what are two characteristics of the upper troposphere pdf

Baroclinicity is much weaker than in the other three seasons, and the PV gradient is also weaker. Contour interval is 1. During the Southern Hemisphere summer (Fig. However, in the SH summer the band is located along the 50S latitude circle, with relatively minor latitudinal excursions, whereas in the SH winter the band is centered near 45S around 0 but appears to split into two bands east of 120E, much as the upper-tropospheric jet is split into two near the same location (Fig. Two characteristics of a unit are 1. Sci.,39, 2440. Explanation: Comparing Figs. J. Atmos. Over the Atlantic, the waveguide passes east-southeastward toward North Africa, then back to southern Asia. In Fig. Figure 9b shows that the most coherent wave propagation occurs near 40N over Asia, with another band of relative maxima in WCI2 located over North America near 45N. 2b), we see that the storm track, at least as depicted by the variance of 300-hPa , is a lot more zonally symmetric, with two relatively weak maxima, one over the northeastern Pacific and the other over the Atlantic. , 1991: Storm tracks in the Southern Hemisphere. 17 and 18 are significantly higher than those observed. upper troposphere for investigations concerning upper troposphere emissions. Corresponding author address: Dr. Edmund K. Chang, Program in Atmospheres, Oceans, and Climate, Massachusetts Institute of Technology, Room 54-1614, Cambridge, MA 02139. Then, over the Indian Ocean the waveguide splits into two, with the main branch deviating northeastward back toward the subtropical waveguide over Australia. Cressman, G. P., 1948: On the forecasting of long waves in the upper westerlies. As discussed earlier, the SH winter storm track (see Fig. With such a definition, the group velocity is exactly equal to the phase speed plus Lx/(2 days), where Lx is the wavelength of the wave. Same as Fig. The schematic waveguide where wave propagation is most coherent is depicted by shaded bands in figures in CY99. Accurate knowledge on the location and temperature of the tropopause comes into play in research topics like stratosphere-troposphere exchange and mixing events between tropospheric and stratospheric air masses in the extra-tropical transition layer (e.g., Gettelman et al . 2a), which basically consists of a band of maxima along 50S and has a weak maximum near 90E. The results are shown in Fig. Lee and Held (1993) conducted a series of numerical experiments using a two-layer quasigeostrophic channel model on a plane and concluded that wave packets are more coherent when the baroclinicity of the basic state is weaker. Characteristics of Wave Packets in the Upper Troposphere - AMETSOC Prevailing winds can cause a milder climate with heavy rain. For both experiments, the equilibrium temperature profile was based on the solstitial experiment, with the thermal equator at 6 latitude in the summer hemisphere. The correlations for the different seasons are 0.78 (NH winter), 0.82 (SH winter), 0.90 (SH summer), and 0.73 (NH summer), respectively. Hence, we can use unltered data in our analyses. We are currently conducting other experiments to investigate this. It should be of convenient size. 1).Throughout the upper troposphere, these trends . To examine the coherence of wave packets in the model, daily fields of the simulated 250-hPa meridional winds were analyzed. In the figure we see clearly that the time-lagged correlation pattern displays a downstream-developing wave train. A ratio greater than 1 indicates that downstream development is preferred, whereas values smaller than 1 indicate upstream development, and values close to 1 suggest that the wave train is simply being advected by the steering level flow. There is also a slightly less coherent band of maxima extending across North America, in which waves over the eastern North Pacific propagate downstream to seed waves near the entrance to the Atlantic storm track. The inter-hemispheric comparisons are based on two months of data (one summer month and one winter month) in . Note that different shades in this figure represent values greater than 0.4, 0.5, and 0.6, respectively. Their results also suggested a split of the southern winter waveguide near 120E, and that wave propagation is most coherent along the subtropical waveguide near the date line. Global winds can cause a longer summer. PDF and lower stratosphere region - NASA Technical Reports Server (NTRS) J. Atmos. Ting, M., and N.-C. Lau, 1993: A diagnostic and modeling study of the monthly mean wintertime anomalies appearing in a 100-year GCM experiment. Soc.,77, 437471. Low Pressure: The upper troposphere is characterized by lower air pressure than that at the surface. }. Examination of lag-correlation maps of at different locations (see CY99) suggests that wave packets propagate out from Asia into the Pacific, then over North America, then turn slightly southeast across the Atlantic toward North Africa back to the subtropical waveguide over south Asia, rather than following the axis of the Atlantic storm track maximum toward northern Europe. Sci.,53, 468481. (PDF) Characteristics of the upper troposphere wind field according to Temperatures typically range from -45C to -90C. First, let us examine the downstream/upstream asymmetry index (Figs. The Big Five personality traits include openness, conscientiousness, extraversion, agreeableness and neuroticism. 9percent Answer: Low Temperature: The upper troposphere is characterized by lower temperatures than those found at the surface. Hence, we see that waves upstream of the split of the storm track do not just continue to spiral poleward, but split into two branches, with a stronger tendency to propagate toward the subtropical branch than toward the higher latitudes. Line segments D E, D F, D G, and D H are radii. As a result, the Hadley circulation in this experiment was weakened, and the baroclinicity of the model climate was slightly reduced. Wallace, J. M., G. H. Lim, and M. L. Blackmon, 1988: Relationship between cyclone tracks, anti-cyclone tracks, and baroclinic waveguides. We have also computed group velocities using the movement of correlation centers between day 0.5 and day +0.5, and the results are basically the same as those shown, with an rms difference between the estimated group velocities being less than 2 m s1. Moist convection moves polluted air from near the surface to the upper troposphere. The results of the study of the spatio-temporal variability of the main characteristics of jet streams and turbulence zones in the upper troposphere of the Northern Hemisphere according to . 18a and 18b. The general circulations of the Northern and Southern Hemispheres are compared with regard to the upper troposphere and stratosphere, using atmospheric structure obtained from multi-channel radiance data from the satellite infrared spectrometer instrument aboard the Nimbus 3 spacecraft. 11, further upstream the waves over this region constitute the poleward branch of waves that had split off from the main storm track at around 70E. Time-lagged correlation maps for the base point 50S, 30E, are displayed in Fig. Similar variations can be seen for the Southern Hemisphere winter, except that the wavelength of the waves appears to be slightly longer. Hence, it is not surprising that by using data only from 45S, Lee and Held found much less coherence in wave propagation in the SH winter than we did here. The southern winter storm track (Fig. Standard deviations of 300-hPa , averaged over 198093, for (a) DJF and (b) JJA. To remove contributions from stationary waves, the 3-month mean from each of the individual seasons has been removed from the data, and the result is referred to as the meridional wind perturbations (). Zonal component of the phase speed for (a) DJF and (b) JJA, estimated by objective tracking of maximum correlation of from day 1 to day +1. In terms of wave propagation, the results for these two experiments are shown in Figs. 10. Open Access Article Optical Turbulence Characteristics in the Upper Troposphere-Lower Stratosphere over the Lhasa within the Asian Summer Monsoon Anticyclone by Kun Zhang 1,2, Feifei Wang 1,2, Ningquan Weng 1,2, Xiaoqing Wu 1,2, Xuebin Li 1,2 and Tao Luo 1,2,* 1 As in CY99, we examined the characteristics of wave packets by computing one-point lag-correlation maps, based on the correlation of the time series of 300-hPa at each grid point on a 5 5 grid between 10 and 70 latitude, with the time series of 300-hPa at every grid point on the globe, with or without time lag. Such a relationship between the group velocity and phase speed cannot be generally true. Data from a GCM experiment were also analyzed and showed that wave packets in the GCM also display such a seasonal variation in coherence. J. Roy. By examining the wave coherence indices, as well as individual correlation maps and Hovmller diagrams of correlations computed along the primary waveguides, it was concluded that wave propagation is least coherent in Northern Hemisphere summer, and that waves in Southern Hemisphere summer are not necessarily more coherent than those in Southern Hemisphere winter. 17ac show that when changes in the Hadley intensity are small, coherence of wave packets decreases with an increase in the baroclinicity [consistent with the results of Lee and Held (1993)], while Figs. Results from experiments using an idealized model suggest that coherence of wave packets depends not only on the baroclinicity of the large-scale flow, but also on the intensity of the Hadley circulation, which acts to tighten the upper-tropospheric potential vorticity gradient. However, our model results do show at least one significant difference from observation, in that the correlations shown in Figs. Figure 7a also shows generally poleward group velocity south of 60S, with the largest negative values of meridional group velocity (cgy) near 150E, again in agreement with Trenberths results. Comparing the GCM simulations to observation, downstream/upstream asymmetry is slightly stronger in the GCM in both NH and SH summer, but weaker over Asia in NH winter. It is not clear what determines the absolute magnitude of packet coherence. J. Atmos. Shaded regions represent values over 30. The observed decline occurred in the upper troposphere and lower stratosphere with winter and spring showing more decline compared with summer and autumn. 8. 6 and Fig. A Comparison of the Structure and Flow Characteristics of the A University of Science and Technology of China Ningquan Weng Xiaoqing Wu Abstract and Figures The high elevation, complex topography, and unique atmospheric circulations of the Tibetan Plateau (TP). J. Atmos. 14. 11d) is about 0.42 near 25S, 150E; and the value of the wave coherence index plotted in Fig. , I. N. James, and G. H. White, 1983: The shape, propagation and meanflow interaction of large-scale weather systems. The properties of the wave packets are mainly illustrated using time-lagged one-point correlation maps performed on . If we compare the orientation of the waveguide to the estimates of the meridional group velocity shown in Fig. The characteristic phase speed of the waves picked out by the correlation analyses can be estimated by objectively tracking the movement of the maximum positive center from day 1 to day +1. Bloomfield, P., 1976: Fourier Analysis of Time Series: An Introduction. In section 4, we will examine the characteristics of wave packet propagation in models. Prevailing winds can cause heavy rains or a dry climate. If needed, exact acceptance dates can be obtained by emailingamsjol@ametsoc.org. The first thing to note is that wave packets are slightly more coherent in the GCM than in observation, as WCI2 for the GCM is generally larger than that in observation by about 0.05. .item01 { It appears that the waves over the subtropical jet maximum in SH winter are a continuation of upstream wave packets propagating along the main body of the storm track near 45S. While the GFDL GCM failed to simulate exactly the observed behavior of wave packets, especially over the winter subtropical waveguides, it did manage to capture the gross seasonal variation in WCI2. Troposphere - an overview | ScienceDirect Topics To see how the coherence of wave packets changes with variations in baroclinicity, two other experiments were performed, in which the baroclinicity of the basic state is changed to one with weaker baroclinicity (T equals 45 K) and another with stronger baroclinicity (T = 80 K). We expect that other factors, such as interactions between moist and dry physics, dynamics of the surface boundary layer, and asymmetry in the basic-state flow, may also affect the absolute magnitude of wave packet coherence. What are two characteristics of the upper troposphere As discussed in Part I, comparing the magnitude of the phase speed to the 700-hPa flow, over the storm track regions, the phase speed is slightly larger than the 700-hPa flow over land, while it is generally less than the 700-hPa flow by about 36 m s1 over the oceans, suggesting that the steering level of waves over land is near or slightly above 700 hPa, while that for waves over the oceans is lower and closer to 800 hPa. The characteristic period of the waves can be found by dividing the wavelength by the phase speed. They also examined the SH summer and winter ECMWF analyses. This point is located within the storm track upstream from the split. First, looking at the correlations at positive lags (Fig. In case I (Figs. 18c and 18d), with additional heating over the thermal equator and cooling entirely in the winter subtropics, the winter Hadley circulation is greatly intensified, while the summer Hadley intensity is not significantly changed. Sci.,40, 15951612. All forcing is zonally symmetric, and no orography is present in the experiments. 8b shows that just as in the other seasons, waves in NH summer midlatitudes also show strong downstream development characteristics (as opposed to simple advection or upstream development), even though coherence of the wave packets may not be as high as in the other seasons (Fig. Part I: Northern Hemisphere winter. In the NH winter, the GCM correctly simulates a split in the waveguide across Asia. Sci.,56, 17081728. (PDF) Characteristics of the Upper Troposphere, Tropopause and the Specifically, the data are from the Satellite Infrared Spectrometer (SIRS) instrument aboard the Nimbus 3 spacecraft. The wave train appears to be slightly more coherent over the subtropical branch, as shown by higher correlations near 25S than near 50S in days +2 and +4. (PDF) Aerosol characteristics and particle production in the upper 13, time-lagged correlation maps for the base point 60S, 145W, are shown. 13b), that value is ignored, and only upstream phases are considered on day 2 and downstream phases on day +2. , and D. B. Yu, 1999: Characteristics of wave packets in the upper troposphere. Characteristics of Wave Packets in the Upper Troposphere. Part I Examining Figs. Make a list of your most unique and strongest professional traits. Lindzen and Hou (1988) showed that displacement of the thermal equator toward the summer hemisphere results in a substantial strengthening of the winter Hadley circulation and tightening of the subtropical potential vorticity gradient. The equilibrium temperature profiles for these two experiments were modified from the control experiment, with heating symmetric about the equator, and a T of 60 K. For the stronger Hadley forcing experiment, we prescribed an additional heating perturbation with amplitude 1 K day1 centered over the equator,4 and cooling perturbations with amplitude 0.5 K day1 centered at 20N and 20S such that the net heating perturbation integrated over the globe was zero. Consistent with this, waves east of 0 on the main storm track show only weak upstream correlations to the high-latitude wave trains and appear to have mainly come from the subtropical branch of the split storm track. Looking toward the upstream side of 45S, 85E (Figs. Such agreements between the model and observations give us confidence that we can use modeling studies to investigate the mechanisms behind the observed seasonal variations, which we will turn to in the next paragraphs. J. Atmos. 1014 in this paper, as well as in figures in CY99 for the NH winter.). 18) computed the localized EP flux for 28-day eddies for January and July in the Southern Hemisphere, using the ECMWF operational analyses for the period 197989. The layer we call home Closest to the surface of Earth, we have the troposphere. Layers of Earth's Atmosphere | Center for Science Education 3a and 3b. , 1991: Storm tracks in the Southern Hemisphere. 2b, we see that the SH winter storm track is definitely not along a single latitude circle. Sci.,45, 24162427. 17 except for (a) the winter storm track in the solstitial experiment, (b) the summer storm track in the solstitial experiment, (c) the winter storm track in the concentrated heating experiment I, (d) its corresponding summer storm track, (e) the winter storm track in the concentrated heating experiment II, and (f) its corresponding summer storm track. In the Southern Hemisphere winter (Fig. Trenberth (1991, Fig. , and D. B. Yu, 1999: Characteristics of wave packets in the upper troposphere. Characteristic wavenumber of the waves picked out by the correlation analysis for (a) DJF and (b) JJA. This poleward spiral appears to follow the spiral of the climatological-mean jet (Fig. As a result, convection-driven boundary layer aerosols in the upper troposphere may enter into the lower stratosphere, which could be the probable cause of observed relative enhancement in aerosol backscatter coefficient during the summer-monsoon periods over the study region during the active monsoon year as compared to the drought year. Amer. Same as Fig. These observations suggest that ground level emissions were lofted to the upper troposphere by wet convective systems which stripped Since Trenberths flux indicates relative group velocity, it is difficult to compare the zonal component to the group velocity estimated here. This research is supported by NSF Grant ATM-9510008. (1980), but with the ageostrophic terms fully included. The link was not copied. 14 (the schematic waveguide for SH summer) are very similar, except that the maximum correlation is generally slightly lower than those shown in Fig. Even if we had taken the base point further toward the south (as far south as 60S, not shown here) but at the same longitude, the split into two branches is still apparent, and the day +4 correlation at the subtropical branch is still higher than the correlation for the branch near 60S. From Figs. For a more extended introduction as well as references to previous works, and more details about the methodology, statistical significance of the results, and the meaning of the indices shown here, please refer to CY99. The sequence of time-lagged correlation maps computed for each individual grid point (e.g., Figs. The results, displayed in terms of zonal wavenumber, are shown in Figs. However, we also found that wave packets in the idealized models are usually significantly more coherent than those observed, suggesting that there are some factors that contribute to determining the coherence of wave packets that are missing in the idealized model experiments. increase in carbon dioxide, explain the relationship between extreme weather and climate change, explain 3 factor which influence the shape of the Earth. Lindzen, R. S., and A. Y. Hou, 1988: Hadley circulations for zonally averaged heating centered off the equator. Wave coherence index (WCI2) for (a) DJF and (b) JJA. Cressman, G. P., 1948: On the forecasting of long waves in the upper westerlies. First, we will examine indices (introduced in CY99) that show the asymmetry between upstream and downstream development and the coherence of wave propagation. As is well known, over data-sparse regions, the analyses are heavily influenced by model extrapolation, both in space and time. ing atmospheric compositions in the troposphere. The results from these two concentrated heating experiments are shown in Figs. The experiments described below have been conducted with a horizontal truncation of T30 (approximately 3.75 3.75 equivalent Gaussian grid), and 10 equally spaced sigma levels in the vertical. Contour interval is 3 m s1. The intensities of the Hadley circulation in these two experiments are much closer to those observed, when compared to that in the solstitial experiment. In CY99 and in this paper, we have documented the basic characteristics of wave packets in the winter and summer seasons of both hemispheres, mainly through examination of time-lagged correlation maps of . The high correlation during December 1993 suggests that the analyses are rather tightly constrained by observations, even in the Southern Hemisphere, giving us confidence that features observed in the Southern Hemisphere are probably real. The index basically indicates how well the waves at each location correlate with upstream waves 2 days earlier and downstream waves 2 days later, thus showing the tendency of the downstream development of waves. Abstract Gridded 300-hPa meridional wind data produced by the ECMWF reanalysis project were analyzed to document the seasonal and hemispheric variations in the properties of upper-tropospheric wave packets. J. Atmos. For this case, we use 50 data from two weather models and thus provide en passant a comparison of these two. The two-way exchange of material that occurs across the tropopause is important for determining the climate and chemical composition of the upper troposphere and the lower stratosphere. Edmon, H. J., B. J. Hoskins, and M. E. McIntyre, 1980: EliassenPalm cross sections for the troposphere. 6a, but the differences are not statistically significant. The properties of the wave packets in this two experiments are shown in Figs. Similar discrepancies are also apparent for the NH winter subtropical waveguide across southern Asia, where cgy also depicts the equatorward deviation of the waveguide near the Mediterranean much better than its poleward deviation over China. 1. 17a), wave packets in both the winter and summer hemisphere appear to be slightly less coherent, even though the baroclinicity in the summer hemisphere is much weaker. The paper proceeds with the presentation of the data and methods and then shows two types of results, statistics from 10 years of data and as an example a case with a vertically quite extended ISSR in the upper troposphere. Since this paper is the second paper in a series, the introduction as well as some of the technical details are kept brief. Psychometric Success notes that a very early personality psychologist . 12. background: #193B7D; Trenberth (1986) defined a localized EllassenPalm (EP) flux vector (Eu), which is a three-dimensional extension of the EP flux discussed in Edmon et al. Furthermore, wave packets in SH winter are just about as coherent as those in SH summer. Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. opacity: 1; 1013 show that wave packets do actually follow the latitudinal excursion of this waveguide as they propagate eastward. Example: "What makes me unique is my ability to easily empathize with and relate to people. Sci.,43, 16571678. Hovmller, E., 1949: The trough-and-ridge diagram. Why geography does not have unique definition and consensus among Geographers? 9a. There is a secondary waveguide that continues to follow the poleward spiral in the storm track, all the way across the southern fringe of the Pacific and the Atlantic. The similarity of wave packet coherence shown in Figs. Over the leeward side of the Andes, there are also indications that some waves tend to deviate northward toward the equator. 1996) and found very little differences in the Northern Hemisphere (NH). The result is displayed in Fig. 1013 are largely consistent with the results of Berbery and Vera (1996). Nakamura, H., 1992: Midwinter suppression of baroclinic wave activity in the Pacific. The troposphere (between 0 and about 15 kilometers) is the first layer above the Earth's surface and contains approximately 85 to 90 % of the mass of the Earth's atmosphere. Twenty cases were found in the dataset, and the average propagation speed of the envelope is found to be 23 m s1, with a standard deviation of 8 m s1. 7. During the summers, the waveguides basically follow the position of the midlatitude jets (see Fig. The wave coherence index (WCI2) for the different seasons is shown in Fig. 17df, we see that the coherence of wave packets indeed increases progressively along with an increase in the Hadley intensity. 1b), the upper-tropospheric jet splits into two over the Indian Ocean, with the stronger subtropical branch passing across Australia and a weaker branch passing south of New Zealand along 60S. 15 and 8). Plumb, R. A., 1986: Three-dimensional propagation of transient quasi-geostrophic eddies and its relationship with the eddy forcing of the timemean flow. 17b and 17c, respectively. Two points should be noted here. Overall, as an indicator of wave coherence, the PV gradient at 330 K appears to do better than the baroclinicity, but not as well as the absolute vorticity gradient at 250 hPa. In fact, in the Northern Hemisphere winter, the variations in the dominant wavenumber poleward of 40N nearly correspond to a constant wavelength of 4000 km. The figures have been produced using GRADS developed by Brian Doty of COLA. 3 and 4 suggests that the longer periods of the waves observed in the Northern Hemisphere summer are associated with slower phase speeds rather than longer wavelengths, as the characteristic wavenumbers of the waves are higher than those in the Northern Hemisphere winter. Over the Atlantic, instead of following the Atlantic storm track maximum toward the northeast, the waveguide passes east-southeastward toward North Africa and southern Asia. 11), the maximum upstream correlation at day 2 (Fig. The correspondence between our estimates of the group velocity in NH winter with the E vector of Hoskins et al. Compared to the control experiment (Fig. It is characterized by decreasing temperature with increasing altitude. Downstream of this point, the wave train appears to split into two paths, with one branch proceeding equatorward toward the southern part of Africa and the second branch following the poleward spiral in the storm track. Berbery, E. H., and C. S. Vera, 1996: Characteristics of the Southern Hemisphere winter storm track with filtered and unfiltered data. In summary, Figs. Quart. The author would also like to thank the anonymous reviewers, whose comments on the original manuscript resulted in significant revisions of this paper and Part I. The author would like to thank D. B. Yu for helping with the data analyses; J. Sloman for editorial comments; Y. Chen and the Scientific Computing Division at NCAR for assistance in accessing the ECMWF and NCEPNCAR reanalysis data; and NCEP, NCAR, and ECMWF for making the data available. Downstream/upstream asymmetry index for (a) DJF and (b) JJA. height: 4px; While results from the solstitial experiment suggest that poleward displacement of the thermal equator can offset the effects of differences in baroclinicity between summer and winter, it is still not clear why wave packets are more coherent in NH and SH winter than in NH summer. 8b at 45S, 85E is simply the average of the magnitude of the two values (0.42). 15 and 8 show a high degree of agreement between GCM and observationthat upper-tropospheric waves in both tend to exhibit a high degree of downstream development characteristics.
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