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1.
The results are presented of hydrological studies in the coastal zone of the Sea of Japan in autumn in different years. It is revealed that the typical density stratification of water is formed there in autumn. The amplitudes are estimated of regular (with the periodicity of tidal harmonic M2) vertical displacements of isotherms in the intermediate layer and maximum values of flow velocity in the surface and bottom layers. It is demonstrated that temperature perturbations are induced at the shelf edge and propagate to the coastal zone with the velocity that is close to the velocity of the first mode of internal gravity waves with the frequency of the tidal harmonic M2.  相似文献   

2.
A chronology of stratospheric aerosol optical depth for the period 1671–1881 is derived from total lunar eclipse colors. It is compared with available proxy time series for the same period and with more refined data for more recent years. Contrary to previous speculations, the stratosphere from 1671 to 1881 seems to have been mostly undisturbed volcanically, with only two or three eruptions having injected into it truly significant amounts of aerosol-producing and climate-altering sulfur gases. It is confirmed that the full record for 1671–2000 shows a marked, though possibly quasiregular, ∼80 year periodicity in stratospheric aerosol optical depth, which appears also in polar ice-core acidity records and in volcanic eruption frequencies.  相似文献   

3.
It is shown by observational data and synoptic analysis that the development of strong convective echo is influenced by the horizontally non-uniform heating, such as the one caused by lake-land distribution. In this paper, a simple linear cell-convection model is established using an appropriate heating field, and the instability of heating convection is theoretically studied. It is found that the heating convection development will be unstable if the heating-caused temperature gradientdT 0/dy is greater than the critical value (dT 0/dy) c which is approximately 0.64°C/10 km, and that the development of convective band has a preferred width of 12.5 km. It will take 25 min for the initial disturbance to increase intensity by 10 times. All these results are in rather good agreement with the squall line process in the lake-land region of Jiangsu Province on June 8, 1979.  相似文献   

4.
The spectral density of temperature fluctuations in the boundary layer has been studied in the range 0.2 to 2 Hz. It is shown that the temperature spectrum is strongly variable from one minute to the next and that the spectral slope tends to increase with the standard deviation of temperature fluctuations and with the stability of the medium. It is shown that C T 2 values computed from short time series (30 s) tend to be smaller than the C T 2 values computed from several minutes of record.Formerly at Laboratoire de Météorologie Dynamique du C.N.R.S. (Paris).  相似文献   

5.
The results of modeling of 89, 90Sr, 137Cs, and 239, 240Pu migration in the Techa River are compared with observed data. It is shown that taking into account of the process of mass exchange between the main stream of a river and underflow is important for adequate modeling of migration and accumulation of radiative substances in a river. It is difficult to obtain results of modeling corresponding to the observed data if the process is neglected. Taking into account the mass exchange is especially important in developing models for long enough rivers that were polluted by radionuclides during long time. Authors believe that, in future, the considered aspects of modeling radioactive substances in rivers can be generalized on chemical polluting substances with similar physical and chemical properties, for example, heavy metals, phenols, etc.  相似文献   

6.
The climate model of atmospheric and oceanic circulation is used to assess a potential of the geoengineering to stabilize the global temperature at the level of +2°C relative to the average for the 20th century. An anthropogenic forcing was set in accordance with the RCP8.5 scenario. The injection of H2S into the stratosphere transformed afterwards into the sulfate aerosol starts when the temperature reaches a threshold of +2°C. The intensity of the injection is chosen so that the estimated global temperature remains close to the threshold. It is demonstrated that the stabilization of temperature by geoengineering is possible within +(2 ± 0.11)°C during the 21st century. The stabilization of temperature by the end of the 21st century needs the yearly injection of 4.5 Mt S in the form of H2S. The specific efficiency of the method is about 0.09°C/Mt of aerosol. It was found that the stabilization of global temperature does not provide the stabilization of mean global precipitation. The maximum influence of aerosol is in the equatorial zone where its specific density in the atmosphere will reach 0.074 g/m2 by the end of the 21st century. Carried out is a comparison of regional features of temperature and precipitation fields with and without geoengineering. It is shown that the geoengineering will decrease significantly the regional anomalies in the most part of regions and will not increase them in the rest part. Estimated is an effect of the rapid growth in global temperature at the dramatic cessation of geoengineering impacts. Considered is a variant of the gradual decrease in geoengineering intensity, when the negative effects will be smoothed.  相似文献   

7.
The effect of the overlapping band of atmospheric gases and its treatment on the calculation of flux and cooling rate due to the long wave radiation is investigated in detail by a new transmission model for overlapping bands, taking the 15 μm band of CO2 as an example. It is found that the presence of band overlapping has a quite significant influence on radiative fluxes and cooling rates in the upper stratosphere and the troposphere, in particular, at the earth's surface. However, in the middle-lower stratosphere, the overlapping effect appears to be insignificant. It is also shown that the usual wide-band transmission model treating the overlapping effect overestimates the net longwave fluxes in the lower stratosphere and, in particular, in the troposphere including the surface. But, in the middle-upper stratosphere, the contrary is the case.  相似文献   

8.
This paper discusses the importance of the aerodynamic characteristics of forest and other similar canopies to modelling of boundary-layer flow and to estimating the diffusivity coefficients of turbulence transfer mechanisms over such canopies.The hypothesis of Marunich (1971) reported by Tajchman (1981) that the zero-plane displacement, d, equals the upward displacement of the flow trajectory, is critically examined. It is concluded that Marunich's hypothesis is conceptually incorrect and that calculations of d based on Marunich's hypothesis are inherently in error.This paper presents a method based on the mass conservation principle and uses wind profiles in and above a forest canopy as the sole input for determining d, z 0 and u *.Sensitivities of calculated results to measurements errors of wind profile data are evaluated. It is found that an error of less than 1% in wind in the logarithmic regime above the canopy can introduce up to 100% errors in calculated values of d, z 0 and u *. It is also found that the high sensitivity to wind data accuracy, characteristic of the present method, can be used as a guide for the selection of high quality canopy wind data.  相似文献   

9.
Summary The prediction of Indian Summer Monsoon Rainfall (ISMR) is vital for Indian economic policy and a challenge for meteorologists. It needs various predictors among which El Niño-Southern Oscillation (ENSO) is the most important. It has been established by various researchers that ENSO and ISMR relationship is weakening in recent years. It has been also argued that changes in ENSO-ISMR relationship may be due to decadal fluctuations, or it may be the indicative of longer-term trends related to anthropogenic-induced climate changes.In the present communication, an attempt is made to discuss the variability and predictability of ISMR in recent years. It is found that three different indices associated with different regions in the tropics and extra-tropics at different levels of the atmosphere-Asian land mass index represented by geopotential height at upper troposphere (A1), Caribbean-North Atlantic index represented by geopotential height at middle troposphere (A2) and tropical Pacific index at surface level (A3) – have different mechanisms to interact mutually and separately with ISMR in different periods. In recent years ISMR shows weak association with A1 and A3 while strong association with A2. Thus, if these three indices could be combined objectively, they can give rise to the predictability of ISMR. This objective combination is achieved here using Artificial Neural Network (ANN) and a model is developed to predict ISMR. This model has predicted reasonably well during the whole period of consideration (1958–2000) with a correlation coefficient of 0.92 in last 11 years (1990–2000) whereas most of the models fail to predict the variability in recent time.Current affiliation: Department of Physics, Federal University of Parana, Curitiba, Brazil.Received June 2002; revised October 1, 2002; accepted November 12, 2002 Published online: April 10, 2003  相似文献   

10.
Friuli Venezia Giulia is a region located in the North-Eastern part of Italy. It has the Adriatic Sea (Gulf of Trieste) on the South and the Julian and Carnic Alps surrounding it on the North. For these geographical properties thunderstorms and precipitations are common events in the plain of this region.The climatology of thunderstorms and rainfalls, considering 6 h interval periods, is studied in this work. It is shown how the thunderstorm frequency, based on the recording of at least three lightning strikes during the 6 h period, is 16%. The occurrence frequency of at least 1 mm of rain accumulated in 6 h is 24%, while that of at least 5 mm in 6 h is 14%.The daily and monthly distributions of these events are then stratified in three classes, based on their “intensity” (weak, medium and strong), and the different behaviors are analysed. Finally, an explanation for the main monthly rain frequency is sought by looking at only two sounding-derived indices and in particular at their annual cycles. The two indices (related to the potential instability and to the water vapour flux) attempt to summarize the “convective” and “flux” mechanisms for producing rain. It is found that in some particular periods of the year the rain-originating process seems well identifiable, while in many others the two processes seem to be concomitant.  相似文献   

11.
The role of clouds in photodissociation is examined by both modeling and observations. It is emphasized that the photodissociation rate is proportional to the actinic flux rather than to the irradiance. (The actinic flux concerns the energy that is incident on a molecule, irrespective of the direction of incidence. The irradiance concerns the energy that is incident on a plane.) A 3-layer model is used to calculate the actinic flux above and below a cloud, relative to the incident flux, in terms of cloud albedo, zenith angle and the albedo of the underlying and overlying atmosphere. Cloud albedo is mainly determined by cloud optical thickness. An expression for the in-cloud actinic flux is given as a function of in-cloud optical thickness. The 3-layer model seems to be an useful model for estimation of photodissociation rates in dispersion models. Further, a multi-layer delta-Eddington model is used to calculate irradiances, actinic fluxes and photodissociation rates of nitrogen dioxide J(NO2) as a function of height in inhomogeneous atmospheres. For the considered wavelength interval [290–420 nm], Rayleigh scattering, ozone absorption and Mie scattering and absorption by cloud drops and aerosols should be taken into account. It is stressed that both models are one-dimensional and as such are unable to deal with partial cloudiness. It is shown that if no clouds are present, the actinic flux depends primarily on the solar zenith angle. The actinic flux usually increases with height. For cloudy atmospheres, another important parameter with respect to the actinic flux is added: cloud optical thickness, which determines cloud albedo. It can be shown that in-cloud characteristics and cloud height are less important in describing the effect of a cloud on the actinic flux (outside the cloud). The in-cloud values of the actinic flux can exceed the values outside the cloud. Finally, using the photostationary state relationship, good agreement is found between model results and aircraft measurements.  相似文献   

12.
According to the data of the Agency for Hydrometeorology of the Republic of Tajikistan, the volume of the Zeravshan glacier significantly reduced in 1927–1991 (by more than 2 km3), and its further degradation by 30–35% is expected by 2050. To monitor the meteorological conditions in the Zeravshan River basin, in particular, the area of the Zeravshan glacier, air temperature variations in 1931–1961 and 1981–2011 are analyzed. It was found that the period of 1931–1961 is characterized by stable air temperature and its significant rise began in 1981. The trend towards the decrease in water discharge of the Zeravshan River is observed in 1931–1961. It is demonstrated that the average long-term runoff decreased from 6.08 km3 in 1931–1961 to 5.36 km3 in 1981–2011. The similar measurements were carried out in the basin of the Yaghnob River being the tributary of the Zeravshan River. It was revealed that the difference in average long-term runoff between the periods of 1931–1961 and 1981–2011 is insignificant and makes up not more than 2%. Besides, it was found that the results of meteorological observations in 1931-1961 do not agree with the real picture of the Zeravshan glacier degradation.  相似文献   

13.
Summary In this paper several circulation pattern classifications developed for different European regions are compared with respect to their mutual dependence. Circulation pattern (CP) classifications – both subjective and objective – for the British Isles, Germany and Greece were considered. Statistical tests were applied in order to investigate the relationships between each pair of CP classifications. It was found that each pair of classifications cannot be considered to be independent. Time dependence in the relationship between CP classifications shows anomalous behavior only when one of the classifications is subjective. This is due to a gradual change in the methodology, and therefore these classifications should be used for climate evolution studies with care. The dependence between each pair of CP classifications was motivation for developing a new CP classification for the whole European continent which is presented. It is shown that for the local precipitation variability almost no information is lost when comparing this new classification with local classifications.  相似文献   

14.
The distribution of suspended particulate matter (SPM) and chlorophyll a in the Caspian Sea water column from April to November in 2008–2016 is analyzed. It is shown that the spatiotemporal variability of SPM concentration is defined by its sources, especially by the autochthonous (primary production) and allochthonous (particulate river runoff, aerosols) components. The effect of marginal filters of rivers on the volume of coming allochthonous SPM is considered. It is revealed that chlorophyll a is a reliable marker of the autochthonous component of SPM and biogenic sedimentation conditions. The stable vertical stratification defines the distribution of allochthonous and autochthonous SPM in the water column. Vertical profiles of these SPM components in the active layer (its thickness is usually up to ~60 m, more rarely to ~100 m) of the sea are similar in April and October-November and differ much in May-September.  相似文献   

15.
Abstract

In this study, the development of a moderate coastal storm with intense precipitation that occurred during 12–14 February 1993 is examined using a high‐resolution version of the Canadian Regional Finite‐element (RFE) model with more realistic physical representations. It is shown that the improved RFE model predicts well the coastal cyclogenesis events and also the distribution and intensity of heavy mixed precipitation (rain and snow) associated with the storm. It is found that the cyclogenesis takes place in response to the low‐level inshore advection of high‐θe air from the maritime boundary layer, and the approach of a mid‐level shortwave trough with a warm pool above that is previously associated with a decaying cyclone upstream. More rapid deepening of the cyclone ensues as intense precipitation falls along the warm and cold fronts near the cyclone centre.

Diagnosis of the control and sensitivity simulations reveals that the low‐level inshore warm advection and the propagation of the stratospheric warm pool contribute more significantly to the surface pressure falls during the incipient stage, whereas the mid‐level shortwave trough plays an important role in the cyclogenesis at later stages. Overall, latent heat release accounts for about 50% of the cyclone's total deepening, in agreement with the presence of a moderate baroclinic environment and the generation of intense precipitation.

The diabatic and kinematic structures near the rain‐snow boundary are examined to gain insight into the influence of melting snow on the cyclogenesis. It is shown that the improved RFE model reproduces well the rain‐snow boundary structures as previously observed. Moreover, a thermally indirect circulation (perturbation) can be seen in the vicinity of the rain‐snow boundary. It is found, however, that melting of snow tends to produce a weak negative or negligible impact on the cyclogenesis, as opposed to previous hypotheses.  相似文献   

16.
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17.
湖南省柘溪水库流域空中水汽资源特征及人工增雨潜力   总被引：1，自引：2，他引：1  
唐林  王治平  丁岳强  张中波 《气象》2006,32(5):29-34
根据湖南省境内怀化和长沙2个探空站的1994—2003年1—12月每日两个时次(北京时间08时和20时)的资料,对柘溪水库库区及流域大气中的垂直气柱水汽含量进行了计算与分析。结果表明,柘溪水库流域全年年平均水汽含量值为3.62g·cm-2。各种天气形势下水汽含量值各不相同,台风外围云系水汽含量值相对较大,为6.01g·cm-2。大气垂直气柱水汽含量交换次数平均为3.04次/月,更新率为9.92天。柘溪流域上空平均每年净输入的水汽含量为234.87×108m3。若对所有的可作业云系施加人工影响,全年平均可能增雨总量达29.843×108m3。  相似文献   

18.
Radiative forcing and climate sensitivity have been widely used as concepts to understand climate change. This work performs climate change experiments with an intermediate general circulation model (IGCM) to examine the robustness of the radiative forcing concept for carbon dioxide and solar constant changes. This IGCM has been specifically developed as a computationally fast model, but one that allows an interaction between physical processes and large-scale dynamics; the model allows many long integrations to be performed relatively quickly. It employs a fast and accurate radiative transfer scheme, as well as simple convection and surface schemes, and a slab ocean, to model the effects of climate change mechanisms on the atmospheric temperatures and dynamics with a reasonable degree of complexity. The climatology of the IGCM run at T-21 resolution with 22 levels is compared to European Centre for Medium Range Weather Forecasting Reanalysis data. The response of the model to changes in carbon dioxide and solar output are examined when these changes are applied globally and when constrained geographically (e.g. over land only). The CO2 experiments have a roughly 17% higher climate sensitivity than the solar experiments. It is also found that a forcing at high latitudes causes a 40% higher climate sensitivity than a forcing only applied at low latitudes. It is found that, despite differences in the model feedbacks, climate sensitivity is roughly constant over a range of distributions of CO2 and solar forcings. Hence, in the IGCM at least, the radiative forcing concept is capable of predicting global surface temperature changes to within 30%, for the perturbations described here. It is concluded that radiative forcing remains a useful tool for assessing the natural and anthropogenic impact of climate change mechanisms on surface temperature.  相似文献   

19.
In this study, a newly developed method, termed moving empirical orthogonal function analysis (MEOF), is applied to the study of midlatitude baroclinic waves over the wintertime North Pacific from 1979 to 2009. It is shown that when the daily, high-pass filtered (2-10 days) meridional wind at 250 hPa is chosen as the variable of the MEOF analysis, typical features of baroclinic waves/storm tracks over the wintertime North Pacific can be well described by this method. It is found that the first two leading modes of the MEOF analysis, MEOF1 and MEOF2, assume quite different patterns. MEOF1 takes the form of a single wave train running in the east-west direction along 40°N, while MEOF2 is a double wave train pattern running in the east-west direction along 50°N and 30°N, respectively. The shift composites of various anomalous fields based on MEOF1 and MEOF2 assume typical baroclinic wave features. MEOF1 represents a primary storm track pulsing with an intrinsic time scale of two days. It shows significant "midwinter suppression" and apparent interannual variability. It is stronger after the mid-1990s than before the mid-1990s. MEOF2 represents a double-branch storm track, also with an intrinsic time scale of approximately two days, running along 50°N and 30°N, respectively. It shows no apparent seasonal variation, but its interannual and decadal variation is quite clear. It oscillates with larger amplitude and longer periods after the mid-1990s than before the mid-1990s, and is heavily modulated by El Niño-Southern Oscillation (ENSO).  相似文献   

20.
A statistical method of estimation and medium-term forecasting of greenhouse gas emission is under consideration. It is shown that availability of significant enough and stable statistical relationships between greenhouse gas emission and a number of indicators of the economy development allows operational estimating and forecasting of greenhouse gas emission in the Russian economy with a lead-time out to several years. It is possible to estimate and forecast both the total emission of all greenhouse gasses in terms of CO2-equivalent and emission of particular greenhouse gases in different sectors of economy. Both miacroeconomic and industrial indicators of the economy development can be used as predictors for building regression forecasting models.  相似文献   

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