Papers by Kristina Katsaros
Experimental Investigation Of The Dependence Of Radar Sackscattering On Wind Speed , Wind Stress And Wave Height
12th Canadian Symposium on Remote Sensing Geoscience and Remote Sensing Symposium,
ABSTRACT
Turbulent Flux of Water Vapor in Relation to the Wave Field and Atmospheric Stratification
Oceanic Origin of the Precipitation Jump in the Sahel
New geophysical algorithms for the special sensor microwave imager
Development of a Microcomputer Program for Data Collection and Processing in Field Experiments
Journal of Geophysical Research: Oceans, 2014
Many studies have been undertaken to evaluate turbulent heat fluxes at the oceanatmosphere interf... more Many studies have been undertaken to evaluate turbulent heat fluxes at the oceanatmosphere interface; less was done on the total net heat flux. We will compare heat budgets at the ocean-atmosphere interface as derived from satellites and from blended products, compare them to in situ observations, identify the location of largest differences, and attempt to explain reasons for these differences. The results over the Atlantic Sector (50 S-50 N) for a 3 year period show that differences in the turbulent fluxes among two widely used approaches are overshadowed by differences in the radiative fluxes. While the maximum difference in sensible and latent heat fluxes can be about 30 W/m 2 , the mean values for latent heat fluxes are 22.27 W/m 2 for January and 5.40 W/m 2 for July. For sensible heat, they are 2.82 W/m 2 for January and 5.64 W/m 2 for July. We show that the maximum difference in net radiative fluxes can be as high as 55 W/m 2 , for January, the mean difference in net SW is 6.31 W/m 2 and in net LW it is 12.14 W/m 2. For July, the respective differences are 29.99 W/m 2 for the SW and 14.31 W/m 2 for the LW. Relationships between the fluxes and satellite derived surface wind speed, total precipitable water, and cloud cover provide insight on the dominant processes that control the net heat flux. This study is intended to present an estimate of uncertainties that still exist in the net heat flux at the ocean-atmosphere interface.
Despite their importance for air-sea interaction and microwave remote sensing of the ocean surfac... more Despite their importance for air-sea interaction and microwave remote sensing of the ocean surface, intrinsic properties of short gravity-capillary waves are not well established. This is largely due to water surface currents and their effects on the direct measurements of wave parameters conducted at a fixed point. Frequencies of small scale waves propagating on a surface which itself is in motion, are subject to Doppler shifts. Hence, the high frequency tail of the wave spectra obtained from such temporal observations is smeared. Conversion of this smeared measured-frequency spectra to intrinsicfrequency (or wavenumber) spectra requires corrections for the Doppler shifts. Such attempts in the past have not been very successful in particular when field data were used. This becomes evident if the amplitude modulation of short waves by underlying long waves is considered. Microwave radar studies show that the amplitude of a short wave component attains its maximum value near the crests and its minimum in the troughs of the long waves. Doppler-shifted wave data yield similar results but much larger in modulation magnitude, as expected. In general, Doppler shift corrections reduce the modulation magnitude. Overcorrection may result in a negligible modulation or even in a strong modulation with the maximum amplitude in the wave troughs. The latter situation is clearly contradictory to our visual observations as well as the radar results and imply that the advection by currents is overestimated. In this study, a differential-advection approach is used in which small scale waves are advected by the currents evaluated not at the free surface, but at a depth proportional to their wavelengths. Applicability of this approach is verified by the excellent agreement in phase and magnitude of shortwave modulation between results based on radar and on wave-gauge measurements conducted on a lake.
Temperature and salinity of the sea surface with particular emphasis on effects of precipitation [microform] /
ABSTRACT
We present a sea scattering model for the radar altimeter. Central to this effort is definition o... more We present a sea scattering model for the radar altimeter. Central to this effort is definition of an idealized omnidirectional spectrum approximation in the high-wavenumber spectral domain. This spectrum is consistent with recent forms showing two distinct energy balance regimes and is constrained to the well-known optical slope observations made by . Scattering prediction relies on the two-scale Kirchhoff method at vertical incidence to treat the dominant quasi-specular scattering but also to permit examination of diffraction caused by high-frequency waves. Using satellite altimeter data, attention is devoted to clarifying relationships between altimeter normalized cross section σ 0 , surface wind speed, and sea surface slope and height variance. Results indicate that Ku-band backscatter for wind speeds above 7 m/s is sensitive, as expected, to changes in total surface roughness, but also to changes in the more highly wind-dependent gravity-capillary range between 2 and 10 cm. Modeled frequency dependencies related to small-scale roughness are compared to global TOPEX Ku-band and C-band altimeter data showing promising agreement. For example, the physically-based development is able to reproduce a well-defined transition between the two frequencies of TOPEX measurements, observed near 7 m/s wind speed, presumably associated with the onset of boundary layer-flow separation and wave breaking events.
Studies of midaltitude cyclone structure with SEASAT scanning multichannel microwave radiometer
ABSTRACT
Special Section - Frontiers of Remote-Sensing of the Oceans and Troposphere from Air and Space Platforms - Introduction
Studies of atmospheric water in storms with the Nimbus 7 scanning multichannel microwave radiometer
ABSTRACT
A model for atmospheric brightness temperatures observed by the special sensor microwave imager (SSM/I)
ABSTRACT
Empirical studies of the microwave radiometric response to rainfall in the tropics and midlatitudes
ABSTRACT
New algorithms for the special sensor microwave imager
ABSTRACT
Morning-evening differences in global and regional oceanic precipitation as observed by the SSM/I
ABSTRACT
Microwave radiometry for monitoring the diverse cloudiness regimes on Earth: A review
ABSTRACT
Microwave radiometer studies of atmospheric water over the oceans, volume 1
ABSTRACT
Uploads
Papers by Kristina Katsaros