On the seasonal dependence of tropical lower-stratospheric temperature trends

Fu, Qiuguo; Solomon, Susan; Lin, Pu

doi:10.5194/acp-10-2643-2010

Cited by 60 publications

(117 citation statements)

References 32 publications

(47 reference statements)

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“…2), which is consistent with findings from Fu et al (2010). There is high consistency between the monthly mean eddy heat flux from ERA-Interim and MERRA, with the differences between both reanalyses being much smaller than the statistical uncertainty.…”

Section: Past Arctic Temperature Changessupporting

confidence: 81%

“…3b) shows no clear overall tendency but a wide spread of the participating models. No clear strengthening of the 45-75 • N 100 hPa eddy heat flux in the last three decades can be identified, but the multi-model mean shows some indications of an increased eddy heat flux in early winter (January) and a decreased eddy heat flux in March, consistent with the findings of Fu et al (2010) and Young et al (2012). The radiative contribution to temperature trends indicates a cooling tendency (−0.16 ± 0.04 K decade −1 ) of the CCMVal2 multi-model mean averaged over the year (Fig.…”

Section: Reproducing the Pastsupporting

confidence: 79%

“…Temperature observations from the Stratospheric Sounding Unit (SSU) provide evidence that variations in wave driving are a major factor controlling global scale variability throughout the depth of the stratosphere (Young et al, 2011). Lower-stratospheric temperature observations from the Microwave Sounding Unit (MSU) indicate a strengthening of the Brewer-Dobson circulation (BDC) from December to February and a weakening from March until May connected to the increase/decrease of planetary wave activity, which leads to a corresponding positive/negative temperature trend (Fu et al, 2010). Ray et al (2010) suggest a small strengthening of the mean circulation in the lower stratosphere and a moderate weakening of the mean circulation of the middle and upper stratosphere.…”

Section: Introductionmentioning

confidence: 99%

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Radiative and dynamical contributions to past and future Arctic stratospheric temperature trends

et al. 2014

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Abstract. Arctic stratospheric ozone depletion is closely linked to the occurrence of low stratospheric temperatures. There are indications that cold winters in the Arctic stratosphere have been getting colder, raising the question if and to what extent a cooling of the Arctic stratosphere may continue into the future. We use meteorological reanalyses from the European Centre for Medium Range Weather Forecasts (ECMWF) ERA-Interim and NASA's ModernEra Retrospective-Analysis for Research and Applications (MERRA) for the past 32 yr together with calculations of the chemistry-climate model (CCM) ECHAM/MESSy Atmospheric Chemistry (EMAC) and models from the ChemistryClimate Model Validation (CCMVal) project to infer radiative and dynamical contributions to long-term Arctic stratospheric temperature changes. For the past three decades the reanalyses show a warming trend in winter and cooling trend in spring and summer, which agree well with trends from the Radiosonde Innovation Composite Homogenization (RICH) adjusted radiosonde data set. Changes in winter and spring are caused by a corresponding change of planetary wave activity with increases in winter and decreases in spring. During winter the increase of planetary wave activity is counteracted by a residual radiatively induced cooling. Stratospheric radiatively induced cooling is detected throughout all seasons, being highly significant in spring and summer. This means that for a given dynamical situation, according to ERA-Interim the annual mean temperature of the Arctic lower stratosphere has been cooling by −0.41 ± 0.11 K decade −1 at 50 hPa over the past 32 yr. Calculations with state-of-the-art models from CCMVal and the EMAC model qualitatively reproduce the radiatively induced cooling for the past decades, but underestimate the amount of radiatively induced cooling deduced from reanalyses. There are indications that this discrepancy could be partly related to a possible underestimation of past Arctic ozone trends in the models. The models project a continued cooling of the Arctic stratosphere over the coming decades that is for the annual mean about 40 % less than the modeled cooling for the past, due to the reduction of ozone depleting substances and the resulting ozone recovery. This projected cooling in turn could offset between 15 and 40 % of the Arctic ozone recovery.

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Section: Past Arctic Temperature Changessupporting

confidence: 81%

Section: Reproducing the Pastsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

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Radiative and dynamical contributions to past and future Arctic stratospheric temperature trends

et al. 2014

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“…They also found a significant weakening of the NH BDC branch during March that is consistent with a change in the seasonal cycle of the circulation. Fu et al (2010) noted that similar high-latitude cooling found in MSU4 during March is consistent with a weakening of the BDC in the NH spring.…”

Section: Introductionsupporting

confidence: 57%

“…Lin et al (2009) found increasing extratropical temperatures in the SH, indicative of a strengthening of the BDC. Fu et al (2010) presented evidence that the seasonality of tropical lower-stratospheric temperature trends is a consequence of changes in the BDC driven by extratropical wave forcing.…”

Section: Introductionmentioning

confidence: 99%

How Robust Are Trends in the Brewer–Dobson Circulation Derived from Observed Stratospheric Temperatures?

et al. 2015

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Most global circulation models and climate-chemistry models forced with increasing greenhouse gases predict a strengthening of the Brewer-Dobson circulation (BDC) in the twenty-first century, and some of them claim that such strengthening has already begun at the end of the twentieth century. However, observational evidence for such a trend remains inconclusive. The goal of this paper is to examine the evidence for observed trends in the stratospheric overturning circulation using a suite of currently available observational stratospheric temperature data. Trends are examined as ''departures'' from the global mean temperature, since such trends reflect the effects of dynamics and spatially inhomogeneous radiative forcing and are to first order independent of the direct radiative effects of increasing well-mixed greenhouse gas concentrations.The primary conclusion of the study is that temperature observations do not reveal statistically significant trends in the Brewer-Dobson circulation over the period from 1979 to the present, as covered by Microwave Sounding Unit and Stratospheric Sounding Unit temperatures. The estimated trends in the BDC are weak in all datasets and not statistically significant at the 95% confidence level. In many cases, different data products yield very different results, particularly when the trends are stratified by season. Implications for the interpretation of recent stratospheric climate change are discussed. The results illustrate the essential need to better constrain the accuracy of future stratospheric temperature datasets.

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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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On the seasonal dependence of tropical lower-stratospheric temperature trends

Cited by 60 publications

References 32 publications

Radiative and dynamical contributions to past and future Arctic stratospheric temperature trends

Radiative and dynamical contributions to past and future Arctic stratospheric temperature trends

How Robust Are Trends in the Brewer–Dobson Circulation Derived from Observed Stratospheric Temperatures?

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

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