Abstract
AbstractThe inter‐annual variability in mid and lower stratospheric temperatures for the period 1984–2019 is decomposed into dynamical and radiative contributions using a radiative calculation perturbed with changes in dynamical heating, trace gases and aerosol optical depth. The temperature timeseries obtained is highly correlated with the de‐seasonalized ERA5 temperature (r2 > 0.6 in the region 15 to 70 hPa, 1992 to 2019–after the Pinatubo volcanic eruption). Ozone and dynamical heating contributions are found to be equally important, with water vapor, stratospheric aerosols, and carbon dioxide playing smaller roles. Prominent aspects of the temperature timeseries are closely reproduced, including the 1991 Pinatubo volcanic eruption, the year‐2000 water vapor drop, and the 2016 Quasi‐biennial oscillation (QBO) disruption. Below 20 hPa, ozone is primarily controlled by transport and is positively correlated to the upwelling. This ozone‐transport feedback acts to increase the temperature response to a change in upwelling by providing an additional ozone‐induced radiative temperature change. This can be quantified as an enhancement of the dynamical heating of about 20% at 70 hPa. A Principal Oscillation Pattern (POP) analysis is used to estimate the contribution of the ozone QBO (±1 K at 70 hPa). The non‐QBO ozone variability is also shown to be significant. Using the QBO leading POP timeseries as representative of the regular QBO signal, the QBO 2016 disruption is shown to have an anomalously large radiative impact on temperature due to the ozone change ( at 70 hPa).
Highlights
The inter-annual variability of temperatures in the tropical lower stratosphere is of interest since temperature in this region controls the entry of water vapor into the stratosphere which can modify the surface radiative balance (Fueglistaler et al, 2014)
The temperature inter-annual variability is reconstructed using the dynamical heating perturbation taken from ERA-5, ozone, water vapor, aerosol optical depth and carbon dioxide perturbations
Identifying the cause of this jump is beyond the scope of the present study, but if we account for this jump by applying a constant offset, we find that the inter-annual variability in ERA5 is captured by the inter-annually evolving fixed dynamical heating calculation (IEFDH) calculation before 1991
Summary
Inter-annual variability in lower tropical stratospheric temperatures has been reconstructed. Aerosol and water wapor contributions are not negligible. Ozone associated with the Quasibiennial oscillation contributes substantially, during the 2016 disruption. Supporting Information: Supporting Information may be found in the online version of this article. What Contributes to the Inter-Annual Variability in Tropical Lower Stratospheric Temperatures?
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