20,557 research outputs found
Linear retrieval and global measurements of wind speed from the Seasat SMMR
Retrievals of wind speed (WS) from Seasat Scanning Multichannel Microwave Radiometer (SMMR) were performed using a two-step statistical technique. Nine subsets of two to five SMMR channels were examined for wind speed retrieval. These subsets were derived by using a leaps and bound procedure based on the coefficient of determination selection criteria to a statistical data base of brightness temperatures and geophysical parameters. Analysis of Monsoon Experiment and ocean station PAPA data showed a strong correlation between sea surface temperature and water vapor. This relation was used in generating the statistical data base. Global maps of WS were produced for one and three month periods
Precipitable water: Its linear retrieval using leaps and bounds procedure and its global distribution from SEASAT SMMR data
Eight subsets using two to five frequencies of the SEASAT scanning multichannel microwave radiometer are examined to determine their potential in the retrieval of atmospheric water vapor content. Analysis indicates that the information concerning the 18 and 21 GHz channels are optimum for water vapor retrieval. A comparison with radiosonde observations gave an rms accuracy of approximately 0.40 g sq cm. The rms accuracy of precipitable water using different subsets was within 10 percent. Global maps of precipitable water over oceans using two and five channel retrieval (average of two and five channel retrieval) are given. Study of these maps reveals the possibility of global moisture distribution associated with oceanic currents and large scale general circulation in the atmosphere. A stable feature of the large scale circulation is noticed. The precipitable water is maximum over the Bay of Bengal and in the North Pacific over the Kuroshio current and shows a general latitudinal pattern
Structural ordering driven anisotropic magnetoresistance, anomalous Hall resistance and its topological overtones in full-Heusler Co2MnSi thin films
We report the evolution of crystallographic structure, magnetic ordering and
electronic transport in thin films of full-Heusler alloy CoMnSi deposited
on (001) MgO with annealing temperatures (). By increasing the from
300C to 600C, the film goes from a disordered nanocrystalline
phase to ordered and finally to the ordered alloy. The saturation
magnetic moment improves with structural ordering and approaches the
Slater-Pauling value of per formula unit for =
600C. At this stage the films are soft magnets with coercive and
saturation fields as low as 7 mT and 350 mT, respectively. Remarkable
effects of improved structural order are also seen in longitudinal resistivity
() and residual resistivity ratio. A model based upon electronic
transparency of grain boundaries illucidates the transition from a state of
negative to positive with improved structural order. The
Hall resistivity () derives contribution from the normal scattering
of charge carriers in external magnetic field, the anomalous effect originating
from built-in magnetization and a small but distinct topological Hall effect in
the disordered phase. The carrier concentration () and mobility () have
been extracted from the high field data. The highly ordered films
are characterized by and of 1.19 10 m and 0.4
cm at room temperature. The dependence of on
indicates the dominance of skew scattering in our films, which
shows a monotonic drop on raising the . The topological Hall effect is
analyzed for the films annealed at 300C. ......Comment: 10 pages, 9 figures, 1 tabl
- …