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Statistical Investigation and Mapping of Monthly Modified Refractivity Gradient over Pakistan at the 700 Hectopascal Level
Last modified: 2016-12-02
Abstract
It is an effort to investigate the spatial-temporal variability of the modified refractivity gradient at the 700 hPa pressure level over Pakistan and its neighbouring regions of Afghanistan, India, Iran and the Arabian Sea using the remote sensing data of the AQUA (AIRX3STM) satellite from 2008 to 2012. Trapping conditions only found in December were spread over Khyber Pakhtunkhwa (Gilgit-Baltistan, Pakistan) with an average value of -182.042 M/Km and showing Leptokurtic distributions. The lowest monthly average value super-refractive conditions existed in the autumn season with a strong monthly correlation (>0.91 M/Km). A very high monthly correlation (0.9 M/Km) was found for the super-refractive conditions over the whole time period. The largest spatial and temporal normal conditions appeared in January with the average value for normal conditions being 132.72 M/Km (found over Zabul, Afghanistan) with Leptokurtic distributions. During May normal conditions were the smallest in spatial extent over Pakistan, India and Afghanistan, showing Platykurtic distributions. Sub-refractive conditions mostly prevailed at all times. The probability for extreme sub-refractive conditions was very high in 2008-2012. The highest average sub-refractive conditions appeared in the winter and autumn seasons (spread around Quetta and Kalam, Pakistan). The highest monthly average sub-refractive conditions with a value of 1,265,188 M/Km were found in January and spread around the Sarbaz River Iran. Correlations for the existence of sub-refractive conditions varied from 0.8 M/Km (moderate strong) to 0.4 M/Km during the autumn to winter season. Permanent super-refractive conditions existed over Baluchistan from February to September.
References
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http://dx.doi.org/10.1016/s1364-6826(01)00111-0 [5]Waheed-uz-Zaman, M. (2013) To Study the Implications of the Evaporation Duct for Ground Waves Path in Pakistan Coastal Water through Statistical Assessment. Journal of American Science, 9, 524-527. [6]Mufti, N. (2011) Investigation into Effects of the Troposphere on Vhf and Uhf Progation and Interference between Co Frequencies Fixed Links. University of Leicester, UK. [7]Falodun, S. and Sjewole, M. (2006) Radio Refractive Index in the Lowest 100-M Layer of the Troposphere in Akure, South Western Nigeria. Journal of Atmospheric and Solar-Terrestrial Physics, 68, 8236-8242. http://dx.doi.org/10.1016/j.jastp.2005.10.002 [8]Grabner, M. and Kvicera, V. (2006) Refractive Index Measurements in the Lowest Troposphere in the Czech Republic. Journal of Atmospheric and Solar-Terrestrial Physics, 68, 1334-1339.
http://dx.doi.org/10.1016/j.jastp.2006.05.005 [9]Von Engeln, A. and Teixeira, J. (2004) A Ducting Climatology Derived from the European Centre for Medium-Range Weather Forecasts Global Analysis Fields. Journal of Geophysical Research, 109.
http://dx.doi.org/10.1029/2003jd004380 [10]Mentes, S. and Kaymaz, Z. (2006) Investigation of Surface Duct Conditions over Istanbul, Turkey. Journal of Applied Meterology and Climatology, 35, 318-329. [11]Babin, S. (1995) Surface Duct Height Distributions for Wallops Island, Virginia, 1985-1994. Journal of Applied Meteorology, 35, 86-87, 89-91.
http://dx.doi.org/10.1175/1520-0450(1996)035<0086:SDHDFW>2.0.CO;2 [12]Reddy, K.K., et al. (2010) Lower Atmospheric Wind Profiler at Gadanki, Tropical India: Initial Results. Meteorologische Zeitschrift, 10, 457-468. http://dx.doi.org/10.1127/0941-2948/2001/0010-0457 [13]Douvenot, R., Fabbro, V., Gerstoft, P., Bourlier, C. and Sillard, J. (2008) A Duct Mapping Method Using Least Squares Support Vector Machines. Radio Science, 43, 1-2.
http://dx.doi.org/10.1029/2008RS003842 [14]Rana, D., Webster, A.R. and Sylvain, M. (1992) Statistical Characterization of Line-of-Sight Microwave Links. Radio Science, 7, 783-796. http://dx.doi.org/10.1029/92RS01151 [15]Webster, A. (1997) Extended Observations of Fading on a Terrestrial Microwave Link. Radio Science, 32, 231-238. http://dx.doi.org/10.1029/96RS02789 [16]Sukra, J. (1987) Worldwide Anomalous Refraction and Its Effects on Electromagnetic Wave Propagation. John Hopking Digest. http://www.jhuapl.edu/techdigest [17]Ko, H., Sari, J. and Skura, J. (1983) Anomalous Microwave Propagation through Atmospheric Ducts. John Hopking Technical Digest. http://www.jhuapl.edu/techdigest [18]Patteron, W., Hattan, C., Lindem, G., Paulus, R., Hitney, H., Anderson, K. and Barrios, A. (1994) Engineer’s Refractive Effects Prediction System. Naval Research and Development Technology. [19]DES DISC (2008) Readme Document for AIRS Level 3 Version 5 Standard Probuct. NASA. [20]Saleem, M. (2015) Atmospheric Ducts: Their Application in Radio Frequency Propagation Using Remote Sensing Techniques. Lap Academic Publisher, Saarbrücken. [21]Recommendation ITU-R (1997) The Radio Refractive Index: Its Formula and Refractivity Data. ITU. [22]Rao, S.G.V.R.K. and Purnachandra Rao, M., (2007) Addendum to “Study on Coastal Atmospheric Effects on Line of Sight Links Located in Visakhapatnam”. AU Journal of Technology, 10, 276-278. [23]Ippolito, L. (2008) Satellite Communications Systems Engineering. Weily, Chichester.
http://dx.doi.org/10.1002/9780470754443 [24]Rogers, L. (1997) Likelihood Estimation of Tropospheric Duct Parameters from Horizontal Propagation Measurements. Radio Science, 32, 79-80. http://dx.doi.org/10.1029/96RS02904 [25]Hitney, H., Richter, J.H., Pappert, R.A., Anderson, K.D. and Baumgartner, G.B. (1985) Tropospheric Radio Propagation Assessment. Proceedings of the IEEE, 73, 265-283.
http://dx.doi.org/10.1109/PROC.1985.13138 [26]Mufti, N., Ullah, H., Rehman, S., Din, I. and Rehman, S. (2015) Analysis of Tropospheric Radio Refractive Conditions in Karachi, Pakistan. 12Th International Bhurban Conference on Applied Sciences and Technology, Karachi, 13-17 January 2015, 617-619.
http://dx.doi.org/10.1109/ibcast.2015.7058569 [27]Ao, C. (2007) Efffect of Ducting on Radio Occultation Measurements: An Assessment Base on High Resolution Radiosonde Soundings. Radio Science, 42, 6-8. http://dx.doi.org/10.1029/2006RS003485