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Scientific question: Small-scale processes

Through the measurement of the position of the entrainment interface (microwave radiometer) as well as the vertical and horizontal velocities (VAD modes of LiDAR), it is possible to measure the rate of entrainment as a function of the gradient Richardson number. This measurement can be used to estimate the downward buoyancy flux at the entrainment interface, and near-surface tower measurements will provide information on the buoyancy flux at ground level. Some questions to be answered, using measurements at all stations, are: 

  • What is the vertical structure of winds, temperature, mixing ratio and Richardson number? How does this change from the transition period of monsoons to fully developed monsoons and during monsoon breaks? 
  • What is the entrainment rate as a function of the (interfacial) ,𝑅𝑖-𝑔.?  Are these changes in consonance with the shear-breakdown mechanism proposed by Bhat & Fernando (2014) as well as laboratory findings of Strang & Fernando (2001)? What is the contribution of convective activities?
  • How does the interfacial ,𝑅𝑖-𝑔. change with the onset and continuation of monsoons? And, can it sustain a substantial downward buoyancy flux?
  • Is the entrainment possible at ,𝑅𝑖-𝑔. > 0.25, and how long does this entrainment last? How does the interfacial stability (Richardson number) change during an entrainment event?
  • How do surface energetics, including incoming and outgoing solar radiation and surface buoyancy flux, evolve?
  • Do the eastward- and northward-propagating disturbances modify the entrainment mechanisms? Time lagged observations from Seychelles and Sri Lanka will be helpful in this regard.