Characteristics of convective gravity waves (CGWs) in Asian summer monsoon region (EQ-40°N, 60°E-150°E) from cloud-top to stratosphere are investigated through an off-line parameterization of CGWs, using 1-hourly NCEP Climate Forecast System Reanalysis (CFSR) data with a horizontal resolution of 1°×1° during 9 years (2002-2010) in July. The CGW parameterization used in this study is an updated version of Choi and Chun (2011) by including nonlinear forcing effects in the cloud-top momentum flux (CTMF) spectrum. In EQ-30°N, zonal CTMF shows its peak at phase speed of 10 m/s. Since the CTMF spectrum is amplified at the phase speed corresponding to the moving speed of convection, the positive part of zonal CTMF is amplified due to eastward moving convective source. As a result, eastward component of the CTMF is much bigger than westward component. On the other hand, peak of the zonal CTMF is at -5 m/s in 30°N-40°N, thus the westward component is bigger than eastward component. The gravity-wave momentum flux (GWMF) spectrum in the stratosphere is also calculated from the CTMF spectrum, considering columnar wave propagation. The GWMF in the stratosphere is reduced by various wave dissipation processes (critical-level filtering, breaking, and radiative damping) from the cloud top to the stratosphere. The critical-level filtering is dominant wave dissipation process, and consequently at z = 30 km westward GWMF is generally reduced under the easterly background wind in all latitudes. However in EQ-10°N where both easterly and westerly shear of the background wind exists, eastward GWMF is also reduced by critical-level filtering, and by wave breaking in the positive peak of CTMF spectrum. Consequently, positive zonal GW drag (GWD) is dominant in EQ-10°N, which is more evident in the westerly phase of quasi-biennial oscillation (QBO-W), whereas relatively small negative zonal GWD exists in 10°N-40°N.

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*email: kangmj@yonsei.ac.kr
*Preference: Oral