Characteristics Shallow and deep Cumulus convection observed during DYNAMO

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Monday, 5 January 2015: 5:00 PM
229AB (Phoenix Convention Center - West and North Buildings)
Denny Alappattu, NPS, Monterey, CA; and Q. Wang, D. Khelif, N. Guy, D. Jorgensen, M. K. Witte, P. Y. Chuang, and C. J. Zappa

During the Dynamics of Madden Julian Oscillation (DYNAMO) field experiment, ocean and atmospheric measurements were carried out over the Topical Indian Ocean (TIO; 8E-EQ and 72E-81E) from NOAA's WP-3D Orion aircraft (WP-3D). This presentation will focus on analyses of the measurements made on 19 November 2011and 28 November 2011 respectively during the suppressed and active phase of the November MJO event. During the experiment, high frequency (25 Hz) measurements of dynamic and thermodynamic variables were made using the instruments attached with the aircraft. C-band and Doppler radars mounted on the lower fuselage and tail of aircraft provided the cloud reflectivity measurements. Atmospheric and oceanic profiles were also collected using the dropsondes and Airborne expendable probes (AXBT/AXCTD). 19 November, 2011 is the only flight when shallow precipitating cumulus clouds were sampled intensively during the experiment. Precipitating cumuli observed in two legs were found to produce cold pools. Cooling of up to 1.5C was observed in surface air temperature and sea surface skin temperature during the cold pool events. Increased wind speed and change in wind direction was also noticed in the cold pools in comparison with the surroundings. Increased temperatures and decreased equivalent potential temperature also observed in the cloud level data. We will discuss the mean vertical structure and the horizontal variability of this cumulus-topped boundary layer. Fluxes of momentum, sensible heat and latent heat calculated using the eddy correlation method will be presented to illustrate the energy and water vapor transport in this type of boundary layer in the DYNAMO domain. On November 28, 2011 during the active phase of the November MJO event, the measurements were made at the edge of an extensive mesoscale convective system. Dropsondes and AXBTs/AXCTDs deployed in a spatially coherent pattern revealed the spatial variability associated with the tropical deep convective system and its impact on the near surface flux exchanges and on the upper ocean. C-band fuselage and from the Doppler tail radars revealed the location and intensity of the precipitating convective cloud. This information is used to orient all measurements in the storm relative coordinate. We will discuss the low-level convergence region of the convection and the associated horizontal variation of the near surface temperature and humidity. The change of such spatial variation in the upper level will also be discussed. Next we will examine the corresponding variability in the upper ocean to address the direct impact of convective precipitation on the upper ocean. Finally, we will discuss the variation of turbulent fluxes at different region of the convection using fluxes obtained with the eddy correlation methods. Spatial variability of the surface fluxes will be discussed at multiple levels. This study provides a complete picture of the convective interaction at the air-sea interface.