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Availability: Archived at NSSDC, accessible from elsewhere


This description was generated automatically using input from the Planetary Data System.

Data Set Overview

This data set consists of a catalog of clouds observed in Mariner 9 and Viking Orbiter images. Seven 'cloud types' were defined according to easily observable objective morphologic criteria. The entire Mariner 9 and Viking Orbiter image data sets (approximately 7400 and over 50000 images, respectively) were examined at least twice, by two separate observers. Cloud occurrences were compiled by examining images for specific cloud morphologies, examining the same area at different times, utilizing limb images, and consulting photomosaics to determine the spatial relations of cloud obscurations. The data set contains details of the cloud occurrences and the images in which they were observed. There is a time gap of several years in the catalog -- the Mariner 9 data cover a time period from Ls (areocentric solar longitude) 293 degrees (Earth year 1972) through Ls 98 degrees (Earth year 1973), and the Viking Orbiter data cover a period from Ls 85 degrees (Earth year 1976) through Ls 140 degrees (Earth year 1980). These data have been used to infer near-surface wind directions, relative wind speed, static stability and humidity constraints, and qualitative atmospheric opacity conditions on a global basis over the martian year. Refer to [KAHN_1984] for further discussion of the data set derivation and analysis, and to [FRENCH_ETAL_1981; HUNT_ETAL_1981; KAHN_GIERASCH_1982; and KAHN_1983] for discussions of related analyses.

This data set is composed of the following fields (listed as the field name followed by a description):

SC_ID Spacecraft id

IMAGE_ID Image id

NORTH_AZ North azimuth in the image

SUN_AZ Sun azimuth in the image

SLANT_RANGE Slant range to image center

PHASE_ANGLE Phase angle at image center

SCALE_FACTOR Image scale factor (km/pixel) at image center

FILTER_NO Filter through which the image was taken

SOL_LON_PER Areocentric solar longitude at spacecraft periapsis

CTR_PT_LAT Latitude on surface of image center point

CTR_PT_LON Longitude on surface of image center point

LOCAL_TIME Local time at image center point (expressed as 1/24 of a local day)

CLOUD_TYPE 1 - Lee wave cloud 2 - Wave cloud 3 - Plume 4 - Streak cloud 5 - Cloud street 6 - Localized Fog 7 - Haze

TYPE_CERTAIN Certainty of type identification: 1 - very certain 2 - Probable 3 - Not very certain WIND_DIR Apparent wind direction (measured counter-clockwise from a line between the center and right edge of the image)

DIR_CERTAIN Certainty of determination of the wind direction 1 - Very certain 2 - Ambiguous by 180 degrees 3 - Ambiguous by less than 90 degrees 4 - Unknown HAZE_OPACITY For cloud type 7, indicates the haze opacity 1 - Thin (features clearly seen) 2 - Partial Obscuration 3 - Opaque HAZE_QUALITY For cloud type 7, indicates if haze was uniform to the edge of the image LIMB_POS For cloud type 7, indicates if the limb was in the image

These data are available on-line from the Planetary Data System (PDS) at:

Alternate Names

  • MR9/VO1/VO2-M-ISS/VIS-5-CLOUD-V1.0


  • Planetary Science: Atmospheres

Additional Information



Questions and comments about this data collection can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Michael H. CarrData ProviderUS Geological
Mr. Ralph KahnGeneral ContactHarvard University
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