HYDR_CVR.DOC
1. TITLE
1.1 Data Set Identification.
Hydrology cover fractions.
(Fixed ; Trent University)
1.2 Data Base Table Name.
Not applicable.
1.3 CD-ROM File Name.
\DATA\HYDR_SOL\HYDR_CVR\nnnn_CVR.sfx
Note: capital letters indicate fixed values that appear on the CD-ROM
exactly as shown here, lower case indicates characters (values) that
change for each path and file.
The format used for the filenames is: nnnn_CVR.sfx, where nnnn is the
terrain type descriptor (see table below). The filename extension
(.sfx), identifies the data set content for the file (see Section 8.2)
and is equal to .HYC for this data set.
Descriptor Terrain Type
---------- ------------
LAND Exposed land not covered by swamp,
intermittent water bodies, glacier
ice, sand dunes, saltmarsh or salt flats
FLAK Perennial freshwater lakes
SWMP Swamp, marsh and other wetlands
SLTW Saltwater, whether marine or terrestrial
ILAK Intermittent water bodies
GLAC Glacier ice, including shelf ice but ex-
cluding pack ice
DUNE Sand dunes
SMRS Saltmarsh
SFLT Salt flats
DSRF Land + Swamp + Sand dunes + Saltmarsh
FRIV Perennial rivers ( * )
IRIV Intermittent rivers ( * )
BAS1 A field showing the major drainage basins
CRYO A field showing the main features of the
cryosphere
RNOF Surface runoff of water in mm per year
RNER Estimated root-mean-square error, in percent,
of RNOF
RICE Runoff of ice in mm per year
1.4 Revision Date Of This Document.
April 8, 1995.
2. INVESTIGATOR(S)
2.1 Investigator(s) Name And Title.
Dr. J.G.Cogley
Department of Geography
Trent University
2.2 Title Of Investigation.
GGHYDRO - Global Hydrographic Data, Release 2.1
Copyright (C) J.G.Cogley 1987,1991,1994
2.3 Contacts (For Data Production Information)
_____________________________________________
| 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