The Sakaeda research group focuses on addressing the following broad questions:
- What governs the dynamics of tropical cloud organization and precipitation on various spatiotemporal scales?
- What are the roles of tropical atmospheric variability in the global climate and weather?
- How do different scales of atmospheric phenomena interact with each other?
Some topics of our research:
- The Dynamics of the Madden-Julian Oscillation (MJO)
- The Diurnal Cycle of Tropical Precipitation and Cloudiness
- Tropical-Extratropical Interactions
- The Convectively-Coupled Equatorial Waves
- Weather-Climate Interactions
The Dynamics of the Madden-Julian Oscillation (MJO)
The MJO is the dominant mode of intraseasonal (~30-90 days) variability in tropical circulation, cloudiness, and precipitation. The MJO is known to influence global circulation and provides sources of predictability on the long-range forecast (sub-seasonal to seasonal timescales). Part of our research focuses on understanding the large-scale dynamics of the MJO, characteristics of cloud and rainfall activity embedded within the MJO, and the interactions between the MJO and the extratropical circulation.
Read more on: What is the MJO?
The Diurnal Cycle of Tropical Precipitation and Cloudiness
The diurnal cycle is one of the fundamental modes of atmospheric variability. This group’s research aims to improve our understanding of the characteristics and mechanisms of the observed diurnal cycle of rainfall and cloudiness in the tropics. We also study how the characteristics of the diurnal cycle vary with large-scale tropical disturbances such as the MJO and convectively-coupled equatorial waves (CCEWs).
Tropical-Extratropical Interactions
Tropical clouds and precipitation can influence global weather and climate, including in areas that are remote from the tropics. For example, the MJO influences the strength of the Hadley cell, location of storm tracks, the frequency and location of midlatitude Rossby wave breaking and blocking. Our group is interested in understanding the role of tropical convective activity on global weather and climate such as its influences on extreme weather, prediction skills, and climate variability.
The Convectively-Coupled Equatorial Waves
There are various modes of waves in the tropics that are known to be coupled to convection. These waves explain a large fraction of tropical cloud and precipitation variability on timescales of days to intraseasonal. Part of our group’s research interests is to understand how and why the CCEWs vary seasonally or interannually, to improve the representation of CCEWs in current weather and climate models, and to understand how the CCEWs modulate regional day-to-day variability of weather such as the diurnal cycle and monsoon onset.
Read more on: what are CCEWs?
Weather-Climate Interactions
Interactions between different scales (e.g., individual clouds and large-scale disturbances, synoptic storms, and planetary global circulation) are important components to all of the research topics within this group. Characteristics of shorter timescale phenomena (i.e., weather) are partly dependent on the background state that is set by longer timescale phenomena (i.e., climate), while the shorter timescale phenomena can feedback onto longer timescale phenomena. Our group research considers the roles of these interactions to study phenomena on the timescales on weather, climate, or in-between.
Current Research Projects:
- Coupling of the Madden-Julian Oscillation and Quasi-Biennial Oscillation through cloud radiative feedback (Support: NSF)
- Diurnal processes over tropical islands and implications to subseasonal to seasonal (S2S) prediction forecasts (Support: NOAA)
- Tropical-Extratropical Interactions Associated with the Madden-Julian Oscillation and Equatorial Waves (Support: NSF)
- Coastal-to-Maritime Transition of Propagating Convective Systems over the West African Coastal Region (Support: NASA)
- Cloud Development and Organization Processes within the Madden-Julian Oscillation (Support: DOE)
Past Research Projects:
- MJO Propagation across the Maritime Continent (Support: NOAA)