Increase In Tropopause Height Research Articles

Influences of Sudden Stratospheric Warming Events on Tropopause Based on GNSS Radio Occultation Data

Sudden Stratospheric Warming (SSW) events have a strong impact on the tropospheric weather and climate. Past researchers have carried out extensive studies investigating the theories of interactions between the stratosphere and the troposphere. However, detailed studies on the influences of the global tropopause are rarely shown. This study uses Global Navigation Satellite System (GNSS) Radio Occultation (RO) data from the years 2007 to 2013 to investigate the influences of different types of SSW events on the tropopause over latitude bands from 30° S to 90° N. It was found that SSW events have strong influences on the tropopause over 60° N–90° N and over 20° N–30° N regions. In 60° N–90° N, SSW events cause a tropopause temperature increase and, therefore, a tropopause height decrease. The increment in the tropopause temperature are more than 10 K and the decrement in the tropopause height is about to 2 km during strong events. Such influences last for about 1.5 months for strong split events and about 10 days for weaker and/or displacement type events. The influences of SSW events on 20° N–30° N are weaker. Only the January 2009 SSW event shows a visible influence on the tropopause layer with a tropopause temperature decrease of about 4 K and a tropopause height increase of about 1 km. Other SSW events share no common characteristics on the tropical tropopause. This is mainly because SSW events are not strong enough to dominate the tropopause variations and other factors, especially the planetary waves in the troposphere, have stronger impacts on the tropopause layer.

The weakening of the tropical circulation is caused by the lifting of the tropopause height

In this study we analyse the physical processes causing the weakening of the tropical circulation in the Coupled Model Intercomparison Project 6 (CMIP6). We apply a diagnostic model for the large-scale tropical circulation (vertical motion) based on the moist static energy for the first baroclinic mode (MSEB) and evaluate the sensitivity of the tropical circulation changes to the changes in advection of moisture and heat, the net radiation, the moist static stability, the baroclinic mode, and to the height of the tropopause. Based on the CMIP6 model simulations we find that the tropical circulation weakens by about 10-15% over the twenty-first century. The analysis of the MSEB model suggests that the primary cause for this weakening of the tropical circulation is the lifting of the tropopause height. This effect is fairly uniform throughout the tropics and present in all model simulations. The tropopause height increase shifts the first baroclinic mode away from lower levels with unstable air masses into high levels of the troposphere where stable air masses lead to a stabilisation of the large-scale circulation. Other factors such as changes in the advection of moisture and heat, increased net heating or increased instability of the lower tropospheric gross moist stability do have strong regional differences, and mostly increase tropical circulations, counteracting the weakening caused by the lifting of the tropopause.

Meridional structure and future changes of tropopause height and temperature

We use a simple, semianalytic, column model to understand better the meridional structure of the tropopause height and future changes in its height and temperature associated with global warming. The model allows us to separate the effects of tropospheric lapse rate, optical depth, outgoing longwave radiation (OLR), and stratospheric cooling on the tropopause height. When applied locally at each latitudinal band, the model predicts the overall meridional structure of the tropopause height, with a tropical tropopause substantially higher than in higher latitudes and a sharp transition at the edge of the extratropics. The large optical depth of the Tropics, due mainly to the large water‐vapour path, is the dominant tropospheric effect producing the higher tropical tropopause, whereas the larger tropical lapse rate actually acts to lower the tropopause height. The dynamical cooling induced by the stratospheric circulation lifts the thermal tropopause in the Tropics further, resulting in it being significantly cooler and higher than in mid‐ and high‐latitudes.The model quantifies the causes of the tropopause height increase with global warming that is found robustly in climate integrations from the fifth Coupled Model Intercomparison Project (CMIP5). The large spread in the increase rate of tropopause height in the CMIP5 model is captured by the simple model, which attributes the dominant contributions to changes in water‐vapour path and lapse rate, with changes in CO2 concentration and OLR having much smaller direct effects. The CMIP5 models also show a small but robust increase in the tropopause temperature in low latitudes, with a much smaller increase in higher latitudes. We suggest that the tropical increase may be caused at least in part by nongrey effects in the radiative transfer associated with the higher levels of water vapour in the Tropics, with near‐constant tropopause temperatures predicted otherwise.

Exploring atmospheric blocking with GPS radio occultation observations

Abstract. Atmospheric blocking has been closely investigated in recent years due to its impact on weather and climate, such as heat waves, droughts, and flooding. We use, for the first time, satellite-based observations from Global Positioning System (GPS) radio occultation (RO) and explore their ability to resolve blocking in order to potentially open up new avenues complementing models and reanalyses. RO delivers globally available and vertically highly resolved profiles of atmospheric variables such as temperature and geopotential height (GPH). Applying a standard blocking detection algorithm, we find that RO data robustly capture blocking as demonstrated for two well-known blocking events over Russia in summer 2010 and over Greenland in late winter 2013. During blocking episodes, vertically resolved GPH gradients show a distinct anomalous behavior compared to climatological conditions up to 300 hPa and sometimes even further up into the tropopause. The accompanying increase in GPH of up to 300 m in the upper troposphere yields a pronounced tropopause height increase. Corresponding temperatures rise up to 10 K in the middle and lower troposphere. These results demonstrate the feasibility and potential of RO to detect and resolve blocking and in particular to explore the vertical structure of the atmosphere during blocking episodes. This new observation-based view is available globally at the same quality so that blocking in the Southern Hemisphere can also be studied with the same reliability as in the Northern Hemisphere.

Characteristics of the Trends in the Global Tropopause Estimated From COSMIC Radio Occultation Data

This paper discusses the variabilities and trends in the global tropopause based on the gridded monthly mean Global Positioning System radio occultation data from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission during July 2006–February 2014. We find that the tropopause height can reflect El Nino–Southern Oscillation (ENSO) events. The correlation coefficient between global tropopause height anomalies and the Nino 3.4 sea surface temperature index is 0.53, with a maximum correlation coefficient of 0.8 at a lag of three months. We present first the detailed investigations about the spatial distribution of trends in tropopause parameters in each 10° $\times$ 5° longitude–latitude grid cell over the globe and find that the rates of change in the tropopause parameters during this time period are high in some particular regions such as the Southern Indian Ocean, Antarctica, Western Europe, North Pacific, and the east coast of North America. An analysis of global monthly means of the tropopause parameters indicates a global tropopause height increase of 0.03 $\pm$ 2.36 m/year during 2006–2014, with a corresponding temperature increase of 0.020 $\pm$ 0.008 °C/year, and a pressure increase of 0.11 $\pm$ 0.059 hPa/year. The upward trend of tropopause height is significantly weaker than that in the past years, which might be attributed to the expected stratospheric ozone recovery associated with the Montreal Protocol, the global warming slowdown, and the abnormal global climate change in recent years. The trends of the tropopause parameters are the most significant over the Southern Indian Ocean and Antarctica during September/October/November, which could be due to the stratospheric ozone recovery.

Effect of tropospheric and stratospheric temperatures on tropopause height

Troposphere is an important layer of the atmosphere because most of the weather phenomena are confined to this layer. Variations in tropopause height significantly depend upon the changes in upper tropospheric and lower stratospheric temperature. Availability of global positioning system radio occultation high vertical temperature profiles on better temporal and spatial scales gives an opportunity to study the tropopause height variations with respect to tropospheric and stratospheric temperatures. Analysing these profiles along with in situ observations, we studied the impact of stratospheric and tropospheric warming or cooling on tropopause height over Indian region. Decrease in stratospheric temperature increases the tropopause height, and increase in tropospheric temperature decreases the tropopause height. Stratospheric temperature is found to have more impact on tropopause height compared to tropospheric temperature, and this impact is more evident over ocean than land. The analysis also brings out a good correlation between stratospheric ozone concentrations and its temperature. In the light of decreasing stratospheric ozone concentrations due to global warming, this study points out towards a possibility of increase in tropopause height.

Time lag between the tropopause height and 7Be activity concentrations on surface air

A strong positive correlation between the seasonal changes of the tropopause height and the concentration of 7Be in the surface air (R = 0.94, p < 0.0001) was observed at 40°N. Moreover, a strong positive correlation was revealed between the activity concentrations of 7Be and the temperature T (°C) (R = 0.97, p < 0.001), confirming that the increased rate of vertical transport within the troposphere, especially during warmer months, has as a result the descent to the surface of air masses enriched in 7Be. The results of the present work suggest that the temperature and the tropopause height are good indicators for transport time of air masses enriched in 7Be to the surface. Higher values of temperature or tropopause height seem to result to shorter transport times. This is attributed to atmospheric convection which provides an effective mechanism for vertical transport of air masses. Increasing tropospheric temperature has generally as a result that convection penetrates more deeply which in turn leads to an increase in tropopause height. But, the atmospheric procedures do not occur immediately after the fluctuations of correlated factors. Thus, a time lag is expected between the tropopause height and 7Be activity concentrations on surface air that might be from hours to days or weeks. The result suggests that 7Be concentrations fully respond within three days after the changes in the tropopause height.

Changes in the tropopause height induced by landing typhoons in China during the last 50 years

AbstractTrends in the thermal tropopause height observed using radiosondes near landing typhoon tracks in China from 1951 to 2008 were analyzed. The main findings were that the majority of tropopause rises induced by typhoons are in the range of 200–500 m, and the maximum tropopause height is observed between 12 and 24 h after the typhoon had passed at each station. Tropopause height increase induced by a super typhoon is more rapid and prominent than that of a typhoon, although the absolute increases are similar. The magnitude of the increase in the tropopause height induced by typhoons has increased over the last 40 years.

A numerical simulation of aerosols’ direct effects on tropopause height

The direct effects of sulfate aerosol, dust aerosol, carbonaceous aerosol, and total combined aerosols on the tropopause height are simulated with the Community Atmospheric Model version 3.1 (CAM3.1). A decrease of global mean tropopause height induced by sulfate, carbonaceous aerosol, and total combined aerosols is found, and a tropopause height increase is induced by dust aerosol. Sulfate aerosol decreases the tropospheric temperature and increases the stratospheric temperature. These effects cause a decrease in the height of the tropopause. In contrast, carbonaceous and total combined aerosols increase both the tropospheric and the stratospheric temperatures, and they also cause a decrease in the height of the tropopause. The changes in the tropopause height show highly statistically significant correlations with the changes in the tropospheric and stratospheric temperatures. The changes in the tropospheric and stratospheric temperatures are related to the changes in the radiative heat rate, cloud cover, and latent heat, but none of these factors absolutely dominate the temperature change.

Effects of sea surface temperature, radiation, cloud microphysics, and diurnal variations on vertical structures of tropical tropospheric temperature: a two-dimensional equilibrium cloud-resolving modeling study

The effects of sea surface temperature (SST), radiation, cloud microphysics, and diurnal variations on the vertical structure of tropical tropospheric temperature are investigated by analyzing 10 two-dimensional equilibrium cloud-resolving model simulation data. The increase of SST, exclusion of diurnal variation of SST, and inclusion of diurnal variation of solar zenith angle, radiative effects of ice clouds, and ice microphysics could lead to tropical tropospheric warming and increase of tropopause height. The increase of SST and the suppression of its diurnal variation enhance the warming in the lower and upper troposphere, respectively, through increasing latent heat and decreasing IR cooling. The inclusion of diurnal variation of solar zenith angle increases the tropospheric warming through increasing solar heating. The inclusion of cloud radiative effects increases tropospheric warming through suppressing IR cooling in the mid and lower troposphere and enhancing solar heating in the upper troposphere. The inclusion of ice microphysics barely increases warming in the mid and lower troposphere because the warming from ice radiative effects is nearly offset by the cooling from ice microphysical effects, whereas it causes the large warming enhancement in the upper troposphere due to the dominance of ice radiative effects. The tropopause height is increased mainly through the large enhancement of IR cooling.

Tropopause and total ozone at mid‐latitudes

Total ozone (TOZ) data and vertical temperature profiles, derived from 12 728 free‐balloon ascents and ground‐based or space‐borne instrumentation during 1984–2002 were analysed to investigate the association between TOZ and tropopause height variations above Athens, Greece. It was found that the synoptic pattern of TOZ is highly variable and the observed short‐term variability of TOZ partially reflects the fluctuations in tropopause height. In addition, the long‐term relation between tropopause height and TOZ variabilities shows that any decrease in TOZ is always accompanied by an increase in tropopause height, with a rate of – 8.5 Dobson unit (DU) km−1 in summer and −11.2 DU km−1 in winter. The linear regression analysis of the de‐seasonalized monthly mean TOZ and tropopause height, indicates a long‐term decrease in TOZ of −7.54±0.99 DU per decade, and an increase in tropopause height of approximately 167±30 m per decade.

Identification of anthropogenic climate change using a second‐generation reanalysis

Changes in the height of the tropopause provide a sensitive indicator of human effects on climate. A previous attempt to identify human effects on tropopause height relied on information from ‘first‐generation’ reanalyses of past weather observations. Climate data from these initial model‐based reanalyses have well‐documented deficiencies, raising concerns regarding the robustness of earlier detection work that employed these data. Here we address these concerns using information from the new second‐generation ERA‐40 reanalysis. Over 1979 to 2001, tropopause height increases by nearly 200 m in ERA‐40, partly due to tropospheric warming. The spatial pattern of height increase is consistent with climate model predictions of the expected response to anthropogenic influences alone, significantly strengthening earlier detection results. Atmospheric temperature changes in two different satellite data sets are more highly correlated with changes in ERA‐40 than with those in a first‐generation reanalysis, illustrating the improved quality of temperature information in ERA‐40. Our results provide support for claims that human activities have warmed the troposphere and cooled the lower stratosphere over the last several decades of the 20th century, and that both of these changes in atmospheric temperature have contributed to an overall increase in tropopause height.

Comment on "Contributions of Anthropogenic and Natural Forcing to Recent Tropopause Height Changes"

Santer et al. ([ 1 ][1]) concluded that an observed increase in tropopause height from 1979 to 1999 resulted, in part, from tropospheric warming due to increased greenhouse gases. They further showed that the largest increases in tropopause height occurred towards the poles, particularly in the

Atmospheric pollution and remote sensing: implications for the southern hemisphere ozone hole split in 2002 and the northern mid-latitude ozone trend

Among the most important aspects of the atmospheric pollution problem are the anthropogenic impacts on the stratospheric ozone layer, the related trends of the total ozone content drop and the solar ultraviolet radiation enhancement at the Earth’s surface level, which originate various dangers for man and ecosystems. The present study is devoted to the total ozone depletion over Antarctica and the mid-latitude zone of the northern hemisphere, by using the remote sensing techniques. The ozone hole over Antarctica in late September 2002 was gradually elongated, and reached finally to the splitting into two holes, probably due to a polar stratospheric major warming, which was presumably taking place. At Athens, the difference in wintertime tropopause height distribution for the pre- and post-Pinatubo period appears a main maximum around 11.3 km, with a secondary one around 9.3 km. This difference in summertime distribution appears one main maximum around 11.3 km and a secondary one around 17.3 km. In addition, any column ozone decrease is always accompanied by an increase in tropopause height, with a rate of −9.4 DU/km in summer, −14.7 DU/km, in winter, during the pre-Pinatubo period and −7.5 DU/km in summer, and −9.3 DU/km, in winter, during the post-Pinatubo period. Also, the linear regression analysis of the deseasonalized monthly mean column ozone indicates a long-term decrease of −2.2 and −3.7 DU per decade, for the pre- and post-Pinatubo period, respectively. Furthermore, the long-term increase of tropopause height at Athens is about 377 and 207 m per decade for the pre- and post-Pinatubo period, respectively. The above-mentioned results suggest that a close connection between the increase of tropopause height, tropospheric warming, and TOC depletion, might exists, depending on the events of volcanic eruptions.

Behavior of tropopause height and atmospheric temperature in models, reanalyses, and observations: Decadal changes

We examine changes in tropopause height, a variable that has hitherto been neglected in climate change detection and attribution studies. The pressure of the lapse rate tropopause, pLRT, is diagnosed from reanalyses and from integrations performed with coupled and uncoupled climate models. In the National Centers for Environmental Prediction (NCEP) reanalysis, global‐mean pLRT decreases by 2.16 hPa/decade over 1979–2000, indicating an increase in the height of the tropopause. The shorter European Centre for Medium‐Range Weather Forecasts (ECMWF) reanalysis has a global‐mean pLRT trend of −1.13 hPa/decade over 1979–1993. Simulated pLRT trends over the past several decades are consistent with reanalysis results. Superimposed on the overall increase in tropopause height in models and reanalyses are pronounced height decreases following the eruptions of El Chichón and Pinatubo. Interpreting these pLRT results requires knowledge of both T(z), the initial atmospheric temperature profile, and ΔT(z), the change in this profile in response to external forcing. T(z) has a strong latitudinal dependence, as does ΔT(z) for forcing by well‐mixed greenhouse gases and stratospheric ozone depletion. These dependencies help explain why overall tropopause height increases in reanalyses and observations are amplified toward the poles. The pronounced increases in tropopause height in the climate change integrations considered here indicate that even AGCMs with coarse vertical resolution can resolve relatively small externally forced changes in tropopause height. The simulated decadal‐scale changes in pLRT are primarily thermally driven and are an integrated measure of the anthropogenically forced warming of the troposphere and cooling of the stratosphere. Our algorithm for estimating pLRT (based on a thermal definition of tropopause height) is sufficiently sensitive to resolve these large‐scale changes in atmospheric thermal structure. Our results indicate that the simulated increase in tropopause height over 1979–1997 is a robust, zero‐order response of the climate system to forcing by well‐mixed greenhouse gases and stratospheric ozone depletion. At the global‐mean level, we find agreement between the simulated decadal‐scale pLRT changes and those estimated from reanalyses. While the agreement between simulated pLRT changes and those in NCEP is partly fortuitous (due to excessive stratospheric cooling in NCEP), it is also driven by real pattern similarities. Our work illustrates that changes in tropopause height may be a useful “fingerprint” of human effects on climate and are deserving of further attention.

Long‐term trend of tropopause over New Delhi and Thiruvananthapuram

Radiosonde observations taken during the past 32 years at New Delhi (28°N, 77°E) and 26 years at Thiruvananthapuram (8°N, 76°E) have been analyzed to examine the long‐term trend of tropopause height (TPH) and tropopause temperature (TPT) at these two stations. It appears that TPH is increasing and TPT is decreasing over the years. The trend of change is not same throughout the period of study. Considering the whole period of data we find that the increase of TPH is in the range of +0.57 to +1.13%/decade and the decrease of TPT is in the range range of −0.53 to −0.94%/decade. Qualitatively this is explainable with the decreasing trend of ozone in the stratosphere.

Correlations between tropopause height and total ozone: Implications for long‐term changes

For the central European station of Hohenpeissenberg, averaging of ozone profiles grouped by tropopause height shows that the ozone mixing ratio profile in the lower stratosphere shifts up and down with the tropopause. The shift is largest near the tropopause and becomes negligible above 20 to 25 km. As a consequence a high tropopause is correlated with low total ozone and a low tropopause with high total ozone. Independent of season, total ozone decreases by 16 Dobson units (DU) per kilometer increase in tropopause height. At Hohenpeissenberg the tropopause has moved up by 150±70 m (2 σ) per decade over the last 30 years. If the −16 DU per kilometer correlation between total ozone and tropopause height is valid on the timescale of years, it is speculated that the observed increase in tropopause height could explain about 25% of the observed −10 DU per decade decrease of total ozone. This is of the same magnitude as the 30% fraction of midlatitude ozone depletion which current stratospheric models have difficulty accounting for. For Hohenpeissenberg the increase in tropopause height appears to be correlated with observed tropospheric warming: At 5 km altitude, for example, temperature has increased by 0.7±0.3 K per decade (2 σ) since 1967.