Climatology of Upper Tropospheric–Lower Stratospheric (UTLS) Jets and Tropopauses in MERRA

Manney, G. L.; Hegglin, Michaela I.; Daffer, W. H.; Schwartz, M.; Santee, M. L.; Pawson, Steven

doi:10.1175/jcli-d-13-00243.1

Cited by 71 publications

(96 citation statements)

References 97 publications

(120 reference statements)

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“…Figure 13 shows the frequency distributions and wind speeds for the upper tropospheric jets. While the frequencies evolve through the seasons (as described in detail by Manney et al, 2014), the patterns of differences are quite consistent: MERRA-2 has fewer (and weaker, as seen in the wind speed differences) jets at high latitude than the other reanalyses. ERA-I shows fewer jets than MERRA-2 throughout the domain and year, except near each pole (where jet frequencies and wind speeds are both slighter higher than those in MERRA-2), and at the maxima of the frequency distributions.…”

Section: Evaluation Of Reanalysis Climatological Annual Cyclementioning

confidence: 74%

“…The bulk of the comparisons presented here are of frequency distributions, calculated as described in more detail by Manney et al (2014). A reference distribution is needed to evaluate differences between the frequency distributions.…”

Section: Comparison Methodologymentioning

confidence: 99%

“…In the following description "grid points" refers to the reanalysis grid and "bins" refer to the coarser latitude-longitude grid on which the 2D histograms are constructed. The issue of consistent normalization is relatively straightforward: the normalization procedure used herein is similar to that described by Manney et al (2014), but for each reanalysis, we calculate the number of grid points that would "fill" each individual bin based on the bin size and the reanalysis grid spacing; the total counts in each bin are then divided by this value. The upper tropospheric and subvortex jet distributions are normalized by the total number of longitude grid points in each bin since the definition of the jets makes it extremely unlikely that more than one jet at the same longitude would be in the same bin -for example, upper tropospheric jets must be separated by either a drop in wind speed to below 30 m s −1 or 10 • in latitude, with a latitude bin size of 3 or 4 • (the values used here and in Manney et al, 2014, respectively); having two jets at one longitude in a single bin would require exceptionally strong wind speed gradients in a region where the jet core wind speed was just above the 40 m s −1 threshold.…”

Section: Comparison Methodologymentioning

confidence: 99%

“…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.…”

Section: Jet and Tropopause Characterizationmentioning

confidence: 99%

“…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). Here we evaluate the representation of these climatological features in the four other most recent high-resolution reanalyses: MERRA-2 (the successor to MERRA), ECMWF's ERA-Interim (ERA-I), JMA's JRA-55, and NCEP's Climate Forecast System Reanalysis (CFSR); comparisons of MERRA-2 with its predecessor are also included.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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Abstract. The representation of upper tropospheric–lower stratospheric (UTLS) jet and tropopause characteristics is compared in five modern high-resolution reanalyses for 1980 through 2014. Climatologies of upper tropospheric jet, subvortex jet (the lowermost part of the stratospheric vortex), and multiple tropopause frequency distributions in MERRA (Modern-Era Retrospective analysis for Research and Applications), ERA-I (ERA-Interim; the European Centre for Medium-Range Weather Forecasts, ECMWF, interim reanalysis), JRA-55 (the Japanese 55-year Reanalysis), and CFSR (the Climate Forecast System Reanalysis) are compared with those in MERRA-2. Differences between alternate products from individual reanalysis systems are assessed; in particular, a comparison of CFSR data on model and pressure levels highlights the importance of vertical grid spacing. Most of the differences in distributions of UTLS jets and multiple tropopauses are consistent with the differences in assimilation model grids and resolution – for example, ERA-I (with coarsest native horizontal resolution) typically shows a significant low bias in upper tropospheric jets with respect to MERRA-2, and JRA-55 (the Japanese 55-year Reanalysis) a more modest one, while CFSR (with finest native horizontal resolution) shows a high bias with respect to MERRA-2 in both upper tropospheric jets and multiple tropopauses. Vertical temperature structure and grid spacing are especially important for multiple tropopause characterizations. Substantial differences between MERRA and MERRA-2 are seen in mid- to high-latitude Southern Hemisphere (SH) winter upper tropospheric jets and multiple tropopauses as well as in the upper tropospheric jets associated with tropical circulations during the solstice seasons; some of the largest differences from the other reanalyses are seen in the same times and places. Very good qualitative agreement among the reanalyses is seen between the large-scale climatological features in UTLS jet and multiple tropopause distributions. Quantitative differences may, however, have important consequences for transport and variability studies. Our results highlight the importance of considering reanalyses differences in UTLS studies, especially in relation to resolution and model grids; this is particularly critical when using high-resolution reanalyses as an observational reference for evaluating global chemistry–climate models.

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Section: Evaluation Of Reanalysis Climatological Annual Cyclementioning

confidence: 74%

Section: Comparison Methodologymentioning

confidence: 99%

Section: Comparison Methodologymentioning

confidence: 99%

Section: Jet and Tropopause Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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Global multiple tropopause features derived from COSMIC radio occultation data during 2007 to 2012

2014

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The spatiotemporal structure of the climatology of multiple tropopauses (MTs) is presented in this paper by using the temperature profiles from the Global Positioning System radio occultation measurements from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission between January 2007 and December 2012. Various climatological characteristics about MTs are studied, including the relationship between the occurrence of double tropopauses (DTs) and jet streams, the interannual variation and the trends of the occurrence of DTs, the seasonal and geographical variations of the occurrence of MTs, and the meridional distributions of the features of MTs in different seasons. Our results agree well with those of earlier studies based on other data sets. In addition, we find some new MT features. A global increase of the occurrence of DTs of about 0.15% ± 0.09% yr À1 (0.13% ± 0.09% yr À1) is found between 2007 and 2012 including (excluding) the sampling errors, respectively. There is an increasing trend of the occurrence of DTs in the extratropics, especially in the subtropics in both hemispheres, and a decreasing trend in the tropics. We also find that the maximum seasonal variation of the occurrence of DTs is located between 30°N and 40°N, which is much stronger than that in the Southern Hemisphere. The occurrence of DTs is much lower from the winter of 2009 to the spring of 2010 than during the same time period of other years.

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The double tropopause and its dynamical relationship to the tropopause inversion layer in storm track regions

et al. 2014

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Using High Resolution Dynamic Limb Sounder observations and ERA-Interim reanalysis this study demonstrates that the warm conveyor belt (WCB) is a mechanism responsible for the relationship between the double tropopause (DT) and the tropopause inversion layer (TIL), a relationship recently suggested in the literature based on idealized model simulations of baroclinic disturbances. Using these data sets, spatial and temporal characteristics of the DT-TIL relationship are examined over a 3 year period, [2005][2006][2007][2008]. In the extratropics, results from satellite data show that as the TIL increases in strength, so does the frequency of the DT, regardless of season or hemisphere. The inverse relationship is found in the tropics. Using only DT profiles, zonal composites of wind, relative vorticity, and temperature from reanalysis data show that as the TIL increases in strength, the upper tropospheric circulation switches from cyclonic to anticyclonic, and the upward vertical motion increases. This result suggests the WCB as a mechanism since it is on the anticyclonic side of the jet and is characterized by the movement of tropical air poleward and upward from the surface. To verify this relationship, the vertical and horizontal development of a synoptic-scale baroclinic system is analyzed over a 4 day period. Results show the equatorward extension of the polar tropopause, and thus the formation of the DT, due to the strengthening of the TIL in the region of vertical motion associated with the WCB. Moreover, this result suggests that air movement within the DT could originate from high latitudes when associated with a baroclinic disturbance.

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Climatology of Upper Tropospheric–Lower Stratospheric (UTLS) Jets and Tropopauses in MERRA

Cited by 71 publications

References 97 publications

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

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

Global multiple tropopause features derived from COSMIC radio occultation data during 2007 to 2012

The double tropopause and its dynamical relationship to the tropopause inversion layer in storm track regions

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