Diurnal Cycle of Convection during Dynamo

Friday, 19 December 2014
Paul E Ciesielski, Deptment of Atmoshpheric Science, Department of Atmospheric Science, Fort Collins, CO, United States and Richard H Johnson, Colorado State Univ, Fort Collins, CO, United States
During the special observing period (SOP) of the DYNAMO/CINDY/AMIE field campaign, conducted over the Indian Ocean from October to November 2011, two sounding networks, one north and one south of the equator, took 4-8 soundings/day. This dataset with 3-hr time resolution offers a unique opportunity to investigate the diurnal cycle of Intertropical Convergence Zone (ITCZ) convection which was present within the southern sounding array (SSA) for extended periods during the SOP. For example, during the first half of October 2011 when the ITCZ was located between 3°S and 8°S, TRMM 3B42 3-h rainfall averaged over the SSA exhibited a prominent diurnal cycle with a late night/early morning maximum and an early evening minimum. The rainfall diurnal range during this period over the SSA was 4.8 mm which was ~50% of the daily mean (10.1 mm). Mean rainfall over the northern sounding array was much lighter (0.9 mm) during this period with a diurnal cycle nearly out of phase with that over the SSA. Using primarily sounding and satellite data, we will explore the characteristics of this diurnally varying convection and what, if any, influence it may have had on the Madden-Julian Oscillation (MJO) signal.