Study of changes in the regime of atmospheric precipitation in the Central Northern Caucasus

Results of statistical analysis of changes in the precipitation regime in the steppe and foothill climatic zones of the Central Northern Caucasus from the data of five weather stations for 1955–2004 on precipitation amount, its diurnal maximum, number of days with precipitation amount of 5 mm or more in different seasons of the year are considered.     

Long-term variations of elements of hydrometeorological regime of the Rybinsk Reservoir

Variations of hydrometeorological variables of the Rybinsk Reservoir area from 1947 to 2005 are analyzed. A special attention is given to the global warming period started since 1976. It is shown that the intensity of air temperature increase on the reservoir shore during recent 30 years made up 0.46–0.56°C/10 years. The maximum increase in the water temperature at shore stations and in the surface layer was registered in July at an increase rate of 0.7–1.2°C/10 years. The change in climate conditions resulted in the increase in low-water runoff, decrease in snowmelt flood volumes, and shift in the time of snowmelt flood start.     

Spatial and temporal variations of thunderstorm activity in the Northern Caucasus

Space distribution is considered of thunderstorm activity in Northern Caucasus during 1936–2006. Area distribution is presented of numbers of days with thunderstorm and of thunderstorm duration. Time variations are analyzed of mean numbers of the days with thunderstorms and of the thunderstorm mean duration, which probably represent a part of climate changes at the area under consideration. The largest variations of thunderstorm activity occur in the western part of the Northern Caucasus, where annual number of the days with thunderstorms reaches 70. Minimum changes in the thunderstorm characteristics occur in the eastern part of the area, with annual number of the days with thunderstorms equal to 25.     

Long-term variations of wind regime in the free atmosphere over the European territory of Russia

The time series of seasonal average values and standard deviations of wind speed components at the isobaric surfaces of 850 and 200 hPa are analyzed on the basis of the data of upper-air observations carried out in 1961–2003 at 18 stations of the Russian Federation territory. The energy spectra of wind speed components in the first and in the second halves of the whole period under study are compared. On the whole, an increase in average values of U-component and decrease in average values of V-component took place both in upper and lower troposphere, and the largest variations occurred in winter season in the upper troposphere. Average coefficients of linear trends of average winter values for the whole region amount to 0.57 and ?0.62 m/s per 10 years for the wind components U and V at the isobaric surface of 200 hPa, respectively. The increase in the standard deviations of both components was registered in the upper troposphere in winter period almost on the whole territory. The average coefficients of linear trends of standard deviations at the isobaric surface of 200 hPa in winter for the whole region amount to 0.53 and 0.61 m/s per 10 years for U- and V-components, respectively. The intensity of the annual cycle and processes of intraseasonal scale both in the lower and upper troposphere increased in the second half of the whole interval under study.     

Human implication of changes in the hydrological regime due to climate change in Northern Greece

This paper examines the impacts of climate change on various forms of water resources and on some critical water management issues. The study area is the Aliakmon river basin including three subbasins of hydrological interest located in northern Greece. A monthly conceptual water balance model was calibrated for each subbasin separately, using historical hydrometeorological data. This model was applied to estimate runoff values at the outlet of each subbasin under different climate change scenarios. Two equilibrium scenarios (UKHI, CCC) referring to years 2020, 2050 and 2100 and one transient scenario (UKTR) referring to years 2032 and 2080 were implied. It was found that reduction of the mean annual runoff and mean winter runoff values, as well as serious reduction of the summer runoff values would occur in all cases and basins. However, the runoff values for November, December and January were increased, whereas the spring runoff values were decreased, leading to a shifting of the wet period towards December and severe prolongation of the dry period. Moreover, the results indicate that all subbasins exhibit almost the same behavior under the different climate change scenarios, while the equilibrium scenarios (UKHI, CCC) seem to give more reasonable and consistent results than the transient scenario (UKTR). Finally, the negative effects of the climatically induced changes on the hydroelectric production and the water use for agricultural purposes in the study basin were assessed.     

Estimating the level of territory vulnerability and climate-related risk of significant grain crop failure in grain-producing regions of Russia

A term ofclimate-related risk ofcrop losses due to adverse hydrometeorological conditions is introduced. The level of territory vulnerability in terms ofcrop production is defined by the relationship between the yield of a given crop and the bioclimatic potential of a territory. The estimates of vulnerability and crop failure risks for some grain crops are presented for the period of 1994–2013. Average for Russia crop failure risk for spring and winter wheat computed taking into account the cultivated areas is 12.5 and 10.6%, respectively. It is revealed that the most parts of the Southern and Volga federal districts are located in the high-risk zone. Areas ofrelatively low risks in terms ofcrop failure for spring and winter wheat are the Siberian and Central federal districts.     

On the role of hydrometeorological factors in formation of the valley-type reservoir anoxic zone

Based on the multiyear researches of the Mozhaisk reservoir oxygen regime and methods of mathematical modeling, dependence of the anoxic zone formation rate on the hydrometeorological factors was studied. These factors define a degree of the water mass stratification and intensity of the production and degradation processes and, hence, the anoxia development rate.     

Dangerous fogs on the territory of Georgia

The statistical structure of dangerous fogs with the visibility of less than 50 m is studied using the observation data of 50 meteorological stations in Georgia for the period of 1961–2006. The contribution of dangerous fogs to the total number of foggy days is estimated. The number of days with dangerous fogs and their duration in different regions of the country are determined and the empirical functions of their distribution, sizes of areas of their expansion, temperature regime, and peculiarities of annual variations are studied.     

Hurricane winds on the territory of Georgia

The statistical structure of hurricane winds is studied using the data of observation at 50 meteorological stations in Georgia for the period of 1961–2008. Determined are the number of days and the duration of hurricane winds in different regions of the country. Studied are the empirical functions of their distribution and the areal limits.     

The effect of an arctic polynya on the Northern Hemisphere mean circulation and eddy regime: a numerical experiment

The feedback of an arctic polynya, which is a large ice-free zone within the sea ice, on the hemispheric climate is studied with the ECMWF T21 GCM. For this purpose a control and an anomaly integration, in which a polynya was introduced in the Kara Sea, are compared. As the GCM, like the real atmosphere, shows a high level of low frequency variability, the mean response to the changed boundary conditions is obscured by internal noise. The necessary significance analyses are thus performed to enhance the signal-tonoise ratio within the framework of an a priori chosen guess pattern and a multivariate test statistic. The sensible and latent heat fluxes increased above the polynya, which resulted in a warming of the lower troposphere above and near the polynya. No statistically significant local or global sea-level pressure changes are associated with this heating. However we find a significant change of hemispheric extent of the geopotential fields at 300 hPa, if we use as guess patterns the eigenmodes of the barotropic vorticity equation. The different mean flow field is accompanied by significant changes of the synoptic transient eddy field. We find a significant variation in the barotropic and baroclinic forcing of the mean flow by the eddies, a change in the location and intensity of the storm tracks and in the conversion between eddy available and eddy kinetic energy. The additional heat flux from the polynya results in a reduction of the meridional heat flux by the synoptic eddies on the western Atlantic.     

Statistical analysis of hydrometeorological characteristics in extreme winters in the northeastern part of the Black Sea

Analyzed are the similarities and differences in the processes of intraseasonal variability of wind conditions in extremely cold and extremely warm real winter seasons 1953/54 and 1965/66. Revealed is the significance of the contribution of calm pauses to the formation mechanism of seasonal characteristics on the whole and, to much greater degree, to the determination of the properties of weather windows. Emphasized is a role of calm pauses as the indicators of weather windows. Studies is the possibility of estimating the severity of winter conditions using a set o characteristics of initial ten-day periods of winter season within the arbitrary annual cycle.     

Application of numerical weather prediction techniques in the operational routine of the hydrometeorological service of the USSR

The purpose of the present paper is to review the application of numerical weather prediction techniques in the daily operational routine of the Hydrometeorological Service of the USSR. The theoretical aspects of numerical weather prediction models used have been discussed by the authors in original papers and will not, therefore, be repeated here.     

Medium-range forecasts of large ice cover discontinuities for hydrometeorological support of navigation in the Arctic basin

A brief characteristic of the Arctic ice cover discontinuities (ICD) is given. Their practical importance for vessels operating in this region as well as necessity of forecasting such indicators as the prevailing disposition of discontinuities and location of zones of their formation and closure are noted. The forecasting technique is based on the method of complex analogs. A summary of forecasts produced for the Arctic navigation areas since 1991 is provided. It is shown, that recent upgrading of the original methodology allowed to produce forecasts in on-line mode, to present digital maps of the forecast data, and to transfer them directly to the vessel’s automated workplace. A number of practical examples are presented for illustrating the navigation efficiency if forecast and actual ICD data are used. The results of forecast verification are given.     

Computation and prediction of the flood runoff of the Eastern Caucasus rivers

Analysis of observational data of the average monthly discharges, air temperatures, and precipitation totals collected at about 100 hydrological and meteorological stations before 2005 revealed that precipitation fallen on the Eastern Caucasus river basins in winter and spring plays the principal role in formation of floods that are observed in the period from April to June. The precipitation and runoff variability over the territory and altitudinal zones was studied and generalized. The hydrograph decomposition and the rivers classification according to their sources of feeding in the flooding period were performed. Analysis of correlation between the flood flow and winter and spring precipitation allowed obtaining reliable multiple regression equations that are suitable for computation and forecasting of the flood flow.     

Climate dynamics of glaciers of the Greater Caucasus for the 20th century

The dynamics of frequency of warm and cold months for warm and cold periods of the year on the whole as well as for the ablation period is studied for glaciers of the Greater Caucasus based on the analysis of maps on anomalies of monthly mean air temperatures for the 1901–2000 period. A relation between the change in frequency of temperature anomalies and the glaciation area is established.     

A hydrometeorological analysis of the severe rainstorm of 20–22 September 1900 over the Gangetic West Bengal

A hydrometeorological study is made of the September, 1900 severe rainstorm which led up to the record rain-falls over Gangetic West Bengal with subsequent disastrous flooding in the Damodar and the Hooghly rivers. The spatial extent of the rainstorm for different durations has been examined by constructing the isohyetal patterns based on rainfall records of stations affected by the storm. Areal rainfalls for 1,2 and 3-day periods are calculated and the values have been compared with similar values from other major rainstorms of the region. The comparison revealed that the September, 1900 rainstorm was the heaviest for 1,2 and 3-day durations for all the areas. The storm contrib-uted rainfalls of 33.0 cm, 52.0 cm and 62.0 cm over an area of 10,000 km2 in 1,2 and 3 days respectively. This rainstorm could, therefore, be considered as an important input in flood and design storm studies in the Gangetic West Bengal region. A relationship between point to areal rainfall has also been developed with a view to evaluate areal PMP estimates.     

北半球100 hPa等压面经向风与臭氧总量年变化

本文用多年平均的北半球100hPa经向风和臭氧总量资料分析了两者的关系,结果发现:臭氧总量的变化与100 hPa经向风密切相关,与100 hPa面上北风相对应的是臭氧高值区,与南风对应的是低值区,前者支配后者.充分说明了臭氧总量变化主要受低层平流层环流影响.     

基于高空与地面观测的阿克苏河流域气候水文要素变化分析

本研究基于地面和高空资料,分析了阿克苏河流域1960—2015年的气候和水文变化特征,并探讨了高空气候变量在径流反演中的作用。结果表明,在全球变化背景下,阿克苏河流域地表温度呈显著升高趋势,线性倾向率为0.18℃/10a（-0.09~0.43℃/10a);流域降水总体呈增加趋势,增加速率为10.42 mm/10a（2.23~21.11 mm/10a)。阿拉木图、伊宁和库车3个高空探测站的0℃层高度总体呈上升趋势。相对于1960—1989年,1990—2015年3个站的0℃层高度分别增加了88.9 m、29.4 m和7.2 m。联合使用地面气温、降水和高空0°层高度资料,能显著提高阿克苏河流域夏季流量反演效果。     

Reconstruction of hydrometeorological time series and its uncertainties for the Kaidu River Basin using multiple data sources

This paper tried to reconstruct the time series (TS) of monthly average temperature (MAT), monthly accumulated precipitation (MAP), and monthly accumulated runoff (MAR) during 1901–1960 in the Kaidu River Basin using the Delta method and the three-layered feed forward neural network with backpropagation algorithm (TLBP-FFNN) model. Uncertainties in the reconstruction of hydrometeorological parameters were also discussed. Available monthly observed hydrometeorological data covering the period 1961–2000 from the Kaidu River Basin, the monthly observed meteorological data from three stations in Central Asia, monthly grid climatic data from the Climatic Research Unit (CRU), and Coupled Model Intercomparison Project Phase 3 (CMIP3) dataset covering the period 1901–2000 were used for the reconstruction. It was found that the Delta method performed very well for calibrated and verified MAT in the Kaidu River Basin based on the monthly observed meteorological data from Central Asia, the monthly grid climatic data from CRU, and the CMIP3 dataset from 1961 to 2000. Although calibration and verification of MAP did not perform as well as MAT, MAP at Bayinbuluke station, an alpine meteorological station, showed a satisfactory result based on the data from CRU and CMIP3, indicating that the Delta method can be applied to reconstruct MAT in the Kaidu River Basin on the basis of the selected three data sources and MAP in the mountain area based on CRU and CMIP3. MAR at Dashankou station, a hydrological gauge station on the verge of the Tianshan Mountains, from 1961 to 2000 was well calibrated and verified using the TLBP-FFNN model with structure (8,1,1) by taking MAT and MAP of four meteorological stations from observation; CRU and CMIP3 data, respectively, as inputs; and the model was expanded to reconstruct TS during 1901–1960. While the characteristics of annual periodicity were depicted well by the TS of MAT, MAP, and MAR reconstructed over the target stations during the period 1901–1960, different high frequency signals were captured also. The annual average temperature (AAT) show a significant increasing trend during the 20th century, but annual accumulated precipitation (AAP) and annual accumulated runoff (AAR) do not. Although some uncertainties exist in the hydrometeorological reconstruction, this work should provide a viable reference for studying long-term change of climate and water resources as well as risk assessment of flood and drought in the Kaidu River Basin, a region of fast economic development.