All of the questions below are linked to descriptive answers in this chapter of the Giovanni Online Users Manual regarding the Giovanni MAIRS instances (monthly and 8-day). Click the question of interest to access the answer.
- What is MAIRS?
- What parameters are in the current Giovanni MAIRS monthly instance?
- How are the GPCP monthly products in MAIRS generated?
- What parameters are in the current MAIRS 8-day interface?
- How are the 8-day 1 km land surface temperature data products generated?
- How is the spatial area of interest selected?
- How are parameters of interest selected?
- What are the “Analysis Options” in the Parameters section?
- How is the time range of interest selected?
- What analysis functions are available?
- How can the plotted visualizations be modified?
- What plotting preferences options are provided for modifying a visualization?
- How can the results of an analysis be downloaded?
- How many output data formats are available?
- What does “Product Lineage” mean?
- How should the use of Giovanni in publications, reports, Web pages, etc. be acknowledged?
The data parameters in the Giovanni MAIRS monthly instance are satellite remote sensing and model data, grouped into atmosphere, land surface, and ocean categories. Current remote sensing data are from sensors such as MODIS-Terra, MODIS-Aqua, AIRS, and SeaWiFS; the model data are from MERRA, GLDAS-NOAH, and NOBM. Both observational and model data will be continually updated with new data products. Click here http://disc.gsfc.nasa.gov/mairs/visualization/mairs-monthly-param
for the parameter list.
The GPCP monthly products in MAIRS Giovanni are generated from monthly GPCP version 2 combination data (http://precip.gsfc.nasa.gov/
). The original 2.5° x 2.5° dataset has been regridded to 1.0° x 1.0° using the Grid Analysis and Display System (GrADS, http://grads.iges.org/grads/grads.html
) developed by the Center for Ocean-Land-Atmosphere Studies (COLA). The regridding method used is box averaging.
Adler, R.F., G.J. Huffman, A. Chang, R. Ferraro, P. Xie, J. Janowiak, B. Rudolf, U. Schneider, S. Curtis, D. Bolvin, A. Gruber, J. Susskind, P. Arkin, E. Nelkin 2003: The Version 2 Global Precipitation Climatology Project (GPCP) Monthly Precipitation Analysis (1979-Present). Journal of Hydrometeorology, 4, 1147-1167.
The currently available parameters in the Giovanni MAIRS 8-day interface are land surface temperature (LST) at 1 km resolution from MODIS-Terra and MODIS-Aqua, covering 60° -150° E, 0°-60° N. Click for parameter list and relevant documents
The MODIS 8-day 1 km land surface temperature (LST) products in Giovanni are processed from MODIS standard 8-day 1 km Land Surface Temperature & Emissivity products (MOD11A2.005 and MYD11A2.005). The original 10° x 10° tiled sinusoidal projected data are mosaicked and reprojected onto an equidistant cylindrical projection (or equirectangular projection) using the nearest point sampling method. The data file covers the entire Asian Monsoon region (60° -150° E, 0°-60° N). This data set comprised daytime and nighttime LSTs averaged over clear-sky conditions, and quality flags. Click here to read more
The spatial area of interest can be selected by either of the two methods described below:
Java applet map: The Java applet map can be utilized to "click and drag" a selection box to designate the spatial area of interest. The colored box on the Java applet map indicates the MAIRS research area. You may change the background map or add layers of political boundaries or costal lines by selecting the icon on the right side of the map.
Geographic coordinates: The geographic coordinates of the corners of the spatial area box can be input individually. This method can be used if Java is not enabled. Note that decimal and not degree (seconds and minutes) coordinates must be entered.
To select data parameters for analysis, click the box next to the parameter of interest. An entire group may be selected by clicking the group box (leftmost column). After this is done, individual parameters may be deselected by clicking in the appropriate check box(es).
Analysis Options in the “Parameter” section allow you to visualize of the following analysis (or data) types:
Parameter: original data of the selected parameter;
Climatology: pre-generated monthly climatology of the selected parameter(s). To discover how the climatology was created, click the 'Climatology Info' button to display the climatology column in the parameter table below, then click on the climatology product link. Note that all of the climatology products are pre-generated.
Anomaly: monthly anomaly of the selected parameter(s):
Xa ( i ) = X (i ) - Xm ( i )
i denotes month (1, 2, ... , 12), Xa(i) represents the anomaly data for the month i, X(i) is the original data of the month i, Xm(i) is the monthly climatology data for the month i.
Note: Time or spatial averages are performed on the anomaly data. For example, when a time average is performed (such as for the "Lat-Lon map, Time-averaged" function, the system calculates the monthly anomaly first and averages the monthly anomalies for each grid point. Similarly, when a spatial average is needed, such as for a Time-series plot, the system calculates the monthly anomaly first and then does the spatial average for each month.
- Parameters that do not have associated climatologies are disabled (they will be unvavailable for selection) when either the climatology or anomaly analysis is selected.
- You must select a parameter (the leftmost column checkbox in the tables below) in order for its climatology or anomaly to be plotted.
The “Begin Date” and the “End Date” for the analysis are selected using the calendrical drop-down menus at the “Temporal” section on the Giovanni interface page. The begining dates and end dates shown next to the menus denote the temporal coverage of Giovanni MAIRS data sets. The temporal coverage range of each parameter is listed in the last column of the parameter list. Error messages will be generated if the beginning date or the end date are out of the data set time range of a selected parameter, or if the end date is before the beginning date.
Each of these output options is briefly described in the Services and Operations
section of the Online Users Manual.
The created image can be modified by refining constraints (spatial area and temporal range) and “Plot Preferences” on the result page, and clicking "Submit Refinements" to create the new image.
Plot preference options are described in the Plot Preferences chapter
of the Giovanni Online Users Manual. Note that the chapter describes the Image X/Y option, which correspond to the Image Width and Image Height adjustment options, respectively. Each analysis function provides slightly different plot preference options.
To download the results of an analysis, click on the "Download Data" link above the visualizations on the Results page. The "Initial Data Retrieval" results are the data files acquired to perform the analysis. The analysis results data are listed as “Input Files” under the name of the operation which generated the visualization.
To download an individual results data file, click on the icon for the desired data format (see below). To download more than one data file in Batch mode, click the desired data files and then click "Download in Batch". To acquire the actual visualization image, click the link to the GIF image or KMZ, if available.
Three numerical and two image data output formats are available. Numerical data is available in HDF, netCDF, and ASCII. Image data output formats are GIF and KMZ. If Google Earth is installed on a user's home computer, clicking the KMZ icon will allow immediate load and display of the visualization in Google Earth.
Clicking the “Product lineage” link above the visualizations on the Results page leads to a page providing short descriptions of the operation steps performed to create the images and data results. The algorithm of each operation step can be obtained by clicking on the name of the operation step.