The structure of the sensing element of a gold-deposited optical fiber sensor was simplified and quantitative analyses of various alcohols with the sensor showed improvement of the performance. The sensor uses surface plasmon resonance (SPR) at the interface of a sample solution and a thin (10 - 70 nm) gold film deposited on half of the exposed core of the optical fiber. The sensor with a film ...

For most weather radars, such as the WSR-88D, reflectivity, radial velocity and spectrum width are the only parameters estimated. Recently, a technique to retrieve near-surface refractivity has been developed by Fabry et al. [1997]. The technique relies on the returned phase from ground clutter which changes according to the refractivity of the atmosphere. Until recently, most refractivity meas...

[1] This paper describes estimation of low-altitude atmospheric refractivity from radar sea clutter observations. The vertical structure of the refractive environment is modeled using five parameters, and the horizontal structure is modeled using six parameters. The refractivity model is implemented with and without an a priori constraint on the duct strength, as might be derived from soundings...

[1] This paper describes the estimation of propagation loss and its statistical properties on the basis of observations of radar sea clutter data. This problem is solved by first finding an ensemble of relevant refractivity model parameters, and each refractivity model is weighted according to its data likelihood function. A parabolic equation propagation model is used both in mapping from envi...

Radio occultation measurements using the Global Positioning System (GPS) and a receiver in low-Earth orbit (LEO) have recently been shown to provide accurate profiles of atmospheric refractivity, pressure, water vapor and temperature with high vertical resolution [e.g. Kursinski et al., 1996]. When a GPS transmitter and receiver pair are on opposite sides of the atmosphere, the radio signal pro...

The atmospheric propagation of GPS signals under multipath conditions and their detection are simulated. Using the multiple phase screen method C/A-code modulated L1 signals are propagated through a spherically symmetric refractivity field derived from a high-resolution radio sonde observation. The propagated signals are tracked by GPS receivers implemented in software and converted to refracti...

Assimilation into numerical weather models of the refractivity, Abel-retrieved from radio occultations, as the local refractivity at ray tangent point may result in large errors in the presence of strong horizontal gradients (atmospheric fronts, strong convection). To reduce these errors, other authors suggested modeling the Abel-retrieved refractivity as a nonlocal linear function of the 3D re...

In this work we have proposed a method based on neural networks to directly retrieve dry and wet refractivity and dry pressure profiles in troposphere (which in turn can be used to obtain temperature and humidity profiles) by using COSMIC GPS radio occultation (RO) data. To overcome the constraint of an independent knowledge of one atmospheric parameter at each GPS occultation, we trained diffe...

Inferring refractivity profiles from radar sea clutter is a complex nonlinear optimization problem. Previous works treat this problem as a model parameter estimation issue by using some idealized refractivity models, such as the Log linear evaporation duct model, bilinear model, and trilinear model, to describe the synoptic structure of the real atmospheric conditions. However, these idealized ...

This paper estimates lower atmospheric refractivity (M-profile) given an electromagnetic (EM) propagation loss (PL) measurement. Specifically, height-independent PL measurements over a range of 10–80 km are used to infer information about the existence and potential parameters of atmospheric ducts in the lowest 1 km of the atmosphere. The main improvement made on previous refractivity estimatio...