Detection of dry season anomaly using radiosonde data during intensive observation period (IOP) in 2017

Abstract

In the period between July - August 2017, Indonesia experiences drought which was caused by The Australian Monsoon wind. Radiosonde data obtained from launches conducted at the Palembang Meteorological Station during the IOP of 17 July - 16 August 2017 and those from cities that represents monsoon area (Pangkalpinang, Jakarta, and Surabaya) were also added to analyze the connection between Australian monsoon and precipitation in Indonesia. During IOP, the Australian Monsoon Index (AUSMI) is weaker than during normal conditions. Australian Monsoon index is normally around 6 m/s. Here, The Australian Monsoon Index chart shows a sinusoidal pattern in which during the peaks and troughs of the index there were drought anomalies in the aforementioned cities. In addition, medium to heavy rainfall also occurs during the Australian Monsoon index peaks and troughs. That conditions are affected by MJO and local influence. When MJO is a negative anomaly, AUSMI Index can be at peak or at the troughs. During the drought anomalies in all of the four cities, moisture profile at the surface to 6000-8000m is very wet (65-100%) with vertical wind profile dominated by the southeasterly-southerly direction.