This documentation describes the record format for the divisional, statewide, regional and national drought files on /pub/data/cirs/climdiv that have the filenames: climdiv-pdsist-vx.y.z-YYYYMMDD climdiv-phdist-vx.y.z-YYYYMMDD climdiv-pmdist-vx.y.z-YYYYMMDD climdiv-sp01st-vx.y.z-YYYYMMDD climdiv-sp02st-vx.y.z-YYYYMMDD climdiv-sp03st-vx.y.z-YYYYMMDD climdiv-sp06st-vx.y.z-YYYYMMDD climdiv-sp09st-vx.y.z-YYYYMMDD climdiv-sp12st-vx.y.z-YYYYMMDD climdiv-sp24st-vx.y.z-YYYYMMDD climdiv-zndxst-vx.y.z-YYYYMMDD climdiv-pdsidv-vx.y.z-YYYYMMDD climdiv-phdidv-vx.y.z-YYYYMMDD climdiv-pmdidv-vx.y.z-YYYYMMDD climdiv-sp01dv-vx.y.z-YYYYMMDD climdiv-sp02dv-vx.y.z-YYYYMMDD climdiv-sp03dv-vx.y.z-YYYYMMDD climdiv-sp06dv-vx.y.z-YYYYMMDD climdiv-sp09dv-vx.y.z-YYYYMMDD climdiv-sp12dv-vx.y.z-YYYYMMDD climdiv-sp24dv-vx.y.z-YYYYMMDD climdiv-zndxdv-vx.y.z-YYYYMMDD nClimDiv STATEWIDE-REGIONAL-NATIONAL DROUGHT MARCH 2014 The major parameters in this file are sequential climatic divisional, statewide, regional and national monthly Standardized Precipitation Index (SPI), and Palmer Drought Indices (PDSI, PHDI, PMDI, and ZNDX). Period of record is 1895 through latest month available, updated monthly. Values from the most recent two calendar years will be updated on a monthly basis. Period of record updates will occur when the underlying data set undergoes a version change. METHODOLOGY: Divisional, statewide, regional and national values in nClimDiv were derived from area-weighted averages of grid-point estimates interpolated from station data. A nominal grid resolution of 5 km was used to ensure that all divisions had sufficient spatial sampling (only four small divisions had less than 100 points) and because the impact of elevation on precipitation is minimal below 5 km. Station data were gridded via climatologically aided interpolation to minimize biases from topographic and network variability. The Global Historical Climatology Network (GHCN) Daily dataset is the source of station data for nClimDiv. GHCN-Daily contains several major observing networks in North America, five of which are used here. The primary network is the National Weather Service (NWS) Cooperative Observing (COOP) program, which consists of stations operated by volunteers as well as by agencies such as the Federal Aviation Administration. To improve coverage in western states and along international borders, nClimDiv also includes the National Interagency Fire Center (NIFC) Remote Automatic Weather Station (RAWS) network, the USDA Snow Telemetry (SNOTEL) network, the Environment Canada (EC) network (south of 52°N), and part of Mexicos Servicio Meteorologico Nacional (SMN) network (north of 24°N). Note that nClimDiv does not incorporate precipitation data from RAWS because that networks tipping-bucket gauges are unheated, leading to suspect cold-weather data. All GHCN-Daily stations are routinely processed through a suite of logical, serial, and spatial quality assurance reviews to identify erroneous observations. For nClimDiv, all such data were set to missing before computing monthly values, which in turn were subjected to additional serial and spatial checks to eliminate residual outliers. Overall, the quality assurance reviews deemed less than 0.25% of the monthly data as being erroneous. Stations having at least 10 years of valid monthly data since 1950 were used in nClimDiv. For temperature, bias adjustments were computed to account for historical changes in observation time, station location, temperature instrumentation, and siting conditions. Changes in observation time are only problematic for the COOP network whereas changes in station location and instrumentation occur in almost all surface networks. As in the U.S. Historical Climatology Network version 2.5, the method of Karl et al. (1986) was applied to remove the observation time bias from the COOP network, and the pairwise method of Menne and Williams (2009) was used to address changes in station location and instrumentation in all networks. Because the pairwise method also largely accounts for local, unrepresentative trends that arise from changes in siting conditions, nClimDiv contains no separate adjustment in that regard. For additional information on how nClimDiv is constructed, please see: http://journals.ametsoc.org/doi/abs/10.1175/JAMC-D-13-0248.1 Historical drought data have been added to this file for the period 1895 to present. The file is updated monthly. All drought data are calibrated using the period 1931-1990 (cf. Karl, 1986; Journal of Climate and Applied Meteorology, Vol. 25, No. 1, January 1986). Drought data include: 1. Palmer Drought Severity Index (PDSI) This is the monthly value (index) that is generated indicating the severity of a wet or dry spell. This index is based on the principles of a balance between moisture supply and demand. Man-made changes were not considered in this calculation. The index generally ranges from -6 to +6, with negative values denoting dry spells and positive values indicating wet spells. There are a few values in the magnitude of +7 or -7. PDSI values 0 to -.5 = normal; -0.5 to -1.0 = incipient drought; -1.0 to -2.0 = mild drought; -2.0 to -3.0 = moderate drought; -3.0 to -4.0 = severe drought; and greater than - 4.0 = extreme drought. Similar adjectives are attached to positive values of wet spells. This is a meteorological drought index used to assess the severity of dry or wet spells of weather. 2. Palmer Hydrological Drought Index (PHDI) This is the monthly value (index) generated monthly that indicates the severity of a wet or dry spell. This index is based on the principles of a balance between moisture supply and demand. Man-made changes such as increased irrigation, new reservoirs, and added industrial water use were not included in the computation of this index. The index generally ranges from - 6 to +6, with negative values denoting dry spells, and positive values indicating wet spells. There are a few values in the magnitude of +7 or -7. PHDI values 0 to -0.5 = normal; -0.5 to -1.0 = incipient drought; -1.0 to - 2.0 = mild drought; -2.0 to -3.0 = moderate drought; -3.0 to -4.0 = severe drought; and greater than -4.0 = extreme drought. Similar adjectives are attached to positive values of wet spells. This is a hydrological drought index used to assess long-term moisture supply. 3. Palmer "Z" Index (ZNDX) This is the generated monthly Z values, and they can be expressed as the "Moisture Anomaly Index." Each monthly Z value is a measure of the departure from normal of the moisture climate for that month. This index can respond to a month of above-normal precipitation, even during periods of drought. Table 1 contains expected values of the Z index and other drought parameters. See Historical Climatology Series 3-6 through 3-9 for a detailed description of the drought indices. 4. Modified Palmer Drought Severity Index (PMDI) This is a modification of the Palmer Drought Severity Index. The modification was made by the National Weather Service Climate Analysis Center for operational meteorological purposes. The Palmer drought program calculates three intermediate parallel index values each month. Only one value is selected as the PDSI drought index for the month. This selection is made internally by the program on the basis of probabilities. If the probability that a drought is over is 100%, then one index is used. If the probability that a wet spell is over is 100%, then another index is used. If the probability is between 0% and 100%, the third index is assigned to the PDSI. The modification (PMDI) incorporates a weighted average of the wet and dry index terms, using the probability as the weighting factor. (Thomas R. Heddinghause and Paul Sabol, 1991; "A Review of the Palmer Drought Severity Index and Where Do We Go From Here?," Proceedings of the Seventh Conference on Applied Climatology, pp. 242-246, American Meteorological Society, Boston, MA). The PMDI and PDSI will have the same value during an established drought or wet spell (i.e., when the probability is 100%), but they will have different values during transition periods. 5. Standardized Precipitation Index (SPxx) This is a transformation of the probability of observing a given amount of precipitation in xx months. A zero index value reflects the median of the distribution of precipitation, a -3 indicates a very extreme dry spell, and a +3 indicates a very extreme wet spell. The more the index value departs from zero, the drier or wetter an event lasting xx months is when compared to the long-term climatology of the location. The index allows for comparison of precipitation observations at different locations with markedly different climates; an index value at one location expresses the same relative departure from median conditions at one location as at another location. It is calculated for different time scales since it is possible to experience dry conditions over one time scale while simultaneously experiencing wet conditions over a different time scale. Table 1 Classes for Wet and Dry Periods Approximate Cumulative Frequency Range Range % PHDI Category Z > 96 > 4.00 Extreme wetness > 3.50 90-95 3.00, 3.99 Severe wetness 2.50, 3.49 73-89 1.50, 2.99 Mild to moderate 1.00, 2.49 wetness 28-72 -1.49, 1.49 Near normal -1.24, 0.99 11-27 -1.50, -2.99 Mild to moderate -1.25, -1.99 drought 5-10 -3.00, -3.99 Severe drought -2.00, -2.74 < 4 <-4.00 Extreme drought <-2.75 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) The following are the range of code values for the National Weather Service Regions, river basins, and agricultural regions: 111 Great Plains 115 Southern Plains and Gulf Coast 120 US Rockies and Westward 121 NWS Eastern Region 122 NWS Southern Region 123 NWS Central Region 124 NWS Western Region 201 Pacific Northwest Basin 202 California River Basin 203 Great Basin 204 Lower Colorado River Basin 205 Upper Colorado River Basin 206 Rio Grande River Basin 207 Texas Gulf Coast River Basin 208 Arkansas-White-Red Basin 209 Lower Mississippi River Basin 210 Missouri River Basin 211 Souris-Red-Rainy Basin 212 Upper Mississippi River Basin 213 Great Lakes Basin 214 Tennessee River Basin 215 Ohio River Basin 216 South Atlantic-Gulf Basin 217 Mid-Atlantic Basin 218 New England Basin 220 Mississippi River Basin & Tributaties (N. of Memphis, TN) 250 Spring Wheat Belt (area weighted) 255 Primary Hard Red Winter Wheat Belt (area weighted) 256 Winter Wheat Belt (area weighted) 260 Primary Corn and Soybean Belt (area weighted) 261 Corn Belt (area weighted) 262 Soybean Belt (area weighted) 265 Cotton Belt (area weighted) 350 Spring Wheat Belt (productivity weighted) 356 Winter Wheat Belt(productivity weighted) 361 Corn Belt (productivity weighted) 362 Soybean Belt (productivity weighted) 365 Cotton Belt (productivity weighted) 450 Spring Wheat Belt (% productivity in the Palmer Z Index) 456 Winter Wheat Belt (% productivity in the Palmer Z Index) 461 Corn Belt (% productivity in the Palmer Z Index) 462 Soybean Belt (% productivity in the Palmer Z Index) 465 Cotton Belt (% productivity in the Palmer Z Index) DIVISIONAL FILE FORMAT: Element Record Name Position Element Description STATE-CODE 1-2 STATE-CODE as indicated in State Code Table as described in FILE 1. Range of values is 01-91. DIVISION-NUMBER 3-4 DIVISION NUMBER - Assigned by NCDC. Range of values 01-10. STATE/REGIONAL/NATIONAL FILE FORMAT: STATE-CODE 1-3 STATE-CODE as indicated in State Code Table above. Range of values is 001-110 for standard states, regions and national, 111-465 for special regions. DIVISION-NUMBER 4 DIVISION NUMBER. Value is 0 which indicates an area -averaged element. REMAINING FILE FORMAT FOR DIVISIONAL/STATE/REGIONAL/NATIONAL: ELEMENT CODE 5-6 05 = PDSI 06 = PHDI 07 = ZNDX 08 = PMDI 71 = 1-month Standardized Precipitation Index 72 = 2-month Standardized Precipitation Index 73 = 3-month Standardized Precipitation Index 74 = 6-month Standardized Precipitation Index 75 = 9-month Standardized Precipitation Index 76 = 12-month Standardized Precipitation Index 77 = 24-month Standardized Precipitation Index YEAR 7-10 This is the year of record. Range is 1895 to current year processed. (all data values are right justified): JAN-VALUE 11-17 Palmer Drought Index format (f7.2) Range of values -20.00 to 20.00. Decimal point retains a position in 7-character field. Missing values in the latest year are indicated by -99.99. Standardized Precipitation Index format (f7.2). Range of values -4.00 to 4.00. Decimal point retains a position in 7-character field. Missing values in the latest year are indicated by -99.99. FEB-VALUE 18-24 MAR-VALUE 25-31 APR-VALUE 32-38 MAY-VALUE 39-45 JUNE-VALUE 46-52 JULY-VALUE 53-59 AUG-VALUE 60-66 SEPT-VALUE 67-73 OCT-VALUE 74-80 NOV-VALUE 81-87 DEC-VALUE 88-94