Maritime Continent as a barrier to the MJO propagation: an analysis of the sensitivity of convection to column moisture

We propose to conduct a comprehensive study of the hypothesis that the sensitivity of deep convection to column moisture is reduced over the Maritime Continent (MC), which leads to the Madden-Julian Oscillation (MJO) propagation barrier. It will include the following two components.
1. The first is an observational component that will make novel use of data obtained through Global Positioning System (GPS) measurements, currently the only all-weather water vapor measurements, from both satellite Radio Occultation missions and surface GPS stations. In particular, data collected by a network of 60 surface GPS stations over Sumatra for earthquake studies will be processed and introduced to the meteorological community. This will provide a unique multi-year dataset with high temporal resolution (5 minutes) and a spatial layout that is well suited for studying how major islands in the Maritime Continent modulate moist convection. We will then combine the GPS data, radiosonde data, and other available water vapor measurements, as well as in situ and satellite rainfall measurements, to characterize the sensitivity of convection to column moisture. Given that the strong diurnal cycle over land is likely a key process for the reduced sensitivity of convection to column moisture, we will further produce the first all-weather characterization of the diurnal cycle of column moisture over the Maritime Continent and its modulation by the MJO.
2. The observational results will be extended using cloud resolving model simulations with the Weather Research Forecast (WRF) model. Simulations with a range of model configurations, including resolution, will be evaluated against the observational results. The best model configurations will then be used to examine the reasons behind the reduced sensitivity of convection to column moisture and the MJO propagation barrier through detailed diagnostics and mechanism-denial experiments. The improved understanding can then be used to interpret behaviors of forecast models.
Our work will produce a unique dataset that contributes to the observations of processes affecting the propagation of the MJO in the Maritime Continent region, as well as an improved understanding of these processes, thus directly address the objectives of this NOAA CVP program call. Given the importance of the MJO, this project will also support core capabilities of NOAA in understanding and modeling of the climate system.