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1.
We use a simplified atmospheric general circulation model (AGCM) to investigate the response of the lower atmosphere to thermal
perturbations in the lower stratosphere. The results show that generic heating of the lower stratosphere tends to weaken the
sub-tropical jets and the tropospheric mean meridional circulations. The positions of the jets, and the extent of the Hadley
cells, respond to the distribution of the stratospheric heating, with low latitude heating displacing them poleward, and uniform
heating displacing them equatorward. The patterns of response to the low latitude heating are similar to those found to be
associated with solar variability in previous observational data analysis, and to the effects of varying solar UV radiation
in sophisticated AGCMs. In order to investigate the chain of causality involved in converting the stratospheric thermal forcing
to a tropospheric climate signal we conduct an experiment which uses an ensemble of model spin-ups to analyse the time development
of the response to an applied stratospheric perturbation. We find that the initial effect of the change in static stability
at the tropopause is to reduce the eddy momentum flux convergence in this region. This is followed by a vertical transfer
of the momentum forcing anomaly by an anomalous mean circulation to the surface, where it is partly balanced by surface stress
anomalies. The unbalanced part drives the evolution of the vertically integrated zonal flow. We conclude that solar heating
of the stratosphere may produce changes in the circulation of the troposphere even without any direct forcing below the tropopause.
We suggest that the impact of the stratospheric changes on wave propagation is key to the mechanisms involved. 相似文献
2.
The response of the lower and middle atmosphere to variations in solar irradiance typical of those observed to take place over the 11-year activity cycle has been investigated. The effects on radiative heating rates of changing total solar irradiance, solar spectral irradiance and two different assumptions concerning stratospheric ozone have been studied with a radiative transfer code. The response in the stratosphere depends on the changes specified in the ozone distribution which is not well known. A general circulation model (GCM) of the atmosphere up to 0.1 mbar (about 65 km) has been used to study the impacts of these changes on the thermodynamical structure. The results in the troposphere are very similar to those reported by Haigh99 using a quite different GCM. In the middle atmosphere the model is able to reproduce quite well the observed seasonal evolution of temperature and wind anomalies. Calculations of radiative forcing due to solar variation are presented. These show that the thermal infrared component of the forcing, due to warming of the stratosphere, is important but suggest a near balance between the longwave and shortwave effects of the increased ozone so that ozone change may not be important for net radiative forcing. However, the structure of the ozone change does affect the detailed temperature response and the spectral composition of the radiation entering the troposphere. 相似文献
3.
J. Langen 《Space Science Reviews》2006,125(1-4):371-379
This paper summarises the workshop session on recent space data. Most presentations addressed the intense solar storm in October–November 2003. Large perturbations of atmospheric trace gas concentrations, notably NO2 and HNO3, were found over extended areas around the magnetic poles in the mesosphere and stratosphere, extending over many weeks in the stratosphere. The impact on total ozone seems to be very limited although some more subtle investigations are still to be done. Several new space instruments with many innovative data products have been introduced. Very good coverage in vertically resolved observations of many chemical species is reached for stratospheric chemistry and dynamics research. Data have already been used to improve stratospheric models. Data continuity is an issue. However, the greatest concern is the lack of any suitable future space instrumentation for tropospheric research (air quality and climate forcing/carbon cycle) as well as UTLS problems (climate/chemistry interaction, stratosphere/troposphere exchange). 相似文献
4.
K. Kodera 《Space Science Reviews》2006,125(1-4):319-330
This paper reviews the solar influence on climate through stratospheric dynamical processes. There are two possible processes,
both being a consequence of the wave-mean flow interaction in the upper stratosphere. One involves changes in the vertical
propagation of planetary waves and the resultant tropospheric circulation change in the extratropics of the winter hemisphere.
The other involves change in the global meridional circulation in the stratosphere and associated convective activity change
in the tropics. These processes have been discussed on an 11-year solar cycle, but they are also applicable for centennial-scale
solar influence on climate. 相似文献
5.
The Influence of Total Solar Irradiance on Climate 总被引:7,自引:0,他引:7
To estimate the effect of the solar variability on the climate, two estimates of the solar intensity variations during the last three centuries have been used as forcing in numerical simulations. The model employed to carry out the experiments was the same coupled global ocean-atmosphere model used in a number of studies to assess the effect of the anthropogenic greenhouse gases on climate. The near surface temperature and the tropospheric temperature distribution shows a clear response to the variability of the solar input. Even the thermohaline circulation reacts on the large amplitudes in the forcing. In the stratosphere, the response pattern is similar as in the observations, however, the 11-year cycle found in the forcing data does not excite an appreciable response. This might be due to the missing parameterisation of the increase in the UV-radiation at the solar cycle maximum and the connected increase of the stratospheric ozone concentration. 相似文献
6.
Recent observational evidence has suggested that variations in solar activity may affect winter stratospheric polar ozone and temperature levels. The paucity of direct sunlight available during this season points strongly to a dynamical mechanism. We have carried out several large ensemble experiments within the middle atmosphere and the coupled middle atmosphere and lower thermosphere to simulate the radiative/dynamical coupling via planetary waves for a range of solar fluxes. In the former case, the model response in the winter stratosphere was linear and of the order of the summer stratopause forcing, whilst in the latter, the level of correlation in the winter stratosphere remained high, but was diluted over a wider volume. The inclusion of the upper atmosphere enhanced the winter polar stratospheric response by a factor of three. 相似文献
7.
L. J. Gray S. A. Crooks M. A. Palmer C. L. Pascoe S. Sparrow 《Space Science Reviews》2006,125(1-4):357-370
Observational evidence of the 11-year solar cycle (SC) modulation of stratosphere temperatures and winds from the ERA-40 dataset
is reviewed, with emphasis on the Northern winter hemisphere. A frequency modulation of sudden warming events is noted, with
warmings occurring earlier in solar minimum periods than in solar maximum periods. The observed interaction between the influence
of the SC and the quasi biennial oscillation (QBO) on the frequency of sudden warmings is noted as a possible clue for understanding
their mechanism of influence. A possible transfer route for the 11-year solar cycle from the equatorial stratopause region
to the lowest part of the stratosphere is proposed, via an influence on sudden warming events and the associated induced meridional
circulation. SC and QBO composites of zonal wind anomalies show anomalous wind distributions in the subtropical upper stratosphere
in early winter. Mechanistic model experiments are reviewed that demonstrate a sensitivity of sudden warmings to small wind
anomalies in this region. Various diagnostics from these experiments are shown, including EP fluxes and their divergence and
also the synoptic evolution of the polar vortex, in order to understand the mechanism of the influence. Some recent GCM experiments
to investigate the SC/QBO interaction are also described. They simulate reasonably well the observed SC/QBO interaction of
sudden warming events and appear to support the hypothesis that tropical/subtropical upper stratospheric wind anomalies are
an important influence on the timing of sudden warmings. 相似文献
8.
9.
The paper summarizes work by the authors over the past ten years on an apparent signal of the 11-year sunspot cycle in the lower stratosphere-upper troposphere. The signal appears as a basic, consistent pattern in correlations between heights of stratospheric constant-pressure levels, at least as high as 25 km, and the solar cycle in which the highest correlations are in the subtropics.The variation of the stratospheric heights in phase with the sunspot cycle are – in the areas of high correlations between the two – associated with temperature variations on the same time scale in the middle and upper troposphere. The spatial distribution of the correlations suggests that the year-to-year changes in tropical and subtropical vertical motions contain a component on the time scale of the solar cycle.In January and February the correlations with the sunspot cycle are smallest. The smallness of the correlations is owing to the fact that they are different in the east and west years of the quasi-biennial oscillation in the equatorial stratospheric winds. The correlation pattern in the east years is the same as in the other seasons and is statistically significant. In the west years the correlations are insignificant outside the arctic, and the positive correlation in the arctic in these years is related to the fact that major midwinter breakdowns of the cyclonic vortex in the west years so far have happened only at maxima in the solar cycle.Until recently reliable continuous series of analyses of the stratosphere were not available for the southern hemisphere. The U.S. National Centers for Environmental Prediction and the National Center for Atmospheric Research have now, however, issued a 23-year series of re-analyzed global data which has made it possible to detect the solar signal on the southern hemisphere. It turns out to be almost the same as that on the northern hemisphere.The correlations between total column ozone and the sunspot cycle are lowest in the equatorial regions, where ozone is produced, and in the subpolar regions, where the largest amounts are found. In the annual mean the largest correlations lie between 5° lat. and 30° lat. We suggest that this distribution of correlations is due to the fact that the subtropical heights of the constant-pressure surfaces in the ozone layer are higher in maximum than in minimum years of the sunspot cycle, and that the higher subtropical heights in the solar maxima depress the poleward transport of ozone through the subtropics and thus create an abundance of ozone. 相似文献
10.
11.
This article reviews our knowledge of long-term changes and trends in the upper atmosphere and ionosphere. These changes are part of complex and comprehensive pattern of long-term trends in the Earth’s atmosphere. They also have practical impact. For example, decreasing thermospheric density causes the lifetime of orbiting space debris to increase, which is becoming a significant threat to important satellite technologies. Since the first paper on upper atmosphere trends was published in 1989, our knowledge has progressed considerably. Anthropogenic emissions of greenhouse gases affect the whole atmosphere, not only the troposphere. They cause warming in the troposphere but cooling in the upper atmosphere. Greenhouse gases such as carbon dioxide are not the only driver of long-term changes and trends in the upper atmosphere and ionosphere. Anthropogenic changes of stratospheric ozone, long-term changes of geomagnetic and solar activity, and other drivers play a role as well, although greenhouse gases appear to be the main driver of long-term trends. This makes the pattern of trends more complex and variable. A?consistent, although incomplete, scenario of trends in the upper atmosphere and ionosphere is presented. Trends in F2-region ionosphere parameters, in mesosphere-lower thermosphere dynamics, and in noctilucent or polar mesospheric clouds, are discussed in more detail. Advances in observational and theoretical analysis have explained some previous discrepancies in this global trend scenario. An important role in trend investigations is played by model simulations, which facilitate understanding of the mechanisms behind the observed trends. 相似文献
12.
13.
C. De Jager 《Space Science Reviews》2005,120(3-4):197-241
14.
Devendraa Siingh R. P. Singh Ashok K. Singh Sanjay Kumar M. N. Kulkarni Abhay K. Singh 《Space Science Reviews》2012,169(1-4):73-121
In the present paper salient features of discharges in the stratosphere and mesosphere (namely sprites, halos, blue starters, blue jets, gigantic jets and elves), are discussed. The electrostatic field due to charge imbalance during lightning processes may lead to stratospheric/mesospheric discharges either through the conventional breakdown based on streamers and leaders or relativistic runaway mechanism. Most (not all) of the observed features of sprites, halos and jets are explained by this processes. Development and evolution of streamers are based on the local transient electrostatic field and available ambient electron density which dictate better probability in favor of positive cloud-to-ground discharges, and thus explains the polarity asymmetry in triggering sprites and streamers. Elves are generated by electromagnetic pulse radiated by return stroke currents of cloud-to-ground/inter-cloud discharges. Generation of the both donut and pancake shape elves are explained. Electrodynamic features of thunderstorms associated with stratospheric/mesospheric discharges are summarized including current and charge moment associated with relevant cloud-to-ground discharges. The hypothesis relating tropospheric generated gravity waves and mesospheric discharges are also discussed. Finally some interesting problems are listed. 相似文献
15.
16.
L. Bengtsson 《Space Science Reviews》2006,125(1-4):187-197
The climate response to changes in radiative forcing depends crucially on climate feedback processes, with the consequence
that solar and greenhouse gas forcing have both similar response patterns in the troposphere. This circumstance complicates
significantly the attribution of the causes of climate change. Additionally, the climate system displays a high level of unforced
intrinsic variability, and significant variations in the climate of many parts of the world are due to internal processes.
Such internal modes contribute significantly to the variability of climate system on various time scales, and thus compete
with external forcing in explaining the origin of past climate extremes. This highlights the need for independent observations
of solar forcing including long-term consistent observational records of the total and spectrally resolved solar irradiance.
The stratospheric response to solar forcing is different from its response to greenhouse gas forcing, thus suggesting that
stratospheric observations could offer the best target for the identification of the specific influence of solar forcing on
climate. 相似文献
17.
Jorge L. Chau Larisa P. Goncharenko Bela G. Fejer Han-Li Liu 《Space Science Reviews》2012,168(1-4):385-417
There are several external sources of ionospheric forcing, including these are solar wind-magnetospheric processes and lower atmospheric winds and waves. In this work we review the observed ion-neutral coupling effects at equatorial and low latitudes during large meteorological events called sudden stratospheric warming (SSW). Research in this direction has been accelerated in recent years mainly due to: (1) extensive observing campaigns, and (2) solar minimum conditions. The former has been instrumental to capture the events before, during, and after the peak SSW temperatures and wind perturbations. The latter has permitted a reduced forcing contribution from solar wind-magnetospheric processes. The main ionospheric effects are clearly observed in the zonal electric fields (or vertical E×B drifts), total electron content, and electron and neutral densities. We include results from different ground- and satellite-based observations, covering different longitudes and years. We also present and discuss the modeling efforts that support most of the observations. Given that SSW can be forecasted with a few days in advance, there is potential for using the connection with the ionosphere for forecasting the occurrence and evolution of electrodynamic perturbations at low latitudes, and sometimes also mid latitudes, during arctic winter warmings. 相似文献
18.
平流层飞艇环境适应性评价模型 总被引:3,自引:0,他引:3
阐述了平流层特别是20km高度左右平流层的环境特点,分析了各种环境因素对长期在此空域中驻留飞行的平流层飞艇性能的影响,在此基础上,建立了平流层飞艇环境适应性评价指标体系。并针对其各评价指标的物理意义不同且数量级相差较大的特点提出了基于物理规划和层次分析法相结合的综合评价模型。算例和分析结论表明:抗风速度余量和产生消耗能量比在平流层飞艇对其飞行环境的适应能力评价中占有重要比重,应成为飞艇总体方案设计和论证时的重点关注指标。 相似文献
19.
This paper studies the response of the middle atmosphere to the 11-year solar cycle. The study is based on numerical simulations
with the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), a chemistry climate model that resolves the atmosphere
from the Earth’s surface up to about 250 km. Results presented here are obtained in two multi-year time-slice runs for solar
maximum and minimum conditions, respectively. The magnitude of the simulated annual and zonal mean stratospheric response
in temperature and ozone corresponds well to observations. The dynamical model response is studied for northern hemisphere
winter. Here, the zonal mean wind change differs substantially from observations. The statistical significance of the model’s
dynamical response is, however, poor for most regions of the atmosphere. Finally, we discuss several issues that render the
evaluation of model results with available analyses of observational data of the stratosphere and mesosphere difficult. This
includes the possibility that the atmospheric response to solar variability may depend strongly on longitude. 相似文献
20.
Studies based on data from the past 25–45 years show that irradiance changes related to the 11-yr solar cycle affect the circulation
of the upper troposphere in the subtropics and midlatitudes. The signal has been interpreted as a northward displacement of
the subtropical jet and the Ferrel cell with increasing solar irradiance. In model studies on the 11-yr solar signal this
could be related to a weakening and at the same time broadening of the Hadley circulation initiated by stratospheric ozone
anomalies. Other studies, focusing on the direct thermal effect at the Earth’s surface on multidecadal scales, suggest a strengthening
of the Hadley circulation induced by an increased equator-to-pole temperature gradient. In this paper we analyse the solar
signal in the upper troposphere since 1922, using statistical reconstructions based on historical upper-air data. This allows
us to address the multidecadal variability of solar irradiance, which was supposedly large in the first part of the 20th century.
Using a simple regression model we find a consistent signal on the 11-yr time scale which fits well with studies based on
later data. We also find a significant multidecadal signal that is similar to the 11-yr signal, but somewhat stronger. We
interpret this signal as a poleward shift of the subtropical jet and the Ferrel cell. Comparing the magnitude of the two signals
could provide important information on the feedback mechanisms involved in the solar climate relationship with respect to
the Hadley and Ferrel circulations. However, in view of the uncertainty in the solar irradiance reconstructions, such interpretations
are not currently possible. 相似文献