J. Jonas | Search NASA

NASA NTRS2021

Response of the Quasi-Biennial Oscillation to historical volcanic eruptions

The impact of volcanic eruptions on surface climate is well-appreciated, but their in situ impact on the Quasi-Biennial Oscillation (QBO) has received comparatively little attention. This study examines the QBO responses to Krakatoa and Pinatubo using five configurations of the NASA Goddard Institute for Space Studies (GISS) Model E2.2 and MERRA-2 reanalysis. A dynamically consistent response is found in terms of static stability, zonal wind, and upwelling. Eruptions are found to bias the QBO towards a westerly state, such that the QBO period response depends upon the phase at the time of eruption. The QBO does not have a clear amplitude response to an eruption, based on these simulations. The underlying mechanisms appear not to be influenced to fi rst-order by interactive composition, sea surface temperatures, or long-term trends in CO2 and ozone-depleting substances.

volcanic eruptions↗

NASA NTRS2020

GISS Model E2.2: A Climate Model Optimized for the Middle Atmosphere. Part 1: Model Structure, Climatology, Variability and Climate Sensitivity

We introduce a new climate model (GISS E2.2) that has been specially optimized for the Middle Atmosphere, and whose output is being contributed to the CMIP6 archive. The top of the model is at a geopotential altitude of 89 km, and parameterizations of moist convection and various forms of gravity wave drag based on tropospheric processes are chosen specifically for this optimization. We first evaluate the model in its configuration as a coupled atmosphere-chemistry model with respect to its simulation of the mean state of the Middle Atmosphere, from the mesosphere down through the Upper Troposphere/Lower Stratosphere. Then we assess its use as a coupled atmosphere-ocean climate model by exploring its mean ocean climatology. To evaluate its variability, we report on its simulation of the primary modes in the troposphere, stratosphere and ocean. Two climate change simulations are presented, the responses to instantaneous increases of 2xCO2 and 4xCO2, run with two different ocean models. Sensitivity studies are performed to illustrate the effect of parameterizations on the model results. We compare these results to the lower vertical resolution/top GISS Model E2.1, whose output has also been submitted to CMIP6. The different choices made for these models are explored. It is shown that important improvements in the circulation above and below the tropopause can be obtained when attention is paid to representation of Middle Atmosphere processes in climate model development.

D. Rind↗