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Legates Surface and Ship Observation of Precipitation

Online Access for Legates Gauge Precipitation 5.3 MB zipped file


Original Archive
Future Updates
Data Set Description
Data Characteristics
Data Format
Data Access
Points of Contact


Observation of Precipitation data set consists of a global climatology of monthly mean precipitation values, using traditional land-based gauge measurements and shipboard estimates spanning the period from 1920 to 1980. The data are corrected for gauge-induced systematic errors caused by wind, wetting on the interior walls of the gauge and evaporation from the gauge. The corrected monthly precipitation values are then interpolated to a 0.5 degree latitude by 0.5 degree longitude grid using a spherically based interpolation procedure (Legates and Willmott, 1990).This global precipitation climatology is used in

  • verification of climate model predictions of precipitation cycles
  • large scale hydrological cycle and ecological studies
  • evaluating climate change


The authors wish to thank the Goddard Earth Sciences Data Information and Services Center (GES DISC, Code 610.2) at the Goddard Space Flight Center, Greenbelt, MD, 20771, for distributing the data; and the science investigators, Dr. David Legates, University of Oklahoma and Dr. Cort Willmott, University of Delaware, for producing these data products.Goddard's contribution to these activities was sponsored by NASA's Mission to Planet Earth program.

Original Archive

This data set was originally archived at the Marshall Space Flight Center.It was moved to the Goddard Space Flight Center Distributed Active Archive Center (GSFC DAAC) in the fall of 1996.

Future Updates The Goddard DAAC will update this data set as new data are processed and made available by the data producers.

Data Set Description

The Legates Surface and Ship Observation of Precipitation data set consists of a global climatology of monthly mean precipitation values spanning the period from 1920 to 1980.The data set is based on rain gauge measurements and shipboard estimates consisting of 24,635 spatially independent terrestrial station records and 2,223 oceanic grid point records.

Terrestrial precipitation measurements:

Global archives of monthly precipitation compiled by Wernstedt (1972), Willmott et al. (1981), and the National Center for Atmospheric Research (Spangler and Jenne, 1984) provided most of the data for this climatology data set.The Wernstedt and Willmott et al. data contain monthly averages for 17,347 and 13,659 stations, respectively.The Spangler and Jenne data, however, contain monthly time-series for 3,679 stations, from which monthly averages were computed.Wernstedt's Canadian data were not used because snowfall was excluded from the averaging.These three data sets provide adequate spatial coverage for much of the terrestrial surface; however, Australia, New Guinea, China, parts of the Far East, and Antarctica are underrepresented.

To improve the spatial resolution in the above-mentioned regions, monthly precipitation averages were obtained from an additional 208 stations in Australia, New Guinea, and Indonesia; 584 stations in China and the Far East; 10 stations in Antarctica; and five stations in the Sahara.

Virtually all station records were used even though they are based on differing time periods.Most of the data, however, were observed between 1920 and 1980; thus, this climatology is largely representative of this 60-year period, with greater weight given to the more recent (data-rich) years.

Oceanic precipitation estimates:

Shipboard gauges are adversely influenced by the aerodynamic effects due to the superstructure of the ship, the influence of roll and pitch, the capture of spray, and the movement of the ship, in addition to the same biases that affectland-based gauges.Averaged shipboard estimates also have a "fair-weather bias"; that is, ships tend to avoid storms and other severe weather.Thus, a serious deficiency of reliable precipitation measurements exists over the oceans, and alternative oceanic precipitation estimates are needed.

These estimates, from Dorman and Bourke (1979, 1981) and Jaeger (1983), contain systematic differences that are resolved by applying multiple linear regression to data from the Atlantic and Pacific Oceans north of 30 degree south latitude.Discrepancies are assumed to be highly correlated with air temperature.

Data Characteristics:

Accumulated surface precipitation
January 1920 - December 1980
Monthly means
0.5° latitude x 0.5° longitude
5.4 Megabytes (compressed)

Data Format:
This data file, in ASCII format, contains integer values in a 361 x 721 element array.Each element represents a gridded mean for a 0.5 x 0.5 degree grid cell, beginning at 90 degree north latitude, 180 degree west longitude and extending to 90 degree south latitude, 180 degree east longitude.

The data file contents are arranged as follows:

 Latitude   Longitude   Jan Mean   Feb Mean   ...   Dec Mean   Annual Mean
   90.0      -180.0       15         11               17          241
   89.5      -180.0       15         10               16          234
  -89.5       180.0        1          4                1           16
  -90.0       180.0        0          2                0            2 

where the monthly means are for the time period from 1920 through 1980.

The data record format is:

              Variable             		 Format        

         Latitude (decimal degrees)   		 F7.2            
         Longitude (decimal degrees)    	 F7.2             
         Corrected precipitation        	 12I5           
         Annual corrected precipitation (mm) 	 I6            


Ocean mask, value -999.9
North to South
89.75°N, 179.75°W
89.75°S, 179.75°E


Dorman, C.E. and R.H. Bourke, 1979.Precipitation over the Pacific Ocean, 30S to 60N.Mon. Wea. Rev., 107, 896-910.

Dorman, C. E. and R.H. Bourke, 1981.Precipitation over the Atlantic Ocean, 30S to 70N.Mon. Wea. Rev., 109, 554-563.

Jaeger, L., 1983.Monthly and areal patterns of mean global precipitation.Variations in the Global Water Budget, A. Street-Perrott et al., Eds., D. Reidel, Dordrecht, p. 129.

Legates, D.R., 1987.A climatology of global precipitation.Publ. in Climatology, 40(1), Neward, DE, 85 pp.

Legates, D.R. and C.J. Willmott, 1990.Mean seasonal and spatial variability in gauge-corrected, global precipitation. Int. J. Climatology, 10, 111-127.

Spangler, W.M.L and R.L. Jenne, 1984.World monthly surface station climatology.National Center for Atmospheric Research. 14 pp.

Wernstedt, F.L., 1972.World Climatic Data. Climatic Data Press.

Willmott, C.J., J.R. Mather, and C.M. Rowe, 1981. Average monthly and annual surface air temperature and precipitation data for the world.Part 1:The eastern hemisphere.Part 2:The western hemisphere.Publ. in Climatology, 34, 395 pp. and 378 pp.

Data Access

Anonymous FTP
The Legates Precipitation data set resides online and may be accessed either directly from this document,

link to legates surface and ship observation of
precipitation data on ftp Legates Surface and Ship Observation of Precipitation


or via anonymous FTP at
password:< your email address >

Points of Contact



Data Producers:

The producer of this data set can be contacted as follows:
Dr. David R. Legates
Department of Geography
College of Geosciences
University of Oklahoma
Norman, OK 73019
405-325-5325 (voice)
405-325-3148 (fax)
Dr. Cort J. Willmott
Department of Geography
Center for Climatic Research
University of Delaware
Newark, DE 19176
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Last updated: Jul 20, 2010 02:41 PM ET