C. Koblinsky

On the effectiveness of Geosat altimeter corrections

Abstract Measurementsof sea level by a satellite altimeter require a number of corrections for atmospheric and geophysical effects. We have examined the effectiveness of a large suite of correction terms for Geosat by studying how each correction affects the variances of altimetric sea-surface height differences. Most corrections were found to provide a significant reduction in variance, the most important exception being certain short-period wet-tropospherecorrections. Our procedure of using height differences implies nothing about the time-invariant parts of corrections.

Large-scale Rossby wave in the mid-latitude South Pacific from altimetry data

We present observations of large-scale Rossby wave propagation in the mid-latitude South Pacific (25°S) from analyzing 4 years of TOPEX/POSEIDON altimetry data. Using wavelet transform we separate phase propagation from amplitude modulation. The dominant Rossby wave has a wavelength of about 40° with a period close to 2 years (phase speed ∼6.4 cm/s). Its amplitude modulates both interannually and intraannually. In addition, we also found a shorter-scale Rossby wave with a wavelength of about 16° and a period close to 9 months.

The measurement of salinity from space: sensor concept

Salinity in the open ocean is important for understanding ocean dynamics and for modeling energy exchange with the atmosphere. The potential exists for obtaining global coverage of sea surface salinity using a microwave sensor in space operating at L-band (1.4 GHz). Work is currently underway at NASAs Goddard Space Flight Center and the Jet Propulsion Laboratory to define a sensor to make this measurement from space. The goal is to achieve spatial resolution on the order of 100 km with a revisit time of 14 days or less and a calibration accuracy equivalent to 0.2 psu. It is planned to combine the radiometer with a radar to help correct for surface roughness. It is believed that such a sensor system can be developed within the confines of a future Earth Sensor System Pathfinder (ESSP) mission.

Ocean surface salinity remote sensing with the JPL Passive/Active L-/S-band (PALS) microwave instrument

Describes the measurements acquired by the aircraft Passive/Active L-/S-band (PALS) instrument from two field campaigns in 1999 and 2000. These measurements were in support of the development of ocean surface salinity remote sensing techniques for the future Aquarius space mission. The 2000 measurements demonstrated the aircraft radiometer stability of /spl plusmn/0.3 K over time periods of 30 minutes with a salinity measurement accuracy of 0.2 PSS (Practical Salinity Scale or parts per thousand).

A sensor to measure salinity in the open ocean from space

The salinity of the open ocean is important for understanding ocean dynamics and for modelling energy exchange with the atmosphere. But existing data are sparse and much of the ocean is unsampled. Sea surface salinity can be measured remotely with passive microwave sensors operating near 1.4 GHz (L-band). Salinity differences have been observed from space and aircraft instruments have demonstrated that salinity can be measured with an accuracy of better than 1 psu. Sensor technology has improved sufficiently to seriously propose a satellite system to map salinity over the open oceans.

Salinity measurements during the Gulf Stream Experiment

The Gulf Stream Experiment was conducted in late summer, 1999, as part of research at the Goddard Space Flight Center on passive, microwave remote sensing of salinity in the open ocean. Measurements were made about 250 km east of Delaware Bay between the waters of the continental shelf and the north wall of the Gulf Stream. The instruments included the airborne L-band radiometers ESTAR and SLFMR. Ships and drifter buoys provided surface truth. Preliminary results show good agreement between the microwave measurements and ship measurements of salinity.

Intermittence and modulation of mesoscale variability

We studied both the fast and slow modulation of mesoscale variability in the western Kuroshio Extension region (along track 119) by analyzing 4-year TOPEX/Poseidon altimetry data. Bulk of the mesoscale variability lies near the axis of the Kuroshio Extension and the western boundary current along the east coast of Japan. It is found that both the intensity and spreading of mesoscale variability in the frequency band has significant, both abrupt and slow, variations. The slow modulation may be mainly caused by low-frequency variation in the background mean flow, while the abrupt change is primarily due to strong nonlinear processes.

Ocean, ice, and climate: the slow dance of a complex system

The time horizon of global change is on scales of years, decades, centuries, and beyond, and this variability can have a tremendous regional impact. The importance of the oceans and cryosphere in climate change increases with time scale because of their large thermal inertia. NASAs Earth Science Enterprise has developed a research strategy to address climate relevant questions about the ocean and cryosphere, such as: how is the global ocean circulation varying on interannual, decadal, and longer time scales?; and what changes are occurring in the mass of the Earths ice cover? This strategy starts with basic exploration utilizing satellite measurements, leads to improved understanding by incorporating data and models, and ends with improved prediction and benefit for the future. In this paper we consider the science and technology challenges for the ocean and cryosphere strategy over the next twenty-five years.