From http://www1.ncdc.noaa.gov/pub/data/cirs/state.README                            
   TIME BIAS CORRECTED
                           STATEWIDE-REGIONAL-NATIONAL
                            TEMPERATURE-PRECIPITATION

                                  NOVEMBER 1995


THE STATEWIDE, REGIONAL, AND NATIONAL DATA

     The major parameters in this file are sequential statewide, regional, and
national monthly precipitation and monthly "time bias corrected" average
temperature.  The period of record is 1895 through the latest month available. 
This file is provided online and is updated monthly.  The data in this file are
used for historical perspectives in the CLIMATE VARIATIONS BULLETIN (Historical
Climatology Series 4-7).

     The monthly values for the most recent one to two years are based on
preliminary data and will change when the final data are analyzed.

     The statewide values are available for the 48 contiguous States and are
computed from the divisional values weighted by area.  The regional values are
computed from the statewide values weighted by area (as defined by T.R. Karl
and W.J. Koss, 1984:  Historical Climatology Series 4-3:  Regional and National
Monthly, Seasonal and Annual Temperature Weighted by Area, 1895-1983).  The
states and area weights for each region are as follows:

     Northeast Region:   CT, 0.02752; DE, 0.01130; ME, 0.18251; MD, 0.05812;
                         MA, 0.04537; NH, 0.05112; NJ, 0.04306; NY, 0.27242;
                         PA, 0.24910; RI, 0.00667; VT, 0.05280

     East North Central Region:    IA, 0.22098; MI, 0.22854; MN, 0.33003; 
                                   WI, 0.22045

     Central Region:     IL, 0.18169; IN, 0.11691; KY, 0.13013; MO, 0.22449;
                         OH, 0.13279; TN, 0.13609; WV, 0.07790

     Southeast Region:   AL, 0.17576; FL, 0.19944; GA, 0.20051; NC, 0.17952;
                         SC, 0.10576; VA, 0.13900

     West North Central Region:    MT, 0.31307; NE, 0.16432; ND, 0.15035; 
                                   SD, 0.16393; WY, 0.20833

     South Region:       AR, 0.09335; KS, 0.14461; LA, 0.08530; MS, 0.08388;
                         OK, 0.12291; TX, 0.46995

     Southwest Region:   AZ, 0.26819; CO, 0.24544; NM, 0.28645; UT, 0.19993

     Northwest Region:   ID, 0.33593; OR, 0.38990; WA, 0.27416

     West Region:        CA, 0.58943; NV, 0.41057

     National (contiguous U.S.) values are computed from the regional values
weighted by area.  The regional weights are as follows:

     Northeast, 0.06021  East North Central, 0.08428   Central, 0.10271
     Southeast, 0.09715  West North Central, 0.15551   South, 0.18822
     Southwest, 0.14053  Northwest, 0.08230            West, 0.08908

     The values in this file may not agree with statewide, regional, and
national values published in other NCDC publications due to:  (1) differences
in the way the regions are defined, (2) the temperature data are adjusted for
time of observation bias, and (3) the most recent months are based on
preliminary data.


DISCUSSION OF THE DIVISIONAL VALUES

     Monthly averages within a climatic division have been calculated by giving
equal weight to stations reporting both temperature and precipitation within a
division.  In the U.S., observers at cooperative stations often take one
observation per day, and the ending time of the climatological day at any
station can vary from station-to-station as well as year-to-year.  Differences
of the 24-hour period over which each observer reports his or her maximum and 
minimum temperature as well as the average temperature [(max + min)/2] affects 
the calculated monthly mean temperature.  Karl, et al. (1986), describe the 
biases that this introduces. These potential biases were rectified by 
adjusting for these varying observation times.  The model described by Karl, 
et al. (1986), was used to adjust the climate division averages such that all 
stations end their climatological day at midnight; i.e., climatological day 
coincides with calendar day.  The time of observation was determined at each 
station within a climate division during January of the years 1931, 1941, 1951,
1965, 1975, and 1984 for the states of California, Colorado, Illinois, Indiana,
New York, North Carolina, and Washington.  The fraction of observers recording 
at various hours of the day was calculated and interpolated for intervening
years (extrapolated for subsequent years).  For these seven states, the ending 
time of observation was grouped into three categories:  AM, PM, and MD. The AM
category included observers who ended their climatological day between 3 AM and
11 AM; the PM category between noon and 9 PM; and the MD category between 10 PM
and 2 AM; all local standard time.  The fraction of observers in these
categories was calculated, and it was assumed the 7 AM observation time  best
represented the AM category; the 5 PM observation time, the PM category;  and
midnight for the MD category.  The reason for the simplification was to  test
if a faster method, requiring significantly less bookkeeping and  keypunching,
could not provide nearly as good results as calculating the  fraction of
observers at each of the 24 hours of the day.

     The time of observation bias model was run by using the latitude and
longitude of each of the centroids of the climate divisions.  The output from
the model was the time of observation bias, with respect to a midnight-to-
midnight climatological day, for each of the possible ending hours of the
climatological day.  Each climate division's monthly average was then adjusted
by weighting the bias at any given hour by the fraction of stations within the
climate division observing at that hour, and subtracting the result for the
reported monthly mean temperature.

     Differences of the biases were small (< 0.3 Deg. F.) for those calculated
by categorizing the ending time of observation into three categories compared
to those obtained from calculating the fraction of stations with observation
times at each of the 24 hours of the day.  This is attributed to the
preponderance of AM observation times falling between 6 AM and 9 AM, and PM
observation times falling between 4 PM and 7 PM.  As a result, by assuming 7 AM
observation for all AM stations and 5 PM for all PM stations, a good estimate
of the median bias is obtained for all AM or PM observations.  Furthermore,
nearly all the MD stations observed at midnight.

     It should also be noted that the borders of the climate divisions in 1951
were not consistent with those defined in 1965.  Due to the substantial
additional effort it would have required locating each station within three or
four climate divisions, as defined today, the change in the statewide
percentage of AM, PM, and MD observation times was applied in equal proportions
to all climate divisions prior to and including 1951.

     Based on small differences between the two methods of estimating the time
of observation bias, the simpler categorical procedure was used for all climate
divisions.  This should effectively eliminate most of the biases (over 2 Deg.F)
in some climate divisions that have become part of the divisional averages.  
These biases affect both trends and actual estimates of divisional averages.   

     Reference:  Karl, et al. (1986):  "A model to estimate the time of
observation bias associated with monthly mean maximum, minimum, and mean
temperatures for the United States" (Thomas R. Karl, Claude N. Williams, Jr.,
and Pamela J. Young, National Climatic Data Center, and Wayne M. Wendland,
Illinois State Water Survey, Journal of Climate and Applied Meteorology,
January 1986, vol. 25, pp. 145-160, American Meteorological Society, Boston,
MA).


STATE CODE TABLE:
 
     Range of values for the states, regions, and nation is 001-110.

          001 Alabama         030 New York
          002 Arizona         031 North Carolina
          003 Arkansas        032 North Dakota
          004 California      033 Ohio
          005 Colorado        034 Oklahoma
          006 Connecticut     035 Oregon
          007 Delaware        036 Pennsylvania
          008 Florida         037 Rhode Island
          009 Georgia         038 South Carolina
          010 Idaho           039 South Dakota
          011 Illinois        040 Tennessee
          012 Indiana         041 Texas
          013 Iowa            042 Utah
          014 Kansas          043 Vermont
          015 Kentucky        044 Virginia
          016 Louisiana       045 Washington
          017 Maine           046 West Virginia
          018 Maryland        047 Wisconsin
          019 Massachusetts   048 Wyoming
          020 Michigan        101 Northeast Region
          021 Minnesota       102 East North Central Region
          022 Mississippi     103 Central Region
          023 Missouri        104 Southeast Region
          024 Montana         105 West North Central Region
          025 Nebraska        106 South Region
          026 Nevada          107 Southwest Region
          027 New Hampshire   108 Northwest Region
          028 New Jersey      109 West Region
          029 New Mexico      110 National (contiguous 48 States)


FILE FORMAT:

Element        Record
Name           Position  Element Description

STATE-CODE        1-3    STATE-CODE as indicated in State Code Table above.
                         Range of values is 001-110.

DIVISION-NUMBER    4     DIVISION NUMBER.  Value is 0 which indicates an area-
                         averaged element.

ELEMENT-CODE       5     1 = Precipitation
                         2 = Temperature (adjusted for time of observation
                               bias)

YEAR              6-9    This is the year of record.  Range is 1895 to current
                         year processed.

JAN-VALUE        10-16   Monthly Temperature format:  Range of values b-50.00
                         to b140.00 degrees Fahrenheit.  Decimals retain a
                         position in the 7-character field.  Missing values in
                         the latest year are indicated by b-99.90.

                         Monthly Precipitation format:  Range of values 00.00
                         to 99.99.  Decimal point retains a position in the
                         7-character field.  Missing values in the latest year
                         are indicated by bb-9.99.

FEB-VALUE        17-23     

MAR-VALUE        24-30     

APR-VALUE        31-37     

MAY-VALUE        38-44     

JUNE-VALUE       45-51     

JULY-VALUE       52-58     

AUG-VALUE        59-65     

SEPT-VALUE       66-72     

OCT-VALUE        73-79     

NOV-VALUE        80-86     

DEC-VALUE        87-93     

