Evaluation of GPS PWV anomaly during ENSO

Water vapor variability during the El Niño-Southern Oscillation (ENSO) events from 2003 to 2007 were analyzed using an anomaly and a percentage method. ENSO indices and sea surface temperature anomalies (SST_a) were employed to detect the ENSO events. The moderate warm ENSO event in 2006/2007 has been observed to have varied effects on the GPS precipitable water vapor (PWV) at four locations in the northern Borneo Island. The moderate warming ENSO event of 2006 saw the rate of the increase in PWV_a for the stations ranging from 0.02 to 0.17 mm month^-1. With a correlation threshold set at ±0.3, the PWV_a and the Trans-Niño Index (TNI) showed significant correlations throughout the five years. Most stations recorded a decrease in the PWV during ENSO events with drop variations ranging within 0.12% to 11.54% between respective stations. Kota Kinabalu recorded the highest percentage response during the 2006 warm ENSO event at -11.59%.