A Simulation of Seasonal Variation of the Stratospheric Circulation with a General Circulation Model

Abstract

Results are presented from a numerical simulation of the stratospheric circulation using a spectral general circulation model of the Meteorological Research Institute. The model has 23 layers in the vertical extending from the surface to approximately 70 km in the middle mesosphere and uses the spectral transform method with a rhomboidal 13 truncation. The model includes all major physical processes as well as realistic radiative transfer. The model also includes Rayleigh damping as a parameterization of gravity wave breaking. The model has been run for two years, and the results are compared with observations.The model generally simulates the overall stratospheric fields of temperature and winds reasonably well. Seasonal variations of the stratospheric fields are also successfully reproduced. Successful aspects of the current simulation include: clear separation of the subtropical and polar night jet streams; stratospheric summer easterlies of the proper speed and extent; interhemispheric differences in the stratospheric circulation; major and minor sudden warming events; and an equatorial semi-annual oscillation. Obviously deficient results include: excessively cold polar night vortices; and much less westerly winds in the equatorial semi-annual oscillation.A simulated final warming in the Northern Hemisphere and a minor warming in the Southern Hemisphere are briefly described, along with the evolution of easterlies from late-winter to spring.

Evaluation and intercomparison of global atmospheric transport models using222Rn and other short‐lived tracers

“…LMD did not report zonal mean concentrations and their data are therefore missing from the corresponding figures below. 30N 60N 90N 9•3S 60S 30S EQ 30N 60N 90N (1000, 850, 700, 500, 400, 300, 250, 200 Chiba, 1990]. Spectral horizontal resolution is R24 and vertical resolution is 23 levels up to 0.05 hPa.…”

Residual Mean Meridional Circulation in the Stratosphere and Upper Troposphere

“…(4) and (5). In this study, X is simply parameterized as (X=-ku) by assuming the height-dependent Rayleigh friction coefficient (ic) used in Shibata and Chiba (1990). The coefficients at 0.05hPa and 3hPa are 5x10-6s-1 and 2x10-7s-1, respectively, and these coefficients are linearly interpolated in log pressure at other heights.…”

Interference of the Diurnal Tide and Normal-Mode Rossby Waves in the Summer Stratosphere

“…The diurnal cycle of solar radiation is explicitly calculated, as well as the seasonal cycle. The details and performance of the R13L23 version can be found in Shibata and Chiba (1990). The time integration has been performed for a period of 10 years, and the data were sampled every 2 hours.…”