SciTech in Oceanography

How to speed up the launch of termial under OSX...

2011-04-14T14:06:00.000-04:00

Recently I noticed that the launch of the mac osx terminal is getting slow and slpw. After google the problem online, I found that it seems to be a problem of the log files. A solution for that is to type the following command in your terminal:

sudo rm -rf /private/var/log/asl/*.asl

For more information, refer to http://osxdaily.com/2010/05/06/speed-up-a-slow-terminal-by-clearing-log-files/

The effects of Tehuantepec and Papagayo Eddies on the Biological Production

2010-03-18T18:57:00.000-04:00

Distribution of chlorophyll in surface ocean observed from space (SeaWiFS, 1997-2000 mean) shows some strong singles in the region where the Tehuantepec and Papagayo eddies occur. It seems that the eddies have some effects on the Biological production. Could we do some little work on that?

Can the low-frequency currents along the EPR result in low-frequency earthquake?

2010-01-05T01:33:00.000-05:00

Recently, Dr. Thurnherr and I just published a paper on GRL: Subinertial variability in the deep ocean near the East Pacific Rise between 9° and 10°N (http://www.agu.org/pubs/crossref/2011/2011GL046675.shtml). When I was thinking about the broader impacts of our work, I came to a question that whether the low-frequency variability we observed in the deep ocean can affect the seismicity near the ridge crest. Prof. Tolstoy’s team at Lamont has written several papers mentioning that tides are related with the seismicity over mid-ocean ridges and that is partly due to the tidal lodging effects. From our study we know the low-frequency variability in the deep ocean near the EPR is related with the westward-propagating mesoscale eddies, which can also affect the bottom pressure over the ridge crest. Actually our bottom pressure data over the ridge crest indeed show some low-frequency variability. It seems natural to have this question that whether the mesoscale eddies have the same effects of tides, right? To test this hypothesis, we need to find a huge microearthquake data, and compare with the features of mesoscale eddies revealed in the satellite data.

References:
[1] D. Stroup, D. Bohnenstiehl, M. Tolstoy, F. Waldhauser, and R. Weekly. Pulse of the seafloor: Tidal triggering of microearthquakes at 9◦50′N East Pacific Rise. Geophys. Res. Lett., 34:15, 2007.
[2] D. Stroup, M. Tolstoy, T. Crone, A. Malinverno, D. Bohnenstiehl, and F. Waldhauser. Systematic alongaxis tidal triggering of microearthquakes observed at 9◦50′N East Pacific Rise. Geophys. Res. Lett., 36, 2009.

How did the mixing at the bottom of the mixed layer change when ENSO happens?

2009-11-10T11:08:00.000-05:00

When ENSO happens, the present theory and observation suggest that the depth of the mixed layer in the eastern and western Pacific Ocean change and the upwelling will therefore be weakened or strengthened. But how about the mixing processes at the bottom of the mixed layer? Maybe we could use some TOGA data to do some research on that.

Recently, there is paper on the variation of mixing with tropical instability waves and it could be a good reference for this possible work.
[1] J. Moum, R. Lien, A. Perlin, J. Nash, M. Gregg, and P. Wiles. Sea surface cooling at the Equator by subsurface mixing in tropical instability waves. Nature Geoscience, 266:761–765, 2009.

如何在Fedora 11上安装Intel C++ Compiler 11.0 和 Intel Fortran Compiler 11.0

2009-10-31T02:52:00.001-04:00

1. 要在Fedora系统上安装 Intel C++ Compiler 11.0 或 Intel Fortran Compiler 11.0，需要libstdc++.so.5，而Fedora 11自带的是libstdc++.so.6.0.10，所以我们要做的第一步是下载并安装 libstdc++.so.5。需要注意的是有两个不同版本的libstdc++.so.5（libstdc++.so.5 (libc6,x86-64) ，libstdc++.so.5 (libc6) ）。读者应当根据自己机器内核选择不同的版本。对于32位的版本，读者可以登入root帐号，利用如下命令安装：
yum install libstdc++.so.5
对于64位的版本，可从下面的地址下载相应的库文件并安装：ftp://ftp.muug.mb.ca/mirror/fedora/linux/releases/10/Everything/x86_64/os/Packages/compat-libstdc++-33-3.2.3-64.x86_64.rpm。安装时候，系统可能会提示已经存在更新的版本，在此情况下，可使用如下命令进行强制安装：
rmp --force compat-libstdc++-33-3.2.3-64.x86_64.rmp

2. Fedora默认的SELINUX的安全模式会阻止Complier的安装，我们可以通过以下的命令解决：
#su
password:
#vim /etc/sysconfig/selinux
将“SELINUX=enforcing”改为“SELINUX=permissive”后保存退出。
#reboot

3. 从intel的官方网站下载l_cproc_p_11.1.059.tgz或l_cprof_p_11.1.059.tgz，并用以下命令解压：
#tar -xzvf l_cproc_p_11.1.059.tgz
然后cd到该目录底下，执行安装的脚本文件：
#./install.sh
接着一路回车就行了。

4.设置环境变量：网友提供的方法是在非安装目录运行如下命令：
#source /bin/iccvars.sh [ia32|intel64|ia64]
or
#source /bin/iccvars.csh [ia32|intel64|ia64]
最后面的参数视OS的具体情况而定。

不过我实验的结果并不成功，我们可以采用直接添加路径的方法解决这个问题，如果你用的是bash的话，方法是在.bashrc文件中添加如下语句：
PATH=$PATH:$HOME/bin:/opt/intel/Complier/11.1/059/bin/intel64
这里/opt/intel/Complier/11.1/059/bin/intel64是icc和ifort所在的目录，请根据具体情况进行相应的修改。

5. 如果一切顺利的话，你现在应该可以利用icc和ifort进行编译了。Enjoy it～

参考资料： http://blog.sina.com.cn/s/blog_5a074c340100dqro.html
http://www.mdbbs.org/thread-19027-1-1.html

How to change the default term of Octave from Aquaterm to X11

2009-10-02T01:21:00.000-04:00

Octave is a great sci software, which is very similar to Matlab. What makes it better than Matlab is the price 0. However, when the Octave is installed on Mac, the default term for figure output is Aquaterm. Although Aquaterm looks pretty good, one big disadvantage is that you can not close the windows by just typing ‘close’ in the terminal and you have to close them manually. Different from Aquaterm, X11 can work with Octave better. You can just use the normal Matlab way (type ‘close’ or ‘close all’) to shut windows down. How to make it? Quit simple, put the following words in ~/.profile, which you can find in your home directory.

export GNUTERM='x11'

Possible Relationship between Arctic Oscillation and the 11-years cycles of solar irradiance

2009-09-25T15:58:00.000-04:00

Is the decadal variability associated with the Arctic Oscillation related with the 11-years cycles of solar radiation?
Lean, J. and Rind, D. (Science, 2001) mentioned many mechanisms through which the solar cycles could affect the earth climate. Is it possible that some positive or negative feedbacks could amplify the small variability exerted by solar with a period around 11 years.
Reference: [1] J. Lean and D. Rind. Earth’s response to a variable sun. Science, 292(5515):234–236, 2001.

Energy source of climate system

2009-09-14T13:29:00.000-04:00

It is said that the sun is the ultimate source of energy for the climate system. It is true for the current state when the tectonic seems pretty quiet, but how about other period when the geosphere was more active? Any such period exists? If so, could the geothermal play some roles in the climate system? Is the energy exported by human itself large enough to affect the climate system? Seems not.

Why do the frequencies of glaciers in the past 2.5 million years change?

2009-08-27T13:51:00.000-04:00

In the pass 2.5 million years, the frequencies of glaciers changed. The last 700,000 years were marked with oscillations of 100,000 years, but prior to 700,000 years ago, the oscillations are much weaker and show frequencies of 41,000. What happened? Did oceans play some roles in this process?

What is the ocean circulation like in the Cretaceous?

2009-08-27T13:32:00.000-04:00

The middle Cretaceous (120-90 million years ago) is substantially warmer than the present. The deep ocean temperature can reach up to 10-20 C. Therefore, the circulation could be totally different from the present state. Furthermore, the carbon cycle and atmospheric circulation could also be different. Any works on these issues?

Evidences show the increasing CO2 happened first due to the intensive volcanism eruption, then the temperature will rise for the greenhouse gas effect.

One thing needs to be noted here is the bathymetry then is totally different from now.

Ocean's likely roles in determining the change of dominant period of Pleistocene glacial cycles?

2009-06-23T17:21:00.000-04:00

Hönisch, B. et al.(Science 2009) mentioned that the dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for as yet unknown reasons.Their reconstruction of the sea surface pCO2 shows a close relationship between atmospheric CO2 concentration and global climate but the drawdown of atmospheric CO2 was not the main cause of the climate transition.

Could the ocean circulation play some roles in this process? The bathymetry changed? The tidal strength changed due to the orbit variation? If so, could the ocean mixing change? Since the ocean mixing is supposed to play essential roles in determining the overturning circulation, ocean mixing pattern changed could then result in overturning circulation change, which would induce variation of heat transport? Finally ~

Whether the latitudinal dependence of ocean mixing is true or not

2009-06-22T12:38:00.000-04:00

Gregg M (2003) proposed a possible relationship between the latitude and the ocean mixing based on microstructure data. However, the data sets he used seems cannot tell the visual relationship between them are real, since the high diffusive region appearing in the mid-latitude are associated with rough topography and the low diffusive region in the low-latitude appear with smooth topography. The decreasing mixing toward low-latitude is thus due to either the changing latitude or the changing topography. More data set are needed to examine the possible relationship.

How to automatically generate file header using Emacs

2009-06-22T12:15:00.000-04:00

When we use emacs to write text files, file headers containing specific information, such as the author, the date of creation, the data of update, can be generated automatically. The following are steps to make it work.

Download the file header2.el. from http://www.emacswiki.org/emacs/header2.el
Add the following to your .emacs file, which you can find in the $home directory. (add-to-list 'load-path' "here is the directory where you store the header2.el")
Then put the following to your .emacs file:
(add-hook 'write-file-hooks 'auto-update-file-header)
(add-hook 'emacs-lisp-mode-hook 'auto-make-header)
(add-hook 'c-mode-common-hook 'auto-make-header)

(add-hook 'tex-mode-hook 'auto-make-header)
4. To make the header personal, you can change the header2.el by comment or uncomment different variables.

Spatial distribution of mixing and the relationship between TKE dissipation rate and N

2009-05-28T17:01:00.000-04:00

Several points that could be mentioned in the paper so-called the spatial distribution of mixing in the Atlantic Ocean.

Kunze’s data show the relationship between N and ϵ qualitatively.

Data sets from Brazil Basin and DYNAMUCK show the relationship (in the ocean interior) quantitively.

How to explain this relationship from the view of dynamics?

Could the second point be an evidence to prove the pattern shown in Kunze’s data real?

Also, Whether this high dissipation associated with high N is a possible sink for the low-mode internal tides seems important as well.

Effects of melting down of ice on the climate system

2009-02-20T17:01:00.000-05:00

What is the eﬀect of melting down of ice cover in the Arctic Ocean? Is it a negative feedback to the climate system? More CO2 could be absorbed due to the removal of ice cover which used to prevent the contact of air and sea water. As a result, the temperature could decline. Is this true or false?

Controlling factors on air-sea CO2 flux

2008-12-10T16:59:00.000-05:00

The relationships of air-sea CO2 ﬂux (pCO2 ) and controlling factors. Could we just calculate the correlation coeﬃcients between the CO2 ﬂux (pCO2 ) and some speciﬁc factor? Or could we utilize the EOF methods to investigate the correlation between the spatial patterns?

Ocean uptake of CO2

Ocean pCO2

Eddy diﬀusivity. Could we approximately use the global tidal dissipation to express the eddy diﬀusivity?

Heat ﬂux

Ocean circulation

Wind

Salinity

Water color

Examine the energy sources of ocean mixing by comparing its spatial distribution with results of baroclinic tide models

2008-12-09T16:56:00.000-05:00

Could we investigate the energy sources of ocean mixing by comparing the ﬁgures of baroclinic tides (Egbert and Ray, 2000) with ﬁgures of eddy diﬀusivity from Kunze et al. (2006). It seems to me that they match each other quite well. Several unmatched hot- spots could be due to other processes, such as wind-generate near-inertial oscillation or lee waves generated by interactions between strong currents or strong eddies with topography.

Use high resolution numerical model to study the sub-grid processes and to test various parameterizations

2008-12-08T16:55:00.000-05:00

How to learn eddy diﬀusivity or eﬀects of sub-grid processes in a numerical model? Could we do that by changing the resolution of the model and then compare the diﬀerent results?

• Using high-resolution model to calculate the diﬀerent quantities, such as velocity, temperature and salinity.

• Using low-resolution model with parameterization to calculate same quantities. Then we can compare the results and ﬁgure out wether the parameterization model works well.

• We could also ﬁgure out the relationships of diﬀusivity or sub-grid process and the grid size.

Bathymetry Spectra and the possible application on studying the generation of internal lee waves

2008-12-07T16:51:00.000-05:00

Goﬀ (1991) showed that the ocean bathymetry has well-behaved horizontal wave- number spectrum. Could this be used to approximate the high-wavenumber component which cannot be resolved with current Smith and Sandwell Data (Smith and Sandwell, 1997)?

St Laurent and Simmons (2006) show a method in the horizontal wave-number space to estimate the internal tides or lee wave generated through the interaction between currents and topography. However, they paid more attention to the internal tides due to the limitation of bathymetry data. Here, Could we beneﬁt from the work mentioned above (Goﬀ, 1991)?

If the answer is Yes, we can estimate the energy of generate lee wave and examine the role it plays in closing the ocean energy budget.

Possible relationships between the intraseasonal oscillation in the deep ocean around EPR and MJO

2008-12-05T16:47:00.000-05:00

MJO can induce low frequency oscillation (Kelvin Waves) in the ocean. And these oscillation can propagate eastward. Many features of low frequency (30-60 days) have been found along the western coastal of North and South American. However, comparing to the upper ocean signals, few have been found in the deep ocean. As I am aware, there is only one paper (Matthews et al., 2007) which shows such an oscillation can penetrate downward to a depth of 1500m.

Due to the presence of the East Paciﬁc Rise, if this downward propagating Kelvin wave can reach it, part of the energy will be trapped and propagate along the ridge. This along-ridge propagating waves could be very important for the material transport in a certain time scale (30-60days). Also, these waves could interact with the topography to either generate lee waves or induce overﬂow, both of which could result in some temporal signals in the mixing events.