Jet characterization in the upper troposphere/lower stratosphere (UTLS): applications to climatology and transport studies

Abstract

A method of classifying the upper tropospheric/lower stratospheric (UTLS) jets has been developed that allows satellite and aircraft trace gas data and meteorological fields to be efficiently mapped in a jet coordinate view. A detailed characterization of multiple tropopauses accompanies the jet characterization. Jet climatologies show the well-known high altitude subtropical and lower altitude polar jets in the upper troposphere, as well as a pattern of concentric polar and subtropical jets in the Southern Hemisphere, and shifts of the primary jet to high latitudes associated with blocking ridges in Northern Hemisphere winter. The jet-coordinate view segregates air masses differently than the commonly-used equivalent latitude (EqL) coordinate throughout the lowermost stratosphere and in the upper troposphere. Mapping O<sub>3</sub> data from the Aura Microwave Limb Sounder (MLS) satellite and the Winter Storms aircraft datasets in jet coordinates thus emphasizes different aspects of the circulation compared to an EqL-coordinate framework: the jet coordinate reorders the data geometrically, thus highlighting the strong PV, tropopause height and trace gas gradients across the subtropical jet, whereas EqL is a dynamical coordinate that may blur these spatial relationships but provides information on irreversible transport. The jet coordinate view identifies the concentration of stratospheric ozone well below the tropopause in the region poleward of and below the jet core, as well as other transport features associated with the upper tropospheric jets. Using the jet information in EqL coordinates allows us to study trace gas distributions in regions of weak versus strong jets, and demonstrates weaker transport barriers in regions with less jet influence. MLS and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer trace gas fields for spring 2008 in jet coordinates show very strong, closely correlated, PV, tropopause height and trace gas gradients across the jet, and evidence of intrusions of stratospheric air below the tropopause below and poleward of the subtropical jet; these features are consistent between instruments and among multiple trace gases. Our characterization of the jets is facilitating studies that will improve our understanding of upper tropospheric trace gas evolution

A Match-based approach to the estimation of polar stratospheric ozone loss using Aura Microwave Limb Sounder observations

“…Figure 6 shows integrated losses for each of the Arctic and Antarctic winters observed by MLS through March 2013. As expected (e.g., Manney et al, 2011;World Meteorological Organization, 2014), Arctic ozone loss is by far the greatest in the 2010/11 winter, with 2 ppmv loss estimated at 450 K (the 26 March end date for this estimate was necessitated by an anomalous temporary shutdown of the MLS instrument; normal operations resumed on 19 April 2011). Consistent with our comparisons for the 2004/05 winter, this estimate is in reasonable agreement with those from other studies, though on the low side.…”

“…Consistent with our comparisons for the 2004/05 winter, this estimate is in reasonable agreement with those from other studies, though on the low side. Manney et al (2011) estimate ∼ 2.5 ppmv of loss at 450 K based on both MLS and ozonesonde observations, while Kuttippurath et al (2012) estimate ∼ 2.5 ppmv loss at 475 K (∼ 19 km) using subtraction of passive ozone (derived by the "Mimosa-Chim" model) from MLS observations. Sinnhuber et al (2011) The 2005/06, 2008/09, 2011/12, and 2012/13 Arctic winters have the smallest losses, in many cases indistinguishable from zero when possible transport errors are factored in.…”

“…The chemical, microphysical, dynamical and radiative processes that give rise to the Antarctic ozone hole each year (Farman et al, 1985;Solomon, 1999;World Meteorological Organization, 2014) also occur in the Arctic, though with less severity and large interannual variability (e.g., Manney et al, 2003;Santee et al, 2003;Manney et al, 2011). This marked hemispheric disparity originates from the greater zonal asymmetry in high northern latitude topography compared to that in the south, leading to reductions in the size and longevity of the Arctic winter polar vortex and increasing its permeability (e.g., Andrews, 1989;Schoeberl et al, 1992;Manney et al, 1994).…”

Reanalysis comparisons of upper tropospheric–lower stratospheric jets and multiple tropopauses

“…If dT /dz drops below −2 K km −1 above the primary thermal tropopause, then the next level above that where the WMO criterion is fulfilled is identified as a multiple tropopause (e.g., Randel et al, 2007;Manney et al, 2011Manney et al, , 2014; this definition follows that of Randel et al (2007), who showed that requiring dT /dz to drop only below −2 K km −1 above the primary tropopause for the relatively coarse resolution reanalyses (rather than −3 K km −1 as is typically used for high-resolution temperature profiles) resulted in multiple tropopause distributions more comparable to those from high-resolution measurements. Linear interpolation is used to locate the tropopause between two adjacent vertical grid points.…”

“…While Davis and Birner (2017) used four of the five modern reanalyses we will compare here, their tropopause and jet-based tropical width diagnostics were based on analysis of zonal mean fields. Manney et al (2011) developed a method for characterizing the upper tropospheric jets, the stratospheric subvortex jet, and multiple tropopauses. Manney et al (2014) used this package to present a detailed climatology of these UTLS jets and multiple tropopauses, and the relationships between them, using GMAO's Modern-Era Retrospective analysis for Research and Applications (MERRA).…”