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					Comparative Precipitation Analysis and Validation of NEXRAD (Stage III)

         Data, Stream Flow Data, and Rain Gauge Data located

                    in the San Antonio River Basin

                            Jayar S. Griffith

                                ES5053
                               Fall 2004
Outline


I.      Title


II.     Author


III.    Abstract


IV.     Introduction


V.      Methods


VI.     Analysis


VII.    Conclusion


VIII.   Tables and Figures


IX.     Reference
I.     Title of the project or paper reviewed

       Comparative Precipitation Analysis and Validation of NEXRAD (Stage
       III) Data, Stream Flow Data, and Rain Gauge Data located in the San
       Antonio River Basin

II.    Name(s) or authors of the paper reviewed

         Jayar S. Griffith

III.   Abstract


           This remote sensing project is a comparative precipitation analysis and
       validation of (NEXRAD Stage III) data, stream flow data, and rain gauge data
       located in the San Antonio River Basin. Validation of NEXRAD Stage III
       data with stream flow data and rain gauge data is used to analyze flooding
       events and create more accurate hydrologic models. This study deve lops the
       understanding for the process of data collection of Hourly Precipitation
       NEXRAD Data, Hourly Stream Flow Data, and Hourly Rain Gauge Data by a
       variety of internet sources. During this project, data management, file
       conversion, and analysis using ArcGIS 9 was used for data comparison. This
       paper does not involve analysis of NEXRAD Stage III data with Rain Gauge
       data due to the lack of access and reformatting of the National Oceanic and
       Atmospheric Administration website.



IV.    Introduction

           The region of study for this project is the 10,800 km2 area of the San
       Antonio River Basin. Heavy rainfall events during 1998 and 2002 in the San
       Antonio River Basin have resulted in two major flooding disasters. The 1998
       flooding event created major flash flooding along major streams and rivers
       along South Central Texas and resulted in the loss of 31 lives and over three
       quarters of a billion dollars in property damage (National Oceanic and
       Atmospheric Administration Service Assessment, 1999). These major
       flooding events have increased the concern for better NEXRAD rainfall
       products to analyze rainfall events and improve flood warning predictions.
       This remote sensing project introduces the fundamental concepts of how
       NEXRAD data is used for analyzing rainfall events and its relation with Rain
     Gauge data and Stream Flow data. The improved functionality and analysis
     of Geographic Information Systems (GIS) was applied to illustrate hourly
     precipitation NEXRAD Stage III data for the month of October 2004 over the
     San Antonio River Basin.

V.   Methods

     Data Collection

         The process to complete this project is as follows: Data collection using
     the internet, data management and conversion, importing to ArcGIS grid with
     a defined projection, data analysis using ArcGIS Spatial Analyst tool and
     Excel Spreadsheet.

         The first step in this project is collection of Hourly Rain Gauge data
     located in the San Antonio River Basin that is used by the NOAA. During a
     continuous search of free accessible data through National Climatic Data
     Center website (http://nndc.noaa.gov), a problem of accessing hourly
     precipitation for each COOP# Rain Gauge Station occurred because of a
     reformat of the NCDC data access website. Rain gauge data must be
     purchased for a fee for Hourly Precipitation format. This prob lem resulted in
     no NEXRAD Stage III and Rain Gauge analysis in this project.

          This project involved a process of data mining of Hourly NEXRAD Stage
     III data and USGS Stream Flow data using the internet. The location of where
     to find the NEXRAD Stage III data from National Weather Service Regional
     Forecast      Center     located      in    New      Braunfels,   Texas      is
     http://dipper.nws.noaa.gov/hdsb/data/nexrad/wgrfc_stageiii.html           (Xie,
     RS5053 Lecture 10). This data is monthly precipitation Stage III data of the
     New Braunfels regional forecast area and is formatted in binary multi-tarred
     files and is converted to ArcGIS grid files by a process (Figure 1) created by
     Dr. Hongjie Xie (Xie et al., 2003). During this process, binary multi-tarred
     files of the October NEXRAD Stage III data are decompressed to ASCII files
     by a process of Unix Perl Script. The ASCII files were converted to ArcGIS
     grid files by using an AML Script in Arc Workstation and defining the grid
     files as polar-stereographic and re-projected to Texas Centric NAD83 Albers
     (Xie, et al, 2003). Final conversion of October NEXRAD Stage III data
     allowed projection using ArcGIS in 4km pixel spatial resolution. Each pixel
     is associated with a precipitation value in millimeters.

         Hourly Stream Flow data was collected from the United States Geological
     Survey Real Time Stream Flow website (http://waterdata.usgs.gov/nwis/rt).
     The network of USGS Stream Flow gauges is located along major creeks
     and rivers in the San Antonio River Basin like Medina River, Cibolo Creek,
     Salado Creek, Leon Creek, Upper and Lower San Antonio River. Hourly 15
     min stream flow data for each stream flow gauge station can be downloaded
      with in the last 31 days from the present day of access through the USGS
      website. Any previous date after 31 days will result in averaged hourly
      discharge and not in 15 min increments. This data was collected for the date
      range from October 8, 2004 zero hour to November 8, 2004, 22nd hour.
      Hourly stream flow data was converted from Text files to Excel Spreadsheet
      and organized by station ID. Each USGS Stream Flow gauge station was
      sub-totaled by the sum of the discharge (cfs) per hour. Discharge in cubic feet
      per second were converted to cubic meters per hour. A rainfall event from
      October 24, 2004-16th hour to October 25, 2004-04th hour is used to compare
      with NEXRAD Stage III data (Figure 2, Sample of USGS Hourly Stream
      Flow Data for Station ID 8181500).

          ArcGIS Shapefiles of the San Antonio Basin, Rain Gauge locations, and
      USGS Stream Flow Stations were provided by Dr. Hongjie Xie. These
      shapefiles were re-projected from Assumed Geographic to Texas Centric
      NAD83 Albers by the use of the Data Management Tool provided in Arc Tool
      Box of ArcGIS. Individual shapefiles of the San Antonio Basin were created
      into four sub-regions: Medina, Cibolo, Upper San Antonio, and Lower San
      Antonio. A 2km buffer was established around each individual sub-region to
      calculate only the amount of precipitation over that region.

VI.   Analysis


          A rainfall event from October 24, 2004-16th hour to October 25, 2004-04th
      hour is used to compare NEXRAD Stage III data with USGS Stream Flow
      data. Using ArcGIS, the sum of total precipitation over a 2km buffer of the
      Medina sub-region was calculated by the Zonal Statistic tool in ArcGIS. The
      sum of precipitation for each hour from October 24, 2004-16th hour to October
      25, 2004-04th hour was calculated and imported to an Excel spreadsheet
      (Figure 3). The precipitation is measured in millimeters and converted to
      meters. Multiplying the zonal statistic sum for each hour over the Medina
      sub-region by the area of the Medina sub-region will give the volume in cubic
      meters.

          USGS Stream Flow gauge 8181500 was used because it was located at the
      bottom of the Medina River in the Medina sub-region. Hourly stream flow
      data of the same rainfall event from October 24, 2004-16th hour to October 25,
      2004-04th hour was used. The discharge rate in cubic meters is used to
      compare with the volume (zonal statistic sum per hour) in cubic meters
      (Figure 3).

          A chart of NEXRAD Stage III data versus Hourly USGS Stream Flow
      data for the rainfall event from October 24, 2004-16th hour to October 25,
      2004-04th hour was created (Figure 4). This chart did not correlate the
      relationship between NEXRAD data and Stream Flow data. Further analysis
       and guidance from Dr. Hongjie Xie identified the problem. During the time
       of organizing the USGS Stream Flow data to an Excel spreadsheet, the wrong
       time zone conversion was used. USGS Stream Flow data is measured in
       Central Time Zone and NEXRAD Stage III data is measured in Universal
       Time Zone resulting in a 6 hour difference and discrepancy as shown in
       Figure 4.

           A new Excel spreadsheet was created with the adjusted time of the USGS
       stream flow data versus NEXRAD Stage III data. This data has a greater
       number in cubic meters in stream flow discharge per hour in the Medina
       sub-region (Figure 5). A more accurate representation of the increased
       precipitation and increased stream flow relationship is shown in Figure 6.
       This chart can be used to validate the NEXRAD data with the Stream
       Flow data for future research.


VII.   Conclusion

           Hourly rain gauge data was unavailable for this project due to the lack
       access and reformatting of the NCDC website. Further search for available
       rain gauge data is needed to validate the NEXRAD Stage III data.

           During the process of data collection and management, the knowledge of
       converting binary multi-tarred Stage III data to ASCII files and then
       converting to ArcGIS grid was demonstrated. Using the file conversion
       process created by Dr. Hongjie Xie made a faster and easier process of using
       the NEXRAD Stage III data in GIS. Future projects will consist of migrating
       the NEXRAD Stage III data to a local network server for easier access and for
       a larger memory space location.

           This project also demonstrated the fundamentals of using ArcGIS and the
       functionality of Spatial Analyst and Projection tools needed to complete this
       project. Applying the NEXRAD grid data with ArcGIS Shapefiles developed
       a useful illustration of a rainfall event over the San Antonio Basin (Figure 7).
       Using this data with conjunction with USGS stream flow data concluded in
       validating the idea that an increase in precipitation will result in an increase in
       stream flow.
 VIII. Tables and Figures




       I.        NEXRAD Stage III Data Conversion




             Figure 1 Xie et al, 2003

       II.       Sample of USGS Hourly Stream Flow Data for Station ID 8181500
                                             discharge   Hour                    m
USGS   8181500     10/10/2004 9:15    4.48   185         10                737   20.86948
USGS   8181500     10/10/2004 9:30    4.48   185         10                716   20.27483
USGS   8181500     10/10/2004 9:45    4.47   184         10                709   20.07661
USGS   8181500     10/10/2004 10:00   4.46   183         10                704   19.93503
                                             737         10 Total          710   20.10493
USGS   8181500     10/10/2004 10:15   4.45   181         11                733   20.75621
USGS   8181500     10/10/2004 10:30   4.44   180         11                762   21.5774
USGS   8181500     10/10/2004 10:45   4.43   178         11                802   22.71007
USGS   8181500     10/10/2004 11:00   4.42   177         11                838   23.72948
                                             716         11 Total          857   24.2675
USGS   8181500     10/10/2004 11:15   4.42   177         12                864   24.46572
USGS   8181500     10/10/2004 11:30   4.43   178         12                861   24.38076
USGS   8181500     10/10/2004 11:45   4.42   177         12                852   24.12591


       Figure 2
              III.                                   Excel Spreadsheet of NEXRAD Stage III (Zonal Statistic sum) versus
                                                     Hourly USGS Stream Flow Data (Station #8181500)
Zonal Statistics with
"Medina_L2_Buffer"
Medina Area =
3.49801 X10^9 sq
meters
                                                                                                                                                             USGS Stream Flow
                                                                                                                                                             Gauge
                                                                                                                                                             # 8181500
                                                                sum,
Hourly Precip.                                       Hour       mm            sum, m       area                           NEXRAD(volume cubic m)             Discharge, cubic m
r10242004_16z                                        16         0             0            3.49801E+09                    0.00E+00                           269.29
r10242004_17z                                        17         0             0            3.49801E+09                    0.00E+00                           314.60
r10242004_18z                                        18         1.75          0.00175      3.49801E+09                    6.12E+06                           315.73
r10242004_19z                                        19         37.12         0.03712      3.49801E+09                    1.30E+08                           293.36
r10242004_20z                                        20         618.54        0.61854      3.49801E+09                    2.16E+09                           293.36
r10242004_21z                                        21         1656.59       1.65659      3.49801E+09                    5.79E+09                           287.42
r10242004_22z                                        22         1350.61       1.35061      3.49801E+09                    4.72E+09                           266.46
r10242004_23z                                        23         834.82        0.83482      3.49801E+09                    2.92E+09                           253.44
r10252004_00z                                        0          439.24        0.43924      3.49801E+09                    1.54E+09                           258.82
r10252004_01z                                        1          570.25        0.57025      3.49801E+09                    1.99E+09                           255.13
r10252004_02z                                        2          333.6         0.3336       3.49801E+09                    1.17E+09                           250.32
r10252004_03z                                        3          67.33         0.06733      3.49801E+09                    2.36E+08                           243.81
r10252004_04z                                        4          0.18          0.00018      3.49801E+09                    6.30E+05                           243.81


                     Figure 3

              IV.                                    Chart of Excel Spreadsheet of NEXRAD Stage III (Zonal Statistic
                                                     sum) versus Hourly USGS Stream Flow Data (Station #8181500)

                                                                                       NEXRAD vs Stream Flow (Medina Watershed)

                                                     350.00




                                                     300.00




                                                     250.00
                        Stream Flow (cubic meters)




                                                     200.00

                                                                                                                                                            Series1

                                                     150.00




                                                     100.00




                                                      50.00




                                                         0.00
                                                          0.00E+00     1.00E+09   2.00E+09        3.00E+09     4.00E+09    5.00E+09   6.00E+09   7.00E+09
                                                                                                  NEXRAD (cubic meters)


                     Figure 4
                  V. Excel Spreadsheet of Correct Time Zone of NEXRAD Stage III (Zonal
                        Statistic sum) versus Hourly USGS Stream Flow Data (Station
                        #8181500)

Zonal Statistics with "Medina_L2_Buffer"
Medina Area = 3.49801 X10^9 sq meters
                                                                                                                                                                    USGS Stream Flow Gauge
                                                                                                                                                                    #81818500
Hourly Precip.                                  Hour           sum, mm              sum, m          area                   NEXRAD(volume cubic m)                   discharge, m
r10242004_16z                                   16             0                    0               3.49801E+09            0.00E+00                                 0
r10242004_17z                                   17             0                    0               3.49801E+09            0.00E+00                                 0
r10242004_18z                                   18             1.75                 0.00175         3.49801E+09            6.12E+06                                 173341.7867
r10242004_19z                                   19             37.12                0.03712         3.49801E+09            1.30E+08                                 3676826.928
r10242004_20z                                   20             618.54               0.61854         3.49801E+09            2.16E+09                                 61267902.16
r10242004_21z                                   21             1656.59              1.65659         3.49801E+09            5.79E+09                                 164089297.4
r10242004_22z                                   22             1350.61              1.35061         3.49801E+09            4.72E+09                                 133781228.9
r10242004_23z                                   23             834.82               0.83482         3.49801E+09            2.92E+09                                 82690965.95
r10252004_00z                                   0              439.24               0.43924         3.49801E+09            1.54E+09                                 43507797.95
r10252004_01z                                   1              570.25               0.57025         3.49801E+09            1.99E+09                                 56484659.37
r10252004_02z                                   2              333.6                0.3336          3.49801E+09            1.17E+09                                 33043897.18
r10252004_03z                                   3              67.33                0.06733         3.49801E+09            2.36E+08                                 6669201.429
r10252004_04z                                   4              0.18                 0.00018         3.49801E+09            6.30E+05                                 17829.44092


                  Figure 5

             V.                             Final Chart of Correct Time Zone of NEXRAD Stage III (Zonal
                                            Statistic sum) versus Hourly USGS Stream Flow Data (Station
                                            #8181500)
                                                                                            NEXRAD vs Stream Flow

                                            180000000


                                            160000000


                                            140000000


                                            120000000
                    Stream Flow (cubic m)




                                            100000000
                                                                                                                                                discharge, m
                                                                                                                                                Linear (discharge, m)
                                            80000000


                                            60000000


                                            40000000


                                            20000000


                                                      0
                                                    0.00E+00       1.00E+09   2.00E+09   3.00E+09   4.00E+09   5.00E+09   6.00E+09   7.00E+09
                                                                                          NEXRAD (cubic m)



                  Figure 6
   VI.     GIS Layout of NEXRAD Stage III Grid data over San Antonio River
           Basin


                                               Hourly Precipitation
                                                  10242004_23
                                                                                                 -


           r10242004_23z
           Value
                   0 - 1.389999986
                   1.389999987 - 5.090000153
                                                 0   25   50   100 Miles
                   5.090000154 - 10.64999962
                   10.64999963 - 18.12000084
                   18.12000085 - 28.20999908                               Created by: Jayar S. Griffith
                                                                           11/24/2004 RS5053 Project
                   28.20999909 - 48.74000168                               Source: USGS, NOAA, TNRIS, Dr. Hongjie Xie
                                                                           Projection: NAD 1983 Albers




Figure 7
   IX. References




       National Oceanic and Atmospheric Administration. South Texas Floods
              October 17-22, 1998. Service Assessment February 1999

       Xie, H., X. Zhou, E.R. Vivoni, J.M.H. Hendrickx. E.E. Small, 2005. GIS
               GIS Based NEXRAD Precipitation Database: Automated Automated
               Approaches for Data Processing and Visualization. Computers and
               Geosciences, Vol. 31, pp. 65-76.


       Xie, Hongjie, 2004 Power Point Slides: L10-Water. 2004


 NEXRAD               Stage           III         data            available      at:
http://dipper.nws.noaa.gov/hdsb/data/nexrad/wgrfc_stageiii.html

USGS Real Time Stream Flow Data available at:
http://waterdata.usgs.gov/nwis/rt

				
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