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- Author or Editor: A. Rozanov x
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Abstract
A 3D hybrid (H) transport scheme has been developed that consists of the Prather (P) scheme for vertical transport and a semi-Lagrangian (SL) scheme for horizontal transport on a spherical surface. Two tests have also been developed to permit evaluation of the performance of any numerical transport scheme for flows similar to those found in the earth’s atmosphere. In the first test, the 2D distributions of the wind field and the 3D distribution of the chemical species concentration are prescribed analytically and the consistent analytical expression for the species sources and sinks is determined from the constituent continuity equation. The analytical expressions for the winds and source and sink are then used by a numerical scheme to calculate the 3D distribution of the species concentration. Comparison of the numerical distribution with the analytical distribution then allows evaluation of the performance of the numerical scheme. This test has been used to compare the P, SL, and H schemes. The test shows that the SL scheme produces errors up to 6% in species concentration. The P scheme has high accuracy (about 1%) but requires substantial amounts of computer CPU time and memory. The accuracy of the H scheme is higher (better than 1.6%) than that of the SL scheme and is close to that of the P scheme. The H scheme is about nine times faster than the P scheme but does require about three times more memory than the SL scheme. In another test, the P, H, and SL schemes are tested for 2D zonally averaged transport of the conservative species “cloud” by analytically calculated wind velocities. Comparison of the results shows that the H scheme is superior to the SL scheme. It is concluded that the H scheme is a computationally efficient, accurate scheme for simulating the 3D global transport of both conservative and nonconservative species.
Abstract
A 3D hybrid (H) transport scheme has been developed that consists of the Prather (P) scheme for vertical transport and a semi-Lagrangian (SL) scheme for horizontal transport on a spherical surface. Two tests have also been developed to permit evaluation of the performance of any numerical transport scheme for flows similar to those found in the earth’s atmosphere. In the first test, the 2D distributions of the wind field and the 3D distribution of the chemical species concentration are prescribed analytically and the consistent analytical expression for the species sources and sinks is determined from the constituent continuity equation. The analytical expressions for the winds and source and sink are then used by a numerical scheme to calculate the 3D distribution of the species concentration. Comparison of the numerical distribution with the analytical distribution then allows evaluation of the performance of the numerical scheme. This test has been used to compare the P, SL, and H schemes. The test shows that the SL scheme produces errors up to 6% in species concentration. The P scheme has high accuracy (about 1%) but requires substantial amounts of computer CPU time and memory. The accuracy of the H scheme is higher (better than 1.6%) than that of the SL scheme and is close to that of the P scheme. The H scheme is about nine times faster than the P scheme but does require about three times more memory than the SL scheme. In another test, the P, H, and SL schemes are tested for 2D zonally averaged transport of the conservative species “cloud” by analytically calculated wind velocities. Comparison of the results shows that the H scheme is superior to the SL scheme. It is concluded that the H scheme is a computationally efficient, accurate scheme for simulating the 3D global transport of both conservative and nonconservative species.
Abstract
An unprecedented stratospheric warming in the Southern Hemisphere in September 2002 led to the breakup of the Antarctic ozone hole into two parts. The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) on the European Environmental Satellite (ENVISAT) performed continuous observations of limb-scattered solar radiance spectra throughout the stratospheric warming. Thereby, global measurements of vertical profiles of several important minor constituents are provided with a vertical resolution of about 3 km. In this study, stratospheric profiles of O3, NO2, and BrO retrieved from SCIAMACHY limb-scattering observations together with polar stratospheric cloud (PSC) observations for selected days prior to (12 September), during (27 September), and after (2 October) the ozone hole split are employed to provide a picture of the temporal evolution of the Antarctic stratosphere’s three-dimensional structure.
Abstract
An unprecedented stratospheric warming in the Southern Hemisphere in September 2002 led to the breakup of the Antarctic ozone hole into two parts. The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) on the European Environmental Satellite (ENVISAT) performed continuous observations of limb-scattered solar radiance spectra throughout the stratospheric warming. Thereby, global measurements of vertical profiles of several important minor constituents are provided with a vertical resolution of about 3 km. In this study, stratospheric profiles of O3, NO2, and BrO retrieved from SCIAMACHY limb-scattering observations together with polar stratospheric cloud (PSC) observations for selected days prior to (12 September), during (27 September), and after (2 October) the ozone hole split are employed to provide a picture of the temporal evolution of the Antarctic stratosphere’s three-dimensional structure.
Abstract
SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) is a spectrometer designed to measure sunlight transmitted, reflected, and scattered by the earth’s atmosphere or surface in the ultraviolet, visible, and near-infrared wavelength region (240–2380 nm) at moderate spectral resolution (0.2–1.5 nm, λ/Δλ ≈ 1000–10 000). SCIAMACHY will measure the earthshine radiance in limb and nadir viewing geometries and solar or lunar light transmitted through the atmosphere observed in occultation. The extraterrestrial solar irradiance and lunar radiance will be determined from observations of the sun and the moon above the atmosphere. The absorption, reflection, and scattering behavior of the atmosphere and the earth’s surface is determined from comparison of earthshine radiance and solar irradiance. Inversion of the ratio of earthshine radiance and solar irradiance yields information about the amounts and distribution of important atmospheric constituents and the spectral reflectance (or albedo) of the earth’s surface.
SCIAMACHY was conceived to improve our knowledge and understanding of a variety of issues of importance for the chemistry and physics of the earth’s atmosphere (troposphere, stratosphere, and mesosphere) and potential changes resulting from either increasing anthropogenic activity or the variability of natural phenomena. Topics of relevance for SCIAMACHY are
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tropospheric pollution arising from industrial activity and biomass burning,
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troposphere–stratosphere exchange processes,
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stratospheric ozone chemistry focusing on the understanding of the ozone depletion in polar regions as well as in midlatitudes, and
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solar variability and special events such as volcanic eruptions, and related regional and global phenomena.
Inversion of the SCIAMACHY measurements enables the amounts and distribution of the atmospheric constituents O3, O2, O2(1Δ), O4, BrO, OClO, ClO, SO2, H2CO, NO, NO2, NO3, CO, CO2, CH4, H2O, N2O, and aerosol, as well as knowledge about the parameters pressure p, temperature T, radiation field, cloud cover, cloud-top height, and surface spectral reflectance to be determined. A special feature of SCIAMACHY is the combined limb–nadir measurement mode. The inversion of the combination of limb and nadir measurements will enable tropospheric column amounts of O3, NO2, BrO, CO, CH4, H2O, N2O, SO2, and H2CO to be determined.
Abstract
SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) is a spectrometer designed to measure sunlight transmitted, reflected, and scattered by the earth’s atmosphere or surface in the ultraviolet, visible, and near-infrared wavelength region (240–2380 nm) at moderate spectral resolution (0.2–1.5 nm, λ/Δλ ≈ 1000–10 000). SCIAMACHY will measure the earthshine radiance in limb and nadir viewing geometries and solar or lunar light transmitted through the atmosphere observed in occultation. The extraterrestrial solar irradiance and lunar radiance will be determined from observations of the sun and the moon above the atmosphere. The absorption, reflection, and scattering behavior of the atmosphere and the earth’s surface is determined from comparison of earthshine radiance and solar irradiance. Inversion of the ratio of earthshine radiance and solar irradiance yields information about the amounts and distribution of important atmospheric constituents and the spectral reflectance (or albedo) of the earth’s surface.
SCIAMACHY was conceived to improve our knowledge and understanding of a variety of issues of importance for the chemistry and physics of the earth’s atmosphere (troposphere, stratosphere, and mesosphere) and potential changes resulting from either increasing anthropogenic activity or the variability of natural phenomena. Topics of relevance for SCIAMACHY are
-
tropospheric pollution arising from industrial activity and biomass burning,
-
troposphere–stratosphere exchange processes,
-
stratospheric ozone chemistry focusing on the understanding of the ozone depletion in polar regions as well as in midlatitudes, and
-
solar variability and special events such as volcanic eruptions, and related regional and global phenomena.
Inversion of the SCIAMACHY measurements enables the amounts and distribution of the atmospheric constituents O3, O2, O2(1Δ), O4, BrO, OClO, ClO, SO2, H2CO, NO, NO2, NO3, CO, CO2, CH4, H2O, N2O, and aerosol, as well as knowledge about the parameters pressure p, temperature T, radiation field, cloud cover, cloud-top height, and surface spectral reflectance to be determined. A special feature of SCIAMACHY is the combined limb–nadir measurement mode. The inversion of the combination of limb and nadir measurements will enable tropospheric column amounts of O3, NO2, BrO, CO, CH4, H2O, N2O, SO2, and H2CO to be determined.
Abstract
The evolution of the tropopause in the past, present, and future climate is examined by analyzing a set of long-term integrations with stratosphere-resolving chemistry climate models (CCMs). These CCMs have high vertical resolution near the tropopause, a model top located in the mesosphere or above, and, most important, fully interactive stratospheric chemistry. Using such CCM integrations, it is found that the tropopause pressure (height) will continue to decrease (increase) in the future, but with a trend weaker than that in the recent past. The reduction in the future tropopause trend is shown to be directly associated with stratospheric ozone recovery. A significant ozone recovery occurs in the Southern Hemisphere lower stratosphere of the CCMs, and this leads to a relative warming there that reduces the tropopause trend in the twenty-first century.
The future tropopause trends predicted by the CCMs are considerably smaller than those predicted by the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) models, especially in the southern high latitudes. This difference persists even when the CCMs are compared with the subset of the AR4 model integrations for which stratospheric ozone recovery was prescribed. These results suggest that a realistic representation of the stratospheric processes might be important for a reliable estimate of tropopause trends. The implications of these finding for the Southern Hemisphere climate change are also discussed.
Abstract
The evolution of the tropopause in the past, present, and future climate is examined by analyzing a set of long-term integrations with stratosphere-resolving chemistry climate models (CCMs). These CCMs have high vertical resolution near the tropopause, a model top located in the mesosphere or above, and, most important, fully interactive stratospheric chemistry. Using such CCM integrations, it is found that the tropopause pressure (height) will continue to decrease (increase) in the future, but with a trend weaker than that in the recent past. The reduction in the future tropopause trend is shown to be directly associated with stratospheric ozone recovery. A significant ozone recovery occurs in the Southern Hemisphere lower stratosphere of the CCMs, and this leads to a relative warming there that reduces the tropopause trend in the twenty-first century.
The future tropopause trends predicted by the CCMs are considerably smaller than those predicted by the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) models, especially in the southern high latitudes. This difference persists even when the CCMs are compared with the subset of the AR4 model integrations for which stratospheric ozone recovery was prescribed. These results suggest that a realistic representation of the stratospheric processes might be important for a reliable estimate of tropopause trends. The implications of these finding for the Southern Hemisphere climate change are also discussed.
Abstract
An accurate quantification of the stratospheric ozone feedback in climate change simulations requires knowledge of the ozone response to increased greenhouse gases. Here, an analysis is presented of the ozone layer response to an abrupt quadrupling of CO2 concentrations in four chemistry–climate models. The authors show that increased CO2 levels lead to a decrease in ozone concentrations in the tropical lower stratosphere, and an increase over the high latitudes and throughout the upper stratosphere. This pattern is robust across all models examined here, although important intermodel differences in the magnitude of the response are found. As a result of the cancellation between the upper- and lower-stratospheric ozone, the total column ozone response in the tropics is small, and appears to be model dependent. A substantial portion of the spread in the tropical column ozone is tied to intermodel spread in upwelling. The high-latitude ozone response is strongly seasonally dependent, and shows increases peaking in late winter and spring of each hemisphere, with prominent longitudinal asymmetries. The range of ozone responses to CO2 reported in this paper has the potential to induce significant radiative and dynamical effects on the simulated climate. Hence, these results highlight the need of using an ozone dataset consistent with CO2 forcing in models involved in climate sensitivity studies.
Abstract
An accurate quantification of the stratospheric ozone feedback in climate change simulations requires knowledge of the ozone response to increased greenhouse gases. Here, an analysis is presented of the ozone layer response to an abrupt quadrupling of CO2 concentrations in four chemistry–climate models. The authors show that increased CO2 levels lead to a decrease in ozone concentrations in the tropical lower stratosphere, and an increase over the high latitudes and throughout the upper stratosphere. This pattern is robust across all models examined here, although important intermodel differences in the magnitude of the response are found. As a result of the cancellation between the upper- and lower-stratospheric ozone, the total column ozone response in the tropics is small, and appears to be model dependent. A substantial portion of the spread in the tropical column ozone is tied to intermodel spread in upwelling. The high-latitude ozone response is strongly seasonally dependent, and shows increases peaking in late winter and spring of each hemisphere, with prominent longitudinal asymmetries. The range of ozone responses to CO2 reported in this paper has the potential to induce significant radiative and dynamical effects on the simulated climate. Hence, these results highlight the need of using an ozone dataset consistent with CO2 forcing in models involved in climate sensitivity studies.
Abstract
Studies have recently reported statistically significant relationships between observed year-to-year spring Antarctic ozone variability and the Southern Hemisphere annular mode and surface temperatures in spring–summer. This study investigates whether current chemistry–climate models (CCMs) can capture these relationships, in particular, the connection between November total column ozone (TCO) and Australian summer surface temperatures, where years with anomalously high TCO over the Antarctic polar cap tend to be followed by warmer summers. The interannual ozone–temperature teleconnection is examined over the historical period in the observations and simulations from the Whole Atmosphere Community Climate Model (WACCM) and nine other models participating in the Chemistry–Climate Model Initiative (CCMI). There is a systematic difference between the WACCM experiments forced with prescribed observed sea surface temperatures (SSTs) and those with an interactive ocean. Strong correlations between TCO and Australian temperatures are only obtained for the uncoupled experiment, suggesting that the SSTs could be important for driving both variations in Australian temperatures and the ozone hole, with no causal link between the two. Other CCMI models also tend to capture this relationship with more fidelity when driven by observed SSTs, although additional research and targeted modeling experiments are required to determine causality and further explore the role of model biases and observational uncertainty. The results indicate that CCMs can reproduce the relationship between spring ozone and summer Australian climate reported in observational studies, suggesting that incorporating ozone variability could improve seasonal predictions; however, more work is required to understand the difference between the coupled and uncoupled simulations.
Abstract
Studies have recently reported statistically significant relationships between observed year-to-year spring Antarctic ozone variability and the Southern Hemisphere annular mode and surface temperatures in spring–summer. This study investigates whether current chemistry–climate models (CCMs) can capture these relationships, in particular, the connection between November total column ozone (TCO) and Australian summer surface temperatures, where years with anomalously high TCO over the Antarctic polar cap tend to be followed by warmer summers. The interannual ozone–temperature teleconnection is examined over the historical period in the observations and simulations from the Whole Atmosphere Community Climate Model (WACCM) and nine other models participating in the Chemistry–Climate Model Initiative (CCMI). There is a systematic difference between the WACCM experiments forced with prescribed observed sea surface temperatures (SSTs) and those with an interactive ocean. Strong correlations between TCO and Australian temperatures are only obtained for the uncoupled experiment, suggesting that the SSTs could be important for driving both variations in Australian temperatures and the ozone hole, with no causal link between the two. Other CCMI models also tend to capture this relationship with more fidelity when driven by observed SSTs, although additional research and targeted modeling experiments are required to determine causality and further explore the role of model biases and observational uncertainty. The results indicate that CCMs can reproduce the relationship between spring ozone and summer Australian climate reported in observational studies, suggesting that incorporating ozone variability could improve seasonal predictions; however, more work is required to understand the difference between the coupled and uncoupled simulations.
