DAILY SURFACE DATA
(OCTOBER 08, 1999)

National Climatic Data Center
151 Patton Ave.
Asheville, North Carolina

FIELD 1: DATA ORIGIN

The original NCDC tapedeck of the dataset. Referred to in some of the tables below.
*** Important Note:  If tapedeck number is 3202 or 3201, this indicates the data are preliminary, with less quality control applied than the final data (indicated by 3200 or 3210).  The 3202 and 3201 data are replaced online by the final data as soon as final data are available.  If tapedeck number is 32UI, this indicates the data are entered by State Climate Services for Idaho with less quality control applied than 3200 or 3210 data. ***

FIELD 2: 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 (value range is 01-91; reference Table "A"). The next four digits refer to the Cooperative Network Index number (value range is 0001-9999). Missing/not assigned = 999999.

FIELD 3: WBAN STATION NUMBER

This 5-character alphanumeric station identifier is assigned by the National Climatic Data Center. It originally referred to Weather Bureau, Army, and Navy (WBAN) stations which mailed weather observational forms to NCDC. These stations normally have more detailed data available than strictly cooperative stations, so stations with WBAN numbers will usually have additional data elements.

FIELD 4: DIVISION NUMBER

These two digits refer to the Cooperative Network Division Number (value range is 01-10; 99 = missing Division Number; reference Table "B").

FIELD 5: METEOROLOGICAL ELEMENT-TYPE

The type of meteorological elements stored in this data record. Range of values are listed below. Note: 'b' in DATA-VALUE indicates ascii blank.

ASMM
Average Cloudiness Midnight to Midnight (begin September 1992 for ASOS sites). This is the average of all available 30-second ceilometer data for the 24-hour period expressed in tenths of cloud cover at or below 12,000 feet. The DATA-VALUES are defined in Reference Table "C".

ASSS
Average Cloudiness Sunrise to Sunset (begin September 1992 for ASOS sites). This is the average of all available 30-second ceilometer data for the period from sunrise to sunset expressed in tenths of cloud cover at or below 12,000 feet. The DATA-VALUES are defined in Reference Table "C".

AWND
Average Daily Wind Speed (begin 1984). Units expressed in miles per hour to tenths. From January 1984 through June 1987 the Element Unit is incorrectly listed as TK (Tenths of Knots), it should be MH (Miles per Hour).

CLDG
Cooling Degree Day (begin 1984). Base 65 degrees Fahrenheit.

DPNT
Departure from Normal Temperature. DATA-VALUE = -00099 to b00099 degrees Fahrenheit.

DPTP
Average Daily Dew-Point Temperature (begin 1984). Units expressed in tenths of degrees Fahrenheit.

DYSW
The different types of weather occurring that day (reference Table "D" if FIELD 1 = 3200, Table "E" if FIELD 1 = 3210).

DYVC
Days with Weather in the Vicinity (begin July 1996). The present (or prevailing) weather occurring at the time of the observation in the vicinity of the station, between 5 and 10 statute miles of the point of observation. NOTE: This element is used beginning July 1996 and is coded in the same manner as the element DYSW. See the description for DYSW for details. (Reference Table "E")

EVAP
Daily evaporation (not reported when temperature below freezing). Unit Measurement, Inches & Hundredths of Inches.

F2MN
Fastest 2-minute Wind Direction and Speed (begin September 1992 for ASOS sites). Direction is expressed in tens of degree from true north. Speed is expressed in miles per hour. When two or more equal speeds have occurred, the most recent speed and direction are entered. Example of DATA-VALUE field XXYYY for wind direction and speed: 22048. Wind is from 220 degrees at 48 miles per hour.

F5SC
Fastest 5-second Wind Direction and Speed (begin September 1992 for ASOS sites). Direction is expressed in tens of degrees from true north. Speed is expressed in miles per hour. When two or more equal speeds have occurred, the most recent speed and direction are entered.

FMTM
Time of Fastest Mile or Fastest 1-minute Wind (begin 1984), or Fastest 2-minute Wind (begin September 1992). Units are expressed in hours and minutes.

FRGB
Base of Frozen Ground Layer. The depth below the surface of the ground at which frozen ground is last struck. Data available through 1964 only for designated stations. DATA-VALUE = b00000 to b00099 expressed in whole inches.

FRGT
Top of frozen ground layer. The depth below the surface of the ground at which frozen ground is first struck. Data available through 1964 only for designated stations. DATA-VALUE = b00000 to b00099 expressed in whole inches.

FRTH
Thickness of Frozen Ground Layer. Base value minus top value. Data available through 1964 only for designated stations. DATA-VALUE = b00000 to b00099

FSIN
Highest Instantaneous Wind Direction and Speed. This is the highest gust or peak reached by the pen of the gust recorder during the 24 hour period. Direction is expressed in 16 Point WBAN Code (Reference Table "F1"). Speed generally expressed in miles per hour. When two or more equal wind speeds occur the most recent is archived.

FSMI
Fastest Mile Wind Direction and Speed. Recorded by stations having triple or multiple register type recording instruments. The speed of a mile of wind occurring in the shortest time is used. This is determined by measuring the jogs on the chart made by the one mile contacts of the anemometer. Speed expressed in miles per hour. Example of value field XXYYY for wind direction and speed: 18045; 18 = wind direction from 169 degrees to 191 degrees. 045 = wind speed 45 miles per hour. FSMI is not digitized for Air Weather Service stations. (Reference Table "F2")

FSMN
Fastest Observed One-minute Wind Direction and Speed. This is used at stations not equipped with recording instruments. It is obtained by observation of an indicator for one minute and using an average value. Direction is expressed in Tens of Degrees Code. Speed expressed in miles per hour. Example of value field XXYYY for wind direction and speed: 18045; 18 = wind direction from 169 degrees to 191 degrees. 045 = wind speed 45 miles per hour. FSMN is not digitized for Air Weather Service Stations. (Reference table "F2")

GAHT
River Gauge Height - Below zero gauge readings. DATA-VALUE = negative values of b00000 to b00999, expressed to the nearest tenth of a foot.

HTDG
Heating Degree Days (begin 1984; however, several stations reported this element as early as 1961). Base 65 whole degrees Fahrenheit.

MNPN
Daily minimum temperature of water in an evaporation pan (effective September 1963). Unit Measurement, Whole Degrees Fahrenheit. (Reference Table "P").

MNRH
Minimum Relative Humidity (through 1955). DATA-VALUE = b00000 to b00100, expressed in whole percent. (AWS stations through January 1958, NWS, FAA, and Navy stations through December 1964. Most stations restarted in 1984; some stations reported this element as early as 1961).

MNTP
Average Temperature (begin 1984). The value is the (Max Temp. + Min Temp.)/2, expressed in whole degrees Fahrenheit. (Reference Table "P").

MXPN
Daily maximum temperature of water in an evaporation pan (effective September 1963). Unit Measurement, Whole Degrees Fahrenheit. (Reference Table "P").

MXRH
Maximum Relative Humidity. DATA-VALUE = b00000 to b00100, expressed in whole percent. (AWS stations through June 1958, NWS, FAA, and Navy stations through December 1964. Most stations restarted in 1986.)

PGTM
Peak Gust Time or Maximum 5-second Wind Speed Time. Value = b00000 to b02359, expressed in hours and minutes. Example: 2359 = 23 hours and 59 minutes. 

PKGS 
Peak Gust Direction and Speed. If two or more equal peak gust speeds occurred on the same day, the first was digitized for the period July, 1968 through December 1972. Beginning in January 1973, the last was digitized. The direction is generally expressed in 16 Point WBAN Code, with the following exceptions:

(1) Air Force stations used 36 Point code from January, 1964 through February, 1967, 16 Point WBAN Code from March, 1967 through June, 1968, and 36 Point code again from July, 1968 through December, 1970. Air Force data was generally discontinued by December, 1970.

(2) Navy stations used 16 Point WBAN Code from the beginning of record through January, 1971, and 36 Point Code from February, 1971 through the present.

Wind speeds are generally expressed in miles per hour through December, 1954, and in knots from January, 1955 to the present. A consistent exception is Navy stations, which used knots for the entire period of record. Example of value field XXYYY after 1954 for wind direction and speed: 44032; 44 = Wind direction from the SE. 032 = Wind speed 032 knots.

Beginning July 1996, wind direction is expressed in 36 Point WBAN Code (Reference Table "F2").

PRCP
Daily precipitation. Precipitation reading for 24 hours ending at time of observation. Trace is less than 0.005 inch. Unit Measurement, Inches to Hundredths.

PRES
Average Daily Station Pressure (begin 1984). Based on eight 3-hourly observations per day. Units expressed in thousandths of inches of Mercury.

PSUN
Daily Percent of Possible Sunshine (begin January 1965). Data Value = b00000 to b00100, expressed in percent.

RDIR
Resultant Wind Direction (begin 1984). DATA-VALUE expressed to the nearest whole degree code. From January 1984 through late 1994 the Meteorological Element Measurement units code is incorrectly recorded as DT (wind direction in tens of degrees). It should be DW (wind direction in whole degrees).

RWND
Resultant Wind Speed (begin 1984). DATA-VALUE is expressed in miles per hour to tenths. From January 1984 through June 1987, the Meteorological Element Measurement Units Code is incorrectly recorded as TK (tenths of knots) and incorrectly recored as MH (miles per hour) from July 1987 through late 1994. It should be TL tenths of miles per hour.

SAMM
Average Cloudiness Midnight to Midnight - (begin September 1992 for ASOS sites). This is the average of all available 30-second ceilometer data for the 24-hour period expressed in oktas of cloud cover at or below 12,000 feet. The DATA-VALUES are defined in Reference Table "C1".

SASS
Average Cloudiness Sunrise to Sunset (begin September 1992 for ASOS sites). This is the average of all available 30-second ceilometer data for the period from sunrise to sunset expressed in oktas of cloud cover at or below 12,000 feet. The DATA-VALUES are defined in Reference Table "C1".

SCMM
Average Sky Cover Midnight to Midnight (begin January 1965). Element not recorded at stations where personnel were not on duty 24 hours a day. See Elements ASMM and STMM for ASOS sites. DATA-VALUES are expressed in tenths and are defined in Reference Table "C".

SCSS
Average Sky Cover Sunrise to Sunset - (begin January 1965). DATA-VALUES are expressed in tenths and are defined in Reference Table "C". See Elements ASSS and STSS for ASOS sites.

SGMM
Average Cloudiness Midnight to Midnight (begin September 1992; end June 1996; derived from GOES satellite data). The areal coverage is approximately 50km by 50km centered on the ASOS site. DATA-VALUE is the average of all satellite scans of the site during the 24-hour period, expressed in oktas of cloud cover occurring above 12,000 feet. The DATA-VALUES are defined in Reference Table "C1".

SGSS
Average Cloudiness Sunrise to Sunset (begin September 1992; end June 1996; derived from GOES satellite data). The areal coverage is approximately 50km by 50km centered on the ASOS site. DATA-VALUE is the average of all satellite scans of the site during period from sunrise to sunset, expressed in oktas of cloud cover occurring above 12,000 feet. The DATA-VALUES are defined in Reference Table "C1".

SLVP
Average Daily Sea Level Pressure (begin 1984). DATA-VALUE expressed in tenths of millibars.

SMMM
Average Sky Cover Midnight to Midnight (begin January 1965). Element not recorded at stations where personnel were not on duty 24 hours a day. See Elements SAMM and SGMM for ASOS sites. DATA-VALUES are expressed in oktas and are defined in Reference Table "C1".

SMSS
Average Sky Cover Sunrise to Sunset - (begin January 1965) DATA-VALUES are expressed in oktas and are defined in Reference Table "C1". See Elements SASS and SGSS for ASOS sites.

SNOW
Daily Snowfall (Snowfall includes sleet). Amount is for 24-hour period ending at observation time. Hail was included with snowfall from July 1948 through December 1955. Hail occurring alone was not included with either snowfall or snow depth before and after that period. Trace is less than 0.05 inch. Unit Measurement, Inches to Tenths. Important Note: For July 1996 to present, this element is not valid and should not be used if FIELD 1 = 3210. NCDC will attempt to correct this problem as soon as resources allow.

SNWD
Snow depth at observation time. (Snow depth is depth of snow on the ground at time of observation. Trace is depth less than 0.5 inch.) Unit Measurement, Whole Inches. See Table "H". Important Note: For July 1996 to present, this element is not valid and should not be used if FIELD 1 = 3210. NCDC will attempt to correct this problem as soon as resources allow.

SNyz
Daily minimum soil temperature (see note below). Unit Measurement, whole degrees Fahrenheit. (Reference Table "P").

SOyz
Soil temperature at observation time (see note below). Unit Measurement, whole degrees Fahrenheit. (Reference Table "P").

STMM
Average Cloudiness Midnight to Midnight (begin September 1992; end June 1996; derived from GOES satellite data). The areal coverage is approximately 50km by 50km centered on the ASOS site. DATA-VALUE is the average of all satellite scans of the site during the 24-hour period, expressed in tenths of cloud cover occurring above 12,000 feet.

STSS
Average Cloudiness Sunrise to Sunset (begin September 1992; end June 1996; derived from GOES satellite data). The areal coverage is approximately 50km by 50km centered on the ASOS site. DATA-VALUE is the average of all satellite scans of the site during period from sunrise to sunset, expressed in tenths of cloud cover occurring above 12,000 feet.

SXyz
Daily maximum soil temperature (see note below). Unit Measurement, whole degrees Fahrenheit. (Reference Table "P").

Note: Positions "y" and "z" of the soil temperatures are encoded using reference Table "I", e.g., SN12 indicates that the daily minimum soil temperatures that follow are measured in an area covered with grass and at a depth of four inches or 10 centimeters.

THIC
Thickness of Ice on Water. Measured each Monday at noon LST, or more frequently if ice conditions are changing rapidly. Data available through December 1964 only for designated stations. DATA-VALUE = b00000 to b00999, expressed in tenths of inches.

TMAX
Daily maximum temperature. (Maximum temperature reading for 24 hours ending at time of observation.) Unit Measurement, Whole Degrees Fahrenheit. Important Note: For 1990 - 1994, this element is often shown as missing if FIELD 1 = 3210 and the max temperature was reported as -10 F or lower. NCDC will attempt to correct this problem as soon as resources allow.

TMIN
Daily minimum temperature. (Minimum temperature reading for 24 hours ending at time of observation.) Unit Measurement, Whole Degrees Fahrenheit. Important Note: For 1990 - 1994, this element is often shown as missing if FIELD 1 = 3210 and the min temperature was reported as -10 F or lower. NCDC will attempt to correct this problem as soon as resources allow.

TMPW
Average Daily Wet-Bulb Temperature (begin 1984). DATA-VALUE = -00199 to b00199, expressed in whole degrees Fahrenheit. (Reference Table "P"). 

TOBS 
Temperature at observation time. Unit Measurement, Whole Degrees Fahrenheit.

TSUN
Daily Total Sunshine. DATA-VALUE = b00000 to b01440, expressed in minutes. (Reference Table "J")

WDMV
24-hour wind movement. Unit Measurement, Whole Miles.

WTEQ
Water equivalent of snow depth. (For principal stations only. Effective October 1963 for snow depth equal or greater than 2 inches). Unit Measurement, Inches to Tenths.

FIELD 6 (27-28): METEOROLOGICAL ELEMENT MEASUREMENT UNITS CODE

The units and decimal position (precision) of the data value for this record (reference Table "K"). See "Known Uncorrected Problems" for additional details.

FIELD 7 (30-35): YEAR-MONTH

This is the year and month of the data record. Range of values is 1850-current year and 01-12. Example: 199512 = December 1995.

FIELD 8 (37-40): DAY OF MONTH and HOUR OF OBSERVATION

DAY:
The day of the month on which the data element was observed. Range of values is 01-31 LST. Will always begin with day 01 and end with day 31.

HOUR OF OBSERVATION:
Contains the hour of the daily observation. Hour of observation is reported using the 24-hour clock with values ranging from 00-23 LST, except in the cases of soil temperatures element-type (where the hour is 99 to indicate missing) and "days with weather" (where the hour is 24). Through June 1967 observations were designated as "AM" or "PM"; these values were set to 06 or 18 respectively during the conversion to TD-3200. From July 1967 through 1981, all observations were set to hour 18 (because the majority are p.m. observations). Beginning January 1982, the actual hour of the observation is indicated.

FIELD 9 (42-47): SIGN AND VALUE OF METEOROLOGICAL ELEMENT SIGN:

The algebraic sign of the meteorological data value is given as either a blank or a minus sign (-). Blank indicates a positive value and a minus sign represents a negative value.

VALUE OF METEOROLOGICAL ELEMENT
The actual data value is given as a five-digit integer. One major exception does exist however, for the DYSW (days with weather code) element-type values as explained in Table "D". A very small number of data values are known to have non-numeric entries.

When a data value is missing, the sign of the data value is set to "-", the data value is set to "99999", flag position 1 is set to "M" and flag position 2 is blank.

Prior to September 1991, when no daily precipitation reading was taken but the amount from that day (if any) is included in a subsequent value, the data value of precipitation is set equal to "00000" and flagged with an "S" in flag position 1. In turn, the successive accumulated amount will be flagged with an "A" in flag position 1. Since September 1991, it has been a practice at NCDC to set the precipitation value to "99999" in this situation; the flagging procedure has not changed.

FIELD 10 (49-49): FLAG1

The Data Measurement FLAG (reference Table "N").

FIELD 11 (51-51): FLAG2

The Data Quality FLAG (reference Table "O").

FIELDS 8-11 are then repeated for each day of the month, beginning with 01 in the DAY field, and ending with 31 in the DAY field. So, the data for DAY 02 will occupy columns 53-67, DAY 03 = 69-83, etc.

TABLES

TABLE "A"
State-Code Table

TABLE "B"
Cooperative Network Division Table

NOTE: The division number for a station may change over time. HAWAII (STATE 51)*

*NOTE: Hawaii (State 51) division numbers were changed during the initial conversion of this file. Divisions within islands no longer exist. Division numbers now represent each island.

PACIFIC ISLANDS (STATE 91)

TABLE "C"
SKY COVER in TENTHS for ELEMENTS: ASMM/ASSS/SCMM/SCSS/STMM/STSS

TABLE "C1"
SKY COVER in OKTAS for ELEMENTS: SAMM/SASS/SGMM/SGSS/SMMM/SMSS

TABLE "D"
DYSW - Daily Occurrence of Weather Table

From 1980 forward, these two-character DYSW element-type codes are stored into the rightmost four characters of the data value portion of the meteorological element. Within the four characters used, the weather codes are entered left justified. Thus, if one type of weather occurs during a day, the data values would appear as OXXOO, where XX is the appropriate weather code. If two types of weather occur, the data value will contain OXXYY, where XX is value 1 and YY is value 2. If more than two types of weather occur on the same day, they will be stored into additional "DLY" records of the element-type code "DYSW" as needed.

NOTE: Prior to 1980, each weather code for DYSW is written as a unique DATA PORTION. Only the left position (XX) of the DYSW code is used (e.g., appears as OXXOO).

TABLE "E"
DYSW/DYVC

TABLE "F1"
FSIN - WIND DIRECTION CODE
(16 Point WBAN Code)

Example of DATA-VALUE field XXYYY for wind direction and speeds:
12037 Wind is from the NNE at 37 miles per hour.

TABLE "F2"
FSMI & FSMN - WIND DIRECTION CODES

TABLE "G"
PKGS - WIND DIRECTION CODE
(36 Point WBAN Code)

TABLE "H"
SNWD

DEPTH of SNOW OBSERVED AT:

DATA-VALUE = b00000 to b09999 in whole inches. Trace of snow depth is less than 0.5 inches. Some Alaska and part-time stations take snow depth measurements at different hours.

TABLE "I"
Soil Temperature Table

(y = Code for soil cover)
(z = Code for soil depth)

NOTE: Soil records are kept since 1982. Some stations may report soil temperatures at observation time twice a day. Separate records will occur for both observation times.

TABLE "J"
TSUN

Conversion of minutes to tenths of hours is:

TABLE "K"
METEOROLOGICAL ELEMENT
MEASUREMENT UNITS CODE

The units and decimal position of the data value for this record. Range of values is listed below.

TABLE "N"
Data Measurement Flag 1

Flag 1 values of "S" and "A" usually occur in pairs (ie. a daily value will have Flag 1 assigned as "S" and the next daily value will have Flag 1 assigned as "A"). For some daily values these flags do not occur in pairs.

Other values occasionally appear in Data Measurement Flag 1 for which documentation is not currently available, e.g., "C" and "s".

TABLE "O"
Data Quality Flag 2

TABLE "P"
Units of Measurement Table

Range of values where b = Blank:

KNOWN UNCORRECTED PROBLEMS AND DATA CAVEATS:

For maximum and minimum temperature, from 1990 - 1994, the value is often shown as missing if FIELD 1 = 3210 and the temperature was reported as -10 F or lower. NCDC will attempt to correct this problem as soon as resources allow.

For snowfall and snow depth data: For July 1996 to present, this element is not valid and should not be used if FIELD 1 = 3210. NCDC will attempt to correct this problem as soon as resources allow.

For October 1990, there are numerous duplicate data records in the daily data. In using the data, choose the data record with the most daily values for the month.

During the period 1984-86 there are numerous entries for element PRCP of "NA" for the Meteorological Element Units Code. These
should be coded as "HI".

In 1988 for states 31-91 (North Carolina to Pacific Islands), the algebraic sign of positive meteorological data values may be coded
as "+" symbols instead of as blanks.

The historical data were converted from existing digital files and placed in the element structure format in 1983. At that time these data were only processed through a gross value check. In January 1984, NCDC instituted greatly enhanced computer algorithms for automated validation of digital archives. The revised edit system performs internal consistency checks, climatological limits checks and serial checks. It is the goal of the NCDC that, as resources permit, these historical files will be brought up to the same level of quality as those from 1984 onward.

Quality control "flags" are appended to each element to show how they fared during the edit procedures and to indicate what, if any, action was taken.

The typical progression of temperature instruments was from liquid-in-glass thermometers, to (1960 series) Hygrothermometers, to (1980 series) Hygrothermometers. Scientists are currently investigating the effect these instrument changes (especially the 1980 series) may have on long term temperature records.

Users should also be aware of a potential for a "lag" in the change of observation times used in the logical record and what is actually in practice at the site (that is, several months may be archived digitally under an "old" observation time before NCDC received notification).

Prior to the 1970's, accumulated amounts of precipitation were not always flagged with the "A". Instead the convention was to treat the value following a series of data values flagged with "S" as an accumulated value.

A very small number of data values are known to have non-numeric entries.

Maximum and minimum temperature--

National Weather Service, and Federal Aviation Stations: These values are determined from stations equipped with maximum and minimum thermometers or recording instruments. For some sites, when instruments were inoperative, values were selected from hourly observations.

U.S. Air Force Stations: From May 15, 1955, for stations taking 24 record observations per day, the maximum and minimun temperatures are determined from hourly observations. The observations at the beginning and ending of day are considered. The values are reported as missing when more than 3 of the hourly observations pertinent to the determination of maximum and minimum temperatures for each 24-hour period are missing or erroneous.

U.S. Navy Stations: When maximum and minimum thermometer readings are not available, the data at most stations are reported as
missing. Some Navy stations determine the maximum and minimum
temperatures from hourly observations when readings from maximum and minimum thermometers are not available.

Hail and Snowfall Amounts--

Although the inclusion of hail amounts with snowfall amounts was discontinued after December 31, 1955, some stations may have hail amounts included with snowfall after this date, as late as 1963 at a few stations. This occurred because on the original manuscript form the same column was used for the entry of snow, sleet and hail, and the entry was not indicated as hail. For NWS sites, hail was again included in snowfall amounts beginning in 1989.

Confidence Factors--

Days with Weather Code: The "days with weather" element-type (DYSW) cannot be used with any measure of confidence when FIELD 1 = 3200. Principal climatological stations operating 24 hours a day are expected to be the most reliable source of "days with weather". Reporting of this element by cooperative observers is not a requirement and criteria for reporting is not definitive. Most cooperative stations do not record this information.