Microwave Anomalous Propagation Conditions in the First 100-m Altitude in a Tropical Location

In-situ measurement of radio climatological parameters of pressure, temperature and relative humidity to investigate anomalous propagation conditions in the first 100-m altitude in a tropical location are presented in this study. The analysis has been based on the dependence of average value of radio refractivity, N, on different times of the day along the year. The results of the analysis was used to determine the vertical radio refractivity gradient and k-factor over this region, which is useful for the determination of optimum performance of digital terrestrial point to point links. The results showed that N-values for the wet months were higher than in the dry months, and it also decreases with increasing altitude. It was also found that maximum values of N averaged over the month occurred at 6:00 h local time, and the minimum N values occurred at 18:00 h. The maximum variation between maximum and minimum N-value over 50 m altitude was 34.07 N-units in the month of September, while maximum variation between maximum and minimum N-value over 100 m height was 54.00 N-units during the month of December. Results of the minimum values of k-factor averaged over the month occurred at 18:00 h local time, and the maximum values averaged over the month occurred at 6:00 h during the year 2012 is analyzed. It was also observed that k-factor is low in the dry months (Jan-Mar and Nov-Dec) while the values rise during the wet months. Overall, results show that propagation in this region is mostly super-refractive.