Interaction of MJO and diurnal cycle observed by radiosonde data during the first YMC campaign in Bengkulu (November 2017 - January 2018)

Abstract

The interaction of MJO and diurnal cycle in the Maritime Continent has been identified from previous studies but more observations are needed to understand it clearly. The first campaign of Years of the Maritime Continent (YMC) was conducted in Bengkulu from 16 November 2017 to 15 January 2018. Among various kind of observations, the three-hourly radiosonde sounding was conducted in Bengkulu station during the campaign. This study analyses the radiosonde data to investigate the thermodynamic profile of the mean diurnal cycle (MDC) at different MJO phases. The MDC of potential temperature anomaly (PTA), relative humidity, winds, convective available potential energy (CAPE) and total precipitable water (TPW) in different MJO phases were compared to the MDC values during the campaign (average condition). The obtained MDC PTA has a similar pattern with the results from the Pre-YMC campaign (November - December 2015). During the active MJO phase (3-4), RH is much higher and the zonal westerly wind is up to 6 m/s faster than the average condition at most of the time and elevation below 15 km, and TPW is amplified about 1-4 mm. In contrast, the condition is reversed during inactive MJO phase (1-2). In addition, the CAPE peaks occurred at 06 - 09 UTC and followed by TPW peaks 6 hours later.