DATA DOCUMENTATION FOR HOURLY PRECIPITATION DATA TD-3240 Greg Hammer and Pete Steurer November 15, 2000 National Climatic Data Center 151 Patton Ave. Asheville, NC 28801-5001 USA TABLE OF CONTENTS TOPIC PAGE INTRODUCTION 1. Data Set ID 4 2. Data Set Name 4 3. Data Set Aliases 4 DESCRIPTION 4. Access Method and Sort for Archived Data 4 5. Access Method and Sort for Supplied Data 6 6. Element Names and Definitions 9 7. Start Date 15 8. Stop Date 15 9. Coverage 15 10. Location 16 11. Keywords 16 12. How to Order Data 16 DATA CENTER 13. Archiving Data Center 16 14. Technical Contact 16 DATA QUALITY 15. Known Uncorrected Problems 17 16. Quality Statement 17 17. Revision Date 17 OTHER DATA SETS 18. Source Data Sets 17 19. Essential Companion Data Sets 18 20. Derived Data Sets 18 SUMMARIZATION 21. References 18 22. Summary 19 1. Data Set ID: 3240 2. Data Set Name: Hourly Precipitation Data 3. Data Set Aliases: HPD 4. Access Method and Sort for Archived Data: Data are archived in a variable length element file structure. Archived data are currently sorted by Station-ID (excluding the Division Number) as the primary key and year, month, and day as secondary keys. Data may also be produced in a fixed length record structure described in topic 5, "Access Method and Sort for Supplied Data". Each record contains one day of one station's occurrences of precipitation. The record consists of a control word and identification portion, and a data portion. The control word is used by the computer operating system for record length determination. The identification portion identifies the observing station, year, month, day, and record element units code. The data portion contains the hour, precipitation occurrence and measurement flags. The data portion is repeated for as many values as occur in the given time interval. It stands to reason that for most hours the non-occurrence of precipitation is prevalent. Therefore, in order to save space in the digital file, there are entries only for: 1. The first day and hour of each month where observations were taken even if no precipitation occurred during that month. 2. Hours with precipitation > zero. 3. Beginning and ending hours of missing periods. 4. Beginning and ending hours of accumulating periods. 5. Beginning and ending periods of deleted data. NCDC archive files are structured as follows: Record Length : Variable with a maximum of 1230 characters Blocked : 12000 characters Media : ASCII 18-track IBM-Type 3480 cartridge Parity : Odd Label : ANSI Standard Label The first eight fields (the ID PORTION of the record) describe the characteristics of the entire record. The DATA PORTION of the record contains information about the element value reported. This portion is repeated for as many values as occur in the daily record of hourly values plus the daily total. Each record is of variable length with a maximum of 1230 characters. Each record contains a station's data for a specific meteorological element for one day. The record format is: Field Width Position Record Type 3 001-003 Station ID 8 004-011 Meteorological Element Type 4 012-015 Meteorological Element Units 2 016-017 Year 4 018-021 Month 2 022-023 Day (right justified 0 filled) 4 024-027 Number of Data Groups that follow 3 028-030 Hour 4 031-034 Value of Meteorological Element 6 035-040 Data Measurement Flag 1 1 041-041 Data Quality Flag 2 1 042-042 Hour, Value of Meteorological Element, Measurement Flag 1 and Quality Flag 2 repeated as many times as needed to contain one day of Hourly values 043-330 Coding Guidelines: The following statements may be used to read variable length records in COBOL or FORTRAN. (1) Typical ANSI COBOL FD INDATA LABEL RECORDS ARE STANDARD RECORD MODE D BLOCK CONTAINS 12000 CHARACTERS DATA RECORD IS DATA-RECORD. 01 DATA RECORD. 02 RECORD TYPE PIC X(3). 02 STATION-ID PIC X(8). 02 ELEMENT-TYPE PIC X(4). 02 ELEMENT-UNITS PIC XX. 02 YEAR PIC 9(4). 02 MONTH PIC 99. 02 DAY PIC 9(4). 02 NUMBER-VALUES PIC 9(3). 02 DAILY-ENTRY OCCURS 1 TO 100 TIMES DEPENDING ON NUMBER-VALUES. 04 HOUR PIC 9(4). 04 DATA-VALUE PIC S9(5)SIGN LEADING SEPARATE. 04 FLAG-1 PIC X. 04 FLAG-2 PIC X. (2) Typical FORTRAN OPEN(10,FILE='FILENAME',ACCESS='SEQUENTIAL',STATUS='OLD' &RFORM='VB',MRECL=1230,TYPE='ANSI',BLOCK=12000) C LAST LINE OF OPEN STATEMENT IS UNISYS UNIQUE CHARACTER*3 RECTYP CHARACTER*8 STNID CHARACTER*4 ELMTYP CHARACTER*2 EUNITS CHARACTER*1 FLAG1, FLAG2 DIMENSION IVALUE(100), FLAG1(100), FLAG2(100), IHR(100) READ (10,20,END=999) RECTYP, STNID, ELMTYP, EUNITS, IYEAR, &IMON, IDAY, NUMVAL, ((IHR(J), IVALUE(J), FLAG1(J), FLAG2(J)), &J=1,NUMVAL) 20 FORMAT (A3, A8, A4, A2, I4, I2, I4, I3, 100(I4, I6, 2A1)) EXAMPLE OF VARIABLE LENGTH RECORD (As seen from a file dump) 0058HPD17001100HPCPHI19810400060020400b00012bb2500b00012bb (The symbol 'b' denotes a blank) DUMP RECORD POSITION POSITION CONTENTS MEANING 1-4 0058 Record control word used by the operating system. (Contains the total number of characters in the record - not available to user programs.) 5-7 1-3 HPD RECORD-TYPE 8-15 4-11 17001100 STATION-ID for state 17, station 0011, Division 00 16-19 12-15 HPCP ELEMENT-TYPE 20-21 16-17 HI ELEMENT-UNITS 22-25 18-21 1981 YEAR 26-27 22-23 04 MONTH 28-31 24-27 0006 DAY OF THE MONTH (Day 06 right justified) 32-34 28-30 002 NUM-VALUES; two data entries to follow 35-38 31-34 0400 TIME-OF-VALUE (Precipitation from 03:01 to 04:00) 39-44 35-40 b00012 DATA-VALUE 45 41-41 b FLAG-1 46 42-42 b FLAG-2 47-50 43-46 2500 TIME-OF-VALUE (daily total) 51-56 47-52 b00012 DATA-VALUE 57 53-53 b FLAG-1 58 54-54 b FLAG-2 In this example for April 6, 1981, hours 0100-0300 and 0500-2400 reported zero precipitation. 5. Access Method and Sort for Supplied Data: In addition to a variable length record structure, users may also receive data in a fixed length record structure as described below. Supplied data are in the same sort as archived data (see topic 4 "Access Method and Sort for Archived Data"). Each record contains one station's specific occurrence for a one hour time interval. The record consists of an identification portion, and a data portion. The identification portion identifies the observing station, element code, year, month, and day. The data portion contains one hourly time interval data value and flags. The data portion is not repeated. It stands to reason that for most hours the non-occurrence of precipitation is prevalent. Therefore, in order to save space in the digital file, there are entries only for: 1. The first day and hour of each month where observations were taken even if no precipitation occurred during that month. 2. Hours with precipitation > zero. 3. Beginning and ending hours of missing periods. 4. Beginning and ending hours of accumulating periods. 5. Beginning and ending periods of deleted data. Fixed Length files are structured as follows: Data Length: 42 characters Blocked: 6300 characters Media: ASCII or EBCDIC Modes - 9 Track or 18 Track, IBM-Type 3480 Cartridges Parity: Odd Label: ANSI standard labeled (ASCII only) or unlabeled File: 1 file per tape Density: 1600, 6250, or 36,000 (cartridge) BPI The first eight tape fields, the ID PORTION of the record, describe the characteristics of the entire record. The DATA PORTION of the record contains information about each element value reported. This portion contains only one hourly occurrence. Each record is fixed with 42 characters. Each record contains a station's hourly time interval for the specified day. The format of a record is: Field Width Position Record Type 3 001-003 Station ID 8 004-011 Meteorological Element Type 4 012-015 Meteorological Element Units 2 016-017 Year 4 018-021 Month 2 022-023 Day (Right Justified) 4 024-027 Number of data Groups that follow 3 028-030 Hour 4 031-034 Value of Meteorological Element 6 035-040 Data Measurement Flag 1 1 041-041 Data Quality Flag 2 1 042-042 Coding Guidelines: The following statements may be used to read fixed length records in COBOL or FORTRAN. (1) Typical ANSI COBOL FD INDATA LABEL RECORDS ARE STANDARD RECORD MODE F BLOCK CONTAINS 6300 CHARACTERS DATA RECORD IS DATA-RECORD. 01 DATA-RECORD. 02 RECORD-TYPE PIC X(3). 02 STATION-ID PIC X(8). 02 ELEMENT-TYPE PIC X(4). 02 ELEMENT-UNITS PIC XX. 02 YEAR PIC 9(4). 02 MONTH PIC 99. 02 DAY PIC 9(4). 02 NUMBER-VALUES PIC 9(3). 02 HOUR PIC 9(4). 02 DATA-VALUE PIC S9(5) SIGN LEADING SEPARATE. 02 FLAG-1 PIC X. 02 FLAG-2 PIC X. (2) Typical FORTRAN OPEN(10,FILE="FILENAME",ACCESS="SEQUENTIAL",STATUS="OLD" &RFORM="FB",MRECL=42,TYPE="ANSI",BLOCK=6300) C LAST LINE OF OPEN STATEMENT IS UNISYS UNIQUE CHARACTER*3 RECTYP CHARACTER*8 STNID CHARACTER*4 ELMTYP CHARACTER*2 EUNITS CHARACTER*1 FLAG1, FLAG2 READ (10, 20, END=999) RECTYP, STNID, ELMTYP, EUNITS, IYEAR, &IMON,IDAY, NUMVAL, IHR, IVALUE, FLAG1, FLAG2 20 FORMAT (A3, A8, A4, A2, I4, I2, I4, I3, I4, I6, 2A1) EXAMPLE OF FIXED LENGTH RECORD (As seen from a file dump) HPD17001100HPCPHI19810400060010400b00012bb (The symbol 'b' denotes a blank) COLUMN CONTENTS MEANING 1-3 HPD RECORD-TYPE 4-11 17001100 STATION-ID for state 17, station 0011, Division 00 12-15 HPCP ELEMENT-TYPE 16-17 HI ELEMENT-UNITS 18-21 1981 YEAR 22-23 04 MONTH (April) 24-27 0006 DAY OF THE MONTH (Day 06 right justified) 28-30 001 NUM-VALUES; One data entry follows 31-34 0400 TIME-OF-VALUES (Precipitation from 03:01 to 04:00) 35-40 b00012 DATA-VALUE (0.12 inches of precipitation) 41 b FLAG-1 42 b FLAG-2 6. Element Names and Definitions: TAPE TAPE RECORD ELEMENT FIELD POSITION NAME CODE DEFINITIONS AND REMARKS 001 1-3 Record-Type The type of data stored in this record. Value is "HPD". ______________________________________________________________________________ 002 4-11 Station-ID This 8-character station identifier is assigned by the National Climatic Data Center. See State Code Table. _________________________________________________________________ 4-5 State-Code STATE CODE as indicated. Range of value is 01 to 48, 50, 51, 66, 67, and 91. STATE CODE TABLE 01 Alabama 28 New Jersey 02 Arizona 29 New Mexico 03 Arkansas 30 New York 04 California 31 North Carolina 05 Colorado 32 North Dakota 06 Connecticut 33 Ohio 07 Delaware 34 Oklahoma 08 Florida 35 Oregon 09 Georgia 36 Pennsylvania 10 Idaho 37 Rhode Island 11 Illinois 38 South Carolina 12 Indiana 39 South Dakota 13 Iowa 40 Tennessee 14 Kansas 41 Texas 15 Kentucky 42 Utah 16 Louisiana 43 Vermont 17 Maine 44 Virginia 18 Maryland 45 Washington 19 Massachusetts 46 West Virginia 20 Michigan 47 Wisconsin 21 Minnesota 48 Wyoming 22 Mississippi 49 Not Used 23 Missouri 50 Alaska 24 Montana 51 Hawaii 25 Nebraska 66 Puerto Rico 26 Nevada 67 Virgin Islands 27 New Hampshire 91 Pacific Islands _____________________________________________________________________________ 6-9 Cooperative Network Index assigned by NCDC Network (Station List) Range 0001 thru Index Number 9999. 10-11 Cooperative Cooperative Network Division Number. Network The division number will always be Division Number 00 in this data set prior to November 1993. Since November 1993, the division number ranges from 01-10. ______________________________________________________________________________ 003 12-15 Element-Type The type of data element stored in this record. Range of values is listed below. HPCP Hourly precipitation data. This is the only data type reported. (Includes the daily total.) ______________________________________________________________________________ 004 16-17 Element-Units The units and decimal position of the data value for this record. Range of values is listed below. HI Hundredths of inches. Data stored and observed to the same accuracy. HT Data stored as hundredths of inches, but is observed to tenths only. (Example, 0.2 inches stored as 00020). Primarily for Fischer-Porter gage sites. ______________________________________________________________________________ 005 18-21 Year This is the year of record. Range of values is generally from 1948-current year processed. (A few stations begin as early as 1900.) ______________________________________________________________________________ 006 22-23 Month Month of record. Range of value is 01-12. ______________________________________________________________________________ 007 24-27 Day Day of record. Range of value 0001-0031. ______________________________________________________________________________ 008 28-30 Number- This denotes the actual number of Reported-Values values. Range of values is 2 to 25. NOTE: A record may contain fewer or more data values than you might expect. A daily record of hourly values may contain as few as 2 data values or as many as 25 data values. Only hours which have recorded precipitation are included (no entry for zero precipitation). There are some exceptions: 1) the begin and end hours of a missing, accumulation or deleted period are reported, 2) the first day and hour of each month that a site is in operation, whether precipitation occurs or not is included. See Flag 1 definitions for further details. ______________________________________________________________________________ 009 31-34 Time-Of-Value This contains the ending time of precipitation 0100-2500. (Example, hour 0200 is defined as the period 0101-0200) The hour is left justified, zero filled. Hour 2500 contains the daily total, and it will always be the last value of a record. Midnight = 2400. Local Standard Time in use. ______________________________________________________________________________ 010 35-40 Data-Value The actual precipitation data value. The data value portion is a five-digit integer with a leading algebraic sign. The sign is blank for positive and "-" represents negative values("-" never used in this data set). Units and decimal position, if appropriate, are indicated in the ELEMENT-UNITS field described in Tape Field 004. Range = 00000-99999. 00000 will be used only on the first hour of each month unless there is precipitation during that hour, in which case the measured value will be provided. On other days during the month without precipitation, no entry will be made. 99999 indicates that the DATA-VALUE is unknown. Beginning with the July 1996 data month, traces of precipitation are archived for first order stations. A trace is indicated by 00000 recorded in this element (Data-Value) and a "T" in FLAG1. ______________________________________________________________________________ 011 41 FLAG1 The Data Measurement Flag. FLAG1 Table (Data Measurement Flag for Hourly Data-Values) a Begin accumulation. A value of 99999 accompanies this flag. For TD3240, it indicates that the accumulation has begun sometime during the hour. A End accumulation (amount is associated with this flag). For TD3240, it indicates the accumulation has ended sometime during the hour. Accumulated period indicates that the precipitation amount is correct, but only the exact beginning and ending times are known. A data value of 99999 occurring on the last day and hour of a month indicates the accumulation continues into the next month (see Flag 1 ?,?) , The "," flag is used at the beginning of a data month when an accumulation is in progress from the previous month. A data value of 99999 always accompanies this flag. This flag is used prior to 1984. { Begin deleted period during the hour (inclusive). The original data were received, but were unreadable or clearly recognized as noise. A value of 99999 accompanies this flag. Primarily used since 1984. Also used in Alaska for 1976-1978. } End deleted period during the hour (inclusive). The original data were received, but were unreadable or clearly recognized as noise. A value of 99999 accompanies this flag. Primarily used since 1984. Also used in Alaska for 1976-1978. [ Begin missing period during the hour (inclusive). A value of 99999 accompanies this flag ] End missing period during the hour (inclusive) A value of 99999 accompanies this flag. Prior to 1984 if precipitation occurred during the last hour of the missing period, the ending missing value appears with a non-zero value (example ?00021]?). Beginning in 1984 the beginning and ending hours of the missing period are recorded as ?99999[? and ?99999]?, respectively. A missing flag indicates that the data were not received. This flag appears on the first and last day of each month for which data were not received or not processed by NCDC. E Evaporation may have occurred. Data may or may not be reliable. This flag was used during the period 1984-1993. g Only used for day 1, hour 0100 when precipitation is zero. T Indicates a "trace" amount. Data value will be zero. "T" flags appear on NWS First Order data only since July 1996. b (blank) no Flag needed. FLAG1 Table (Data Measurement Flag for Daily Total Data Values) I Incomplete or Inexact daily total occurring only with hour 2500. Value is not a true 24-hour amount. One or more periods are missing and/or an accumulated amount has begun but not ended during the daily period. P A daily total excludes erroneous values (those flagged q, Q, {, or }. A "P" flag will also be present when an accumulation has ended (but not begun) during the daily period. T TRACE, Flag1 will contain a ?T? flag in the daily total if no values other than a TRACE occurred during the 24 hour period. b (blank) no Flag needed. ______________________________________________________________________________ 012 42 FLAG2 The Data Quality Flag. FLAG2 Table (Data Quality Flag) Z Used since January 1996. Indicates probable amounts as a result of melting frozen precipitation. When assigned to a daily total, it indicates some or all of the total contains values assigned a flag of Z. This flag may be used to identify those sites that are deficient in which the manner the snow shields are employed. R Used since January 1996. Indicates data values are suspect with regard to the times or period of occurrence. When assigned to a daily total, it indicates data with suspect "times" are included in the daily amount. Q Prior to 1996. Indicates value failed an extreme value test (value will be present); data are to be used with caution. Extremes tests were: 1) If the value was not an accumulated precipitation total, the value failed the one-hour statewide 100 year return period precipitation. 2) If the value was an accumulated precipitation total, the value failed the 24-hour statewide extreme precipitation total. This flag was assigned during a 1997 NCDC rehabilitation of the 1900-1995 TD3240 archive. Since January 1996. A single erroneous datum (value will be present). Lowest data resolution is hourly. This data value is excluded from the daily total. This flag is rarely used in TD3240 since 1996. q Used since January 1996. An hourly value excludes one or more 15 minute periods. Lowest data resolution is 15 minutes. ______________________________________________________________________________ EXAMPLES OF HOW FLAGS ARE USED. NOTE: blank = b Example 1: precipitation accumulation from Month 1, day 02 to Month 2, day 04. Month Day Hour Data Value 01 0002 0500 00030bb Precip. 0.3 inches 1000 99999ab Accumulation begins 2500 00030Ib Incomplete daily total 01 0031 2400 99999Ab Accumulation continues 2500 00000Ib Incomplete daily total 02 0001 0100 99999,b Accumulation continues 2500 00000Ib Incomplete daily total 0004 1400 00390Ab Accumulation ends 2500 00390Pb Incomplete daily total Example 2: Accumulated precipitation for 1 monthly only. 01 0002 1000 99999ab Accumulation begins 2500 00000Ib Incomplete daily total 0031 2400 00320Ab Accumulation ends 2500 00320Pb Incomplete daily total Example 3: Accumulated, deleted, and missing precipitation data through months 01 and 02. 01 0001 0100 00000gb First record of the month 0002 1100 99999ab Accumulation begins 2500 00000Ib Incomplete daily total 01 0031 2400 99999Ab Accumulation continues 2500 00000Ib Incomplete daily total 02 0001 0100 99999,b Accumulation continues 1400 00630Ab Accumulation ends 1500 99999{b Deleted data begins 2500 00630Pb Incomplete daily total 02 0028 1300 99999}b Deleted data ends 1400 99999[b Missing data 2400 99999]b Missing data 2500 00000Pb Incomplete daily total Example 4: Precipitation charts or forms were never received at NCDC for months 1 and 2. 01 0001 0100 99999[b Missing data 2500 00000Ib 0031 0100 99999]b 2500 00000Ib 02 0001 0100 99999[b 2500 00000Ib 0028 0100 99999]b 2500 00000Ib Example 5: Missing precipitation data through months 11and 12 that ends on hour 1 day 1 of month 12 (rare occurrence of unmatched flag pair in month): Month Day Hour Data value 11 0001 0100 99999[b Missing data begins 2500 00000Ib 0030 2400 99999]b Missing data ends 2500 00000Ib 12 0001 0100 99999]b 2500 00000Ib Missing data ends (unmatched flag pair) 7. Start Date: 1900. Most stations begin in 1948. 8. Stop Date: Present 9. Coverage (Latitude-Longitude Box) a. Southernmost Latitude: 14S b. Northernmost Latitude: 66N c. Westernmost Longitude: 135E d. Easternmost Longitude: 64W 10. Location: a. Atlantic Ocean b. North America c. Pacific Ocean Area coverage includes the United States, Puerto Rico, Virgin Islands and U.S. protectorates located in the Pacific. 11. Keywords: a. precipitation b. rain c. rainfall d. storm events e. dry day f. wet day g. rainfall depth h. rainfall duration I. rainfall intensity j. hydrology k. HPD l. TD3240 m. Rain gage 12. How to Order Data: Ask NCDC's Climate Services about the cost of obtaining this data set. Phone 828-271-4800; FAX 828-271-4876; e-mail orders@ncdc.noaa.gov 13. Archiving Data Center: National Climatic Data Center Federal Building 151 Patton Avenue Asheville, NC 28801-5001 14. Technical Contact: Data Base Administrator National Climatic Data Center Federal Building 151 Patton Avenue Asheville, NC 28801-5001 Phone 828-271-4994; 15. Known Uncorrected Problems: Hours with zero precipitation occur for times other than the first day and hour of a month. 16. Quality Statement: Initially from August 1948 to September 1951, data were keyed on punched cards by the regional Weather Records Processing Centers. Then the task was transferred to the National Climatic Data Center (NCDC) in Asheville, NC. The hourly precipitation data file was transferred from punched cards to magnetic tape (TD-9657) during the late 1960s. Data before 1984 were converted from existing digital files (TD-9657) to an element structure format (TD3240). These (historical) data were processed through a gross value check only. Beginning in January 1984, the hourly precipitation data were processed through a completely revised system which directly produced the element structure database file. This system was further enhanced beginning with the January 1996 data month. The 1996 interactive quality control system introduced many features. Data are subjected to new computer editing procedures reducing the manual handling of the data. Data are interactively quality controlled at NCDC using spatiotemporal techniques in a variety of ways. To make the pre-1996 data consistent with the January 1996 processing system, these historical data were re-processed in 1997. The rehabilitated data covered the 1900 through 1995 period and contains more than 53 million observations. Approximately 400 thousand inconsistencies were identified and corrected as a result of this effort. These inconsistencies were categorized into 22 error patterns. In addition to this effort, "last look" quality assurance software was implemented on near-real time HPD data (post 1996) sent to the archive each month. The"last look" software uses similar checks as the rehabilitation software and should result in maintaining consistency between the historical data and operationally received data. 17. Revision Date: 199707. This documentation revised the previous documentation which was prepared in July 1996. This new documentation accounts for the format changes resulting from the new January 1996 processing system. 199802. Revised Quality Flag2 codes. Removed X and updated Q. 18. Source Data Sets: TD-3240 Hourly precipitation data is derived (except for stations which record on an hourly basis) from data collected in the TD-3260 Hourly Precipitation Data-15 Minutes system. 19. Essential Companion Data Sets: The use of NCDC's Station History file (TD9767) is required in order to determine metadata on each station (name, location, elevation, etc.). This can be accomplished by comparing the station number in bytes 1 through 6 of this data set with the corresponding station number in the Station History data set. 20. Derived Data Sets: This data set is used to produce the monthly publication entitled ?Hourly Precipitation Data?. It has also been used in various rainfall event statistic data sets produced by NCDC and elsewhere. An NCDC event data set is archived in TD9651 and entitled ?Hourly Precipitation Data Rainfall Event Statistics?. It is also used to create an inventory of HPD (TD3340 - Hourly Precipitation Data Inventory). 21. References: Tollerud, E.I., Govett, M.W., Steurer, P.M., and Moninger, W.R., 1997: New access and display routines for hourly precipitation data and metadata using CD-ROMs and the World Wide Web. Preprints, 105th Conf. on Applied Meteorology, Reno, Nevada, American Meteorological Society. Steurer, P.M., 1997: Hourly Precipitation Data rehabilitation for the period 1900-1995. NOAA/NCDC TD3240 Documentation Series, Asheville, NC, 5 pp. Hammer, G.R. and Steurer, P.M., 1997: Data set documentation for Hourly Precipitation Data. NOAA/NCDC TD3240 Documentation Series, Asheville, NC, 18 pp. Hammer, G.R. and Reek, T., 1997: The Processing of Recording Rain Gage Data at the National Climatic Data Center. Proceedings of the 13th Conference on Hydrology, Long Beach, California, American Meteorological Society, 223-226. Collander, R.S., Tollerud, E.I., Li, L., and Lazar, A., 1993: Hourly precipitation data and station histories: A research assessment. Proceeding of the 8th Symposium on Meteorological Observations and Instrumentation, Anaheim, California, American Meteorological Society. National Weather Service Observing Handbook No. 2: Cooperative Station Observations, July 1989, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service, Observing Systems Branch, Silver Spring, MD. Phillips, C., 1985: An objective method for minimizing non-precipitation effects in precipitation data from punched paper tape. Proceedings of the International Conference on Interactive Information and Processing Systems for Meteorology, Oceanography and Hydrology, Los Angeles, California, American Meteorological Society, 178-182. 22. Summary: The observations in the Hourly Precipitation Data File were taken by observers at principle (primary) stations, secondary stations, and cooperative observer stations operated by the National Weather Service (NWS), and the Federal Aviation Agency (FAA). Approximately 5,500 stations have recorded precipitation data through the period of this digital file. Initially from August 1948 to September 1951, data were keyed on punched cards by the regional Weather Records Processing Centers. Then the task was transferred to the National Climatic Data Center (NCDC) in Asheville, NC. The hourly precipitation data file was transferred from punched cards to magnetic tape (TD-9657) during the late 1960s. This data file was then converted to the element file structure during 1984. Several recording (weighing) rain gage instruments were used in measuring hourly precipitation, but by September 1963 many Fischer-Porter precipitation gage instruments with automated readout, recorded on paper tape, were phased in. By early 1965, about 200 of these were in operation and they became the primary recording instrument. In 1996, there were approximately 2,400 Fischer-Porter gages in operation. The Universal Rain gage is the other primary instrument used to create this data file. It has an automated readout recorded on paper charts. In 1996, there were approximately 100 Universal Rain gage stations in the HPD system. Station and dates of commissioning of weighing rain gages are in the Station History listings available at the NCDC in Asheville, NC. Fischer-Porter precipitation gages record data on punched paper tapes. A device known as the Mitron reader translates the data at NCDC. The Universal Rain gage records data on paper charts. The precipitation recorded on the charts is then digitized. The data from the Surface Climate Information Archive and Dissemination System (SCIADS) or primary stations is also entered into the TD3240. The data in this file are a combination of original observations of hourly and daily accumulated precipitation. Precipitation values are checked and edited as necessary by an automated and manual edit. Data before 1984 were converted from existing digital files (TD-9657) to the element structure format. These (historical) data were processed through a gross value check only. Beginning January 1984, the hourly precipitation data were processed through a completely revised system which produces the element structure database file. This system was further enhanced beginning with the January 1996 data month. The new interactive quality control system introduced many features. Data are subjected to new computer editing procedures reducing the manual handling of the data. To make the pre-1996 data consistent with the January 1996 processing system, the historical data were re-processed in 1997. The rehabilitated data covered the 1900 through 1995 period and contained more than 53 million observations. Approximately 400 thousand inconsistencies were identified and corrected as a result of this effort. These inconsistencies were categorized into 22 error types. In addition to this effort, "last look" quality assurance software was implemented on HPD data (post 1996) operationally sent to the archive each month. The "last look" software uses similar checks as the rehabilitation software and should result in maintaining consistency between the historical data and operationally received data. 19