U.S. HISTORICAL CLIMATOLOGY NETWORK MONTHLY (USHCN) Version 2.5.0 (Last Updated: 10 October, 2012) 1. INTRODUCTION 1.1 OVERVIEW In October 2012, a revision to the USHCN version 2 datasets was released as version 2.5. The version 2.5 processing steps are essentially the same as in version 2.0, but the increase in version number change reflects modifications that have been made to the underlying database as well as coding changes to the pairwise homogenization algorithm (PHA) that improve its overall efficiency. These modifications are listed in more detail in Table 1 of the USHCN version 2 website: http://www.ncdc.noaa.gov/oa/climate/research/ushcn and in the techical documents linked to therein. The composition of the network remains unchanged at 1218 stations, but the data formats and reprocessing frequency have changed. USHCN version 2.5 is now produced using the same processing system used for GHCN-Monthly version 3. This reprocessing consists of a construction process that assembles the USHCN version 2.5 monthly data in a specific source priority order (one that favors monthly data calculated directly from the latest version of GHCN-Daily), quality controls the data, identifies inhomogeneities and performs adjustments where possible. 1.2 INTERNET ACCESS WEBPAGE: http://www.ncdc.noaa.gov/oa/climate/research/ushcn FTP: ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2.5 1.3 DOWNLOADING AND INSTALLING WINDOWS (example): USHCN v2.5 files are compressed into gzip format by element. Data files are all of the format ushcn.element.latest.dataset.tar.gz where element=tmax, tmin, tavg, or prcp; and, dataset=raw, tob, or FLs.52i. The data will untar/uncompress into a directory called ushcn.version.date where version=2.5.0 and date=the year, month and day (yyyymmdd) that the data were last reprocessed and updated. Element definitions are as follows: tmax = monthly mean maximum temperature tmin = monthly mean minimum temperature tavg = average monthly temperature (tmax+tmin)/2 prcp = total monthly precipitation See section 2.2 for a definition of the dataset types For more information on gzip, please see the following web site: www.gzip.org and for potential software that can compress/decompress gzip files, please see: www.gzip.org/#faq4 LINUX (example): wget ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2.5/ushcn.tmax.latest.FLs.52i.tar.gz tar -zxvf ushcn.tmax.latest.FLs.52i.tar.gz (alternatively, if "tar" does not support decompression, a user can try: wget ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2.5/ushcn.tmax.latest.FLs.52i.tar.gz gzip -d ushcn.tmax.latest.FLs.52i.tar.gz tar -xvf ushcn.tmax.latest.FLs.52i.tar.gz) Note: the data are placed in their own separate directory, that is named according to the following specification: ushcn.v2.x.y.YYYYMMDD where x = integer to be incremented with major modifications to the processing system and/or database y = integer to be incremented with minor modifications to the processing system and/or database YYYY = year specific dataset was processed and produced MM = month specific dataset was processed and produced DD = day specific dataset was processed and produced Three files (per element) should be present in the directory along with the station list (ushcn-v2.5-stations.txt). 2. STATION LIST AND DATA FORMATS FORMAT OF "ushcn-v2.5-stations.txt" ---------------------------------------- Variable Columns Type ---------------------------------------- COUNTRY CODE 1-2 Character NETWORK CODE 3 Character ID PLACEHOLDERS ("00") 4-5 Character COOP ID 6-11 Character LATITUDE 13-20 Real LONGITUDE 22-30 Real ELEVATION 33-37 Real STATE 39-40 Character NAME 42-71 Character COMPONENT 1 (COOP ID) 73-78 Character COMPONENT 2 (COOP ID) 80-85 Character COMPONENT 3 (COOP ID) 87-92 Character UTC OFFSET 94-95 Integer ----------------------------------------- These variables have the following definitions: COOP ID is the six-digit U.S. Cooperative Observer Network station identification code. Note that the first two digits in the Coop Id correspond to the state. LATITUDE is latitude of the station (in decimal degrees). LONGITUDE is the longitude of the station (in decimal degrees). ELEVATION is the elevation of the station (in meters, missing = -999.9). STATE is the U.S. postal code for the state. NAME is the name of the station location. COMPONENT 1 is the Coop Id for the first station (in chronologic order) whose records were joined with those of the HCN site to form a longer time series. "------" indicates "not applicable". COMPONENT 2 is the Coop Id for the second station (if applicable) whose records were joined with those of the HCN site to form a longer time series. COMPONENT 3 is the Coop Id for the third station (if applicable) whose records were joined with those of the HCN site to form a longer time series. UTC OFFSET is the time difference between Coordinated Universal Time (UTC) and local standard time at the station (i.e., the number of hours that must be added to local standard time to match UTC). 2.2 DATA Monthly data in the USHCN v2.5 data use a "3 flag" format similar to that used within the Global Historical Climatology Network-Daily (GHCN-Daily) and GHCN-Monthly (version 3) datasets. 2.2.1 DATA FORMAT Variable Columns Type -------- ------- ---- ID 1-11 Integer YEAR 13-16 Integer VALUE1 17-22 Integer DMFLAG1 23-23 Character QCFLAG1 24-24 Character DSFLAG1 25-25 Character . . . . . . . . . VALUE12 116-121 Integer DMFLAG12 122-122 Character QCFLAG12 123-123 Character DSFLAG12 124-124 Character Variable Definitions: ID: 11 character alfanumeric identifier: characters 1-2=Country Code ('US' for all USHCN stations) character 3=Network code ('H' for Historical Climatology Network) digits 4-11='00'+6-digit Cooperative Observer Identification Number YEAR: 4 digit year of the station record. VALUE: monthly value (MISSING=-9999). Temperature values are in hundredths of a degree Celsius, but are expressed as whole integers (e.g. divide by 100.0 to get whole degrees Celsius). Precipitation values are in tenths of millimeters, but are also expressed as whole integers (e.g. divide by 10.0 to get millimeters). DMFLAG: data measurement flag, nine possible values: blank = no measurement information applicable a-i = number of days missing in calculation of monthly mean temperature (currently only applies to the 1218 USHCN V2 stations included within GHCNM) QCFLAG: quality control flag, seven possibilities within quality controlled unadjusted (qcu) dataset, and 2 possibilities within the quality controlled adjusted (qca) dataset. Quality Controlled Unadjusted (QCU) QC Flags: BLANK = no failure of quality control check or could not be evaluated. D = monthly value is part of an annual series of values that are exactly the same (e.g. duplicated) within another year in the station's record. I = checks for internal consistency between TMAX and TMIN. Flag is set when TMIN > TMAX for a given month. L = monthly value is isolated in time within the station record, and this is defined by having no immediate non- missing values 18 months on either side of the value. M = Manually flagged as erroneous. O = monthly value that is >= 5 bi-weight standard deviations from the bi-weight mean. Bi-weight statistics are calculated from a series of all non-missing values in the station's record for that particular month. S = monthly value has failed spatial consistency check. Any value found to be between 2.5 and 5.0 bi-weight standard deviations from the bi-weight mean, is more closely scrutinized by exmaining the 5 closest neighbors (not to exceed 500.0 km) and determine their associated distribution of respective z-scores. At least one of the neighbor stations must have a z score with the same sign as the target and its z-score must be greater than or equal to the z-score listed in column B (below), where column B is expressed as a function of the target z-score ranges (column A). ---------------------------- A | B ---------------------------- 4.0 - 5.0 | 1.9 ---------------------------- 3.0 - 4.0 | 1.8 ---------------------------- 2.75 - 3.0 | 1.7 ---------------------------- 2.50 - 2.75 | 1.6 W = monthly value is duplicated from the previous month, based upon regional and spatial criteria and is only applied from the year 2000 to the present. Quality Controlled Adjusted (QCA) QC Flags: A = alternative method of adjustment used. M = values with a non-blank quality control flag in the "qcu" dataset are set to missing the adjusted dataset and given an "M" quality control flag. X = pairwise algorithm removed the value because of too many inhomogeneities. DSFLAG: data source flag for monthly value: Blank = Value was computed from daily data available in GHCN-Daily Not Blank = Daily data are not available so the monthly value was obtained from the USHCN version 1 dataset. The possible Version 1 DSFLAGS are as follows: 1 = NCDC Tape Deck 3220, Summary of the Month Element Digital File 2 = Means Book - Smithsonian Institute, C.A. Schott (1876, 1881 thru 1931) 3 = Manuscript - Original Records, National Climatic Data Center 4 = Climatological Data (CD), monthly NCDC publication 5 = Climate Record Book, as described in History of Climatological Record Books, U.S. Department of Commerce, Weather Bureau, USGPO (1960) 6 = Bulletin W - Summary of the Climatological Data for the United States (by section), F.H. Bigelow, U.S. Weather Bureau (1912); and, Bulletin W - Summary of the Climatological Data for the United States, 2nd Ed. 7 = Local Climatological Data (LCD), monthly NCDC publication 8 = State Climatologists, various sources B = Professor Raymond Bradley - Refer to Climatic Fluctuations of the Western United States During the Period of Instrumental Records, Bradley, et. al., Contribution No. 42, Dept. of Geography and Geology, University of Massachusetts (1982) D = Dr. Henry Diaz, a compilation of data from Bulletin W, LCD, and NCDC Tape Deck 3220 (1983) G = Professor John Griffiths - primarily from Climatological Data 3. HOW TO CITE Users are requested to cite the version number (version 2.0 for version 2 or version 2.5.x.YYYYMMDD for version 2.5.0 and above) as well as Menne, M.J., C.N. Williams, and R.S. Vose, 2009: The United States Historical Climatology Network monthly temperature data?Version 2. Bulletin of the American Meteorological Society, 90, 993-1007. 4. CONTACT 4.1 QUESTIONS AND FEEDBACK NCDC.USHCN@noaa.gov 4.2 OBTAINING ARCHIVED VERSIONS At this time, the National Climatic Data Center does not maintain an online ftp archive of daily processed GHCNM versions. The latest version always overwrites the previous version and thus represents the latest data, quality control, etc. However, if you need to obtain a previous version, please email: NCDC.USHCN@noaa.gov with your request and please specify the specific version needed.