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1.
Using the data of meteorological information reanalysis, a statistical analysis of dates of the main sudden stratospheric warmings observed in 1958–2014 has been performed and their inhomogeneous distribution in winter months with maximums in the beginning of January, from the end of January to the beginning of February, and in the end of February has been shown. To explain these regularities, a climatological analysis of variations in the amplitudes and vertical components of Eliassen–Palm fluxes created by large-scale planetary waves (PWs), as well as of zonal-mean winds and deviations of temperature from their winter-average values in high northern latitudes at heights of up to 50 km from the surface has been carried out using the 20-year (1995–2014) collection of daily meteorological information from the UK Met Office database. During the aforementioned intervals of observing more frequent sudden stratospheric warmings, climatological maximums of temperature perturbations, local minimums of eastward winds, and local maximums of the amplitude and Eliassen–Palm fluxes of PWs with a zonal wavenumber of 1 in the high-latitude northern stratosphere were found. Distinctions between atmospheric characteristics averaged over two last decades have been revealed.  相似文献   

2.
Distinctions between the longitudinal structures of circulation in the stratosphere and mesosphere/lower thermosphere of the Northern and Southern hemispheres are investigated on the basis of the temperature and geopotential distributions obtained with a SABER instrument (TIMED satellite) in the months of February and August in 2002–2005. The positions of the winter cyclone and polar vortex at stratospheric and mesospheric heights in 2002–2005 are compared to the climatic data over 1978–1998. At stratospheric heights, the mean position of the polar vortex’s center over several years changed insignificantly during the specified years (several degrees in latitude and longitude) in both the Southern and Northern hemispheres. At mesosphere/lower thermosphere heights, the polar vortex occupies the same position in the Southern Hemisphere each year during 2002–2005, and this position agrees with the estimates for 1996–1997. Parameters of stationary planetary waves with the zonal wave number 1 (SPW1) in the fields of temperature, geopotential, and wind are calculated from data on the temperature and geopotential. The height profiles of SPW1 amplitudes and phases calculated from the SABER instrument data for August in the Southern Hemisphere are in good agreement with the profiles of amplitudes and phases obtained from the direct wind measurements with HRDI and WINDII instruments. A strong interannual variability of SPW1 parameters is observed in the Northern Hemisphere. The calculation of the Eliassen-Palm flux and its divergence has shown that SPW1 penetrates into the mesosphere mainly from the stratosphere and slows down the zonal mean flux. However, in the Southern Hemisphere, there is a regular additional SPW1 source with the center at a height of about 65 km and a latitude of 55°S. Such a SPW1 source is, on average, absent in the Northern Hemisphere during 2002–2005; however, in some years (for example, in February 2004), its existence is possible.  相似文献   

3.
The SBUV/SBUV2 (65° S–65° N) and Bodeker Scientific (90° S–90° N) satellite databases have been used for composite and cross-wavelet analyses of the spatio-temporal variability of phase relations between a 11-year cycle of solar activity (SA) and quasi-decennial oscillations (QDOs) of total ozone content (TOC). For globally average TOC values, the QDO maxima coincide in phase with the solar-activity maxima, and amplitude variations of TOC correlate with those of the 11-year solar cycle. According to the analysis of amplitude and phase of QDOs for the zonal average TOC fields, a QDO amplitude is about 6–7 Dobson Units (DU) in the high northern and southern latitudes, and it does not exceed 2–3 DU in the tropic regions. The latitudinal TOC variations are distinguished by a delay of the quasi-decennial oscillation phase in the southern latitudes in comparison with the northern latitudes. The TOC maxima phase coincides with the SA maxima phase in the tropic regions; the TOC variations go ahead of the SA variations, on average, in moderate and high latitudes of the Northern Hemisphere; the TOC variations are behind the SA variations in the Southern Hemisphere. The phase delay between TOC QDO maxima in the northern and southern latitudes appears to increase in the course of time, and the TOC quasi-decennial variations in the Arctic and Antarctic subpolar regions occur approximately in an antiphase over the last two decades.  相似文献   

4.
The spatial structure of surface air temperature (SAT) anomalies in the extratropical latitudes of the Northern Hemisphere (NH) during the 20th century is studied from the data obtained over the period 1892–1999. The expansion of the mean (over the winter and summer periods) SAT anomalies into empirical orthogonal functions (EOFs) is used for analysis. It is shown that variations in the mean air temperature in the Arctic region (within the latitudes 60°–90°N) during both the winter and summer periods can be described with a high accuracy by two spatial orthogonal modes of variability. For the winter period, these are the EOF related to the leading mode of variability of large-scale atmospheric circulation in the NH, the North Atlantic Oscillation, and the spatially localized (in the Arctic) EOF, which describes the Arctic warming of the mid-20th century. The expansion coefficient of this EOF does not correlate with the indices of atmospheric circulation and is hypothetically related to variations in the area of the Arctic ice cover that are due to long-period variations in the influx of oceanic heat from the Atlantic. On the whole, a significantly weaker relation to the atmospheric circulation is characteristic of the summer period. The first leading variability mode describes a positive temperature trend of the past decades, which is hypothetically related to global warming, while the second leading EOF describes a long-period oscillation. On the whole, the results of analysis suggest a significant effect of natural climatic variability on air-temperature anomalies in the NH high latitudes and possible difficulties in isolating an anthropogenic component of climate changes.  相似文献   

5.
A number of numerical experiments were performed with the use of the middle and upper atmosphere model (MUAM). In these experiments, the atmospheric response to an external excitation in the troposphere was calculated and internal stratospheric vacillations caused by the interaction of stationary planetary waves (SPWs) with the zonal mean flow were modeled. The MUAM is shown to well reproduce the known high-frequency global resonance responses of the atmosphere to an external excitation. The results of modeling show that the stratospheric vacillations caused by the interaction of SPWs and the mean flow are responsible for the generation of low-frequency normal modes in the lower and middle atmosphere. The activity of normal atmospheric modes in the troposphere and stratosphere is noted to increase simultaneously with the development of sudden stratospheric warmings. However, in order to understand which process is primary, an additional analysis of the results of numerical experiments and stratospheric data is necessary. It is inferred that, for an adequate modeling of stratospheric vacillation cycles, atmospheric general circulation models must be capable of reproducing global resonance properties of the atmosphere.  相似文献   

6.
北极放大的时空变化特征及其与北极涛动的联系   总被引：1，自引：1，他引：0  
The Arctic near-surface air temperatures are increasing more than twice as fast as the global average–a feature known as Arctic amplification(AA).A modified AA index is constructed in this paper to emphasize the contrast of warming rate between polar and mid-latitude regions,as well as the spatial and temporal characteristics of AA and their influence on atmospheric circulation over the Northern Hemisphere.Results show that AA has a pronounced annual cycle.The positive or negative phase activities are the strongest in autumn and winter,the weakest in summer.After experiencing a remarkable decadal shift from negative to positive phase in the early global warming hiatus period,the AA has entered into a state of being enlarged continuously,and the decadal regime shift of AA in about 2002 is affected mainly by decadal shift in autumn.In terms of spatial distribution,AA has maximum warming near the surface in almost all seasons except in summer.Poleward of 20°N,AA in autumn has a significant influence on the atmospheric circulation in the following winter.The reason may be that the autumn AA increases the amplitude of planetary waves,slows the wave speeds and weakens upper-level zonal winds through the thermal wind relation,thus influencing surface air temperature in the following winter.The AA correlates to negative phase of the Arctic oscillation(AO) and leads AO by 0–3 months within the period 1979–2002.However,weaker relationship between them is indistinctive after the decadal shift of AA.  相似文献   

7.
Evidence has been found for the teleconnection of Indian Ocean Dipole mode (IOD) events in the southern high latitude sea surface pressure field, although the mechanisms that might lead to such far-reaching links remain unresolved. Based on the teleconnection pattern between IOD and the climate anomaly in the upper troposphere, we propose one such mechanism here: the energy propagation theory of the atmospheric planetary wave. Ray traces of the atmospheric planetary waves suggest that the energy propagation of the waves could be responsible for the teleconnection between IOD and tropospheric climate anomalies in southern high latitudes.  相似文献   

8.
The reproduction of dynamic processes in the stratosphere at extratropical latitudes is considered in calculations of the atmospheric module of the global climate model of the Institute of Numerical Mathematics, Russian Academy of Sciences, with an upper boundary of 0.2 hPa (~60 km) for the period from 1979 to 2008 in comparison with the data observational. Changes in temperature, zonal wind, activity of planetary waves, heat fluxes in the lower stratosphere, and sudden stratospheric warmings with the displacement and splitting of the polar vortex, as well as the distribution of associated circulation anomalies in the troposphere, are analyzed.  相似文献   

9.
Over the Southern Ocean the dominant modes of the atmospheric field are known as the Southern Annular Mode (SAM) or Antarctic Oscillation, and the Pacific South American (PSA) pattern. Statistical analysis of sea surface wind (SSW) from satellite observation revealed two leading modes of SAM-like and PSA patterns. In the high latitudes, the SAM-like pattern of the SSW had a large amplitude over the Bellingshausen Basin and Australian-Antarctic Basin, with opposite phase between the two basins. On the intraseasonal time scale, large-scale sea surface height (SSH) also had notable variability, showing a basin-scale anti-phase mode over the two basins. To explain the response of oceanic variations to these atmospheric modes, we analyzed the relationship between the dominant modes of wind stress and large-scale SSH on the intraseasonal time scale. The SAM-like pattern of wind stress was correlated with the SSH variation over the two basins. The SSH basin mode was most simply explained by a simple barotropic response to the SAM-like mode of wind stress, with the curl of opposite phase between the two basins. We conclude that the zonal asymmetry of the wind field of the SAM plays an important role in driving the antiphase SSH basin modes.  相似文献   

10.
Internal gravity wave (IGW) data obtained during the passage of atmospheric fronts over the Moscow region in June–July 2015 is analyzed. IGWs were recorded using a group of four microbarographs (developed at the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences) located at distances of 7 to 54 km between them. Regularities of variations in IGW parameters (spatial coherence, characteristic scales, propagation direction, horizontal propagation velocity, and amplitudes) before, during, and after the passage of an atmospheric front over the observation network, when the observation network finds itself inside the cyclone and outside the front, are studied. The results may be useful in studying the relationships between IGW effects in different physical fields at different atmospheric heights. It is shown that, within periods exceeding 30 min, IGWs are coherent between observation points horizontally spaced at distances of about 60 km (coherence coefficient is 0.6–0.9). It is also shown that there is coherence between wave fluctuations in atmospheric pressure and fluctuations in horizontal wind velocity within the height range 60–200 m. A joint analysis of both atmospheric pressure and horizontal wind fluctuations has revealed the presence of characteristic dominant periods, within which cross coherences between fluctuations in atmospheric pressure and wind velocity have local maxima. These periods are within approximate ranges of 20–29, 37–47, 62–72, and 100–110 min. The corresponding (to these dominant periods) phase propagation velocities of IGWs lie within an interval of 15–25 m/s, and the horizontal wavelengths vary from 52 to 99 km within periods of 35 to 110 min, respectively.  相似文献   

11.
Diurnal-period internal waves were observed near Point Conception California, using an array of moorings extending 120 km along the inner shelf. The waves have an along-shelf coherence scale of at least 50 km, and appear to propagate nearly straight onshore. Wave amplitudes vary over time, depending on thermal stratification and the amplitude of the diurnal sea breeze oscillation. Barotropic tides and vorticity over the mid-shelf are not correlated with internal wave amplitude. Large amplitude internal waves, with supercritical Froude numbers, are observed in mid-summer. Although such waves may drive vertical mixing and cross-shelf transport of passive particles, there is no significant correlation between wave amplitude and invertebrate settlement in the Santa Barbara Channel.  相似文献   

12.
The development of a volcanic plume from the Shiveluch volcano explosion on November 16, 2014, is analyzed using a complex of geophysical methods. The start of the explosion was detected by seismic data. The World Wild Lightning Location Network (WWLLN) allowed the localization of volcanic lightning discharges that occurred during the first stage of the eruption plume. Satellite IR monitoring data made the plume structure obvious. An electrostatic fluxmeter mounted 113 km apart from the volcano recorded the first disturbances of the atmospheric electrical potential gradient (PG) at a distance of 90 km from the eruption cloud front. Two distinct PG anomalies, of 50 and 32 min in length and of more than 100 V/m in amplitude, recorded in 2 h, indicate two separate eruption formations formed by this time. The propagation velocities of two parts of the plume close to the wind speeds at altitudes of temperature inversions (9–10 and 12 km), according to balloon sensing, point out to the plume layering and propagation at two altitudes.  相似文献   

13.
According to the Holton-Tan hypothesis [1], oscillations of the equatorial stratospheric wind change the conditions of the vertical and meridional propagation of planetary waves in extratropical regions, which can cause quasi-biennial oscillations (QBOs) at middle and polar latitudes. To verify the Holton-Tan hypothesis, the intensity of the winter wave activity of the atmosphere in the Northern Hemisphere was estimated at different phases of the quasi-biennial oscillation of the equatorial stratospheric zonal wind. As it turned out, a higher level of the wave activity expected at the easterly phase of the equatorial QBO is characteristic only of the period when the winter circulation is established. At the end of winter a higher level of the wave activity is observed at the westerly QBO phase, which contradicts the Holton-Tan hypothesis. Small but nevertheless noticeable distinctions in the wave activity at low tropospheric levels suggest that the quasi-biennial periodicity of the wave activity at middle latitudes can be caused by oscillations of synoptic processes between the predominantly zonal and meridional forms of the circulation, as was indicated by Pogosyan and Pavlovskaya [2, 3].  相似文献   

14.
Observations of multidecadal variability in sea surface temperature (SST), surface air temperature and winds over the Southern Hemisphere are presented and an ocean general circulation model applied towards investigating links between the SST variability and that of the overlying atmosphere. The results suggest that the dynamical effect of the wind stress anomalies is significant mainly in the neighbourhood of the western boundary currents and their outflows across the mid‐latitudes of each Southern Hemisphere basin (more so in the South Indian and South Atlantic than in the South Pacific Ocean) and in the equatorial upwelling zones. Over most of the subtropics to mid‐latitudes of the Southern Hemisphere oceans, changes in net surface heat flux (particularly in latent heat) appear to be more important for the SST variability than dynamical effects. Implications of these results for modelling and understanding low frequency climate variability in the Southern Hemisphere as well as possible links with mechanisms of decadal/interdecadal variability in the Northern Hemisphere are discussed.  相似文献   

15.
Quantitative estimates of the sensitivity of the number and size of extratropical cyclones in the Northern Hemisphere to changes in the surface temperature are obtained with the use of NCEP/NCAR reanalysis data over a 60-year period and are compared with estimates on the basis of a relatively simple model of the cyclonic and anticyclonic activities in the atmosphere of extratropical latitudes associated with characteristics of atmospheric temperature stratification (MMPKh model). The model estimates are also obtained for a dry and moist atmosphere. With the use of the reanalysis data, extratropical latitudes are, on the whole, characterized by a general decrease in the number of cyclones and the density of their packing in extratropical latitudes as the surface temperature increases. However, in the MMPKh model for moist atmosphere, estimates of the parameter of sensitivity of the number of cyclones at midlatitudes and at extratropical latitudes in the Northern Hemisphere as a whole are close to those based on the reanalysis data. The influences of the meridional gradient of the surface temperature and the vertical temperature gradient in the troposphere on changes in the number and size of extratropical cyclones are estimated from the reanalysis data and model calculations. It is noted that the most significant changes in annual mean variations in the number and size of extratropical cyclones are associated with the vertical temperature gradient in the troposphere. In this case, an increase in the vertical temperature gradient in the troposphere decreases the size of cyclones. The relative influences of the vertical and meridional temperature gradients are different for different latitudinal zones.  相似文献   

16.
The evolution of identical twin errors from an atmospheric general circulation model is studied in the linear range (small errors) through intermediate times and the approach to saturation. Between forecast day 1 and 7, the normalized error variance in the tropics is similar to that at higher latitudes. After that, tropical errors grow more slowly. The predictability time τ taken for tropical errors to reach half their saturation values is larger than that for mid-latitudes, especially for the planetary waves, thus implying greater potential predictability in the tropics.
The discrepancy between mid-latitude and tropical τ is more pronounced at 850 hPa than at 200 hPa, is largest for the planetary waves, and is more pronounced for errors arising from wave phase differences (than from wave amplitude differences).
The spectra of the error in 200 hPa zonal wind show that for forecast times up to about 5 d, the tropical error peaks at much shorter scales than the mid-latitude errors, but that subsequently tropical and mid-latitude error spectra look increasingly similar.
The difference between upper and lower level tropical τ may be due to the greater influence of mid-latitudes at the upper levels.  相似文献   

17.
Planetary waves are key to large-scale dynamical adjustment in the global ocean as they transfer energy from the east to the west side of oceanic basins; they connect the forcing in the ocean interior with the variability at its boundaries; and they change the local heat content, thus coupling oceanic, atmospheric, and biological processes. Planetary waves, mostly of the first baroclinic mode, are observed as distinctive patterns in global time series of sea surface height anomaly (SSHA) and heat storage. The goal of this study is to compare and validate large-scale SSHA signals from coupled ocean-atmosphere general circulation Model for Interdisciplinary Research on Climate (MIROC) with TOPEX/POSEIDON satellite altimeter observations. The last decade of the models’ time series is selected for comparison with the altimeter data. The wave patterns are separated from the meso- and large-scale SSHA signals by digital filters calibrated to select the same spectral bands in both model and altimeter data. The band-wise comparison allows for an assessment of the model skill to simulate the dynamical components of the observed wave field. Comparisons regarding both the seasonal cycle and the Rossby wave field differ significantly among basins. When carried within the same basin, differences can occur between equal latitudes in opposite hemispheres. Furthermore, at some latitudes the MIROC reproduces biannual, annual and semiannual planetary waves with phase speeds and average amplitudes similar to those observed by the altimeter, but with significant differences in phase.  相似文献   

18.
A high resolution modeling study is undertaken, with a 2.5-dimensional nonhydrostatic model, of the generation of internal waves induced by tidal motion over the ridges in Luzon Strait. The model is forced by the barotropic tidal components K1, M2, and O1. These tidal components, along with the initial density field, were extracted from data and models. As the barotropic tide moves over the Luzon Strait sills, there is a conversion of barotropic tidal energy into baroclinic tidal energy. Depressions are generated that propagate towards the Asian Seas International Acoustics Experiment (ASIAEX) test site on the Chinese continental shelf. Nonlinear effects steepen the depressions, frequency and amplitude dispersion set in, and disintegration into large amplitude solitary waves occurs. The effects of varying the initial density field, tidal component magnitudes, as well as adding a steady background current to represent the occasional excursions of the Kuroshio Current into the strait, are considered.Depressions are generated at each of the two sills in Luzon Strait which radiate away, steepening and evolving into internal solitary wave trains. Baroclinic fluxes of available potential energy, kinetic energy and linear are calculated for various parameter combinations. The solitary wave trains produced in the simulations generally consist of large amplitude wave trains alternating with small amplitude wave trains. During strong tidal flow, Kelvin–Helmholtz type instabilities can develop over the taller double-humped sill. The solitary waves propagating towards the ASIAEX test site have been observed to reach amplitudes of 120–250 m, depending on the tidal strength. ASIAEX observations indicate amplitudes up to 150 m and the Windy Island Experiment (WISE) measurements contain magnitudes over 200 m. The model results yield solitary wave amplitudes of 70–300 m and half widths of 0.60–3.25 km, depending on parameter values. These are in the range of observations. Measurements by Klymak et al. (2006), in the South China Sea, exhibit amplitudes of 170 m, half widths of 3 km and phase speeds of 2.9 m s?1. Model predictions indicate that the solitary waves making up the wave packet each experience different background currents with strong near surface shear.The energy in the leading soliton of the large amplitude wave trains ranges between 1.8 and 9.0 GJ m?1. The smaller value, produced using barotropic tidal currents based on the Oregon State University data base, is the same as the energy estimated to be in a solitary wave observed by Klymak et al. (2006). Estimates of the conversion of barotropic tidal energy into radiating internal wave energy yield conversion rates ranging between 3.6% and 8.3%.  相似文献   

19.
The well-known climate shift that occurred around 1976/1977 in the marine ecosystem of North Pacific Ocean was preceded by changes in the early 1970s over Northeastern Asia. In this paper long-term variability of Siberian High and Aleutian Low parameters, seasonal discharge of Siberian rivers and air temperature and precipitation regime in their watersheds are examined in data sets covering 1945–1995. It was found that the change in seasonal values of Siberian river discharges is a consequence of an atmospheric climatic shift that occurred in the early 1970s over North Asia. This shift was induced by a change in atmospheric circulation pattern in the Eurasian sector and Pacific sector of the Northern Hemisphere after 1970. It resulted in changes in position and intensity of the Siberian High and Aleutian Low before and after the 1970s, which induced a different pattern of precipitation in West and East Siberia. There was an increase in winter precipitation over West Siberia but a decrease over East Siberia. The period after 1970s is characterized by higher amplitude of all parameters and increases in the year-to-year variability.  相似文献   

20.
The paper concentrates on the response of the atmospheric circulation non-tropical regions of the Northern Hemisphere to considerable sea surface temperature anomalies regularly occurring in the equatorial Pacific Ocean, related to the El Niño event. It has been established that during El Niño, zonal western circulation and meridional southern circulation tend to decay (being ?2.6% and ?5.4% respectively), while meridional northern circulation intensifies (+8.0%). The paper examines regional peculiarities of the non-tropical atmospheric response to the processes taking in the tropics. It is shown that atmospheric circulation reconstruction is most essential in the Siberian (10.4%) and Pacific (10.2%) sections and is minimal (4.3%) in the Atlantic region. These peculiarities of the regional atmospheric circulation reconstruction may be taken into account to predict short-term climatic variations in the Northern Hemisphere.  相似文献   

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