SOWER (Soundings of Ozone and Water in the Equatorial Region): Overview and Highlights

Abstract:

The Soundings of Ozone and Water in the Equatorial Region (SOWER) has been accumulating observational evidences of atmospheric dehydration taking place in the Tropical Tropopause Layer (TTL) since initiation in 1998. SOWER data successfully characterize the nature of TTL dehydration in which the cold-trap is effectively functioning between 360 K and 380 K isentropes while some moistening taking place before the air parcel reaches 400 K. The first attempts of the TTL water vapor ‘match’ suggest the threshold of nucleation being 146 ± 19 % in relative humidity with respect to ice with the typical dehydration time scale of about an hour in the lower TTL. Simultaneous observations by lidar and Optical Particle Counters near the cold point tropopause reveale cirrus clouds within the aerosol layer composed of liquid phase aqueous sulfuric acid particles. The estimated concentrations of cloud particles and aerosols are not consistent with the interpretation of cloud formation in liquid phase aerosol particles.
 In February 2014, a series of ozone (ECC) and water vapor (CFH) sonde observations was conducted at Biak (1.2^oS, 136.1^oE) collaborating with LAPAN, Indonesia. The sea surface temperature in the western tropical Pacific showed positive anomalies. The convective activities were relatively low in the eastern Indian Ocean to the Maritime Continent, while an eastward propagation of active convection associated with intraseasonal oscillation was observed. This campaign was not simply an extension of the previous ones, but was intended to provide correlative data for ATTREX/CONTRAST/CAST aircraft campaigns. Unfortunately the coordination did not run as originally intended. A sequence of independent sonde data, however, may provide some useful information for airborne observations. This paper presents an overview of the project and introduces the highlights of the findings obtained.