Data Sources for Daily and Monthly Lat-Lon Sea-Level Pressure Grids
DATA SOURCES FOR DAILY AND MONTHLY LAT-LON SEA-LEVEL PRESSURE GRIDS
Data in this collection were assembled by the Data Support Section of the Scientific Computing Division, National Center for Atmospheric Research from several sources:
Period
Data Source
Jan 1899 - Jun 1939
NWS Extended Forecast Division digitized data from historical charts and quality-control work was done by NOAA/ERL. More details are available below.
Jul 1939 - Nov 1944
Data for this period were digitized by MIT from historical charts received from the Extended Forecast Lab. More details are available below.
Dec 1944 - Dec 1945
Data for this period were received from the United Kingdom.
Jan 1946 - Mar 1955
Data for this period were digitized at the National Climatic Data Center under a Navy contract from historical weather charts. More details are available below.
Apr 1955 - Mar 1960
For this period, points were hand read from historical charts by the 433L ESSPO Project. More details are available below.
Apr 1960 - Jun 1962
Data for this period were digitized at the National Climatic Data Center under a Navy contract from historical weather charts.
Jul 1962 - Dec 1993
Data for this period come from operational analyses from US Navy, Monterey with a few gaps filled by NCEP analyses.
Jan 1994 - Jun 2007
Data for this period come from the 2.5 degree NCEP operational final (FNL) analyses.
Jul 2007 - current
Data for this period come from the 1 degree NCEP operational final (FNL) analyses.
More details on sources of data:
Grids from historical maps, Jan 1899 - Jun 1939 (13Z):
This data, which originated at the National Climatic Center, Asheville, N.C., was sent to the Extended Forecast Lab; from there a copy was sent to the NOAA Environmental Research Laboratories. There, Mr. Cotton and others spent about 1.5 man years comparing each point to the average of surrounding values. They checked each difference greater than 10 mb with the original maps to see whether a correction was necessary. Errors greater than 10 mb were likely discovered and corrected by this process. Data are missing where historical maps could not be analyzed. Eastern Russia (40-80N,35-150E) is missing for 1916-1920, for 3 months in 1921, for one month each in 1922 and 1931, and for 6 months each in 1938 and 1939. The grids were on a diamond latitude/longitude grid (5-degree latitude spacing, 10-degree longitude spacing), 20N-80N, with no data at 75N. There are no pole values.
Grids from MIT, Jul 1939 - Nov 1944 (12Z):
MIT read values from charts from the Extended Forecast Lab. The data are for each 5 degrees of latitude and even 10 degrees of longitude for 15N-80N. Data for 85N is present for 10 days.
Grids from Navy, Jan 1946 - Mar 1955 (12Z), Apr 1960 - Jun 1962 (12Z), Jul 1962 - current (00Z,12Z):
The grids from the historical series maps for January 1946 to March 1955 and April 1960 to June 1962 were digitized with a curve follower at NCC under a Navy contract. These data were then analyzed by the Navy's operational objective analysis program that is used on current data. These grids include manual bogus to put in tropical storms. There is no data at 15N.
Grids from the 433L ESSPO Project, Apr 1955 - Mar 1960 (00Z,12Z):
Data for every other point in the NMC octagonal grid were manually read from charts for this period. There is no data at 15N.
