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The YOTC Portal is under development. More information will be coming soon.

 General YOTC

YOTC-GS L3

YOTC-GS L2

TRMM Dataset

Mirador

 


What is YOTC?

YOTC stands for Year of Topical Convection. It is a program that is focused on parameters relevant to the research of tropical convection and covers a temporal period of May, 2008 through April, 2010. The program is a collaborative effort of organizations from around the world and includes a comprehensive compilation of Satellite, model and in-situ data sets.

 


What is YOTC-GS?

YOTC-GS stands fro Year of Tropical Convection - Giovanni System. It is based on the Giovanni system. Giovanni is a web-based application developed byt he GES DISC that provides a simple and intuitive way to visualize, analyze, and access vast amounts of Earth science remote sensing data without having to download the data.  It is comprised of a number of interfaces, called instances, each tailored to meet the needs of different Earth science research communities.

 


How do I know which YOTC-GS version to use?

Currently we have two version of the YOTC-GS system. The first version, YOTC-GS L3, is based on the current Giovanni system and features only Level 3 data. The second system, YOTC-GS L2, is the new Giovanni system being developed and contains currently only Level 2 data. The two systems will be combined by the completeion date and release of the first version of the system and will contain new functinalities the current Giovanni system doesn't have.

 


How do I access the data?

 

The data can be access through one of the YOTC-GS interfaces, Mirador or by directly accessing the primary archive of the data. To access the primary archive of the data you can get the information from the dataset pages under the Data Holdings section of the YOTC Portal.


 How do I access the full data set of a product I want?

 

To access the primary archive of the data you can get the information from the dataset pages under the Data Holdings section of the YOTC Portal.

 


 Where can I find documentation on the products?

 

Documentation on the products can be found by clicking in the product in the table on the Data Holdings page.

 


What is the Guide Map?

 

The Guide Map is just a tool to guide the user to where the coverage data for the product is. For some products, a collection level 3 parameter that is a related parameter to the level 2 data will be seen on the Guide Map. For some products, a related parameter does not exist so another parameter from the same data collection was used, and lastly some products just have the blue marble map because there is no data available yet in level 3 to match it up with.

 

In some cases you may select a bounding box (for a map) or a point (for a profile) that looks like it has data but the results return nothing. This is because the data used in the Guide Map is just that, a guide, but will not always reflect the actual data contained in a grid cell for a level 2 product.

 


 

 How do I update the Spatial Selection Map?

 

  1. Select the data set, product and parameters in the first section "Vertical Profile Parameter". Select either the Ascending or Descending radio button.
  2. Pick a year, month and date from the drop down menus in the "Date" section.
  3. Click on the "Update Selection Map" button to update the image map in the "Selection Map" section. The image map will be a relevant data product and parameter to the data set selected for the same day selected.

 


 How do I know what parameter I am creating visualization for?

 

The parameter you are generating a plot or map for is the same parameter in the "Select Parameter" section that you selected.  The parameter is also listed on the result plot or map generated from the data.

 


 Can I zoom in to a particular region?

 

You can zoom on the "Selection Map" by utilizing the buttons on the left panel.

 


 How can I view the data that the profile or map was created from?

 

In the "Profile" panel there are two check boxes at the bottom. The second checkbox states "View Data". When you click on the checkbox a new panel will appear with the output of the point data selected. You can save this output by copying the data and saving it as text. New functionality is in development to save the data in another format and to have a download button for easier usability.

 


 Can I save the profile image?

 

You can right click on the mouse and save the image.

 


 How do I know what granules were used to generate the profile data for TRMM and AIRS?

 

In the "Profile" panel there are two check boxes at the bottom. The second checkbox states "View Lineage". When you click on the checkbox a new panel will appear with the data granules that were search results from your input of the data archive.  These granules were used when determining the closest profile.

 


 What parameters shown in the selection map for TRMM?

 

For TRMM, they are TRMM L2 surface rain parameters.

If you select 2A12 (2A25), it is 2A12 (2B31) surface rain.

 


How can I use this tool?

a) Select a vertical profile parameter.

b) Select a date

c) Select a point of interest

d) Click "Get Profile(s)"

 


How does this tool work?

For a given point, the system fetches the Level-2 data files from the archive and extracts the nearest profile.

 


Can I fine tune the plot?

Yes. You can fine tune the plot by specifying your own max min and change the plot size.

 


Can I view the profile in ASCII?

Yes. To view the data in ASCII, click "View Data". To view lineage, click "View Lineage".

 


Can I type in my point of interest?

Yes, you can type in the latitude and longitude in "Search Coordinates"

 


I can't get any profile, why?

There are several possibilities:

a) You might click a point outside the swath.

b) For TRMM, the nearest point returns all zero values, indicating a large spatial variation. Please note that the map shown in "Selection Map" is an areal average.

 


For other parameters, do I need to change the selection map?

No, if the date remains the same. Simply select the parameter you want and click "Get Profile(s)".


What is Mirador?

Mirador is a simplified interface for searching, browsing, and ordering Earth science data at NASA Goddard Earth Sciences Data and Information Services Center (GES DISC). Mirador is designed to be fast and easy to learn.



How can I retrieve data?

Retrieving data is simple using Mirador. Type in the search parameters describing the data you want, add it to the cart, then checkout. You will be able to download your data using several different methods.



What do I search for?

Mirador is a tool used to search for Earth science data. You can search for anything from an instrument or satellite name, to the names of measurements you are looking for (i.e. Calibrated Radiances).



Is Mirador data free?

Yes. The data is archived at NASA's Goddard Earth Sciences Data and Information Services Center (GES DISC).



Do I need to register?

No. All of the data at NASA's Goddard Earth Sciences Data and Information Services Center (GES DISC) is online and available for immediate FTP download.



How do I subset data?

Several, but not all of the data sets available through Mirador may be subsetted spatially, by parameter, by channel, or by variable. The particular type of subsetting that can be performed varies according to the data set. When files from any data set that can be subsetted are chosen to be added to the Mirador shopping cart, a subsetting service for that data set can be selected from a page displaying the Available Services for each data set. Once you choose a subsetting service and select "Continue to Shopping Cart", those files added to the shopping cart will be subsetted when you download them, either individually from the Shopping Cart page, or in bulk when you checkout.


When I try to download subsetted data, why am I told the data is not available for downloading?

If you select a spatial subsetting bounding box for a data set that does not have global spatial coverage, it is possible that your bounding box does not overlap the spatial coverage of the file being subsetted. In that case, when you attempt to download the file, a web page will be displayed that says that the file is not available for downloading. This is less likely to happen if the bounding box used for subsetting is the same as the bounding box used as the location when searching for files.
 



How do I convert data to NetCDF?

Several, but not all of the collections available through Mirador may be converted to NetCDF. When files from any data set that can be converted to NetCDF are chosen to be added to the Mirador shopping cart, a Convert to NetCDF service for that data set can be selected from a page displaying the Available Services for each data set. Once you choose "Convert to NetCDF" and select "Continue to Shopping Cart", those files added to the shopping cart will be converted when you download them, either individually from the Shopping Cart page, or in bulk when you checkout.



How do I find data which coincide with hurricanes?

On either the Mirador homepage, or at the top of any subsequent pages, is a form containing a field for Events. Many different kinds of events can be entered there, such as hurricanes, typhoons, storms, ozone, and aerosols. Hurricane data is constantly being added to the database so there is no way as yet to view a list of what hurricane data is in Mirador. So just enter a hurricane name of your choice in the event field, such as Bud, Katrina, Yagi, Yutu, Ewiniar, Ioke, John, Florence... Place a physical parameter or collection description in the keyword field. You may also limit the search by placing a time constraint in the time span fields. Results will come back that are constrained by the event you entered. Also, a 'Did You Mean' box is offered to allow you to narrow the results even more, perhaps by specifying the intensity of the event (hurricane and typhoon positions are recorded as they pass through various levels, such as tropical depression, tropical storm, category 1, category 2, etc).



How do I download related data products?

To download AIRS LEVEL 1B related data products together, put AIRS L1B in the keyword field.
(AIRHBRAD, AIRVBQAP, AIRIBQAP, AIRIBRAD, AIRVBRAD, AIRABRAD)

To download AIRS LEVEL 2 related data products together, put AIRS L2 in the keyword field.
(AIRH2CCF, AIRH2RET, AIRX2RET, AIRI2CCF, AIRX2SUP, AIRH2SUP).

To download AIRS LEVEL 3 related data products together, put AIRS L3 in the keyword field.
(AIRX3STD, AIRH3STD)

To download AIRS LEVEL 3 monthly related data products together, put AIRS monthly in the keyword field.
(AIRX3QPM, AIRH3QPM, AIRX3STM, AIRH3STM, AIRH3ST8)

To download AIRS LEVEL 3 5 day products together, put AIRS pentad in the keyword field.
(AIRX3QP5,AIRH3QP5,AIRX3QM5,AIRH3QM5)

To download AIRS LEVEL 3 8 day products together, put AIRS 8 day in the keyword field.
(AIRX3ST8, AIRH3ST8).


 

I want to download a large volume of data for a particular dataset.  What is the best way to do that?

For obtaining large numbers of data files, we recommend the Mirador search tool:

  1. Go to http://mirador.gsfc.nasa.gov/index.shtml
  2. Enter your search criteria in the Keywords blank to locate your desired datasets. If you know that product's "shortname" (e.g.,, "TRMM_3A12"), that is the best bet. Otherwise type in multiple terms to constrain the search better. (The search uses a Google appliance, so many of the usual tricks will work.)
  3. In the Time Span textbox, enter your time span of interest.
  4. In the Location textbox, enter your spatial area of interest.
  5. Click the "Search GES-DISC" button.
  6. The result page from the search will supply a list of products. Note the approximate estimate of number of files and total size for that product. If you are very confident this set of files is the one you want, you can check the box by the data product and click "Add Selected Files to Cart". Otherwise, click on the View Files button under the listing of the desired product to see the first page of files in that product. Add files by checking the boxes and clicking "Add Selected Files to Cart", or instead of checking, click "Add All Files in All Pages to Cart".
  7. The next page is the service selection page – you can "Continue to Shopping Cart" or apply available services first. (Depending on the product, these may include subsetting, reformatting or download through HTTP instead of FTP.)
  8. After you continue to the shopping cart, select "Checkout" in the Cart Options at the top. In the Checkout page, you will see buttons that generate a list of URLs for all of the files in the shopping cart, along with instructions on how to download them in a batch.
  9. Clicking on one of the "URL List" buttons in the Checkout page will bring up this list in a new window in your browser. Save this to a file on your computer, and then feed this to an FTP utility such as wget or curl as indicated in the instructions. Note that other, more advanced options for download are also available in the "More Download Options" tab.

What is the Algorithm behind the lat/lon maps produced?

The projected maps of uses code developed here at the GES DISC called simap. The simap algorithm is in essence a conversion of the geolocation information of the data from spherical coordinates (latitude, longitude) to the two-dimensional  device (pixel) map space. Since the map space can have its own coordinate system, sometimes we say we convert from one coordinate system (that of data) to another (that of the map). The standard IDL mapping function, COVERT_COORD, is used in the core of the approach. For the purposes of YOTC, only the simple cylindrical projection is used as coordinate system of the map space.
 
Assuming every data point has a geolocation information, and the coordinate system of the map space has been defined, the result of the mapping is that every data point is assigned a new address (row,column) in the digital 2D map space. This is in essence the coordinate system transformation. Along the way, the algorithm checks the dimensions of the data and the geolocation arrays, and attempts to interpolate geolocations if they don't match that of the data. E.g. in the case of MODIS L1B, the internal geolocations are interpolated (refined) to match that of the data.
 
It is possible to define the target 2D map space to have a resolution finer than that of the original data. I.e. the target map can be set such that the resulting pixel size is smaller than that of the data. Or we also say "the map has finer resolution than the data". In this case, to avoid unfilled map space, the algorithm over-samples the data to simulate finer resolution, which practically means data pixels are simply replicated. Such may be the case with AIRS Level 2 standard retrieval granules, where data arrays have 30x45 (columns x rows) with a pixel size on the order of 45 km. A map of such size would appear as a tiny box in the browser window. Thus, it would make sense to request 5-km resolution map instead, which will appear as an image about nine times larger.
 
On the opposite end, it is possible to request the target map space to have a coarser resolution than the original data. Such may be the case with MODIS 1-km data. Projecting one MODIS granule at this resolution will produce a map of approximately 2000x2000 pixels. Image that size will take a long time to load on slower internet connections. Thus, to speed up the initial previews, it will again make sense to request 5-km resolution map, which will result in an image five times smaller. During this process, about 5 data pixels fall into one map pixel on top of each other, hence the last one to fall is the one that will be visible.

 


What is the Search Type?

 

The Search Type is provided in either Nearest Profile or Grid Cell and is used when a 3 dimensional parameter is selected and the output is a profile. The Nearest Profile will return the closest profile to the lat/lon point you selected in the Guide Map. The Grid Cell will return multiple profiles that are within the grid cell, or within a designated distance from the lat/lon point you selected in the Guide Map.

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Last updated: May 22, 2012 01:41 PM ET