Investigation of GPS PWV variation during lightning activity due to topographic effects

We have investigated the different variation in PWV during the occurrence of lightning activities at four selected stations due to topography effects for two pre-monsoons in Peninsular Malaysia. From the selected stations, analyses were split into two categories based on the topography features that associated with water vapor sources. The first category is for KRAI and MERS stations, which distant from the sea but nearby the Kelantan River and flanked by the Titiwangsa (West) and Tahan (East) Ranges. For both stations, the lightning was detected to occur between 1 and 2 hours before the PWV abruptly decreased. Whilst the second category is for MUAD and UKMB stations which both located at flat terrain and far away from the coast. For these stations, the lightning was recorded occurred about 1 to 4 hours before the PWV reached a second peak. Results showed that PWV at KRAI took 8 to 13 hours to reach the peak value, while MERS which located nearby the sea only took 6 to 8 hours. Moreover, only one maximum peak is recorded for PWV of the first category that occurred around 12:00 LT to 14:00 UT. For the second category, the peak value for the PWV variation is recorded twice with the first peak around 8:00 LT to 12:00 LT and around 16:00 LT to 21:00 LT for the second peak. As a result, the difference in PWV during first inter-monsoon (in May) was 2.53 mm higher than the second inter-monsoon (in November) which is only 0.91 mm, indicated that the topographical features has been detected to effect the PWV variation in these selected stations.