Characteristics of precipitable water over Peninsular Malaysia from satellite and in situ data

Variations as well as distribution patterns of total precipitable water vapour (WST) and layered precipitable water vapour (W) over Peninsular Malaysia using data retrieved and archived by the Satellite Application Facilities on Climate Monitoring (CM SAF), Deutscher Wetterdienst, Germany, for the period 2001-2011 are analysed using simple regression method. The lower and middle layers of W are observed to exhibit bimodal annual oscillations, which arc in phase with WST at all the climatic regions, with a pair of minima and maxima in each case. The primary and secondary minima occur in February and August, while their maxima counterparts are noticed around November and May/June respectively. These oscillations are synchronous to the movement of the prevailing monsoons. The satellite and radiosonde products are compared at the seasonal scale and the results show good agreement, with con-elation coefficients between 0.60-0.98 and mean bias range of-0.60-0.59 kg m(-2) throughout the study area. Also at the seasonal scale WST and W exhibit significant agreement at all the stations for which radiosonde records were available. The difference between W, from the two sources of measurements arc relatively uniform, irrespective of the satellite value, at all the layers and to a large extend, throughout the period of the year. While the satellite precipitable water is greater than its radiosonde counterpart at the middle and upper layers, the reverse is, however, the case for the lower layer in all the climatic regions. These differences are more as a result of instrumentation than the variability of the atmosphere.