SEPTEMBER 9, 1999 HOURLY PRECIPITATION DATA (PRIMARILY U.S.) National Climatic Data Center 151 Patton Ave. Asheville NC 28801-5001 USA Field numbers are shown with column positions in parenthesis. FIELD 1 (1 - 6): COOPERATIVE STATION NUMBER This 6-character alphanumeric station identifier is assigned by the National Climatic Data Center. The first two digits refer to a state code (see below). The next four digits refer to the Cooperative Network Index number (value range is 0001-9999). Missing/not assigned = 999999. (1 - 2): 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 Optional Field (8 - 37): STATION NAME This 30-character alphanumeric field is displayed if the data selection is for data with Station Name. Spacing for all fields following are adjusted 31 characters (e.g., Division Number that is in positions 8 - 9 without the station name is in positiions 39 - 40 with the station name selected). FIELD 2 (8 - 9): COOPERATIVE DIVISION NUMBER Cooperative Network Division Number. The division number will always be 00 in this data set prior to November 1993. Since November 1993, the division number ranges from 01-10. FIELD 3 (11 - 14): ELEMENT TYPE The type of data element stored in this record. The value is shown below. HPCP Hourly precipitation data. This is the only data type reported. (Includes the daily total.) FIELD 4 (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. FIELD 5 (19 - 22): 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.) FIELD 6 (24 - 25): MONTH Month of record. Range of value is 01-12. FIELD 7 (27 - 28): DAY Day of record. Range of value 0001-0031. FIELD 8 (30 - 33): 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 is used. FIELD 9 (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 Field 5. Range = 00000-99999. On days during the month without precipitation, no entry is 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. FIELD 10 (42): FLAG1 The Data Measurement Flag. FLAG1 Table (Data Measurement Flag for Hourly Data-Values) a Begin accumulation. A value of 99999 accompanies this flag. It indicates that the accumulation has begun sometime during the hour. A End accumulation (amount is associated with this flag). 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. M Missing data. No data available for this period. 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. M Missing data. No data available for this period. b (blank) no Flag needed. FIELD 11 (44): 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 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, and 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 value (value will be present). Lowest data resolution is hourly. This data value is excluded from the daily total. This flag is rarely used 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 FIELDS 8-11 are then repeated for each hour of the day, beginning with 0100 in the TIME field, and ending with 2500 in the TIME field. So, the data for Hour 0200 will occupy columns 46 - 60, Hour 0300 = 62 - 76, etc. 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 Administration (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 1948 there were over 3,000 universal rain gage stations in the HPD system. 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 are also entered into the database. 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.