The work present the analysis of the long variation of avalanche activity of former USSR (CIS) mountains by the data of regular observations. There were determined the periods of activigation and reduction of avalanche formation with different synchronization of separate groups of regions. The common territorial time curves of the avalanche activity were derive for 11 of 13 mountains areas of CIS being analyzed. For Tien Shan and Caucasus the generel tendencies of the long-term variation of avalanche formation was differentiated in more details. For some regions the relationship is established between the avalanche formation and climatic factors (air temperature, winter precipitation).The tendency to the avalanche activity decrease on the course of the last few years, revealed on the basis of the analysis is testified by the independent observational data

Kakurina, Y. G.

Kanaev, L. A.

English

Norwegian Geotechnical Institute (NGI) Digital Archive

151Some results of long-term variability of avalancheactivity of CIS mountainsL.A.Kanaev, Y.G.KakurinaCentral Asian Research Hydrometeorological Inslitute(SANIGMI)72, K.Makhsumova,700052 Tashkent, UzbekistanABSTRACT. The work present the analysis of the long variation of avalanche activity offormer USSR (CIS) mountains by the data of regular observations. There weredetermined the periods of activigation and reduction of avalanche formation withdifferent synchronization of separate groups of regions. The common territorial timecurves of the avalanche activity were derive for 11 of 13 mountains areas of CIS beinganalyzed. For Tien Shan and Caucasus the generel tendencies of the long-term variationof avalanche formation was differentiated in more details. For some regions therelationship is established between the avalanche formation and climatic factors (airtemperature, winter precipitation).The tendency to the avalanche activity decrease on thecourse of the last few years, revealed on the basis of the analysis is testified by theindependent observational data.INTRODUCTIONThe problem of studying the long-termvariations of hydrometeorological characteristics, e.g. :precipitation, river flow, avalanche activity and other isof great scientific and practical importance, that is whyit attracts the attention of scientists since the long time.Druzhinin I.P.(l970) determined that sudden change ofthe sun activity is the cause of the turning point of thelong-term trend of numerous natural processes,includingatmospheric circulation and relevant meteorologicalelements.The problems of the long-term variation ofavalanching in former USSR attracted the attention ofsuch scientists as V.I.Turmanina (1970),A.D.Oleinikov(l983),Y.G. Kakurina ( l 987),Y.F.Okolov(l986),Y.M.Sezin (1982) determined the relationshipbetween the avalanche activity and atmosphericcirculation, it may be envisaged also,that avalanchingperiods can be connected with regularity of theatmospheric processes which are mainly determined bythe turning points of sharp variations corresponding toII-years periods. In this regard this work attemptsfollowing the former investigations, to present the long-term variations of avalanche activity on the Europeanterritory of CIS, Caucasus,Kazahkstan, Central Asia,Siberia and Far East.In their trends there weredistinguished the period with the low and high numberof avalanches, comparing with the mean long-termvalues. And there was also revealed the homogeneity ofthe intensity of variations of avalanching in separatenregions. Here it was taken into account that thetendency of the extreme avalanche activuty wasobserved in the years,preceeding sun reference years i.e.,in the years of the change of the sign of the solar activityincrement. This is described in (Kakurina,1987).DATAThe long-term variations of the avalancheactivity were estimated by the data of the areas ofstationary comprehensive avalanche observations. Thelongest data series characterize such areas as Khibins(54 years), Eastern Caucasus (42 years),Western TienShan (34 years). The data series of the majority of thesnow-avalanche stations (SAS) has observational periodless than 20 years(62,4 %), and their data were used onlyfor Siberia and Far East territories. With the purpose ofsynchronous analysis 30-year period of observationsfrom 1960-61 up to 1989-90 was taken as the mostrepresentative one (with the most comprehensiveobservational data). 43 stations were selected fromwhich 17 are on the European territory of CIS andCaucasus, 13 - Kazakhstan and Central Asia and 13 -Siberia and Far East.METHODIn the study of the long-term vanatrons ofdifferent elements the running averaging were used. Theessence of this technique is in the smoothing of theobservations series by averaging through consequentyear periods. One can more clearly imagine the cyclicvariations without any displacement of the interphaselimits between the cycles of the intensive and lowavalanche activity when applying the differentialintegral curves or summarized curves of deviations fromthe mean long-term value (Ed.of & G.P.Kalinin,1967),for the construction of which the continuosobservational series is used. For the calculations of suchcurves f(t)=S(k¡-1 )/Cv,the deviation of moduluscoefficient of chronologie series of the avalanchingoccurence from their mean value (kav-l) wereconsequently symmarized. The distinguishing of theperiods of the intensive and low avalanche activity wasmade on the main turning curve points. The time periodin which k¡",-I >O, corresponds to the phase of increaseof the avalanche activity and the period in which kav-I<O corresponds to its decrease, i.e.,at kav-I = (lk-11l),where Ik is the end coordinate of integral curve, In -the beginning one,n - number of years in the takenperiod. For the determination of general regulaties ofcyclic variations three principal gradations were used:phases of the increased, moderate and decreasedavalanche activity. The detection of these phases wasmade on differential integral curves by the principalturning points.Negligible waves in the change ofavalanche activity caused not by macrosynopticprocesses, but, probably, by local anomalies, were nottaken into account.RESULTThe use of differential integral curves makes itpossible to investigate the cyclic variations of avalancheactivity by the data of snow-avalanche stations ofdifferent regions,i.e. to reveal the degree of phasesynchronity or asynchronity of avalanche formation.For the solution of this problem 3 types of synchronouscurves of avalanche activities were chosen and averagedfrom 13 avalanche prone areas(Khibins,Carpatians,Northern Caucasus,Caucasus,Zailiyskiy Alatau, Tien Shan, Pamir, Altai,Kuznetskiy Alatau, Baikal region, Zabaikalje,N orthEast, Sakhalin Island ). The first type includes the curveswith avalanching decrease phase (14-17 years duration)and avalanching increase phase (15-17 year duration).Such regions as Khibins, Carpatians, Caucasus,somebasins of Tien Shan, North East, Kuznetskiy andZailiyskiy Alatau, Northern Caucasus and SakhalinIsland belong to this type. In the last 4 regions lessqualitative information was used, basing on the limitedactual but restored by the regression equations ofobservational series. The Caucasus region is subdividedinto 2 subregions: Western Caucasus and EasternCaucasus. In the western subregion the phase of theavalanching increase is longer with module coefficientk,= l,n.The second subregion is characterized bysignificanly less duration of this phase (for 3 years) andgreater module coefficient k¡=1,97. It can be supposedthat this is connected with continental nature of theEastern Caucasus climate. The second type includes thecurves where the phase of low avalanching activity is 9-12 years at 15-17 years duration of the increasedavalanche activity. Such regions as Pamir, Zabaikaljeand some basins of Tien Shan belong to this type. Thethird type is characterized by 16 year - period of theincreased avalanching and 8-11 year period of thereduced avalanche activity. Some regions of Tien Shan,Baikal region and Altai belongs to this type. It is to bementioned that for Altai the duration of period of theavalanche activity increasing is limited by theincomplete data series. The most avalanche studied area- the Tien Shan region was differentiated by all 3 curvestypes. Here even within one mountain region like the152Western Tien Shan some snow-avalanche stationsbelong to the l-st type (Kamchik. Naugarzan), the other- to the 2-nd (Angren, Kyzylcha) and some - to the thirdone (Dukant, Oigaing). In a whole, the identification ofmore detailed characteristics of periodical processeswithin one big region can, from one side, testify to thebad availability of statistical sampling, and fromanother side - it demonstrate some sub-genetical effectsof avalanche-formation. However, the snow-avalanchestations, where constructive metamorphizm is moreactive or due to the wind activity growth caused by lowtemperature and insignificant snow cover are mainlyrelated to the first type. It should be noticed the regions,identified before as belonging to the first type, are alsocharacterized by relatively active wind activity,excludingZailiyskiy Alatau. The snow-avalanche stations withsufficiently large snow amount and suppressedconstructive metamorphism are related to the 3-rd type.As for the 2-nd type the avalanching conditions ofAngren and ltagar are nearly the same, but Kyzylcha bythe snow accumulation conditionch and weak windactivity is objectively attributed more to the 3-rdtype,that's why its inclusion into the 2-nd type subregioncan't be explained yet (Table I).Table lDistribut ion oj the longest duration oj diffrentavalanche formation phases (n) and their averagemodule coefficient (KJ,Kl,K3) jar regionsAvalanche formation phasesNg Regions low hight moderateactivity activity activityn I k! n I kz n I koI Khibins 15 0.74 14 1.29 - -2 Carpatians 14 0,76 15 1,28 - -3 Northern 15 0,37 10 1,84 5 1,10Caucasus4 Caucasus I 14 0,22 16 1,71 - -type5 Caucausus 2 15 0,35 13 1,97 - -type6 Zailiyskiy 15 0,56 6 2.06 9 1,02Alatau7 Tien Shan l Il 0,62 16 1,30 l 0,97type8 Tien Shan 2 10 0,38 15 1,49 - -type9 Tien Shan 3 15 0,73 6 1,77 - -type10 Pamir 12 0,55 15 1,35 - -I l Altai Il 0,76 3 1,86 - -12 Kuznetskiy 14 0,40 Il 1,88 3 l,OSAlatau13 Baikal 8 0,62 7 1,44 - -region14 Zabaikalje 9 0,50 17 1,33 - -IS North East 18 0,38 12 1,99 - -16 Sakhalin 17 0.60 8 l,58 - -Average 14 0,53 12 1,63 4 1,03The longer duration of the increase or decreaseavalanche activity is up to 18 years, while the most oftenrecorded duration of the decrease phase of avalancheactivity doesn't exceed 14 years, and of its increase - notmore than 12 years. The shortest period of the suddenincrease of avalanche activity was recorded in 1968-1969in the 3-rd subregion of Tien Shan, which ischaracterized by abnormal increase of avalanche activityobserved along - with the general pattern of itsdecrease.As the analysis of the natural anomalies of thatperiod shows(Aksarin, I973,&Konovalov ,1973) thehydrometeorological cataclysms at this time weredetermined by the intensive development of the northernmeridional processes during 4 months of winter period(1968-1969) and by the formation of blockinganticyclones on the eastern part of European territory ofUSSR, characterized by extreme stability during 2months, which caused the abnormal intensive andextensive precipitation which, in turn, determinedextensive avalanches in the areas, where they were notrecorded before. The interesting result was observed inthe analysis of the territorial distribution of modulecoefficient of the increase and decrease phases of theavalanche activity. It was determined that to the southand east from Khibins the module coefficients of thedecrease phase of avalanche activity drop: Khibins(k,=0,74), Caucasus (k¡=0,3S), Kuznetskiy Alatau(k,=0,40), Tien Shan (k¡=0,S4), Zabaikalje (k¡=O,SO),North East (k¡=0,38); and they increase for the phasesof the increased avalanche activity: Khibins(b= l ,71),Kuznetskiy Alatau (kr= I ,88),Caucasus(b=I,7I), Tien Shan (k2=I,SS), Altai (k2=1,86), NorthEast (kz= 1,98). As it is known, the effect ofconteninentality becomes more manifested in thesouthern and eastern directions which is also reflected inthe module coefficients distribution. The analysis ofdifferential integral curves of avalanche activity hasshown that the starting time,duration and modulecoefficients of the increase and decrease phases ofavalanche activity are different at different stations.N evertheless, despite the individual features of the long-term variations of avalanche activity, in certain regionsthe similar character of these phase beginning wasobserved. The diagramm (Fig. I) was constructed forgetting more clear idea of the spatial distribution of thelong-term variations of avalanche activity. Considerablesimilarity is observed in the change of phase of cyclicvariation of avalanche activity,practically in all regionsexcept Tien Shan and Zabaikalje. Up to the middle of70-s everywhere the phase of weak avalanche activity isobserved, then the phase of its increase follows. In TienShan subregion with the curve of 3-d type the increase ofavalanche activity is noted since 1962 ; in the 2-ndsubregion (2 type) - since 1969; in the 3-rd subregion (Itype)- since 1983. It is like "even transition" of the phaseof the increased avalanche activity from one region intoanother,i.e. the increased avalanche activity in onesubregion is compensated by weak avalanche activity inother two subregions. Synphase change of the avalancheactivity in the distinguished areas are connected with thedirection of the principal air flows, cyclones andanticyclone movement, and, correspondingly, byprecipitation amount and air tempetature. The degree ofthe avalanche danger in winter is determined not onlyby the snow amount or total precipitation; such factors153as precipitation regime and temperature conditions ofthe cold period are also playing significant role(Oleinikov ,1983,1988).Region1234567B9101112131415161960/61 1970/71 1960/61 1990/91 Years_-1 CJ-2 _-3 k::::::1-4Fig.l Diagramm of cyclic variations of the avalancheactivity in mountain regions of CIS] - low activity, 2 - high activity, 3 - moderate activity, 4 -data is absent.For the substantiation of these results the effort wasmade to assess the degree of correlation between theavalanche activity in certain winter periods andprecipitation regime and air temperature of the cold halfyear. As it is show in Table 2, the significance of thiscoefficients is rather high.Table 2Value of correlation coefficients of the relationshipbetween the avalanche activity and totalprecipitation (Kx) and mean winter air temperature(Kt) basen on the data of some snowavalanchestations (SAS) for irregular S-years periodNameSAS Correlation coefficientsKx KtAngren 0,57 0,92Naugarzan 0,71 0,68Severtsov glacier 0,74llagar 0,66Serebryansk 0,68 0,92Luzhba 0,87Ornsukchan 0,76 -The sampled cycles of the long-term vanatrons of theavalanche activity for Tien Shan and Pamir were testedon independent material. The data of observations atthe snow-avalanche stations of different types were usedfor 1990-91 - 1993-94. The tendensy for the avalancheactivity decrease for Tien Shan subregions and itsincrease for Pamir was confirmed, besides in 1990-91 -1991-92 the change of the increase of avalanche activitywas recorded on Pamir, and in 1992-93 and further thedecrease of avalanche activity was recorded as it can beexpected following the choozen phase of definiteduration. Despite the obtained practical effect, it israther untimely to draw the conclusion that every newcycle of the avalanche activity variation is the repetitionof the preceeding one, that is why the forecast of theavalanche activity insensity on the basis of the derivedtendencies is to be further clarified. Nevertheless, thedetermined regularities are not only presented as a basisof independent testing, but they also serve as certainexperimental corroboration of possible long-termvariations of climate as an argument determining anavalanche activity.SUMMARYThe main results can be formulated as follows:- on CIS territory the regions are identified withsynchronous variations of avalanche activity for whichthe longest durations of the phases of low, moderate andhigh avalanche activity are estimated;- for different CIS regions the tendency was defined forthe correlation between the long-term change of weatherconditions and temporal indices of avalanche formationintensity, which, mainly have regional character;- on the basis of the carried out investigations one cansuppose that the indices of the avalanche activityintensity are functionally related to the continentalcharacter of the conditions,because the modulecoefficients become lower with the increase ofcontinentality degree.ACKNOWLEDGEMENTSThe authors express their thanks to the staff ofthe CIS Glavgidromets who provided themeteorological and snow-avalanche data.REFERENCESl. Aksarin N.N.(1973). The techniques for the long-term forecasting of the river flow and precipitationfor the Central Asia territory by the integral index ofatmospheric circulation.Proceed. of SARNIGMI,vo1.3(84),p.5l1542. Aksarin N.N.,Abramenkov N.N.,KonovalovV.G.(1973).The analysis of the spatial and temporalvariations of the meteorological factors of runoff inSyrdarja river basin during an extremely wetyears.Proceed. of SARNIGMI,voI.3(81),p.2-50.3. Avalanche geography.(1992).Edited byS.M.Myagkov, L.A.Kanaev. Published by MoscowUniversity,M.,p.140-298.4. Druzhinin I.P.(l970). The changes of the long-termtrend of the natural processes on the Earth andsudden changes of solar activity.Geographical issues,collection 79,"Mysl"Publishing house,M.,p.15-50.5. Izhboldina V.A(l975).Aerosynoptical conditions ofthe formation and avalanching of the snow driftavalanches on Kolskiy peninsula.Snow andavalanche studies in Khibins.L.,p.51-63.6. Kakurina Y.G.(l987).The results of the analysis ofthe temporal variations of avalanche activity on theUSSR territory based on the Inventory of USSRavalanches.Proceed.of 2-nd all Union Conference onavalanches.L.,Gidrometeoizdat,p.124-130.7. The long-term variations of runoff and probabilitytechniques of it's calculation (1967) .Edited byV.D.Bykov, G.P.Kalinin. Published by MoscowUniversity,M.,278 p.8. Okolov V.F.(l986).The relationship between theavalanche activity and atmosphericcircualtion.Published by Moscow University,M., 14p.9. Oleinikov AD.(l983).Types of winters and characterof the avalanche activity. MGI, vo1.47, p.98-l03.10.Oleinikov AD.(1988).The winters with the highestdegree of avalanche danger in Elbrus area. MGr.Vol.64, p.106-ll0.ll. Sezin V.M.(1982) Synoptic conditions for snowavalanche events in the mountains of the WesternTien Shan.MGI,voI.42,p.94-l OO.12.Turmanina V.I.The effect of intrasecular rythms ofwetting on vegetation. Geographical issues.Collection 79."Mysl"Publishing House, M., 1970,p.168-l81.* MGI - Data of Glaciological Studies

Some results of long-term variability of avalanche activity of CIS mountains

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Some results of long-term variability of avalanche activity of CIS mountains

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