Data processing for the DMSP microwave radiometer system

A software program was developed and tested to process microwave radiometry data to be acquired by the microwave sensor (SSM/T) on the Defense Meteorological Satellite Program spacecraft. The SSM/T 7-channel microwave radiometer and systems data will be data-linked to Air Force Global Weather Central (AFGWC) where they will be merged with ephemeris data prior to product processing for use in the AFGWC upper air data base (UADB). The overall system utilizes an integrated design to provide atmospheric temperature soundings for global applications. The fully automated processing at AFGWC was accomplished by four related computer processor programs to produce compatible UADB soundings, evaluate system performance, and update the a priori developed inversion matrices. Tests with simulated data produced results significantly better than climatology

A study of radiometric emission from a rough sea surface

The equations which describe the emissivity of a rough ocean surface are developed. The theory includes effects of large scale and small scale wave structure and the influence of shadowing by the large ocean waves. Also included are investigations of the emission properties of foam and the influence of the thermal boundary layer on the brightness temperature characteristics of the ocean surface

Sea brightness temperature and effects of spray and whitecaps

Following the approach of Tang [1974], the microwave brightness of the sea surface is recalculated with recent parameterizations in terms of wind velocity for the slope distribution and whitecap coverage of the sea surface and the contribution of sea spray. The difference between this revised calculation with no free parameters and the earlier one becomes more significant as the wind velocity increases; it reaches 10 K or more at a wind velocity of 20 m s-1. Present predictions compare favorably with experimental results, suggesting that this model does include the essential physical mechanisms

Measurements of the complex dielectric constant of volcanic ash from 4 to 19 GHz

Dielectric data in volcanic ash at weather radar wavelengths (centimeter range) are extremely sparse and are crucial for radar sensing of ash clouds and for imaging of volcanic terrains. This study extends previous data to include a wavelength range of 1.5–7.5 cm and volcanic ash compositions of 50–75% silica. The real part of the complex permittivity, ε′, of volcanic ash is 6 ± 0.5 (1σ) for all wavelengths. The imaginary part, ε″, ranges from 0.08 to 0.27. Both ε′ and ε″ show higher values at lower SiO2 concentration. It is safe to assume in any weather radar applications that the reflectivity factor is K = |(ε − 1)/(ε + 2)|2 = 0.39 ± 0.02 (1σ), regardless of composition or wavelength. The results will help quantify radar observations of volcanic clouds

Specific absorption rate in neonates undergoing magnetic resonance procedures at 1.5 T and 3 T.

MRI is finding increased clinical use in neonatal populations; the extent to which electromagnetic models used for quantification of specific absorption rate (SAR) by commercial MRI scanners accurately reflect this alternative scenario is unclear. This study investigates how SAR predictions relating to adults can be related to neonates under differing conditions when imaged using 1.5 T and 3 T MRI scanners. Electromagnetic simulations were produced in neonatal subjects of different sizes and positions within a generic MRI body transmit device operating at both 64 MHz and 128 MHz, corresponding to 1.5 T and 3 T MRI scanners, respectively. An adult model was also simulated, as was a spherical salt‐water phantom, which was also used in a calorimetry experiment. The SAR in neonatal subjects was found to be less than that experienced in an adult in all scenarios; however, the overestimation factor was variable. For example a 3 T body scan resulting in local 10 g SAR of 10.1 W kg(−1) in an adult would deposit 2.6 W kg(−1) in a neonate: an approximately fourfold difference. The SAR experienced by neonatal subjects undergoing MRI is lower than that in adults in equivalent situations. If the safety of such procedures is assessed using adult‐appropriate models then the result is a conservative estimate. © 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons, Ltd

Is the thermodynamic behavior of the noble fluids consistent with the Principle of Corresponding States?

The applicability of the Principle of Corresponding States (PCS) for the noble fluids is discussed. We give the thermodynamic evidences for the dimerization of the liquid phase in heavy noble gases like argon, krypton etc. which manifest itself in deviation from the PCS. The behavior of the rectilinear diameter of the entropy and the density is analyzed. It is shown that these characteristics are very sensitive to the dimerization process which takes place in the liquid phase of heavy noble gases.Comment: 23 pages, 11 figure

A yearlong comparison of plot‐scale and satellite footprint‐scale 19 and 37 GHz brightness of the Alaskan North Slope

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95289/1/jgrd9836.pd

Monte Carlo Simulations of the microwave emissivity of the sea surface

A Monte Carlo model is developed to calculate the microwave emissivity of the sea surface based on the Kirchhoff approximation combined with modified Fresnel coefficients. The modified Fresnel coefficient depends on the incident angle of the electromagnetic wave and the height variance of small‐scale roughness, which is an approximation to account partly for the scattering effect from small ripples. The advantage of the Monte Carlo model is its inherent capability to treat multiple scattering events. Using a two‐dimensional Gaussian distribution for the sea surface slope variability, the model is capable of simulating the azimuthal dependency of the microwave emission caused by the alignment of waves perpendicular to the wind direction. Good agreement between model calculations and measurements is obtained