A climatology-based model for long-term prediction of radar beam refraction

Abstract

Hitherto, radar beam bending has been predicted using four-thirds earth or standard atmosphere. A new and more accurate model has been developed using a mix of raytracing and climatology.Usually a microwave beam traveling through the atmosphere bends towards the earth with a radius of curvature greater than the earth's surface. However, seasonal and climatic variations influence the amount and direction of bending, and at times create temperature or moisture inversions that tend to redirect the energy along the earth's surface leaving gaping holes where there is no coverage.In this work, iterative raytracing is used to determine the most direct path from the radar to the target through the climatologically predicted refractive atmosphere. Height measurement error is calculated by comparing the geographic path to the refracted path. Only vertical refractivity variation is taken into account, and the effects of ducting and exponential refractivity are both modeled.As a test, the model computed height errors at 17 locations worldwide for a hypothetical target at 10,000 feet and 60 nautical miles. The predicted errors varied from 100 feet to 2260 feet as against the standard atmosphere predicted height error of 804 fi. The model traces to all targets when no ducting is modeled, to all targets outside the duct with surface ducting, and to some targets outside the duct with elevated ducting. In the remaining cases, adjacent rays sometimes cross, causing ambiguity in the estimation and, usually, tracing failure.

The Sensitivity of Single Polarization Weather Radar Beam Blockage Correction to Variability in the Vertical Refractivity Gradient

“…The idea that assuming normal propagation conditions for radar observations may not always be a good choice-though it is probably the best option as a first guess-is by no means new and the use of climatological refractive data for a specific radar site was already proposed, for example, in the European Cooperation in the Field of Scientific and Technical Research (COST) 73 Project (Newsome 1992) and, in a different context, evaluated by Pittman (1999) to improve radar height measurements.…”

Space‐frequency maximal ratio combining for low‐elevation radar target

“…It is also necessary to evaluate the effects of anomalous propagation of radio waves [9][10][11][12][13] and of angular spread of the received wave due to diffused reflection by the sea surface [14], as well as interference waves such as sea surface reflection clutter.…”

Analysis of an Altitude Detection Accuracy by a Weather Effect for Long Range and Multi Function Radar

“…이 방법은 지면에서 측정한 굴절율로부터 굴절 변화율을 예측하기 위하여 CRPL 모 델을 일반적으로 사용하며, 국내에서 측정된 기상 자료를 이용하여 파라미터가 보완된 모델이 연구되었다 [4] . 으로 이루어진 지구에 대하여 식 (1)을 반복적으로 계산 하여 레이더에서 송신된 신호가 특정 위치의 표적에 도 달할 때까지의 경로를 계산하여 탐지 고각을 결정하는 방법이다 [7], [8] . 일반 기상 환경에서 굴절율 지수 감수 모델의 굴절율 의 특성은 식 (2)로부터 결정된다 [2] .…”