atmos:citation:research:gpsoccultation
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+ | ====== GPS Occultation ====== | ||
+ | ==== Explanation of Data ==== | ||
+ | |||
+ | The idea of using radio occultations to obtain atmospheric profiles is a relatively new research endeavor. | ||
+ | |||
+ | The COSMIC project began in April 2006 with the lanch of six GPS satellite receivers. | ||
+ | |||
+ | These atmospheric profiles created from the GPS receivers have shown to be very accurate in the upper atmosphere. | ||
+ | |||
+ | ==== References ==== | ||
+ | |||
+ | **[[http:// | ||
+ | R. A. Anthes, C. Rocken, and Y.-H. Kuo\\ | ||
+ | // | ||
+ | 2000 | ||
+ | |||
+ | **[[http:// | ||
+ | R. A. Anthes, P. A. Bernhardt, Y. Chen, L. Cucurull, K. F. Dymond, D. Ector, S. B. Healy, S.-P. Ho, D. C. Hunt, Y.-H. Kuo, H. Liu, K. Manning, C. McCormick, T. K. Meehan, W. J. Randel, C. Rocken, W. S. Schreiner, S. V. Sokolovskiy, | ||
+ | //Bulletin of American Meteorological Society// | ||
+ | 2007 | ||
+ | |||
+ | **[[http:// | ||
+ | W. Schreiner, C. Rocken, S. Sokolovskiy, | ||
+ | // | ||
+ | 2007 | ||
+ | |||
+ | **[[http:// | ||
+ | Juha-Pekka Luntama, Gottfried Kirchengast, | ||
+ | //Bulletin of American Meteorological Society// | ||
+ | 2008 | ||
+ | |||
+ | **[[http:// | ||
+ | Paul W. Staten and T. Reichler\\ | ||
+ | //AGU Fall Meeting// | ||
+ | 2008 | ||
+ | |||
+ | **[[http:// | ||
+ | Paul W. Staten and T. Reichler\\ | ||
+ | //SPARC General Assembly// | ||
+ | 2008 | ||
+ | |||
+ | **[[http:// | ||
+ | Paul W. Staten and T. Reichler\\ | ||
+ | //7th EMS Annual Meeting/8th ECAM// | ||
+ | 2007 | ||
+ | |||
+ | **{{: | ||
+ | Lidia Cucurull\\ | ||
+ | //NOAA Workshop on GNSS RO Improvements to Weather Forecasts// | ||
+ | |||
+ | **{{: | ||
+ | North Dakota Center of Excellence in Space Technology and Operations\\ | ||
+ | |||
+ | **[[http:// | ||
+ | Lidia Cucurull\\ | ||
+ | //JCSDA DA Colloquium, Stevenson, WA//\\ | ||
+ | 2009 | ||
+ | |||
+ | ===== Getting Access to Data ===== | ||
+ | |||
+ | |||
+ | In order to gain access to the data, a username and password must be created. | ||
+ | |||
+ | * Go to the left hand side where it says "CDAAC Data Access" | ||
+ | * Click on the Data User Agreement and click agree | ||
+ | * Fill in the rest of the information | ||
+ | * A user name and a password will be sent to the provided e-mail address. | ||
+ | This can take up to seven days, but will most likely arrive within a day or two. | ||
+ | |||
+ | ===== Getting Data ===== | ||
+ | |||
+ | |||
+ | ==== Wget ==== | ||
+ | |||
+ | Here is the command for Wget to download data from the COSMIC site: | ||
+ | |||
+ | '' | ||
+ | http:// | ||
+ | |||
+ | |||
+ | * Note: There is a data format outline on the COSMIC website which provides information on the different types of data at http:// | ||
+ | |||
+ | * Note: This command is to get the atmPrf data. For this data, the syntax is: cosmic-io.cosmic.ucar.edu/ | ||
+ | |||
+ | * Note: The ncpPrf data is data based from a model. | ||
+ | |||
+ | ==== Bash Script ===== | ||
+ | |||
+ | A bash script was written to download this data. This script will create a subdirectory for each day of the year and download all available data for that day into that subdirectory. | ||
+ | |||
+ | |||
+ | < | ||
+ | X=1 # Initialize starting value for x | ||
+ | while [ $X -le 367 ]; do # Loop over certain values of x. | ||
+ | if [ $X -ge 1 ]; then # For days 1 through 9 | ||
+ | if [ $X -lt 10 ]; then | ||
+ | if [ ! -e " | ||
+ | mkdir " | ||
+ | cd 2008_00${X} | ||
+ | # It is important to use -l 1 so that it doesn' | ||
+ | wget -nd -np -l 1 -r -w 2 --http-user=xxxxx --http-passwd=xxxxx http:// | ||
+ | cd .. # Go down a level | ||
+ | fi # end if | ||
+ | fi # end if | ||
+ | fi # end if | ||
+ | if [ $X -ge 10 ]; then # same as above, just for days 10 through 99 | ||
+ | if [ $X -lt 100 ]; then | ||
+ | if [ ! -e " | ||
+ | mkdir " | ||
+ | cd 2008_0${X} | ||
+ | # It is important to use -l 1 so that it doesn' | ||
+ | wget -nd -np -l 1 -r -w 2 --http-user=xxxxx --http-passwd=xxxxx http:// | ||
+ | cd .. | ||
+ | fi | ||
+ | fi | ||
+ | fi | ||
+ | if [ $X -ge 100 ]; then # Same as above, just for days 100 to 366 (leap year) | ||
+ | if [ $X -lt 367 ]; then | ||
+ | if [ ! -e " | ||
+ | mkdir " | ||
+ | cd 2008_${X} | ||
+ | # It is important to use -l 1 so that it doesn' | ||
+ | wget -nd -np -l 1 -r -w 2 --http-user=xxxxx --http-passwd=xxxxxx http:// | ||
+ | cd .. | ||
+ | fi | ||
+ | fi | ||
+ | fi | ||
+ | X=$( (X+1) ) | ||
+ | done | ||
+ | |||
+ | </ | ||
+ | |||
+ | ===== Software ===== | ||
+ | |||
+ | |||
+ | === ncBrowse === | ||
+ | |||
+ | So far, ncBrowse is the best program for plotting GPS data; however, a program for plotting aircraft data is still being searched for. (Note: The aircraft data works with ncBrowse but plotting vs time, not altitude.) | ||
+ | |||
+ | How to use: | ||
+ | |||
+ | * Open ncBrowse using the command: '' | ||
+ | * Go to file, then open file | ||
+ | * Find the file needed (must end be netcdf format) | ||
+ | * After the file is loaded, click on New Map | ||
+ | * Next, the x and y-axis variables can be chosen by dragging them to the proper spot | ||
+ | * Name the plot and hit done | ||
+ | * On the main screen, scroll to the bottom of the variable list to find the new plot | ||
+ | * Double click to open plot and Parameter Editor | ||
+ | * Can also just double click on a variable from the list to plot without making a new map. | ||
+ | |||
+ | ncBrowse is also helpful when looking at the structure and organization of a netcdf file. The structure of the data can be viewed as a tree or as a table for clarity. | ||
+ | |||
+ | |||
+ | === ncplot === | ||
+ | |||
+ | ncplot will plot netCDF files | ||
+ | |||
+ | Depending on the version you have, things might be a little different. | ||
+ | |||
+ | ncplot will allow you to select certain variables to plot, it will usually be against a set variable which is defined in the netCDF file. | ||
+ | |||
+ | How to Use: | ||
+ | |||
+ | To start ncplot: | ||
+ | |||
+ | '' | ||
+ | |||
+ | ncplot will then either open one or two windows, depending on the version. (If older version, one window will open with the different variables listed, if newer version, two windows will open, one is a graph and the other is where different variables are listed.). | ||
+ | |||
+ | Next, select the variable you want to plot versus the assigned variable that was defined in the netCDF file, usually time or distance. | ||
+ | |||
+ | There is basic modification allowed in ncplot, but if you need more specific modification, | ||
+ | |||
+ | |||
+ | |||
+ | === ncdump === | ||
+ | |||
+ | This command allows all the information to be seen that is in a netcdf file. The command can be used as follows: '' | ||
+ | |||
+ | |||
+ | It is always a good idea to look at the data first to be familiar with what kind of variables are available. ncdump will also list the variables with the units and the long names. | ||
+ | |||
+ | === ncview === | ||
+ | |||
+ | This program also loads netcdf files and makes specified plots. |