Upward mass fluxes in tropical upper troposphere and lower stratosphere derived from radiative transfer calculations

Yang et al. [1] quantified vertical velocity and upward mass fluxes in tropical lower stratosphere based on radiative heating rate calculations using the Fu-Liou radiation model along with 8-year Southern Hemisphere Additional Ozonesondes balloon-borne measurements of temperature and ozone and cryogenic frost-point hygrometer measured water vapor. The impact of tropospheric clouds on stratospheric heating rates was considered using cloud distributions from the International Satellite Cloud Climatology Project. Since the radiative heating rate in the lower stratosphere can be as small as 0.1-0.2 K/day, an accurate radiative heating rate calculation including all radiatively active species is required. In this paper, we revisit the calculations in Yang et al. [1] by developing a line-by-line radiative transfer model (LBLRTM-D4S) for multiple scattering atmospheres. We consider the cloud impact using the cloud fields based on active lidar and radar observations from CALIPSO and CloudSat so that the quantification of upward mass fluxes in tropical lower stratosphere can be extended to tropical upper troposphere. The annual mean mass fluxes and vertical velocities from LBLRTM-D4S are ∼14 kg m−2 day−1 and 0.77 mm s−1, respectively, at 120 hPa (15.5 km), and ∼1.2 kg m−2 day−1 and 0.13 mm s−1 at 60 hPa (19.5 km). We examine the accuracy of three commonly used efficient radiation models including Fu-Liou, RRTM, and SBDART in estimating tropical upward mass fluxes against the LBLRTM-D4S results.

► Developing a line-by-line (LBL) radiative transfer model for multiple scattering atmospheres. ► Evaluating upward mass fluxes in tropical upper troposphere and lower stratosphere using the LBL calculations. ► Considering the cloud impact using CALIPSO and CloudSat observations that resolve the cloud vertical structures. ► Evaluating efficient radiation models using LBL in estimating tropical upward mass fluxes.