Seasonal variability of alongshore geostrophic velocity relative to 500 dbar is examined from 23 years
of hydrographic data along two sections off central California (one off Point Sur and the other off Point
Conception). The seasonal cycles are determined by least square fits of the gappy data records to
harmonics...
A new method is developed for studying large-scale temporal variability of ocean currents from
satellite altimetric sea level measurements at intersections (crossovers) of ascending and descending orbit
ground tracks. Using this method, sea level time series can be constructed from crossover sea level
differences in small sample areas where altimetric...
In a recent paper, Sandwell and Agreen [1984; hereafter SA]
presented figures of global seasonal wind speed and sea state
as measured by the GEOS 3 satellite altimeter. Since that
time, Chelton and McCabe [1985; hereafter CM] have found
that problems exist in the algorithms used to retrieve wind
speed...
The scheduled February 1985 launch of a radar altimeter aboard the U.S. Navy satellite Geosat has
motivated an in-depth investigation of wind speed retrieval from satellite altimeters. The accuracy of sea
surface wind speed estimated by the Seasat altimeter is examined by comparison with wind speed
estimated by the Seasat...
Sea surface temperature (SST) is measured from space by advanced very high resolution radiometer (AVHRR), scanning multichannel microwave radiometer (SMMR), high resolution infrared sounder (HIRS) and VISSR atmospheric sounder (VAS). Typical accuraces have been reported from 0.5°C regionally to 2.0°C on a global basis. To evaluate the accuracy of the...
A series of satellite sea surface temperature (SST) intercomparison workshops were conducted under NASA sponsorship at the Jet Propulsion Laboratory. Three different satellite data sets were compared with each other, with routinely collected ship data, and with climatology for the months of November 1979, December 1981, March 1982, and July...
Tide gauges are designed to measure changes in water level relative to land. However, vertical motions of the earth's crust manifest themselves as apparent water level changes in tide gauge records. These crustally induced changes are often small in amplitude relative to the wide range of oceanic processes which affect...
A previous altimeter wind speed retrieval algorithm was developed on the basis of wind speeds in the the limited range from about 4 to 14 ms¯¹. In this paper, we use a new approach which gives a wind speed model function applicable over the range 0 to 21 ms¯¹. The...
Currents and winds measured over the continental shelf and upper continental slope during the first
half of 1984 are analyzed to determine the character of the flow off central California (Point Conception
to San Francisco). The mean flow was poleward from Point Conception to Point Sur, in opposition to
the...
Ambiguity in wind direction has long been an impediment to applications of wind observations from the Seasat scatterometer (SASS). Three months of unambiguous global SASS vector winds (7 July-10 October 1978) have recently become available from the Goddard Space Flight Center(GSFC) Laboratory for Atmospheric Sciences. The directional ambiguities were removed...
Three months of vector wind observations from the Seasat-A satellite scatterometer (SASS) are used to construct gridded fields of monthly average wind stress and wind stress curl over the global ocean. These fields are examined to identify features either poorly resolved or not present in wind stress fields constructed from...
The variability of sea level and surface geostrophic currents in the Southern Ocean is investigated from the first 26 months of unclassified Geosat altimeter data (November 1986 to December 1988). Because of problems unique to Geosat, it has been necessary to develop new techniques for analyzing the height data. These...
The sea-state bias in Geosat altimeter range measurements expressed as a percentage of significant
wave height (SWH) is examined as a function of SWH. The bias is shown to be approximately
a fixed -3.5% of SWH for SWH smaller than about 4 m. For larger SWH, the bias decreases in...
A Geosat altimeter wind speed algorithm is derived by cross-calibrating Geosat and Seasat
altimeter estimates of the normalized radar cross section σ₀ and modifying an existing Seasat
altimeter wind speed model function to obtain a model function appropriate for Geosat observations.
It is argued that the σ₀ distribution measured by...
A formalism is presented for quantifying the sampling error of an arbitrary linear estimate of a time-averaged quantity constructed from a time series of irregularly spaced observations at a fixed location. The method is applicable to any irregularly sampled time series; it is applied here to satellite observations of chlorophyll...
Seasat scatterometer and altimeter data are analyzed to investigate time-dependent Sverdrup dynamics in the Southern Ocean (40°S to 60°S) over seasonal time scales. Sverdrup dynamics are shown to be inadequate to describe the circulation in the South Atlantic and Indian oceans. The Sverdrup circulation in the South Pacific is reasonable...
A mean reference surface and time-dependent orbit errors are estimated simultaneously for
each exact-repeat ground track from the first two years of Geosat sea level estimates based on
the Goddard Earth model (GEM)-T2 orbits. Motivated by orbit theory and empirical analysis of
Geosat data, the time-dependent orbit errors are modeled...
The circulation of the southwestern Atlantic Ocean is dominated by the Subtropical Gyre
and the confluence of the Brazil and Malvinas currents. Observations indicate that the latitude
of this confluence changes seasonally, lying farther north during the austral winter than during
the summer. This phenomenon has important consequences for the...
A simple statistic is derived for quantifying the potential for the aliasing of tidal errors in a given linear estimate of sea surface height constructed from altimeter data. The existence of M2 tidal constituent errors in Geosat data processed in the traditional way (i.e., with orbit errors removed using least...
The wind speed and significant wave height (H1/3) dependencies of the sea state is in altimeter estimates of sea level, expressed in the form ∆hSSB=bH1/3, are examined from least squares analysis of 21 cycles of collinear TOPEX data. The bias coefficient b is found to increase in magnitude with increasing...