Radar data 1B51 represents the data collected at the radar site.  Each 1B51 file stores multiple volume scans collected over hourly intervals (termed granules) in HDF.  Fields stored are reflectivity, differential reflectivity, and Doppler velocity out to a maximum of 230 km range.  The file content description for 1B51 can be obtained from the Volume 3 - Levels 1 File Specifications provided by the TRMM Data and Information System (TSDIS).  It is available at: http://tsdis02.nascom.nasa.gov/tsdis/Documents/ICSVol3.pdf.

    There are no problems with the file conversion at this time.  Future modifications will be made if radar parameters change, such as the recent addition of polarimetric capabilities to the Kwajalein radar.

    More information about the availability of radar Level 1B  (1B51) data can be found at the JCET home page:  http://trmm.gsfc.nasa.gov/jcetop/level_1.html.

Last updated:  10/1/98

    Radar data 1C51 represents quality controlled reflectivity fields.  Only the corrected reflectivity and the mask are stored.  The mask is designed so that the raw, uncorrected reflectivity can be obtained by subtracting the mask field from the corrected reflectivities.  The 1C51 data are HDF files storing multiple volume scans, however, only a subset of the volume scans are retained from 1B51:
 
    1) Volume scans with 4 or more tilt angles ("full volumes").
    2) Every full volume is saved a half hour before or after the satellite passes over the site (satellite coincidence).
    3) Otherwise, two full volumes are saved during non-coincidence, one full volume in the first half hour and another in the second half hour.

    Each full volume scan in 1C51 is used to produce the corresponding series of level 2 products.

    The purpose of the 1C51 algorithm is to remove non-meteorological radar echoes that adversely affect the quality of the higher level products, such as clutter associated with insects, birds, chaff, wildfires, and anomalous propagation (AP).  The algorithm was designed and implemented in Rosenfeld et. al. (1995), and is described in more detail in the JCET home page (see below).  Eight adjustable parameters, three echo height thresholds and five radar reflectivity thresholds, are used to optimize the performance of the algorithm.  Optimum performance is time consuming and requires an analyst to select different sets of parameters on a per volume scan basis, and on
occasions performing several iterations while adjusting one or more of the parameters.

    The file content description for 1C51 can be obtained from the Volume 3 - Levels 1 File Specifications provided by the TRMM Data and Information System
(TSDIS).  It is available at:  http://tsdis02.nascom.nasa.gov/tsdis/Documents/ICSVol3.pdf.

    The QC algorithm performance, and a more detailed description, is documented at the JCET home page: http://trmm.gsfc.nasa.gov/jcetop/level_1.html.The algorithm has difficulty in removing AP in the presence of precipitation, particularly at farther ranges (beyond 100 km) from the radar, but otherwise performs well.

    Future improvements are likely to the algorithm in order to make it less labor intensive, and it may also require further refinements that address site-specific problems.

Last updated:  10/1/98
 
References

Rosenfeld, D., E. Amitai, and D. B. Wolff, 1995:  "Classification of rain regimes by the three-dimensional properties of reflectivity fields", J. Appl. Meteor., 34, 198-211.

    Product 2A52 determines the fraction of rainfall in any given volume scan.  It is computed by counting the number of 2x2 km pixels in the radar rainfall product (2A53) with rainfall rates greater than zero and dividing by the total number of pixels in the radar scan. The product was created in order to have easily accessible statistics for use by the TRMM data system and science users.

    The file content description for 2A52 can be obtained from the Volume 4 - Levels 2 and 3 File Specifications provided by the TRMM Data and Information System (TSDIS).  It is available at: http://tsdis02.nascom.nasa.gov/tsdis/Documents/ICSVol4.pdf.

    There are no known problems with this product.

Date posted:  10/1/98

    Product 2A53 is an instantaneous rain rate map in Cartesian coordinates with 2 km horizontal resolution.  It is created by mapping the interpolated basescan map of reflectivities into rain rates using Z-R tables generated by the site PIs.  The values in product 2A53 are in mm/hr.

    The accuracy of this product is directly related to the accuracy of the Z-R tables provided by the site PIs.  The methodology used to create the tables is totally PI-dependent.

    The file content description for 2A53 can be obtained from the Volume 4 - Levels 2 and 3 File Specifications provided by the TRMM Data and Information System (TSDIS).  It is available at:  http://tsdis02.nascom.nasa.gov/tsdis/Documents/ICSVol4.pdf.

    Product 2A54 is an instantaneous map in Cartesian coordinates with 2 km horizontal resolution that identifies the surface precipitation as either convective or stratiform.

    It is created by looking for peaks in the interpolated basescan map of reflectivities and defining them as convective cores.  All identified peaks and surrounding areas are labeled convective and all remaining points are labeled stratiform.

    There are two criteria for identifying convective cores.  First, all points with reflectivities greater than or equal to 40 dBZ are defined as convective cores.  Second, any points not meeting the previous condition but which are greater than the average intensity of the surrounding area by at least the reflectivity difference indicated by a cosine-type function are defined as convective cores.  This second criteria needs some explanation.  The cosine function expresses reflectivity difference (dB) as a function of mean background reflectivity (dBZ).  As the mean background reflectivity increases, the reflectivity difference required, decreases.  The background
reflectivity is the linear average of nonzero radar echoes within a radius of 11 km around the point in question.

    Once a point is declared a convective core, all surrounding points within an intensity-dependent radius around that point are also labeled convective.  The convective radius (km) is a step-function of mean background reflectivity (dBZ) and ranges from 1 to 5 km.  Radius increases with increasing background reflectivity.

    The file content description for 2A54 can be obtained from the Volume 4 - Levels 2 and 3 File Specifications provided by the TRMM Data and Information System (TSDIS).  It is available at:  http://tsdis02.nascom.nasa.gov/tsdis/Documents/ICSVol4.pdf.

    There are no known problems with this algorithm.

References

Steiner, M., R. A. Houze Jr., and S. E. Yuter: Climatological Characterization of Three-Dimensional Storm Structure from Operational Radar and Rain Gauge Data. Journal of Applied Meteorology, 34, 1978-2007, September 1995.

    Product 2A55 is actually three different products which are generated for each radar VOS that is processed:

    1.     a 3-D reflectivity grid in Cartesian coordinates with 2 km horizontal resolution and 1.5 km vertical resolution
    2.     a vertical profile
    3.     a statistical summary of the Cartesianized reflectivities which is used  to generate a CFAD (Contoured Frequency by Altitude Diagram)

    The interpolation to Cartesian space is done via the SPRINT algorithm which was developed by NCAR (National Center for Atmospheric Research).

    The vertical profile is based on the interpolated 3-D reflectivity volume.  It provides an average of the reflectivities in each level of the reflectivity volume (1.5 km, 3.0 km, 4.5 km, . . . 18.0 km).  A vertical profile of all points is calculated as well as vertical profiles of several subsets of points (over land, over sea, in convective regions, in stratiform regions, in anvil regions, and so forth).

    The CFAD data is also based on the interpolated 3-D reflectivity volume.  It is an array that contains the number of pixels counted in specified height-reflectivity bin pairs for each category for which a vertical profile is calculated.

    The file content description for 2A55 can be obtained from the Volume 4 - Levels 2 and 3 File Specifications provided by the TRMM Data and Information System (TSDIS).  It is available at:  http://tsdis02.nascom.nasa.gov/tsdis/Documents/ICSVol4.pdf.

    There are no known problems with this algorithm.

References

Yuter, S. E., and R. A. Houze Jr., 1995b: Three dimensional kinematic and microphysical evolution of Florida cumulonimbus.  Part II:  Frequency distributions of vertical velocity, reflectivity, and differential reflectivity. Monthly Weather Review, 123, 1941-1963.At this time, there is no information available.

    Product 3A53 is a rainfall accumulation map in Cartesian coordinates with 2 km horizontal resolution.  It is created by translating the rain rate products (2A53) into rain accumulations and adding them up over a 5-day period.  The dates and times of all volumes used to create 3A53 are saved as metadata.  Therefore, the user knows how many data gaps there were and how accurate the accumulation map is.  Time gaps are handled in the following way.  If the time gap between successive 2A53 products is 75 minutes or less, then the rain rate from the first 2A53 product is applied to the gap between products and is added to the 5-day accumulation.  If not, then nothing is added to the total and the rain rate from the first 2A53 product is disregarded.

    The file content description for 3A53 can be obtained from the Volume 4 - Levels 2 and 3 File Specifications provided by the TRMM Data and Information System (TSDIS).  It is available at:  http://tsdis02.nascom.nasa.gov/tsdis/Documents/ICSVol4.pdf.

    There are no known problems with this algorithm.

    Product 3A54 is a rainfall accumulation map in Cartesian coordinates with 2 km horizontal resolution. It is created by translating the rain rate products (2A53) into rain accumulations and adding them up over a month.  The dates and times of all volumes used to create 3A54 are saved as metadata.  Therefore, the user knows how many data gaps there were and how accurate the accumulation map is.  Time gaps are handled in the following way.  If the time gap between successive 2A53 products is 75 minutes or less, then the rain rate from the first 2A53 product is applied to the gap between products and is added to the monthly accumulation.  If not, then nothing is added to the total and the rain rate from the first 2A53 product is disregarded.

    The file content description for 3A54 can be obtained from the Volume 4 - Levels 2 and 3 File Specifications provided by the TRMM Data and Information System (TSDIS).  It is available at:  http://tsdis02.nascom.nasa.gov/tsdis/Documents/ICSVol4.pdf.

    There are no known problems with this algorithm.

    Product 3A55 is two different products:

    1. The average vertical profile for the month
    2. The sum of a month's worth of 2A55 CFAD data.

    See the descriptions of the 2A55 vertical profile and CFAD products for details.

    The file content description for 3A55 can be obtained from the Volume 4 - Levels 2 and 3 File Specifications provided by the TRMM Data and Information System (TSDIS).  It is available at:  http://tsdis02.nascom.nasa.gov/tsdis/Documents/ICSVol4.pdf.

    There are no known problems with this algorithm.