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FEDERAL SERVICE NO. 1 HYDROMETEOROLOGY AND ENVIRONMENTAL MONITORING
HYDROMCTE<»РОЛОГНЧВЛШ НАУЧНО-ИССЛЕДОВАТЕЛЬСКИЙ ЦЕНТР Р Г 6 Ой РОССИЙСКОЙ ФЕДЕРАЦИИ
SHEVELENA OLGA VASILEVNA
STRUCTURE OF ASHKHM "KGNIH FRONTON I! 11 about the guide koshyaktishshkh PHENOMENON OVER THE SOUTH OF EASTERN EUROPE
Siacialyust 11.00.09 - Mk "gzhfoyaogin, climatology,
ASH "ORKSH" A!
NN geSH "KsShIA uchchioy IPMI" NI knndiditi (> g kik muk
The work was carried out at the Hydrometeorological Research Center of the Russian Federation
Scientific supervisor doctor of physical and mathematical sciences, professor Shanina I.11.
Official opponents: doctor fia "mat. Sci., Prof. Belov N.11 Candidate of Geographical Sciences Velinsky O.K.
Leading organization High Mountain Geophysical Institute, Nalchik
The defense will take place No./0 1993. in hour. at the meeting of the Specialized Council K. 024. About. 02 Hydrometeorological Research Center at the address: 123376, Moscow, B. Predtechensky per., d. 9-13, Rosgidromettsentr.
The dissertation can be found in the library of Rosgkdro-mettsentr.
Scientific Secretary
Specialized Council ^S&lL^ A-I. Terrible
0B111DYA HLRLC.1 ERIST SHA WORKING
RELEVANCE OF THE TOPIC. Convective activity, widespread in the atmosphere, is one of the most important weather-forming factors. Such important and sometimes dangerous weather conditions, like showers, thunderstorms, squalls, tornadoes, etc. At the same time, forecasting of convective activity is often "not free from subjectivity", since convective centers are meascale phenomena and are, therefore, far outside the scale interval that is described by operationally applied currently numerical models.
However, as a rule, an active convegade (leading to the development of showers, thunderstorms, hail, squalls) develops within larger-scale zones characterized by certain properties of the air mass (temperature, humidity, vertical movements, stratification). The emergence of such zones favorable for convective activity is also successfully described in the framework of the numerical prediction of pressure, temperature, humidity and wind. For the forecast of the characterized zones, called active convection zones, an automated method for forecasting active convection zones has been developed in the Department of Aviation Meteorology of the Hydrometeorological Center of the Russian Federation. However, despite the rather high accuracy of this technique for the European territory of the country as a whole (the total accuracy for the warm season of 1992 was 6?. 6%), for the south of the forecast territory, the accuracy of this method is
is significantly lower than the average. This indicates the need to improve the methodology for predicting active convection zones for these areas. On the other hand, there is no doubt that the use of large-scale characteristics of thermobaric fields as an addition to the particle method, which is predominantly used at present, cannot but give a positive effect in predicting AO zones.
At the same time, using large-scale characteristics of fields for predicting mesoscale phenomena, one cannot refuse to study meascale phenomena as such, both in theoretical terms and in terms of attracting new field data, especially where we are talking about ordered convection, which is currently insufficiently studied in comparison with purely thermal instability.
The listed aspects of the problem of studying and predicting convective activity determine the relevance of this work.
THE PURPOSE OF THE WORK is to follow the conditions for the occurrence of ordered convection from the standpoint of the theory of hydrodynamic instability, to analyze the synoptic conditions for the formation of ordered convective structures, and, further, to identify and use the most informative large scale characteristics as predictors to improve the currently used method for automatic prediction of active convection zones.
OBJECTIVES OF THE RESEARCH, based on the purpose of the work, are formulated as follows:
1) Investigation of the conditions for the development of ordered convective structures (kosh. active bands) in order to clarify some aspects of the question of the predominant orientation of band structures in the ranges of gravitational-inertial waves and shorter wavelengths
new convective and gravitational modes.
2) A detailed analysis of the conditions for the formation of the observed quasi-periodic structures in the fields of cloudiness and precipitation in specific cases.
3) General physical-statistical analysis of the conditions for the development of both ordered and disordered convection over the south of the European part of the CIS in order to identify large-scale characteristics that can serve as predictors in the forecast of AOA.
4) Establishment of diagnostic links and development of an improved method for predicting the active convection southern regions European pure country.
RESEARCH METHOD. The methods of the theory of hydrodynamic instability (LLI of the conditions for the development of ordered convective structures and their predominant orientation in the ranges of gravitational-inertial waves and shorter-wavelength modes) are applied in the work; synoptic method - elements of the climatological method (to identify the general patterns of circulation conditions in the study area); methods of mesometeorological analysis, in particular, isentropic analysis (to study the internal structure of baroclinic aons and the conditions for the formation of ordered convective structures in them); computational physico-statistical and synontic-statistical methods (to search for prognostic relationships between large-scale characteristics of thermobaric fields and the possibility of "! Ioziikio-" 1
of active convection).
MATERIALS USED The following materials were used to complete the assigned tasks:
Synoptic (surface) charts (1U85-1992)
Maps of baric topography 850 - 300 g1!a (19B-1992)
Consolidated radar K £ 1r "Sh (1988-1991)
Maps of semi-diurnal precipitation totals (1988-1991)
Satellite MK and TV images, including images from the VO radar (1986-1992)
Object analysis archive data on magnetic tapes (1985-1992)
Output data of the half-life ten-uroin prognostic model, operationally used in the Hydrometeorological Center of the Russian Federation (1989-1992)
Data from the experimental pluviographic test site of UKRNIGYI (1985-1988)
The calculations were carried out at the Hydrometeorological Center of the Russian Federation at KS-1060, partly on a personal computer.
SCIENTIFIC NOVELTY ¡YULU "SHSHU. IN THE DISSERT OF THE RESULTS.
1. For the first time, an analysis was made of the conditions for the growth of mesoscale waves that are not parallel to the front (in a special case of the fulfillment of conditions (1)) and conclusions were drawn about the ratio of growth rates of the edict! ny waves and symmetrically unstable waves, moreover, the latter are ok; were growing more rapidly, and therefore, prevailing in ep(al conditions. This conclusion is consistent with observations.
2. For the first time, a detailed historical analysis of tre; the dimensional structure of air masses in which precipitation layers developed and it was shown that such structures, parallel to the wind, wind shear (hence, average layer temperatures) developed in two typical situations characterized by the presence of shallow layers possible development convection and significantly baroclinic and unsteady.
3. For the first time, a physico-statistical analysis of the relationships between the parameters of static instability and the parameters that rasterize processes of the "grid" scale, on the one hand, and the presence or absence of active convection, on the other hand, has been carried out.
based on the output of the objective analysis operational scheme.
4. A new improved version of the methodology for calculating and constructing a map of active convection zones based on output prognostic data has been developed.
These main new conclusions are submitted for defense.
WORK APPROVAL. The main results of the work were reported at seminars of the department of aviation meteorology, the report on the topic of the dissertation was included in the program of the 3rd All-Union Conference on Aviation Meteorology (Suadal, 1990); the main results obtained in the course of the work and related to the development of a prognostic methodology were included in the reports of the OAM HMC on topics 1. 2v.1 (1991) and VII. Zzh. 1(1992). Some results are published in articles:
1. Borisova V. V., Shakina N. II, Sheveleva O. V., Isanthropic analysis of the conditions formed "1 precipitation bands detected by a side-scan satellite radar. Tr. GMTs RF, 1992, issue 324.
2. Skrintunova E. E., Shakina N. P., Sheveleva O. V. Improved method for forecasting active convection zones over the south of Eastern Europe, deposited manuscript.
PRACTICAL VALUE OF THE WORK. The developed improved technique for automated forecasting of active convection zones based on the results of author's and operational tests provides a significant increase in the success of forecasting AK zones. The methodology has been prepared for consideration at the CMKD. Implementation is expected in the RCFC Moscow and GAMC Vnukovo.
STRUCTURE AND SCOPE OF WORK. The dissertation consists of an introduction, four chapters, a conclusion and a list of references and includes 149 printed pages, including 18 tables and 35 figures. The list of references includes 108 titles.
The introduction substantiates the relevance of the dissertation topic, formulates the purpose and objectives of the study, and briefly outlines the main content of the work.
The first chapter gives a description of the problem, discusses the fundamental foundations of convection forecasting using the particle method and methods for predicting conditions favorable for convective activity over large areas.
Most of the existing methods for predicting convection are based on the following scheme:
1) the forecast of the state of the atmosphere, which add up? to the moment of interest; vertical profiles of temperature and humidity are practically predicted at 6, 12 or 18 hours;
2) the degree of stability of this state is estimated - the possibility of convection from the ground or from the upper levels. Depending on the energy reserves of instability, convection of one intensity or another can develop. For the prediction, use the threshold values of the instability energy or any quantities associated with it, starting from which! a significant probability of the development of one form or another of convection
There are many developments aimed at objectifying the forecast of convective activity. As a rule, the author either follow the path of simple activation of known calculation methods (for example, variants of the particle method), or modify!
known calculation methods, create special algorithms. At present, Roshydromettsengr has a method developed at ZAM for calculating active convection zones, which is based on the method of N. V. Lebedeva for predicting intramass!unsection and predictive discriminant functions proposed by [\ E Reshetov for predicting convection in baroclinic zones. The technique uses the output data of the operational numerical forecasting scheme used in the Roshydrometeorological center (multilevel ^adiabatic hemispherical model by L. V. Berkovich).
In addition to the effect of thermal instability, which causes disordered convection, it is necessary to take into account the fact that in the real atmosphere the horizons - "th scales of the layers from which convection develops are quite large (10 km), 1 at such scales the layers with wind shear turn out to be burning - untally inhomogeneous in temperature, which creates additional reserves of potential energy, which can serve as a source for the development of movements that equalize temperature contrasts, "which movements, due to baroclinic instability, can develop with indifferent and even weakly stable stratification; with unstable stratification, the actions of these melisms lead to the formation of more intense convective phenomena. An additional impetus to the development of convective movements is often given by a forced rise in air, the intensity of which is determined by dynamic factors.
Often, convection is most intense on the fronts. Since the fronts are baroclinic zones, the conditions for the development of convection here are affected by hydrodynamic instability. The vertical movements caused by it serve as an additional forcing factor for convection or suppress e. Hydrodynamic, in particular, inertial instability
is of great interest from the point of view of improving the forecast convective phenomena. The most studied particular case of this type of instability - symmetrical instability - leads to the development of vertical motion bands parallel to the front. Conditions created in saturated air are especially favorable for their development, i. within cloud layers.
IN THE SECOND CHAPTER, an analysis and solution of the linear problem "on inertial instability in frontal zones" is carried out. This task It was set up with the aim of revealing the atmospheric conditions in which convective structures in the form of rolls, non-parallel to the front, are predominantly developed. Observations show that such structures are quite rare; as a rule, cloudy bars are extended along the wind shear, which corresponds to the direction parallel to the front. We consider not the general case of the problem, but a particular case of the characteristic ratio of the parameters of the waves and the main flow
k7" - pg, (1)
where kit wave numbers along the x and z axis, respectively, r is the Coriolis parameter.
This case is still more general than the previously studied case of so-called symmetric perturbations. Like the simplest cases 1=0 or V=0, it lends itself to an analytical solution (unlike the general ray).
G * - 1b + "[ ik (co + ki) +
+ (kA + 1g) (o ^ kiANg (kg +) + 1 g "1 (d" - O (2)
where cO is the complex frequency, k, 1, m are wave numbers according to axes k, y, g respectively. And * "- Brent-Väisälä frequency, n -<*■
A study was made of the conditions for the existence of neutrally stable and growing (and conjugate decaying) values for different wavelengths, different stratification, and layer thickness. Further, the influence of the flow parameters on the wave growth index, which is found as one of the roots of the cubic equation (dispersion relation), is investigated.
It was found that structures not parallel to the front are unstable and can grow in a wide range of conditions, but their growth is slower than that of bands parallel to the front, so that the latter should dominate. Waves of the type under study, in contrast to symmetrically unstable waves, form ordered band structures oriented not necessarily parallel to the Front; they form an arbitrary angle with a direction parallel to the front. An analysis of the dispersion relations showed that waves of arbitrary orientation can exist in a flow with a shear and, at the same time, be both neutrally stable and unstable in a wide range of conditions, including those with a sufficiently high degree of stability. However, their growth is slower than that of the bands parallel to the front, which is why the latter should dominate. The energy source of growing disturbances not parallel to the front is the kinetic energy of the air flow with vertical wind shear; thus, the source is the same as for baroclinic-unstable perturbations. The considered waves are mesoscale (wavelength 30 - 300 km.) and differ from the baro-wedge-unstable waves of the synoptic scale primarily
its non-hydrostatic properties.
Thus, the few cases of development of convective bands not parallel to the front that are known from observations cannot be explained by instability of the gravitational-inertial type. Unfortunately, the literature lacks detailed data on the parameters of nonparallel hollows and fronts near which they were observed.
Whether 1>g;< условий развития упорядоченных конвективных струк-ур (независим« от их ориентации) приводит к общему выводу.что существование таких структур определяется параметрами более крупномасштабных движений (т.е. движений с характерными размерами, по крайней мере на порядок превышающими размеры конвективных структур). К таким параметрам относится прежде всего сдвиг ветра(связанный с горизонтальным градиентом температуры) и степень статической устойчивости (см. ур-ние (2)). Кроме того, поскольку для развития неустойчивости благоприятны насыщенные влагой слои, к определяющим параметрам следует отнести те, которые характеризуют условия упорядоченного подъема воздуха(давление, лапласиан давления) и степень его увлажнения.
CHAPTER THREE analyzes the observed three-dimensional structure of the air flow under conditions when ordered systems of precipitation bands were recorded on the Earth's surface. Observations made with the help of a satellite side-track radar (SB radar) indicate the presence of "traces" of the passage of ordered rainfall systems. The "wavelength" of parallel bands of moistened soil in the 9 cases used for analysis varies from 10 to 35 km; thus, we are talking about a substantially "subgrid" scale of the phenomenon. For a more detailed analysis of the thermobaric field in the atmosphere,
sphere in the dates closest to the observations, an isentropic analysis was applied according to the technique previously developed at the OAM and repeatedly used for the purposes of mesoscale analysis. Within the framework of this technique, the profiles of temperature and wind components are restored using cubic splines, after which the heights of isentropic surfaces and vertical ones are calculated. movement of particles on these surfaces. The method of isentropic analysis makes it possible to determine with great accuracy the position of isentropic surfaces and the value of the potential Ertel vortex, which are material invariants of the hydrostatic flow; it also allows calculating vertical movements on each isosurface independently, which makes it possible to exclude the accumulation of errors with height. As a result of the analysis of the state of the atmosphere at the time of the development of stripe structures in the fields of cloudiness and precipitation, 2 classes of characteristic conditions were identified.
The first class includes situations associated with the warm sector of the cyclone: the phenomenon is formed in the air of the warm sector near the baroclinic zone of the warm front under conditions of its erosion, the development of convection is limited along the vertical
air intake. The first class of situations is associated with the rear of the cyclone: instability develops in cold air under a stable (frontal) layer. However, in a number of moments the situations of both classes turn out to be quite similar. In the cases studied above, over those areas where bands of non-uniform soil moistening were observed, the structure of the atmosphere included layers of the probable development of wave movements with stratification approaching moisture indifferent. The layers are characterized by limited vertical thickness (up to 4 km). The wind in these cases, as a rule, changes little with height in direction, while its speed usually increases, and for cases of the 1st class
characteristic is its value of 3-5m/s near the ground and 15-E0m/s in the area of the tropopause; for the second class 5-10 and .25-30m/s respectively. The direction of the wind is parallel to the observed bands. The phenomenon under study is repeatedly associated with wave formation at the front or with the area where the front changes sign due to the angycyclonic curvature of the isohypse. In other cases (grade 2), the phenomenon develops in the absence of a pronounced frontal zone, but in the presence of increased baroclinicity in the middle troposphere and with values of the Frontogenetic function corresponding to the frontogenetic. That is, at the moment of the development of the phenomenon, the instationarity of the baroclinic zone necessarily takes place. At the same time, the formation of strip structures associated, for example, with well-developed, rapidly moving atmospheric fronts, was not recorded. which would be well traced throughout the entire thickness of the atmosphere and would retain the sign of the frontogenetic function at successive moments of time. Perhaps it is the transformation of the baroclinic zone that plays a certain role, creating specific conditions for the formation of quasi-periodic sediment fields.
In addition, in the third chapter, comparative analysis fields of vertical motions calculated by the method of entropic analysis (moreover, the values of the verti kMSHSH5s of motions were obtained that are well consistent with each other in time 1 "Y Space), with the fields of vertical motions calculated by the generally accepted method. On the whole, the fields of vertical motions assigned to both method, give a summary picture of the distribution of vertical movements.However, in the case of calculation by the method of isentropic analysis, the results turn out to be less smoothed and more detailed, which is an advantage "of this method
THE FOURTH CHAPTER is devoted to physical and statistical analysis
conditions for the development of active convection over the study area and the improvement of the method of objective forecasting of active convection zones. The climatic characteristics of precipitation and convective phenomena over the territory under consideration are given. Relationships between various stratification parameters and synoptic processes are analyzed, a system of potential predictors is selected, and a discriminant analysis of the sample is performed. The following predictors were recognized as the most informative:
1) O, TK (Mahalanobiea distance 1681.21)
2) aH&o > O, NK (Mahalanobis distance 1643.01) (3)
3) dT, B, TK (Mauchlanobis distance 1638.37)
4) 0, ¡^ , HK (Mahalanobis distance 1628.67), Here dH^ is the Laplacian of the geopotential of the isobaric surface 850 hPa. This value in itself is quite informative as a separation criterion. So, when using 4 H^ as the only predictor with its threshold value Yuda, the success of the forecast turned out to be as follows: overall accuracy 74. OH, accuracy of the prediction of the presence of active convection 62. O7., accuracy of the prediction of its absence 79. 3 Pre-prediction of the presence of active convection 65.17., warning of her absence - 83.57 ..
O is the total dew point deficit on the isobaric surfaces 850, 700, BOOGSH "As applied to our materials, the separation criterion for this value is its value of 34 *, in contrast to the value of 2B", used in the method of N. E. Lebedeva, which, apparently, explained climatic features study area
dT « - the difference between the temperature of dry and wet thermometers on the surface of 850 hPa, i.e., the value characterizing the proximity of air vapor to saturated.
Table 1 Characterization of separation success using combinations of three and four most informative parameters
Predictors
justifying suit
oh|n£i|ots |AK | AK
pre-adventure
criteria
Rubinstein
discriminatory
functions (I, - for proshoa and al. cash. (C, - for the forecast is absent, phenomena.
b, -0. 058^+0. 430+0. 897TH--9. 425
1^=0. 031d|^+0. 6310+0. 766Ж--10.064
b, -0.115dCi+0.2380+0. 004NK--4.749
b^-0.095aH^O. 3250+0. 005NK--7.902
b, -0.57dT -0, 3160+0.93TK-9.16 |_x -0.888^T +0. 4070+0. 783 GK--10.823
b -0.1450+0. OZbTs^+0.002NK--3.376
b-o. 2260+0.044^+0.003NK--7.706
and -0.088R^+4T +0.3490+0.8791"
10. 455 G-O. 067^^5+1. 217LT +0.4320+ +0.745-К-11.586
I_I-■ ■ ■ *
suffocating proximity of air vapor to saturation. It was found that the threshold value should be considered the value of dT ~ 3.5*. This value turns out to be very informative when calculating according to the data of the archive of object analysis (general accuracy 777., Bagrov's criterion 0.60, Obukhov's criterion O. 54), but when calculating according to the data of a numerical forecast, the success of the forecast using &T sharply decreases, which is explained by the insufficient accuracy of the forecast parameters humidity in the current operational scheme in comparison with the forecast of pressure characteristics
leniya. Given this, for use in an improved
leniya. With this in mind, a discriminant function is proposed for use in the improved technique, which includes the pressure characteristic itself.
Нloc¿ geopotential of the isobaric surface 1000 rila, which characterizes the magnitude of the surface pressure. Being used as the only predictor, this value, with the criterion of separating 117dams, provides the following success of the forecast: overall skill 69.7Z, predictability for the presence of the phenomenon 51.1%, accuracy of the forecast for its absence 94.3%, warning for the presence of the phenomenon 96.4%, warning of its absence 45.2%.
For each of the combinations (.) were obtained on a dependent sample the values of justification and warning, Bagrov's and Obukho's criteria, as well as Rubinshtein's criterion, which takes into
known phenomena for the threshold probability Р=0. b (Table 1). Further, discriminant functions were found for each combination of three parameters.
In addition, calculations were made for private samples obtained from the general sample by splitting according to the values of individual parameters. Generally; splitting into partial samples did not lead to a significant improvement in the results.
Based on these results, an improved method for automated prediction of active convection zones was formulated. The first of the dcdcriminant functions (3) is used. The methodology includes the following steps
1) Calculation of the Laplacians of the geopotential on the surface of 850r11&.
2) “Calculation of convection parameters: altitude and condensation temperature.
3) Calculation of humidity characteristics: its total deficit on the surfaces of 850, 700, 500 hPa, as well as temperature differences
dry and wet bulb near the ground.
4) Calculation of the values of the discriminant function
1 ^.115-^0.240 b 0.004 "NK -4.749 (4)
5) Calculation of the probability of occurrence of the phenomenon.
$) Based on the probability values, a map of active convection is automatically constructed. The zone is contoured with an isoline at 25% probability values (according to the division criteria above). In addition, those parts of the zone where the occurrence of active convection can be considered almost unconditional (probability value of 607 or more) are highlighted.
The methodology was tested in a quasi-online mode at the Laboratory for Testing New Methods of Forecasts in accordance with
Rice. 1. Sub-region of the forecast territory, for which an improved method for forecasting active convection zones was developed.
topic 1.2v.1 on the material of the warm season of 1992.
Although this methodology was developed only for a part of the European territory of the country (Fig. 1), but in the process of solving topic 1.2c. 1, in the course of tests, an attempt was made to generalize it for the entire ETC, which to a certain extent justified itself. The forecast success characteristics for the territory for which the methodology was directly developed turn out to be higher than for the entire territory as a whole, and, all the more, higher than for its northern and central parts: And they are quite high even for the north of the ETC. Forecast success characteristics are presented in Table 2. So, beating the justification for the whole
Tab. 2. Indicators of the success of the forecast according to the proposed method
1 | Success rates d. - Dpy throughout Europe- 1 For not >: h correct. For the southern
| forecast, X th territory of the country part (Fig. 4.6) part
| 1 (natural repeat-
capacity 48.5 53.2 43.6
| general negotiability 70. 8 66. 7 78. 1
| justification pro-
the presence of the phenomenon 76. 7 76. 2 84. 0
| justification pro-
gnosis of absence yavl. 67.5 60.9 75.2
|
| phenomena B7. g 54.5 61.4
warning from
the absence of a phenomenon 83.7 80.6 90.9
Bagrov's criterion 0.411 0.345 0.54
1 Obukhov criterion 0.497.0.35 0.521
of the territory as a whole is 70.8%, the accuracy of the forecast for the presence of the phenomenon is 76.77., the accuracy of the forecast for the absence of the phenomenon is 67.5%, the warning of the phenomenon is 57.27, the warning of its absence is 87. for the southern part of the territory, these indicators are higher by 4-8. Bagrov and Obukhov's criteria are 0.411 and 0.497 in the first case and 0.54 and 0.621 in the second. For comparison, we present the success rates obtained on the same material when predicting by the previously adopted method. They are: total justification 67. 5X, Tab. 3. Forecast success indicators according to the proposed method in case of transition to the probabilistic form of the forecast
1 | The predicted probability of occurrence of AK 1 2 1 ........ 1 (its actual recurrence-| |most for the given gradation- | 1 tsiiD 1 1 |
| 90-100 ■ 1 1 | 95.2 |
| 80-90 | 97.8 |
| 70-80 | 96.6 |
| 60-70 | 90.7 |
| 50-60 | 82.3 |
| 40-50 | 76.5 |
| 30-40 I p.o " |
| 20-30 | 51.2 |
| 10-20 I 48.7 |
| 0-10 1 | 28.5 | | |
the justification of the forecast of the presence of the phenomenon is 60.6%, the justification of the forecast of the absence of the phenomenon is 76.6X, the warning of the phenomenon is 76.8%, the warning of its absence is 60.3%, The methods give a tangible gain even for the north of the territory, not to mention its southern part.
In table. 3 shows the characteristics of the probabilistic form of the forecast. The values of the actual frequency of occurrence of the phenomenon are somewhat "shifted" to the side large values, which is explained by the difference in the sample sizes of absence and presence of the phenomenon. The real threshold value is about 25%, which confirms the correct choice of the separation criterion for an alternative form of forecast.
MAIN RESULTS AND CONCLUSIONS
1. By analytically solving the equation for inertially unstable waves, a class of waves is selected from the spectrum of its solutions, the wavelengths of which satisfy the condition ku "" TG, their phase velocities, growth rates and other characteristics are determined under certain conditions. The purpose of this study was an assessment of the possibility of the development of wave structures located at an arbitrary angle to the line of the atmospheric front. It was found that, although such waves will exist in a wide range conditions, being both neutrally stable and unstable, yet their growth rates, ceteris paribus, turn out to be less, and the growth rate
it is larger than that of previously studied symmetrically unstable waves that form stripe structures oriented parallel to the front. From this we conclude that the latter should prevail under real conditions, which is confirmed by field data.
2. The synoptic conditions for the formation of small-scale band structures of heterogeneous soil moisture were studied and classified. The purpose of this study is to find out how the three-dimensional structure of the flow and its large-scale characteristics are related to the possibility of the formation of mesoscale inhomogeneities in the fields of meteorological elements. It was revealed that there are 2 classes of conditions for their formation, the first of which is associated with the warm sector of the cyclone and includes the presence of an eroded atmospheric front (often warm) with characteristic wind speeds of 3-5 m/s near gemli and 15-20 m/s in the region of the tropopause; the convection development layer has a small vertical thickness (1.5-3 km) and is limited by downward vertical movements. The second class is associated with the rear of the cyclone and is characterized by an exacerbation of the baroclinic zone with wind speeds of 5-10 and 25-30 m/s, respectively; the development of convection in cold air is limited by a layer of increased stability located at a height of 3-6 km. The structure of the fields of meteorological elements was restored by the method of isentropic analysis
3. In the process of research (item 2), it was found that when calculating vertical motions using the isentropic analysis method, which excludes the accumulation of errors with height, it is possible to obtain fields of vertical motions that are in good agreement in time and space. There is general agreement with the fields of vertical movements calculated from
operational model adopted at Roshydrometcenter, however,
isentropic analysis gives a less blurred and smoother picture, which is an advantage.
4. A statistical study of the possibility of using various large-scale ("grid") characteristics of the air flow as predictors was carried out. The study was carried out for the territory of the south of the European part of the country on the material of 3 warm seasons (1988-1990). Those quantities (the Laplacians of the geopotential of various isobaric surfaces, the horizontal temperature gradient, etc.) are selected, which, already with the existing database, have proven themselves as significant predictors in the forecast of active convection. Other quantities, such as frontogenesis, advection angle, etc., were rejected for the reason that when they are calculated using finite-difference approximations of derivatives, excessive smoothing occurs and, consequently, the loss of the predictive value of the calculated values (although, of course, the corresponding hydrodynamic quantities are significant for the formation of mesoscale fields of cloudiness and precipitation).
5. Using the method of discriminant analysis, on the indicated material, relationships were established between the selected values, which allow predicting the occurrence of active convection based on data in the corners of the regional grid (based on the material of object analysis, i.e. within the framework of the RR concept). The following combinations of predictors turned out to be optimal :
a) the Laplacian of the geopotential of the isobaric surface is 8P0gPn, the total moisture deficit on the surfaces is 500, 700,850 rila, the temperature (or height) of the condensation level.
b) the difference between the temperature of the air and the temperature of the wetted
thermometer “a isobaric surface 850 hPa, total moisture deficit on isobaric surfaces 500, 700, 850 hPa, temperature of the level of condensation.
b) total moisture deficit, geopotential of the isobaric surface 1000 hPa, height of the condensation level.
How much less successful forecasting was obtained for some other combinations of parameters, including in the Laplacian of the geopotential on the surface of 300 Pa, the horizontal temperature gradient on the surface of 850 hPa.
u. A method for calculating active convection zones has been developed, which is included as a local one in the recommendations for introduction into the automated forecast scheme based on the output data of the numerical operational hemispheric mode w. The technique has passed the author's and operational tests, it is expected to be implemented in F 11.311 ^> well and GAMC Vnukovo.
Usage: in all areas of human activity, where it is important to know in advance about the occurrence of such situations, which are accompanied by significant material damage. Essence: measured at various points in the atmosphere values atmospheric pressure air temperature and humidity. The values of the maximum vertical convective air velocity and the vertical velocity of large-scale ordered movement at the level of 850 hPa are determined from them. Additionally, measure the amplitude daily course vertical velocity of large-scale ordered air movement at the level of 850 hPa. The forecast of natural convective phenomena is given when performing given condition. EFFECT: increased reliability of forecasting any of the known types of spontaneous convective hydrometeorological phenomena or their combination.
The invention relates to meteorology, and more specifically to methods for predicting such dangerous and spontaneous convective hydrometeorological phenomena (showers, hail, squalls) in specific areas the globe, which are developed on the basis of taking into account data on the values of meteorological parameters in the previous day and can be most effectively used in all areas of human activity, where it is important to know in advance about the possibility of such situations that are accompanied by significant material damage. There is a method for predicting spontaneous convective hydrometeorological phenomena, which consists in measuring the values of atmospheric pressure, temperature and air humidity at various points in the atmosphere, which determine the value of the maximum vertical convective air velocity (Guide to short-term weather forecasts. Part 1. L .: Gidrometeoizdat, 1986, pp. 444-448). The disadvantage of this method is the limited use only for the forecast of one of the dangerous convective phenomena, namely hail. Of the known closest in technical essence and the achieved result is a method for predicting spontaneous convective hydrometeorological phenomena, which consists in measuring the values of atmospheric pressure, temperature and air humidity at various points in the atmosphere, which determine the value of the maximum vertical convective air velocity and the vertical velocity of large-scale ordered movement on level of 850 hPa (Guidelines for the diagnosis and prognosis of dangerous and especially hazardous precipitation, hail and squalls according to meteorological radars and artificial Earth satellites. / N.I. Glushkova, V.F. Lapchev. Moscow: Roshydromet, 1996, p. 112-113). The disadvantage of the known method is the limited use only for forecasting one of the types of dangerous convective phenomena, namely showers. As a result, the reliability of forecasting other dangerous convective phenomena (hail, squalls), which in some cases are observed simultaneously with showers, is not high. The technical result of the invention is to increase the reliability of forecasting any of the known types of natural convective hydrometeorological phenomena or their combination. This technical result is achieved by the fact that in the method for predicting spontaneous convective hydrometeorological phenomena, including measuring the values of atmospheric pressure, temperature and air humidity at various points in the atmosphere, determining from them the values of the maximum vertical convective air velocity and the vertical velocity of large-scale ordered movement at the level of 850 hPa, according to the invention, the amplitude of the daily variation of the vertical velocity of the large-scale ordered air movement at the level of 850 hPa is additionally measured, and the forecast of natural convective phenomena is given when the condition is met
Where: c 1 , c 2 , c 3 , c 4 are empirical coefficients, the values of which for the warm period of the year are, for example: c 1 = 2 (s / m), c 2 = -0.52 (12 h / hPa) , c 3 = -0.16 (12 h/hPA), c 4 = -90; W m - the value of the maximum vertical convective velocity (m/s); 850 - the value of the vertical velocity of large-scale ordered air movement at the level of 850 hPa (hPa/12 h); 850 - the value of the amplitude of the daily variation of the vertical velocity of large-scale ordered air movement at the level of 850 hPa (hPa/12 h). Proposed technical solution complies with the conditions of patentability "Novelty", "Inventive step" and "Industrial applicability", since the declared set of features: measurement of atmospheric pressure, temperature and air humidity at various points in the atmosphere, determination of the values of the maximum vertical convective air velocity and vertical speed of large-scale ordered movement at the level of 850 hPa, additional measurement of the amplitude of the daily variation of the vertical velocity of the large-scale ordered movement of air at the level of 850 hPa, and forecasting of spontaneous convective phenomena when the condition
C 1 W m +c 2 850 +c 3 850 +c 4 0,
Where: c 1 , c 2 , c 3 , c 4 - empirical coefficients, the values of which for the warm period of the year are, for example: c 1 = 2 (s / m), c 2 = -0.52 (12 h / hPA) , c 3 = -0.16 (12 h/hPA), c 4 = -90; W m - the value of the maximum vertical convective velocity (m/s); 850 - the value of the vertical velocity of large-scale ordered air movement at the level of 850 hPa (hPa/12 h); 850 - the value of the amplitude of the daily variation of the vertical velocity of the large-scale ordered air movement at the level of 850 hPa (hPa/12 h) provides an unobvious result; increasing the reliability of forecasting any of the known types of natural convective hydrometeorological phenomena or their combination. The method proposed in the present invention for predicting spontaneous convective hydrometeorological phenomena can be used in all areas of human activity where it is important to know in advance about the possibility of such situations that are accompanied by significant material damage.
CLAIM
A method for predicting spontaneous convective hydrometeorological phenomena of the warm half-year, which consists in measuring at various points in the atmosphere, the values of atmospheric pressure, temperature and air humidity, which determine the value of the maximum vertical convective air velocity and the vertical velocity of large-scale ordered movement at the level of 850 hPa, characterized in that additionally, the amplitude of the daily variation of the vertical velocity of the large-scale ordered air movement at the level of 850 hPa is measured, and the forecast of natural convective phenomena is given when the condition is metC 1 W m +c 2 850 +c 3 850 +c 4
To predict thunderstorms, heavy rainfall and other phenomena associated with the development of powerful cumulus and cumulonimbus clouds, N.V. Lebedeva suggested using the data of morning sounding of the atmosphere to calculate the parameters of convection, according to which the possibility of the occurrence of certain convective phenomena is determined. These options include:
1) The total dew point temperature deficit at the levels of 850.700 and 500 hPa (ΣD, °С). This parameter indirectly takes into account the influence of entrainment and characterizes the possibility of cloud formation in the 850–500 hPa layer. If ΣD>25°С, then further calculations are not made, since with high dryness of air in the lower half of the troposphere, convection does not lead to the formation of cumulonimbus clouds. If ΣD≤25°С, then the second parameter is calculated.
2) Dew point temperature deficit near the ground or at the upper boundary of the surface inversion at the time of maximum convection development (Do, °С). If Do>20°C, then the level of condensation is located at a height of more than 2.5 km, therefore, precipitation will not reach the surface of the earth, and further calculations are not made. At such a height of the level of condensation, and, consequently, the height of the lower boundary of the clouds, a rain drop will have time to completely evaporate on its way to the ground. If the level of condensation is below 2 km and there are favorable conditions for the occurrence of convection, then in this case all other parameters should be determined.
3) The thickness of the convectively unstable layer (CIL) is (ΔНcns, hPa). Each particle of this layer will participate in convection up to high altitudes. The greater the SNS thickness, the greater the probability of formation of cumulonimbus clouds, the more likely the development of thunderstorm activity (the SNS thickness is determined by the aerological diagram).
4) Condensation level (Ncond., km). The level of condensation indicates the average position of the height of the lower limit of the cumulonimbus clouds. Determination of the level of condensation is also carried out according to the aerological diagram.
5) Convection level (Hconv., km). The level of convection allows you to determine the average position of the tops of cumulonimbus clouds. It is quite obvious that the higher this level, the more powerful the “thunderstorm” clouds should be.
6) Air temperature at the level of convection (Tconv, °С). It has been established that the lower this temperature, the more likely showers and thunderstorms.
7) The average deviation of the temperature on the state curve (T") from the temperature on the stratification curve (T). This deviation is denoted ΔT and is determined by the formula:
Where: T" and T are the temperatures on the state curve and the stratification curve, respectively, at levels that are multiples of 100 hPa, n is the number of whole layers with a thickness of 100 hPa, starting from the level of condensation and up to the level of convection.
It is quite obvious that the greater ΔТ, the greater the degree of air instability, and, consequently, the more intensively convection can develop.
8) Average vertical power of convective clouds (ΔHc.o, km). This value is defined as the difference between the heights of the convection level and the level of condensation. The larger this value, the more likely the occurrence of convective phenomena and the greater their intensity.
According to the results of the calculation of these eight convection parameters in accordance with Table. 1 N.V. Lebedeva proposes to evaluate the possibility of the occurrence of convective phenomena.
Justification of the forecast of the presence of thunderstorms according to the method of N.V. Lebedeva is 80%, and their absence is 89%.
| ∑D(850-500),°C | (Tmax-Tdmax),°C | ΔΗ kns, hPa | Nkond, km | Nconv, km | Tconv,°C | ∆T°C | ΔH, km | convective phenomena |
|---|---|---|---|---|---|---|---|---|
| >25 | >20 | - | - | - | - | - | - | Convection development is not expected |
| ≤25 | ≤16 | >10 | ≈1.5 | ≥6 | <-22.5 | >4 | ≈4.5 | Light showers with a chance of thunderstorms or dry thunderstorms |
| ≤20 | ≤14 | >20 | ≈1.5 | >5 | -22.5<Т<-10 | ≥3 | >3.5 | Light rain shower without thunderstorm |
| ≤20 | ≤14 | >30 | ≈1.5 | ≥8 | <-22.5 | ≥3 | >6.5 | Showers, occasional thunderstorms |
| ≤16 | ≈10 | >60-100 | 1.5>H>1.0 | >8 | <-22.5 | ≥3 | ≥7.5 | Heavy rain showers and thunderstorms |
| ≈16 | ≈10 | - | 1.5>H>1.0 | >8 | <-22.5 | >3 | ≥7.5 | hail |
