Abdulhadi Abu-Almal

Bio: Abdulhadi Abu-Almal is an academic researcher. The author has contributed to research in topics: Earth radius. The author has an hindex of 1, co-authored 1 publications receiving 24 citations.

Calculation of Effective Earth Radius and Point Refractivity Gradient in UAE

Abstract: A large set of 14 years of reliable local radiosonde meteorological data, from 1990 to 2003, has been used to calculate the effective Earth radius and point refractivity gradient in the United Arab Emirates. The obtained values are used to investigate their impact on the design of microwave links. The cumulative distribution of the refractivity gradient in the first 65 meters above the ground surface, the monthly distribution for the median value of the k-factor, as well as their comparison with the ITU-maps are provided. Both experimental and global standard values are applied to specific link budget calculations.

Statistical Analysis of Refractivity Gradient and $\beta_{0}$ Parameter in the Gulf Region

Abstract: In this communication, nine years of local radiosonde meteorological data, from 1997 to 2005, have been used to calculate the vertical refractivity gradient, ΔN, in the lowest atmospheric layer above the ground surface. The values obtained are used to estimate the parameter β0, which represents the probability of non-standard propagation. Hourly, monthly and yearly distributions of ΔN in the first 100 meters above the ground are given. Monthly and yearly variations of the mean of ΔN and β0 are provided and the β0 values are compared with the ITU maps.

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

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 6.73km 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 flve 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 65m above the ground for flve locations within South Africa. Standard error of the mean and confldence interval for both annual averages and seasonal averages of point refractivity gradient is calculated to re∞ect 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 conflrm 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 re∞ections 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.

New Methodology for Predicting Vertical Atmospheric Profile and Propagation Parameters in Subtropical Arabian Gulf Region

Abstract: A new simplified approach is proposed to evaluate the vertical refractivity profile within the lowest 1 km of atmosphere from the analysis of surface refractivity $\bm{N}_{\bm{s}}$ in areas where upper-air data are not available. Upper-air measurements from the nearest available radiosonde location with similar surface profile to these sites are utilized. The profiles of $\bm{N}_{\bm{s}}$ and refractivity extrapolated to sea level $N_o$ obtained from surface meteorological data using both fixed stations and radiosonde are investigated and compared. Vertical refractivity gradient $\boldsymbol{\Delta} {\bm{N}}$ is evaluated at three atmospheric layer heights within the first kilometer above the ground in addition to propagation parameters relevant to each atmospheric layer. At six sites, different approaches are compared for the analysis of three important parameters; namely effective earth radius factor $k$ anomalous propagation probability parameter ${\boldsymbol{\upbeta}_0}$ and point refractivity gradient at 65 m not exceeded for 1% of time $dN_1$ . The ${\bm{k}}$ -factor parameter is investigated using a new weighted average approach of $\boldsymbol{\Delta} {\bm{N}}$ at 65-m, 100-m, and 1-km layers above the ground. The results are compared with the latest ITU maps and tables for the same area.

New Approaches and Algorithms for the Analysis of Vertical Refractivity Profile Below 1 km in a Subtropical Region

Abstract: In this communication, 17 years of high resolution surface and radiosonde meteorological data from 1997-2013 for the subtropical Gulf region are analysed. Relationships between the upper air refractivity, Nh, and vertical refractivity gradient, ΔN, in the low troposphere and the commonly available data of surface refractivity, Ns are investigated. A new approach is discussed to estimate Nh and ΔN from the analysis of the dry and wet components of Ns , which gives better results for certain cases. Results are compared with those obtained from existing linear and exponential models in the literature. The investigation focusses on three layer heights at 65 m, 100 m and 1 km above ground level. Correlation between the components of Ns with both Nh and ΔN are studied for each atmospheric layer. Where high correlations were found, empirical models are derived from best-fitting curves.

Climatological Beam Propagation Conditions for China’s Weather Radar Network

Abstract: The vertical refractivity gradient (VRG) is critical to weather radar beam propagation. The most common method of calculating beam paths uses the 4/3 Earth radius model, which corresponds to standard refraction conditions. In the present work, to better document propagation conditions for radar electromagnetic waves, which is essential for hydrology and numerical weather forecast models to more fully benefit from observations taken from the new-generation weather radar network in China, VRG spatial and temporal variations in the first kilometers above the surface are explored using 6-yr sounding observations. Under the effects of both regional climatic and topographic conditions, VRG values for most of the radars are generally smaller than those of the standard conditions for much of the year. There are similar or slightly larger values at only a few radar sites. Smaller VRG values are more frequent and widespread, especially during rainy seasons when weather radar observations are important. In s...