Spaceborne imaging radar: monitoring of ocean waves

A well-organized, very low energy ocean swell system off the East Coast of the United States was tracked with the Seasat synthetic aperture radar from deep water, across the continental shelf, and into shallow, water. The results indicate that spaceborne imaging radar may be used to accurately measure ocean wavelength and direction, even in coastal areas and in the presence of a mixed ocean.     

Seasat synthetic aperture radar: ocean wave detection capabilities

A preliminary assessment has been made of the capability of the Seasat synthetic aperture radar to detect ocean waves. Comparison with surface and aircraft measurements from five passes of the satellite over the Gulf of Alaska indicates agreement to within about - 15 percent in wavelength and about +/- 25 degrees in wave direction. These results apply to waves 100 to 250 meters in length propagating in a direction predominantly across the satellite track, in sea states with significant wave height (H((1/3))) in a range of 2 to 3.5 meters.     

Ganymede: radar surface characteristics

Radar observations of Ganymede, at X-band, show that the surface is unusually bright and has unusual polarization properties. A model of the surface based on large numbers of random ice facets (hence vacuum-ice interfaces) is able to account for these characteristics.     

Light scattering in central arctic ocean: some winter profiles

Measurements for light scattering in an Arctic water column reveal strong gradients and variability of the order of 15 percent in depths of less than 500 meters. The region of variability appears to persist from day to day and is roughly associated with the typical hydrographic features of the region. No definite nephelocline was observed.     

Venus: global surface radar reflectivity

Observations of the surface of Venus, carried out by the Pioneer Venus radar mapper at a wavelength of 17 centimeters, reveal a global mean reflectivity at normal incidence of 0.13 +/- 0.03. Over the surface, variations from a low of 0.03 +/- 0.01 to a high of 0.4 +/- 0.1 are found, with Theia Mons, previously identified as possibly volcanic, showing a value of 0.28 +/- 0.07. Regions of high reflectivity may consist of rocks with substantial inclusions of highly conductive sulfides.     

Carbon dioxide in the ocean surface: the homogeneous buffer factor

The amount of carbon dioxide that can be dissolved in surface seawater depends at least partially on the homogeneous buffer factor, which is a mathematical function of the chemical equilibrium conditions among the various dissolved inorganic species. Because these equilibria are well known, the homogeneous buffer factor is well known. Natural spatial variations depend very systematically on sea surface temperatures, and do not contribute significantly to uncertainties in the present or future carbon dioxide budget.     

Venus: mapping the surface reflectivity by radar interferometry

The surface reflectivity of Venus obtained by radar interferometry at a wavelength of 3.8 centimeters has been mapped for a region extending approximately from -80 degrees to 0 degrees in longitude (Carpenter's definition) and from -50 degrees to +40 degrees in latitude. The map is free from the twofold range-Doppler ambiguity because the interferometer fringe pattern makes possible the separation of two points of equal range and Doppler shift. The map presents many new features and clearly delineates features already observed. Most notably, the map shows large circular regions of significantly lower reflectivity than their surroundinigs.     

基于雷达高度计的辽东湾海冰外缘线提取及其变动规律

为了分析利用雷达高度计资料提取海冰外缘线的精度,推进高度计在中国海冰遥感监测中的应用进展,本研究中基于Jason-2高度计沿岸和水文专用产品(PISTACH),提取了2008—2016年间辽东湾海冰外缘线,并与高分一号(GF-1)观测结果进行了对比验证,最后分析了辽东湾外缘线变动与国家海洋局葫芦岛海洋站气温观测数据的关系.结果表明:2013年末至2016年初3个冰期内的验证试验显示,基于Jason-2高度计判定的海冰外缘线延伸范围与基于GF-1遥感影像提取的结果符合良好,两者提取的海冰外缘线延伸距离均方差为2.81 n mile,并且海冰外缘线变动规律与气温数据变动规律一致;对2008年6月—2016年10月期间共8个冰期的辽东湾海冰外缘线的变动规律分析显示,2010年冰情最为严重,辽东湾海冰外缘线自海岸起沿Jason-2高度计轨道往南延伸约90 n mile,2014年和2015年的冰情较轻,延伸距离均小于40 n mile,另外,延伸距离的变动与葫芦岛的10日滑动平均气温呈明显的滞后响应关系,当滞后4 d时,两者的相关性最强,相关系数为-0.56.研究表明,基于雷达高度计资料可以准确地提取辽东湾海冰外缘线,本研究结果对于中国海冰数据产品的开发和数值模拟的改进与验证具有重要参考.     

基于雷达高度计的辽东湾海冰外缘线提取及其变动规律

为了分析利用雷达高度计资料提取海冰外缘线的精度,推进高度计在中国海冰遥感监测中的应用进展,本研究中基于Jason-2高度计沿岸和水文专用产品(PISTACH),提取了2008—2016年间辽东湾海冰外缘线,并与高分一号(GF-1)观测结果进行了对比验证,最后分析了辽东湾外缘线变动与国家海洋局葫芦岛海洋站气温观测数据的关系。结果表明:2013年末至2016年初3个冰期内的验证试验显示,基于Jason-2高度计判定的海冰外缘线延伸范围与基于GF-1遥感影像提取的结果符合良好,两者提取的海冰外缘线延伸距离均方差为2.81 n mile,并且海冰外缘线变动规律与气温数据变动规律一致;对2008年6月—2016年10月期间共8个冰期的辽东湾海冰外缘线的变动规律分析显示,2010年冰情最为严重,辽东湾海冰外缘线自海岸起沿Jason-2高度计轨道往南延伸约90 n mile, 2014年和2015年的冰情较轻,延伸距离均小于40 n mile,另外,延伸距离的变动与葫芦岛的10日滑动平均气温呈明显的滞后响应关系,当滞后4 d时,两者的相关性最强,相关系数为-0.56。研究表明,基于雷达高度计资料可以准确地提取辽东湾海冰外缘线,本研究结果对于中国海冰数据产品的开发和数值模拟的改进与验证具有重要参考。     

Hydrated salt minerals on Ganymede's surface: evidence of an ocean below

Reflectance spectra from Galileo's near-infrared mapping spectrometer (NIMS) suggests that the surface of Ganymede, the largest satellite of Jupiter, contains hydrated materials. These materials are interpreted to be similar to those found on Europa, that is, mostly frozen magnesium sulfate brines that are derived from a subsurface briny layer of fluid.     

Dimethyl sulfide in the surface ocean and the marine atmosphere: a global view

Dimethyl sulfide (DMS) has been identified as the major volatile sulfur compound in 628 samples of surface seawater representing most of the major oceanic ecozones. In at least three respects, its vertical distribution, its local patchiness, and its distribution in oceanic ecozones, the concentration of DMS in the sea exhibits a pattern similar to that of primary production. The global weightedaverage concentration of DMS in surface seawater is 102 nanograms of sulfur (DMS) per liter, corresponding to a global sea-to-air flux of 39 x 10(12) grams of sulfur per year. When the biogenic sulfur contributions from the land surface are added, the biogenic sulfur gas flux is approximately equal to the anthropogenic flux of sulfur dioxide. The DMS concentration in air over the equatorial Pacific varies diurnally between 120 and 200 nanograms of sulfur (DMS) per cubic meter, in agreement with the predictions of photochemical models. The estimated source flux of DMS from the oceans to the marine atmosphere is in agreement with independently obtained estimates of the removal fluxes of DMS and its oxidation products from the atmosphere.     

Zonal temperature-anomaly maps of Indian ocean surface waters: modern and ice-age patterns

Maps of sea surface temperature anomalies in the Indian Ocean in modern and ice-age times reveal striking changes in its surface circulation. During the last glacial maximum (18,000 years before the present), the Indian Ocean had colder average zonal surface temperatures, a cooler and less extensive Agulhas Current, a distinct eastern boundary current, and decreased upwelling and a weaker southwest monsoon in its northwestern region.     

Venus: estimates of the surface temperature and pressure from radio and radar measurements

The radio brightness temperature and radar cross section spectra of Venus are in much better accord with surface boundary conditions deduced from a combination of the Mariner V results and the radar radius than those obtained by the Venera 4 space probe. The average surface temperature and pressure are approximately 750 degrees K and 90 atmospheres.     

The role of the tropical super greenhouse effect in heating the ocean surface

Measurements made by a Fourier transform infrared (FTIR) spectroradiometer operating in the middle infrared (5 to 20 micrometers, with a spectral resolution of one inverse centimeter) imply that there is an anomalously large greenhouse effect over equatorial oceans that is caused by water vapor. As sea-surface temperature increased from 297 to 303 degrees kelvin, the net infrared cooling at the surface decreased by 30 to 50 watts per square meter. Thus, according to the FTIR data, the super greenhouse effect that had been inferred from satellite measurements contributes directly to radiative heating of the sea surface. The data demonstrate that most of this heating occurs in the middle infrared by means of the continuum emission window of water vapor and that tropical deep convection contributes substantially to this super greenhouse effect.     

Equatorial jet in the Indian ocean: theory

A nonlinear numerical model and a simple analytical theory explain the basic features of the equatorial surface jet in the Indian Ocean recently reported by Wyrtki. The observed width of this transient current, 500 kilometers, is given theoretically by twice the baroclinic equatorial radius of deformation. The numerical model reproduces all Wyrtki's observations of this natural phenomenon.     

Oxygen supersaturation in the ocean: biological versus physical contributions

A method based on measurements of dissolved molecular nitrogen, molecular oxygen, and argon can distingish biological from physical contributions to oxygen supersaturation in the ocean. The derived values of biological O(2) production can be used as a check on estimates of total organic productivity measured by instantaneous rates of carbon-14 assimilation. Application to the shallow summer O(2) maxima in the North Pacific gyres shows that about 72% of the O(2) supersaturation maximum at 28 degrees N and about 86% of the maximum at 40 degrees N are due to net photosynthetic production.