Dr. J.G.Cogley Department of Geography Trent University
_____________________________________________ | Contact 1 | ______________|______________________________| 2.3.1 Name |Dr. J.G.Cogley | 2.3.2 Address |Department of Geography | |Trent University | City/St.|Peterborough, Ontario, Canada | Zip Code|K9J 7B8 | 2.3.3 Phone |705-748-1454/1440 | FAX |705-748-1205 | 2.3.4 Email |GCOGLEY@TRENTU.CA | ______________|______________________________| 2.4 Requested Form of Acknowledgment. Please cite the following publication when these data are use: J.G. Cogley, GGHYDRO - Global Hydrographic Data, Release 2.1 Copyright (C) J.G.Cogley 1987,1991,1994. Department of Geography, Trent University, Peterborough, Ontario, Canada. 3. INTRODUCTION 3.1 Objective/Purpose. This data set provides global areal coverage of different hydrological terrains. 3.2 Summary of Parameters. Ninteen types hydrological terrains. 3.3 Discussion. This is a global data set which contains hydrographic data on the areal extent (coverage) of different kinds of terrain, and on the distribution of mean terrestrial surface run-off. The data consists consists of nineteen files, which are listed in section 8.2. 4. THEORY OF MEASUREMENTS The hydrological coverage data was derived from published maps (see section 12.2), by J.G.Cogley at Trent University. This documentation does not describe the methods used to produce these maps. 5. EQUIPMENT 5.1 Instrument Description. Not applicable. 5.1.1 Platform (Satellite, Aircraft, Ground, Person...). Not applicable. 5.1.2 Mission Objectives. Not applicable. 5.1.3 Key Variables. Not applicable. 5.1.4 Principles of Operation. Not applicable. 5.1.5 Instrument Measurement Geometry . Not applicable. 5.1.6 Manufacturer of Instrument. Not applicable. 5.2 Calibration. Not applicable. 5.2.1 Specifications. Not applicable. 5.2.1.1 Tolerance. Not applicable. 5.2.2 Frequency of Calibration. Not applicable. 5.2.3 Other Calibration Information. Not applicable. 6. PROCEDURE 6.1 Data Acquisition Methods. The hydrological cover data was aquired from J.G. Cogley at Trent University. 6.2 Spatial Characteristics. 6.2.1 Spatial Coverage. The coverage is global. Data in each file are ordered from North to South and from West to East beginning at 180 degrees West and 90 degrees North. Point (1,1) represents the grid cell centered at 89.5 N and 179.5 W (see section 8.4). 6.2.2 Spatial Resolution. The data are given in an equal-angle lat/long grid that has a spatial resolution of 1 X 1 degree lat/long. 6.3 Temporal Characteristics. Time invariant. 6.3.1 Temporal Coverage. Not applicable. 6.3.2 Temporal Resolution. Not applicable. 7. OBSERVATIONS 7.1 Field Notes. Not applicable. 8. DATA DESCRIPTION 8.1 Table Definition With Comments. Not applicable. 8.2 Type of Data. -------------------------------------------------------------------------------- | 8.2.1 | | | | |Parameter/Variable Name | | | | -------------------------------------------------------------------------------- | | 8.2.2 | 8.2.3 | 8.2.4 | 8.2.5 | | |Parameter/Variable Description |Range |Units |Source | -------------------------------------------------------------------------------- |LAND | | |J.G. | | |Exposed land not covered by swamp, |min = 0 |[%] |Cogley | | |intermittent water bodies, glacier |max = 100 | | | | |ice, sand dunes, saltmarsh or salt | | | | | |flats. | | | | | | | | | | -------------------------------------------------------------------------------- |FLAK | | |J.G. | | |Perennial freshwater lakes. |min = 0 |[%] |Cogley | | | |max = 100 | | | | | | | | | -------------------------------------------------------------------------------- |SWMP | | |J.G. | | |Swamp, marsh and other wetlands. |min = 0 |[%] |Cogley | | | |max = 100 | | | | | | | | | -------------------------------------------------------------------------------- |SLTW | | |J.G. | | |Saltwater, whether marine or |min = 0 |[%] |Cogley | | |terrestrial. |max = 100 | | | | | | | | | -------------------------------------------------------------------------------- |ILAK | | |J.G. | | |Intermittent water bodies. |min = 0 |[%] |Cogley | | | |max = 54 | | | | | | | | | -------------------------------------------------------------------------------- |GLAC | | |J.G. | | |Glacier ice, including shelf ice |min = 0 |[%] |Cogley | | |but excluding pack ice. |max = 100 | | | | | | | | | -------------------------------------------------------------------------------- |DUNE | | |J.G. | | |Sand dunes. |min = 0 |[%] |Cogley | | | |max = 100 | | | | | | | | | -------------------------------------------------------------------------------- |SMRS | | |J.G. | | |Saltmarsh. |min = 0 |[%] |Cogley | | | |max = 46 | | | | | | | | | -------------------------------------------------------------------------------- |SFLT | | |J.G. | | |Salt flats. |min = 0 |[%] |Cogley | | | |max = 96 | | | | | | | | | -------------------------------------------------------------------------------- |DSRF | | |J.G. | | |Land + Swamp + Sand dunes + |min = 0 |[%] |Cogley | | |Saltmarsh. |max = 100 | | | | | | | | | -------------------------------------------------------------------------------- |FRIV | | |J.G. | | |Perennial rivers * |min = 0 |[counts]* |Cogley | | | |max = 66 | | | | | | | | | -------------------------------------------------------------------------------- |IRIV | | |J.G. | | |Intermittent rivers * |min = 0 |[counts]* |Cogley | | | |max = 59 | | | | | | | | | -------------------------------------------------------------------------------- |BAS1 | | |J.G. | | |A field showing the major drainage |min = -1 |[NA]$ |Cogley | | |basins. |max = 33 | | | | | | | | | -------------------------------------------------------------------------------- |CRYO | | |J.G. | | |A field showing the main features |min = 0 |[NA]$ |Cogley | | |of the cryosphere. |max = 9 | | | | | | | | | -------------------------------------------------------------------------------- |RNOF | | |J.G. | | |Surface runoff of water in mm per |min = 0 |[mm] |Cogley | | |year. |max = 5010 |[yr]^-1 | | | | | | | | -------------------------------------------------------------------------------- |RNER | | |J.G. | | |Estimated root-mean-square error, |min = 0 |[mm] |Cogley | | |in percent, of RNOF |max = 500 |[yr]^-1 | | | | |no value = -999| | | | | | | | | -------------------------------------------------------------------------------- |RICE | | |J.G. | | |Runoff of ice in mm per year. |min = -840 |[mm] |Cogley | | | |max = 1060 |[yr]^-1 | | | | | | | | -------------------------------------------------------------------------------- * FRIV and IRIV do not give areal coverage; rather they represent stream frequency in counts per grid box, with the number of counts lying in the range 0 - 100. $ See section 9.2.1 for descriptions of BAS1 and CRYO values. 8.3 Sample Data Base Data Record. Not applicable. 8.4 Data Format. The CD-ROM file format is ASCII, and consists of numerical fields of varying length, which are space delimited and arranged in columns and rows. Each column contains 180 numerical values and each row contain 360 numerical values. Grid arrangement ARRAY(I,J) I = 1 IS CENTERED AT 179.5W I INCREASES EASTWARD BY 1 DEGREE J = 1 IS CENTERED AT 89.5N J INCREASES SOUTHWARD BY 1 DEGREE 90N - | - - - | - - - | - - - | - - | (1,1) | (2,1) | (3,1) | 89N - | - - - | - - - | - - - | - - | (1,2) | (2,2) | (3,2) | 88N - | - - - | - - - | - - - | - - | (1,3) | (2,3) | (3,3) | 87N - | - - - | - - - | - - - | 180W 179W 178W 177W ARRAY(360,180) 8.5 Related Data Sets. GRDC River flow data on this CD-ROM. 9. DATA MANIPULATIONS 9.1 Formulas. 9.1.1 Derivation Techniques/Algorithms. Not available at this revision. 9.2 Data Processing Sequence. 9.2.1 Processing Steps and Data Sets. DSRF: DSRF is short for "dry surface". This field is simply the sum of the percentages in LAND, SWMP, DUNE and SMRS, and does not therefore represent independent information. FRIV, IRIV: The stream frequency counts FRIV and IRIV were obtained by the same process of recording information at grid intersections as outlined above. They should be interpreted cautiously, for they simply represent the number of template intersections, out of a possible total of 100, underlain by "blue-line features" on the map. They may be influenced strongly by the habits of the various cartographers who made the maps. The amount of blue-line detail on a small-scale map appears to depend significantly on cartographic judgment or preference. As for ILAK, no information is available on the frequency with which intermittent streams flow; however in IRIV the use of dashed lines at high latitudes was ignored. Streams which flow only in summertime, at latitudes where they would be expected to be frozen in winter, were recorded as perennial streams. CRYO: CRYO is short for "cryosphere", of which CRYO portrays the main features in a semi-quantitative way. In creating CRYO the first step was to make a modified copy of MS05, in which cells containing more than 90 percent glacier ice (from GLAC) were marked separately. These glacial cells were then categorized as ice sheet or ice shelf, using topographic information from another dataset and from maps of Antarctica (there are no ice shelves in the Northern Hemisphere sufficiently extensive to show up at 1x1 resolution). For non-glacial land cells, the extent of permafrost was recorded in one of four categories: absent or extremely restricted; restricted; common; ubiquitous. Of these terms, the last three correspond vaguely to the terms sporadic, discontinuous and continuous, which are often used in studies of the regional distribution of permafrost. However the spatial resolution of GGHYDRO is coarser than that of most such studies, and the traditional terms are used differently in different studies. For these reasons it was Table 2 - Character Codes in CRYO code Explanation ---- ----------- 0 No land 1 Permafrost restricted 2 Permafrost common 3 Permafrost ubiquitous 4 Permafrost absent or extremely restricted 7 Ice shelf 9 Ice sheet thought better to choose a new terminology -- some judgment was required in allotting cells to categories when the sources of information were mutually inconsistent and showed considerable fine- scale variability. Note that "ubiquitous" means that permafrost is or is believed to be"present beneath all exposed land surfaces", implying nothing about the thermal state of the ground beneath bodies of water or glacier ice. (In particular, subsea permafrost off the coasts of the Arctic Ocean is not represented in CRYO.) The phrase "absent or extremely restricted" is intended to embrace high mountain peaks in low latitudes. Only a few such peaks are known to be underlain, or not underlain, by permafrost, but its presence must be considered likely beneath many of them. The principal sources of information for the distribution of permafrost were maps in Kudryavtsev et al. (1978 - USSR), the Hydrological Atlas of Canada (1978 - Canada), Washburn (1980 - Alaska, Greenland), Pewe (1983 - contiguous United States), Fujii and Higuchi (1978 - Mongolia) and Zhou and Guo (1983 - China). CRYO is one of the three fields in GGHYDRO which are alphanumeric as opposed to numeric (the others being BAS1 and BAS2). That is, the data are represented by characters rather than by numbers (Table 2), as described in sections 2 and 3. This is the first release of CRYO, and is provisional. Although the major regions of permafrost in the high latitudes of the Northern Hemisphere are represented from the best available sources, no reliable information has yet been located on the presence or absence of permafrost in the Andes, Patagonia, East Africa, south and southwest Asia, or New Zealand. Exposed land in Antarctica has been assumed to be underlain by ubiquitous permafrost. BAS1: BAS1 shows the major drainage basins of the world's landmasses, in- cluding regions of internal drainage; there is a special category for cells which are arheic, that is, cells from which there is no surface runoff. The drainage divides of about 200 of the world's larger drainage basins were first transferred from topographic maps in The Times Atlas of the World (1977) onto a cylindrical equidistant graticule; maps of larger scale were consulted in areas of low relief, and also in Greenland and Antarctica. The MS05 landmask was also copied onto the graticule. A coarse version of the system of divides was then prepared by assigning Table 3 - Character Codes in BAS1 code Explanation code Explanation ---- ----------- ---- ----------- 0 No land 16 Assale -1 No runoff 17 Blanche 1 Internal (local/regional) 18 Bulloo 2 Arctic Ocean 19 Eyasi 3 Atlantic Ocean 20 Frome 4 Mediterranean Sea 21 Gholkarteniz 5 Indian Ocean 22 Issyk Kul 6 Pacific Ocean 23 Mar Chiquita 24 Nazas 7 Caspian Sea 25 Rudolf 8 Aral Sea 26 Rukwa 9 Lake Balkhash 27 Poopo 10 Lop Nor 28 Tengiz 11 Helmand/Seistan 29 Urmia 12 Lake Chad 30 Van 13 Makgadikgadi 31 Uvs Nor 14 Lake Eyre 32 Hyargas Nor 15 Abbe 33 Tsaidam each 1x1 land cell to one of a small number of composite basins, as listed in Table 3. Only the largest features of the drainage pattern can be shown clearly at a resolution of 1 degree, so that many smaller basins of internal drainage remain undifferentiated. Cells with no surface water runoff were identified by relying on the fields FRIV and IRIV: if there were no streams in the cell, and no other evidence of surface water, it was assumed not to yield any runoff. In Greenland and Antarctica the surface topography was used as an indicator of the direction of ice "runoff". RNOF, RNER, RICE: These fields contain the annual average of surface water runoff from land surfaces (in mm/yr), the estimated uncertainty in the surface water runoff (in percent), and the annual average of "runoff" of glacier ice (in mm/yr), respectively. The fields were derived from maps in a considerable number of sources, of which Korzun et al. (1977) was the most important. RNOF: Because runoff is a dynamic quantity it is harder to measure reliably than the static (or very slowly changing) fields of section 1a, and maps of hydrological quantities like runoff are therefore less reliable than maps of hydrographic properties such as the extent of salt flats or wetlands. For this reason a working resolution of 2 degrees by 2 degrees was adopted when transferring information from runoff maps to digital storage, and an effort was made to quantify the error in the runoff estimates. Transparent 2x2 degree graticules were prepared to fit the source maps and were overlaid upon them, and the runoff was estimated by eye for each 2x2 cell. Where runoff isopleths were complex, numerous point readings were taken and averaged. For cells containing large lakes, only the runoff from land portions of the cell was recorded. Surface runoff is negative over some parts of the Earth's land surface -- for example in the centres of enclosed drainage basins, and in places where large rivers like the Nile flow across deserts, losing water steadily -- but this phenomenon was not allowed for in RNOF. (It is difficult to obtain accurate estimates of the magnitude of negative runoff, which will generally be small.) An estimated runoff of 1 mm/yr should be taken to mean that the actual runoff is probably indistinguishable from zero. However where an element of RNOF is 0 the implication is that the runoff is indeed zero, because the cell in question contains no hydrographic evidence of surface runoff (FRIV, IRIV, and other fields denoting the occurrence of surface water, all being zero). The land mask for RNOF consisted of all 2x2 cells passing a 5 percent threshold similar to that described above under MS05. However RNOF itself, and RNER and RICE, are presented at 1x1 resolution: 1x1 land cells in MS05 were assigned the runoff estimated for the 2x2 cell to which they belong, and ocean cells were assigned runoff of zero. This is a waste of storage space, but the inefficiency is outweighed by the convenience of having a common spatial resolution for all fields in the dataset. RNER: The error estimates in RNER take account of three kinds of error: in the original measurements of stream discharge and water level; in the preparation of maps like those of Korzun et al. (1977); and in the con version of the mapped information to digital form. Measurement errors are typically around ten percent, although better measurements are possible when special care is taken; in addition longer series of measurements are less uncertain than shorter ones. Mapping errors arise from two main sources, interpolation and extrapolation: the mapmaker must convert measurements of stream discharge to estimates of runoff at points in between measurement stations, and must also -- because the measurement network is not complete -- extrapolate measured information to estimate the runoff from regions where no measurements have been made. Digitizing error arises mainly from the uncertainty in estimating spatial averages of mapped runoff by eye. Mapping and digitizing errors were studied by comparing the work of different mapmakers and map readers, and RNER reflects the results of these studies (described in more detail in a forthcoming publication). In particular, errors are greater in mountainous terrain where measurement, mapping and map reading are all more difficult than in areas of gentler topography, and errors are made very large in very dry regions by requiring the absolute error to be at least 5 mm/yr. This means, for example, that an estimated runoff of 2 mm/yr has an estimated uncertainty of 250 percent. Cells with zero runoff, and cells in the interiors of the ice sheets, have errors of zero, and ocean cells are assigned the meaningless error of -999. RICE: The runoff of solid water from Greenland and Antarctica was estimated from maps in Reeh (1984), Giovinetti and Bentley (1985), and other sources. These estimates must be considered highly uncertain, although since the measurements are so sparse it is not practical to make formal estimates of the error. It was assumed that in the accumulation zones of the ice sheets the runoff is equal to the annual accumulation of snow. In the ablation zone of Greenland the solid runoff is highly negative because the ice gained by inflow from the accumulation zone is nowhere near sufficient to balance the ice lost by melting. The quantity recorded in RICE is a crude estimate of the amount of summer meltwater runoff which comes from glacier ice rather than from snowfall of the previous winter. 9.2.2 Processing Changes. Not available at this revision. 9.3 Calculations. 9.3.1 Special Corrections/Adjustments. Not available at this revision. 9.4 Graphs and Plots. None. 10. ERRORS 10.1 Sources of Error. See in description of RNER in section 9.2.1. 10.2 Quality Assessment. 10.2.1 Data Validation by Source. See in description of RNER in section 9.2.1. 10.2.2 Confidence Level/Accuracy Judgment. See section 9.2.1. 10.2.3 Measurement Error for Parameters and Variables. See in description of RNER in section 9.2.1. 10.2.4 Additional Quality Assessment Applied. See section 9.2.1. 11. NOTES 11.1 Known Problems With The Data. Not available at this revision. 11.2 Usage Guidance. Not available at this revision. 11.3 Other Relevant Information. Not available at this revision. 12. REFERENCES 12.1 Satellite/Instrument/Data Processing Documentation. Not available at this revision. 12.2 Journal Articles and Study Reports. Fujii,Y., and K.Higuchi, 1978. Distribution of alpine permafrost in the Northern Hemisphere and its relation to air temperature. in Proceed- ings, 3rd International Conference on Permafrost, 1:366-371. Natl. Res. Cncl., Ottawa. Giovinetti,M.B., and C.R.Bentley, 1985. Surface balance in ice drainage systems of Antarctica. Antarctic Journal of the U.S., 20:6-13. Hydrological Atlas of Canada, 1978. [Plate 32 - Permafrost.] Fisheries and Environment Canada, Ottawa. Korzun,V.I., et al., 1977. Atlas of World Water Balance. 34p., 65 sheets. Gidrometeoizdat, Leningrad. Kudryavtsev,V.A., K.A.Kondrat'eva and N.N.Romanovskii, 1978. Zonal and regional patterns of formation of the permafrost region in the U.S.S.R., in Proceedings, 3rd International Conference on Permafrost, 1:419-426. Natl. Res. Cncl., Ottawa. Pewe,T.L., 1983. Alpine permafrost in the contiguous United States: a review. Arctic and Alpine Research, 15:145-156. Reeh,N., 1984. Greenland ice-sheet mass balance and sea-level change, in Glaciers, Ice Sheets and Sea Level: Effect of a CO2-induced Climatic Change, 155-171. U.S.Dept. Energy, Washington,D.C. The Times Atlas of the World - Comprehensive Edition, 1977. Times Books, London. Washburn,A.L., 1980. Geocryology. 406p. Wiley, New York City. Zhou,Y., and D.Guo, 1983. Some features of permafrost in China, in Perma-frost. 4th International Conference Proceedings, 1020-1023. Natl. Academy Press, Washington, D.C. 12.3 Archive/DBMS Usage Documentation. Contact the EOS Distributed Active Archive Center (DAAC) at NASA Goddard Space Flight Center (GSFC), Greenbelt Maryland (see Section 13 below). Documentation about using the archive or information about access to the on-line information system is available through the GSFC DAAC User Services Office. 13. DATA ACCESS 13.1 Contacts for Archive/Data Access Information. GSFC DAAC User Services NASA/Goddard Space Flight Center Code 902.2 Greenbelt, MD 20771 Phone: (301) 286-3209 Fax: (301) 286-1775 Internet: daacuso@eosdata.gsfc.nasa.gov 13.2 Archive Identification. Goddard Distributed Active Archive Center NASA Goddard Space Flight Center Code 902.2 Greenbelt, MD 20771 Telephone: (301) 286-3209 FAX: (301) 286-1775 Internet: daacuso@eosdata.gsfc.nasa.gov 13.3 Procedures for Obtaining Data. Users may place requests by accessing the on-line system, by sending letters, electronic mail, FAX, telephone, or personal visit. Accessing the GSFC DAAC Online System: The GSFC DAAC Information Management System (IMS) allows users to ordering data sets stored on-line. The system is open to the public. Access Instructions: Node name: daac.gsfc.nasa.gov Node number: 192.107.190.139 Login example: telnet daac.gsfc.nasa.gov Username: daacims password: gsfcdaac You will be asked to register your name and address during your first session. Ordering CD-ROMs: To order CD-ROMs (available through the Goddard DAAC) users should contact the Goddard DAAC User Support Office (see section 13.2). 13.4 GSFC DAAC Status/Plans. The ISLSCP Initiative I CD-ROMs are available from the Goddard DAAC. 14. OUTPUT PRODUCTS AND AVAILABILITY 14.1 Tape Products. None. 14.2 Film Products. None. 14.3 Other Products. None. 15. GLOSSARY OF ACRONYMS CD-ROM Compact Disk (optical), Read Only Memory DAAC Distributed Active Archive Center EOS Earth Observing System GSFC Goddard Space Flight Center IDS Inter disciplinary Science ISLSCP International Satellite Land Surface Climotology Project NASA National Aeronautics and Space Administration