Data Atmosphere GNV38

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These three African climate data sets originate from manuscripts that were received by ESRI from FAO, as part of work performed under a UNEP contract to a) construct a World and Africa GIS Database, and b) conduct a Desertification and Mapping project, both on behalf of UNEP and FAO. The source climate maps were prepared directly from original hand-drawn maps, provided by FAO on stable basemap copies at a 1:5,000,000 scale. Isolines plotted on the FAO/AGS basemaps were then manually digitized by ESRI. The final products were later rasterized at UNEP/GRID-Geneva for the African Database at spatial resolutions of 30 seconds and 2 minutes latitude/longitude (approx. one and four kilometers, respectively).

Precipitation is "average annual", and is expressed in terms of millimeters (mm.) per year; Average Days of Precipitation ("Wet Days") is number of days per year; and Average Windspeed is expressed in terms of meters per second (note that this is not maximum windspeed, nor is there any directional content included in this data set). It is GRID's assumption that the definition of a "wet day" is one in which enough precipitation occurred on a given day so as to be recordable by a gauging station at a particular location.

The three FAO/Agrhymet Africa data files all cover the entire African continent at a spatial resolution of two minutes (120 seconds) of latitude/longitude, or approximately 3.7 kilometers. The data files consist of 2191 rows (lines, records) by 2161 columns (elements, pixels, samples) each. Their common upper-left or northwest corner origin is 38 degrees, 0 minutes and 45 seconds North latitude (38d 00' 45" N), and -20 degrees, 1 minute and 15 seconds West longitude (-20d 01' 15" W); and they extend to -35 degrees, 1 minute and 15 seconds South latitude (-35d 01' 15" S), and 52 degrees, 0 minutes and 45 seconds East longitude (52d 00' 45" E) at their terminal point in the lower-right or southeast corner. Each data file comprises 4.74 Megabytes.

The proper reference for these data sets is "Final Report: UNEP/FAO World and Africa GIS Data Base; December 1984." Prepared by ESRI - Environmental Systems Research Institute, 380 New York Street, Redlands, CA., USA 92373 (one full volume including appendices). The source to credit is the FAO/UNEP Desertification and Mapping Project, as rasterized by UNEP/GRID (date of process 1986).

UNEP/GRID Legend for Data Set: Mean Annual Rainfall (Africa; FAO/Agrymet)

Class # Millimeters per annum ------- --------------------- 1 0 - 50 2 51 - 100 3 101 - 150 4 101 - 200 5 151 - 200 6 201 - 250 7 201 - 300 8 201 - 400 9 251 - 300 10 251 - 400 11 301 - 350 12 301 - 400 13 351 - 400 14 401 - 450 15 401 - 500 16 401 - 600 17 451 - 500 18 451 - 550 19 501 - 550 20 501 - 600 21 551 - 600 22 601 - 700 23 601 - 800 24 601 - 1000 25 701 - 800 26 801 - 900 27 801 - 1000 28 901 - 1000 29 1001 - 1500 30 1501 - 2000 31 2001 - 3000 32 > 3000

UNEP/GRID Legend for Data Set: Number of Wet Days (Africa; FAO/Agrymet)

Class # No. of Wet Days/Year ------- -------------------- 1 0 2 1 - 20 3 21 - 40 4 41 - 60 5 61 - 80 6 61 - 100 7 61 - 120 8 81 - 100 9 81 - 120 10 101 - 120 11 > 120

UNEP/GRID Legend for Data Set: Mean Annual Wind Velocity (Africa; FAO/Agrymet)

Class # Windspeed in meters/second ------- -------------------------- 1 0.0 - 0.5 2 0.5 - 1.0 3 1.0 - 1.5 4 1.5 - 2.0 5 2.0 - 2.5 6 2.5 - 3.0 7 3.0 - 3.5 8 3.5 - 4.0 9 4.0 - 4.5 10 4.5 - 5.0 11 5.0 - 5.5 12 5.5 - 6.0 13 > 6.0

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