/South Transport

This is a plot of North and South heat transport of the HyCOM model versus depth. North is in the positive direction and South is in the negative direction. The upper 1000 meters shows a positive velocity with a maximum at the surface of about 4.5 degrees C meters per second. Below the upper 1000 meters the current velocity is about zero.

Speed

This is a plot of the overall speed versus depth. Speed was calculated by taking the square root of the product of the square of the North/South velocity and adding it to the square of the East/West velocity. Speed is at a maximum near the surface at about 0.175 meters per second.

The Navy’s Predictions are Correct

Friday, June 18th, 2010

So today's task was to look at Cook's data and compare it with the Navy's HYCOM model predictions. Now knowing how to do both in MATLAB we set off to produce some profile plots to make the comparison easier.

Cook Temperature Profile

HYCOM Temperature Profile

This is a comparison of Cook and HYCOM Temperature profiles. Both were constructed using data from Cook and HYCOM on June 18, 2010. Seeing that both show the same descending trend and are close in top and bottom temperatures Cook has confirmed what the HYCOM model predicted.

Cook Salinity Profile

HYCOM Salinity Profile

This is a comparison of Cook and HYCOM salinity profiles. Both were constructed using data from Cook and HYCOM on June 18, 2010. Seeing that both show a similar descending trend and have similar top and bottom salinities, the HYCOM prediction was proven to have been correct using Cook's data. The small difference seen at the surface between the two profiles is due to the heading error of Cook, which we are currently still working to fix.




Learning MATLAB

Thursday, June 17th, 2010

After a crash course in MATLAB from John yesterday, we started the morning by pulling the newest data file from Cook and plotting it in MATLAB. The blue and yellow show the down casts and the red and cyan show the up casts.

June 17, 2010 Depth v. Temperature

This plot is a Depth versus Temperature from Cook's last up and down casts. It shows the surface temperature being around 30 degrees Celsius and declining with depth to a minimum of 5 degrees Celsius. The thermocline can be seen from about 200m to 600m.

June 17, 2010 Depth v. Salinity

This is a plot of Depth versus Salinity from Cook's last up and down casts. The surface salinity is 36.35 psu and the salinity at 1200m is 34.6 psu. The halocline appears around 200m and extends down to about 900m.

June 17, 2010 Surface Salinity

While analyzing our plots we came across something that doesn't look quite right. We had some questions as to why the upper 40m of the salinity plot.  We think this could be due to Cook's current flight pattern which would not allow the sensors to have the right flow through them to provide accurate data.

June 17, 2010 Depth v. Density

This is the plot for Depth v. Density for Cook's last up and down casts. The density at the top is around 1023.5 Kg/m^3. The density decreases with depth to a density of 1032.5 Kg/m^3 at a depth of 1200m.

We will continue to plot CTD data for Cook and will be having another lesson from John today in order to learn to plot the HyCom data.

Cook May See an Unmarked Eddy

Thursday, June 17th, 2010

From Cook's data it appears to be in a clockwise eddy, however the Altimetry says that it should be in a counterclockwise eddy.

The HyCOM data says that the currents are southward and nearly perpendicular to eastward currents reported by Cook. The differences in the information provided by Cook, the Altimetry, and the HyCOM make this an interesting area to examine with the glider.