A. INTRODUCTION
This readme.txt file describes characteristics of the data and
metadata files for the North America Drought Monitor (NADM) input
indicator files. Specifically, this file describes:
-- how to read the data files (PCTPCP, SPI, Palmer Indices) for
the input indicators used in North America drought and climate
monitoring
-- how to read the metadata files that describe information about
the stations that are in the input indicator data files
B. DESCRIPTIONS
1. METADATA FILES
The metadata files identify the stations that are used in the
input indicator data files. There are four metadata files,
arranged by zones of North America:
ak-metadata.txt (Alaskan stations)
can-metadata.txt (Canadian stations)
mex-metadata.txt (Mexican stations)
us48-stn-metadata.txt (stations in the contiguous U.S.)
us48-div-metadata.txt (climate divisions in the contiguous U.S.)
These files are read using the following record formats:
can-metadata.txt (Canadian stations)
us48-stn-metadata.txt (stations in the contiguous U.S.)
us48-div-metadata.txt (climate divisions in the contiguous U.S.)
columns 1-11: GHCN-D station ID or climate division (8-9: state,
10-11: division)
columns 12-18: latitude (to hundredths of degrees, positive = north)
columns 19-26: longitude (to hundredths of degrees, negative = west)
columns 27-27: blank
columns 28-29: Province or State abbreviation
columns 30-30: blank
columns 31-74: Station or climate division name
ak-metadata.txt (Alaskan stations)
mex-metadata.txt (Mexican stations)
columns 1-11: GHCN-D station ID
columns 12-18: latitude (to hundredths of degrees, positive = north)
columns 19-26: longitude (to hundredths of degrees, negative = west)
columns 27-27: blank
columns 28-67: station name
2. PCTPCP DATA FILES
The PCTPCP files contain the current year-month percent of long-
term average (1951-2001) precipitation for nine timeframes:
current month, most recent 2 months, most recent 3 months, most
recent 6 months, most recent 12 months, most recent 24 months,
most recent 36 months, most recent 48 months, and most recent 60
months. Values greater than 100.0 are wetter than average, and
values less than 100.0 are drier than average. There is one file
for each of the four North America zones:
curr-pctpcp-ak.txt (Alaska stations)
curr-pctpcp-cn.txt (Canadian stations)
curr-pctpcp-mx.txt (Mexican stations)
curr-pctpcp-us-stn-lower48.txt (stations for contiguous U.S.)
curr-pctpcp-us.txt (climate divisions in the contiguous U.S.)
The first record in each file is a header record. The records
that follow have the following format (values of -99.9 indicate
current data are missing):
columns 1-11: GHCN-D station ID or climate division (8-9: state,
10-11: division)
columns 12-12: blank
columns 13-16: year
columns 17-19: month
columns 20-24: number of years of data in the data base
columns 25-31: 1-month percent of long-term average (1951-2001)
precipitation (PCTPCP)
columns 32-38: 2-month PCTPCP
columns 39-45: 3-month PCTPCP
columns 46-52: 6-month PCTPCP
columns 53-59: 12-month PCTPCP
columns 60-66: 24-month PCTPCP
columns 67-73: 36-month PCTPCP
columns 74-80: 48-month PCTPCP
columns 81-87: 60-month PCTPCP
3. SPI DATA FILES
The SPI files contain the monthly Standardized Precipitation
Index (SPI) values for seven timeframes for each year and month
in the period of record. The period of record may vary from
station to station. The standardizing period for the SPI is
1951-2001. Positive values of the SPI indicate wet conditions
and negative values dry conditions, with more extreme values
indicating more extreme anomalies. The seven timeframes are:
current month, most recent 2 months, most recent 3 months, most
recent 6 months, most recent 9 months, most recent 12 months, and
most recent 24 months. There is one file for each of the four
North America zones for each timeframe, for a total of 28 data
files. Each file is named using the following naming convention:
NNmon-spi-CC.txt,
where NN = the timeframe (01, 02, 03, 06, 09, 12, 24) and CC =
the zone (ak = Alaskan stations, cn = Canadian stations, mx =
Mexican stations, us = Lower-48 climate divisions and us-stn-lower48 =
Lower-48 stations).
Each record in the data files has the following format:
columns 1-11: GHCN-D station ID or climate division (8-9: state,
10-11: division)
columns 12-12: blank
columns 13-14: element code (see Element Code Table below)
columns 15-15: blank
columns 16-19: year
columns 20-26: SPI value for January (-99.99 = missing code)
columns 27-33: SPI value for February (-99.99 = missing code)
columns 34-40: SPI value for March (-99.99 = missing code)
columns 41-47: SPI value for April (-99.99 = missing code)
columns 48-54: SPI value for May (-99.99 = missing code)
columns 55-61: SPI value for June (-99.99 = missing code)
columns 62-68: SPI value for July (-99.99 = missing code)
columns 69-75: SPI value for August (-99.99 = missing code)
columns 76-82: SPI value for September (-99.99 = missing code)
columns 83-89: SPI value for October (-99.99 = missing code)
columns 90-96: SPI value for November (-99.99 = missing code)
columns 97-103: SPI value for December (-99.99 = missing code)
------------------
Element Code Table
------------------
Code Description
---- ------------
71 1-month SPI
72 2-month SPI
73 3-month SPI
74 6-month SPI
75 9-month SPI
76 12-month SPI
77 24-month SPI
4. PALMER INDEX DATA FILES
The Palmer Index files contain the monthly Modified Palmer
Drought Index (PMDI), Palmer Hydrological Drought Index (PHDI),
and Palmer Z Index (ZNDX) values for each year and month in the
period of record. The period of record may vary from station
to station. The calibration period for the Palmer Indices is
1951-2001. Positive values of the indices indicate wet
conditions and negative values dry conditions, with more
extreme values indicating more extreme anomalies. Currently
there is one file for each index for the contiguous U.S. stations
and climate divisions, and for Mexico, for a total of 9 data files.
The files are named using the following naming convention:
LLLL-mx.txt
LLLL-us-stn.txt
LLLL-us-div.txt
where LLLL refers to the index (pmdi, phdi, or zndx).
Each record in the data files has the following format:
columns 1-11: GHCN-D station ID or climate division (8-9: state,
10-11: division)
columns 12-12: blank
columns 13-14: element code (see Element Code Table below)
columns 15-15: blank
columns 16-19: year
columns 20-26: value for January (-99.99 = missing code)
columns 27-33: value for February (-99.99 = missing code)
columns 34-40: value for March (-99.99 = missing code)
columns 41-47: value for April (-99.99 = missing code)
columns 48-54: value for May (-99.99 = missing code)
columns 55-61: value for June (-99.99 = missing code)
columns 62-68: value for July (-99.99 = missing code)
columns 69-75: value for August (-99.99 = missing code)
columns 76-82: value for September (-99.99 = missing code)
columns 83-89: value for October (-99.99 = missing code)
columns 90-96: value for November (-99.99 = missing code)
columns 97-103: value for December (-99.99 = missing code)
------------------
Element Code Table
------------------
Code Description
---- ------------
6 PHDI
7 Z-Index
8 PMDI