Calculation of Effective Earth Radius and Point Refractivity Gradient in UAE

Abu-Almal, Abdulhadi; Al-Ansari, K.

doi:10.1155/2010/245070

Cited by 20 publications

(12 citation statements)

References 1 publication

(2 reference statements)

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“…The surface refractivity gradient dN/dh , which for convenience we denote dN 1 , is determined by the following formula (AbouAlmal et al, ; Abu‐Almal & Al‐Ansari, ):

d N_{1} = \frac{((), N_{2} - N_{1})}{(h_{2} - h_{1})},

where N 1 and N 2 are the refractivity values at heights h 1 and h 2 , respectively. In this paper we consider h 2 = 65 m and h 1 = 0 m.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Long‐Term Evolution of The Surface Refractivity for Arctic Regions

et al. 2019

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In this paper, local meteorological data for a period of 35 years (from 1979 to 2013) from Kuujuaq station have been used to calculate the surface refractivity, N (a link for the data is available in the acknowledgements), and to estimate the vertical refractivity gradient, dN1, in the lowest atmospheric layer above the ground. Monthly and yearly variations of the mean of N and dN1 are provided. The values obtained are compared with the corresponding values from the ITU maps. The long‐term trend of the surface refractivity is also investigated. The data demonstrate that the indices N and dN1 are subject to an evolution that may have significance in the context of climate change. Monthly means of N show an increasing departure from ITU‐R values since 1990. Yearly mean values of the dN1 show a progressive decrease over the period of study. Seasonal means of dN1 show a decrease over time, especially for summer. Such a trend may increase the occurrence of superrefraction. However, currently available ITU‐R recommendations for microwave link design assume a stationary climate, so there is a need for a new modeling approach.

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“…The surface refractivity gradient dN/dh , which for convenience we denote dN 1 , is determined by the following formula (AbouAlmal et al, ; Abu‐Almal & Al‐Ansari, ):

d N_{1} = \frac{((), N_{2} - N_{1})}{(h_{2} - h_{1})},

where N 1 and N 2 are the refractivity values at heights h 1 and h 2 , respectively. In this paper we consider h 2 = 65 m and h 1 = 0 m.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Long‐Term Evolution of The Surface Refractivity for Arctic Regions

et al. 2019

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“…The concept of effective earth as considered in radio and radar communication is seen to be a theoretical value used for the earth radius instead of the actual earth radius; the effective earth radius is used to correct for refraction that is caused by the atmosphere. The effective earth radius factor (k) can be calculated [12,14,16,17];…”

Section: Effective Earth Radiusmentioning

confidence: 99%

“…Particularly, the k-factor is largely dependent on one of the most important parameters of radio wave propagation known as refractivity gradient as considered in the lowest 65m from the ground level [9,10,11]. Variations in refractivity may cause radio waves to bend while propagating through dissimilar layers of the atmosphere [12]. Notably, these variations are determined by atmospheric conditions such as pressure, temperature and humidity which tend to vary with respect to geographical location as well as time of the year.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Clear-Air Atmospheric Effective Earth Radius (K-Factor) in Calabar

Ezenugu¹

2017

IJICS

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Microwave radio propagation in terrestrial radio links over the years has earned increased application and there has been renewed attention of studies concerning techniques for estimating the probability of multipath fading distributions. Particularly, the secondary radio parameters remain very important in carrying out these estimations especially the concept of effective earth radius. This study was carried out in Calabar, South-south Nigeria with three years atmospheric parameters data obtained from Nigerian Meteorological Agency (NIMET). International Telecommunication recommendation models were used in obtaining point refractivity gradient with which the effective earth radius factor was determined. The result showed a yearly average value of 1.626091667 for the k-factor and yearly average value of -125.50845 for the point refractivity gradient. There are also monthly and seasonal variations in the two parameters. The highest k-factor of 1.8263 occurred in January whereas the least k-factor of 1.3396 occurred in November.

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“…Multipath fading can only occur if this refractivity gradient in the atmosphere varies with height [2]. Refractivity gradient is estimated from (6) where N 1 and N 2 are the refractivity at heights h 1 and h 2 respectively [17]:…”

Section: Geoclimatic Factor Determinationmentioning

confidence: 99%

“…It is worth noting that radiosonde soundings do not report climatic parameters (i.e., temperature, humidity and pressure) at definite heights. Therefore, the value of dN 1 is estimated using (6) where N 1 is considered at the h 1 value nearest to 65 m height, so that h 1 falls within 65 ± 10% m [17]. Generally, for the design of radio communication systems, the essential statistics of the effects of propagation pertain to that of the worst month.…”

Section: Geoclimatic Factormentioning

confidence: 99%

Statistical Estimation of Fade Depth and Outage Probability Due to Multipath Propagation in Southern Africa

Asiyo¹,

Afullo²

2013

PIER B

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Abstract-This study builds on the earlier work by Odedina and Afullo on Multipath fading in Durban. Their work was based on multipath measurements in Durban over a 6.73 km Line-of-Sight (LOS) link. This submission uses the geoclimatic factor approach and ITU-R recommendations P530-14 to obtain the multipath fading occurrence in five cities in South Africa, including Durban. Three-year radiosonde data is used in estimating the percentage of time that a certain fade depth is exceeded and hence outage probability due to atmospheric multipath propagation, assuming the given fade depth leads to the received signal falling below the squelch level. We employ the Inverse Distance Square technique to estimate point refractivity gradient not exceeded for 1% of the time in the lowest 65 m above the ground for five locations within South Africa. Standard error of the mean and confidence interval for both annual averages and seasonal averages of point refractivity gradient is calculated to reflect possible deviation in the given readings. These values of point refractivity gradient obtained are used in determining the geoclimatic factor K. The results presented show monthly, seasonal and annual variation of both point refractivity gradient and geoclimatic factor K. The results confirm that the geoclimatic factor K is region based. The percentage of time a given fade depth is exceeded for a single frequency increases rapidly with increasing path length. This is due to the fact that as the path length increases so do the multiple reflections leading to multipath propagation, which can result in either signal enhancement or multipath fading. A comparison of fade depth and outage probabilities is made with the earlier work in Durban and Rwanda in Central Africa.

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Calculation of Effective Earth Radius and Point Refractivity Gradient in UAE

Cited by 20 publications

References 1 publication

Long‐Term Evolution of The Surface Refractivity for Arctic Regions

Long‐Term Evolution of The Surface Refractivity for Arctic Regions

Estimation of Clear-Air Atmospheric Effective Earth Radius (K-Factor) in Calabar

Statistical Estimation of Fade Depth and Outage Probability Due to Multipath Propagation in Southern Africa

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