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Abstract
This article restates some of the important features in an idealized jet stream complex and presents cross sections showing the structure of jet streams during selected synoptic situations.
The jet stream complex consists of the Arctic Front jet stream, two mid-latitude jet streams, and the Subtropical jet stream. The two mid-latitude jet streams, when existing individually, may be identified as the Interpolar Front and Polar Front jet streams, respectively, but when combined are simply termed the Polar Front jet stream. In various synoptic situations this complex is expanded to a state in which each jet stream is a completely distinct entity, or it may be telescoped to such a degree that all jet streams are merged in one broad belt of high speed winds. Synoptic examples are given for four well-defined types of jet stream complex: (1) Arctic, Polar and Subtropical jet streams distinctly separated; (2) separate mid-latitude jet streams (Interpolar and Polar jet streams) and the Subtropical jet stream; (3) mid-latitude westerly jet stream field over a well-developed ridge; (4) combining of the mid-latitude westerly jet stream and the Subtropical jet stream. Descriptions of the air masses, lapse rates, tropopauses and wind profiles in the jet stream complex are given.
Abstract
This article restates some of the important features in an idealized jet stream complex and presents cross sections showing the structure of jet streams during selected synoptic situations.
The jet stream complex consists of the Arctic Front jet stream, two mid-latitude jet streams, and the Subtropical jet stream. The two mid-latitude jet streams, when existing individually, may be identified as the Interpolar Front and Polar Front jet streams, respectively, but when combined are simply termed the Polar Front jet stream. In various synoptic situations this complex is expanded to a state in which each jet stream is a completely distinct entity, or it may be telescoped to such a degree that all jet streams are merged in one broad belt of high speed winds. Synoptic examples are given for four well-defined types of jet stream complex: (1) Arctic, Polar and Subtropical jet streams distinctly separated; (2) separate mid-latitude jet streams (Interpolar and Polar jet streams) and the Subtropical jet stream; (3) mid-latitude westerly jet stream field over a well-developed ridge; (4) combining of the mid-latitude westerly jet stream and the Subtropical jet stream. Descriptions of the air masses, lapse rates, tropopauses and wind profiles in the jet stream complex are given.
Abstract
Axially symmetric thermal convection in a rotating environment with a friction layer is investigated by numerically integrating an appropriate system of equations. The study examines the influence of the friction layer upon dry adiabatic thermal convection and the resulting vortex formation process by making comparative computer runs, with and without addition of the friction layer, for four values of ambient-vertical vorticity.
The analysis shows that the addition of a friction layer has a significant influence on the resulting velocity distributions. Friction-induced radial convergence adds to the central updraft of the rising thermal and increases its rate of rise. This friction layer enhancement increases with larger rotation rates and consequently overcomes the correspondingly increased rotational suppression. The vortex height is observed to be greater for the friction layer runs. Additionally, the vortex is observed to have a smoother but less intense profile of tangential velocity with the friction layer present and breaks contact with the ground as a result of the non-slip surface boundary condition.
The friction layer reduces considerably the tangential velocity of the vortex formed by the buoyant cloud under all circumstances, but the rate of rise of the cloud is hardly affected unless the environmental vorticity is in excess of 10−3 sec−1.
Abstract
Axially symmetric thermal convection in a rotating environment with a friction layer is investigated by numerically integrating an appropriate system of equations. The study examines the influence of the friction layer upon dry adiabatic thermal convection and the resulting vortex formation process by making comparative computer runs, with and without addition of the friction layer, for four values of ambient-vertical vorticity.
The analysis shows that the addition of a friction layer has a significant influence on the resulting velocity distributions. Friction-induced radial convergence adds to the central updraft of the rising thermal and increases its rate of rise. This friction layer enhancement increases with larger rotation rates and consequently overcomes the correspondingly increased rotational suppression. The vortex height is observed to be greater for the friction layer runs. Additionally, the vortex is observed to have a smoother but less intense profile of tangential velocity with the friction layer present and breaks contact with the ground as a result of the non-slip surface boundary condition.
The friction layer reduces considerably the tangential velocity of the vortex formed by the buoyant cloud under all circumstances, but the rate of rise of the cloud is hardly affected unless the environmental vorticity is in excess of 10−3 sec−1.
An electronic system to study ATS photographs is described. Cloud pictures are scanned by a TV camera which inputs cloud data onto memory discs from which the data can be recalled and displayed on a cathode-ray tube. Display options include time-lapse, variable magnification and frame-to-frame differencing. Electronic cursors permit digital readout of displacements of identifiable cloud elements. Data handling techniques and the computer-data process for this system are described.
An electronic system to study ATS photographs is described. Cloud pictures are scanned by a TV camera which inputs cloud data onto memory discs from which the data can be recalled and displayed on a cathode-ray tube. Display options include time-lapse, variable magnification and frame-to-frame differencing. Electronic cursors permit digital readout of displacements of identifiable cloud elements. Data handling techniques and the computer-data process for this system are described.
Accurate and reliable predictions and an understanding of future changes in the stratosphere are major aspects of the subject of climate change. Simulating the interaction between chemistry and climate is of particular importance, because continued increases in greenhouse gases and a slow decrease in halogen loading are expected. These both influence the abundance of stratospheric ozone. In recent years a number of coupled chemistry–climate models (CCMs) with different levels of complexity have been developed. They produce a wide range of results concerning the timing and extent of ozone-layer recovery. Interest in reducing this range has created a need to address how the main dynamical, chemical, and physical processes that determine the long-term behavior of ozone are represented in the models and to validate these model processes through comparisons with observations and other models. A set of core validation processes structured around four major topics (transport, dynamics, radiation, and stratospheric chemistry and microphysics) has been developed. Each process is associated with one or more model diagnostics and with relevant datasets that can be used for validation. This approach provides a coherent framework for validating CCMs and can be used as a basis for future assessments. Similar efforts may benefit other modeling communities with a focus on earth science research as their models increase in complexity.
Accurate and reliable predictions and an understanding of future changes in the stratosphere are major aspects of the subject of climate change. Simulating the interaction between chemistry and climate is of particular importance, because continued increases in greenhouse gases and a slow decrease in halogen loading are expected. These both influence the abundance of stratospheric ozone. In recent years a number of coupled chemistry–climate models (CCMs) with different levels of complexity have been developed. They produce a wide range of results concerning the timing and extent of ozone-layer recovery. Interest in reducing this range has created a need to address how the main dynamical, chemical, and physical processes that determine the long-term behavior of ozone are represented in the models and to validate these model processes through comparisons with observations and other models. A set of core validation processes structured around four major topics (transport, dynamics, radiation, and stratospheric chemistry and microphysics) has been developed. Each process is associated with one or more model diagnostics and with relevant datasets that can be used for validation. This approach provides a coherent framework for validating CCMs and can be used as a basis for future assessments. Similar efforts may benefit other modeling communities with a focus on earth science research as their models increase in complexity.
Abstract
Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC)3 project was established in 2016 (www.ac3-tr.de/). It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, shipborne, and satellite data of physical, chemical, and meteorological properties of the Arctic atmosphere, cryosphere, and upper ocean that are available for the Arctic climate research community. Short-term changes and indications of long-term trends in Arctic climate parameters have been detected using existing and new data. For example, a distinct atmospheric moistening, an increase of regional storm activities, an amplified winter warming in the Svalbard and North Pole regions, and a decrease of sea ice thickness in the Fram Strait and of snow depth on sea ice have been identified. A positive trend of tropospheric bromine monoxide (BrO) column densities during polar spring was verified. Local marine/biogenic sources for cloud condensation nuclei and ice nucleating particles were found. Atmospheric–ocean and radiative transfer models were advanced by applying new parameterizations of surface albedo, cloud droplet activation, convective plumes and related processes over leads, and turbulent transfer coefficients for stable surface layers. Four modes of the surface radiative energy budget were explored and reproduced by simulations. To advance the future synthesis of the results, cross-cutting activities are being developed aiming to answer key questions in four focus areas: lapse rate feedback, surface processes, Arctic mixed-phase clouds, and airmass transport and transformation.
Abstract
Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC)3 project was established in 2016 (www.ac3-tr.de/). It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, shipborne, and satellite data of physical, chemical, and meteorological properties of the Arctic atmosphere, cryosphere, and upper ocean that are available for the Arctic climate research community. Short-term changes and indications of long-term trends in Arctic climate parameters have been detected using existing and new data. For example, a distinct atmospheric moistening, an increase of regional storm activities, an amplified winter warming in the Svalbard and North Pole regions, and a decrease of sea ice thickness in the Fram Strait and of snow depth on sea ice have been identified. A positive trend of tropospheric bromine monoxide (BrO) column densities during polar spring was verified. Local marine/biogenic sources for cloud condensation nuclei and ice nucleating particles were found. Atmospheric–ocean and radiative transfer models were advanced by applying new parameterizations of surface albedo, cloud droplet activation, convective plumes and related processes over leads, and turbulent transfer coefficients for stable surface layers. Four modes of the surface radiative energy budget were explored and reproduced by simulations. To advance the future synthesis of the results, cross-cutting activities are being developed aiming to answer key questions in four focus areas: lapse rate feedback, surface processes, Arctic mixed-phase clouds, and airmass transport and transformation.
