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1.
Despite the potential impact of winter soil water movements in cold regions, relatively few field studies have investigated cold‐season hydrological processes that occur before spring‐onset of snowmelt infiltration. The contribution of soil water fluxes in winter to the annual water balance was evaluated over 5 years of field observations at an agricultural field in Tokachi, Hokkaido, Japan. In two of the winters, soil frost reached a maximum depth of 0·2 m (‘frozen’ winters), whereas soil frost was mostly absent during the remaining three winters (‘unfrozen’ winters). Significant infiltration of winter snowmelt water, to a depth exceeding 1·0 m, occurred during both frozen and unfrozen winters. Such infiltration ranged between 126 and 255 mm, representing 28–51% of total annual soil water fluxes. During frozen winters, a substantial quantity of water (ca 40 mm) was drawn from deeper layers into the 0–0·2 m topsoil layer when this froze. Under such conditions, the progression and regression of the freezing front, regulated by the thickness of snow cover, controlled the quantity of soil water flux below the frozen layer. During unfrozen winters, 13–62 mm of water infiltrated to a depth of 0·2 m, before the spring snowmelt. These results indicate the importance of correctly evaluating winter soil water movement in cold regions. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

2.
Winter conditions play an important role for the largest lake in Europe—Lake Ladoga. The ice cover lasts for 171 ± 3 days on average from the early November until the mid‐May. We investigated the ice regime of Lake Ladoga using a constructed ice database of aircraft surveys and satellite images. More than 1250 surveys of the lake's ice cover from 1943 to 2010 were collected and analysed to determine mean and extreme ice conditions for winters of different types of severity. The time series of ice cover percentage over the lake was plotted. On average, 18 observational ice charts were made every winter. Individual ice phenology records show considerable year‐to‐year variation. For this reason, records typically have been combined and analysed as groups (categories). Extremely cold winters were determined as winters with complete ice cover that lasts more than three months which is approximately 90% quartiles from all winters with complete ice cover. The lake surface was completely covered with ice for more than three months during 5 seasons. Extremely warm winters when the maximum ice cover was less than 70% of the lake area occurred during 5 seasons as well. A basic relationship between the winter severity as winter maximum of accumulated freezing degree‐days (AFDD) and the earlier derived Relative Ice Cover Index (RICI) was established. We have used teleconnection indices such as North Atlantic Oscillations (NAO) and Arctic Oscillation (AO) for the period from October to May for estimation of different types of Lake Ladoga's ice conditions. The AO index in winter months and local winter maximum of AFDD explained much of the interannual variation in ice cover. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

3.
The literature relevant to how solar variability influences climate is vast—but much has been based on inadequate statistics and non-robust procedures. The common pitfalls are outlined in this review. The best estimates of the solar influence on the global mean air surface temperature show relatively small effects, compared with the response to anthropogenic changes (and broadly in line with their respective radiative forcings). However, the situation is more interesting when one looks at regional and season variations around the global means. In particular, recent research indicates that winters in Eurasia may have some dependence on the Sun, with more cold winters occurring when the solar activity is low. Advances in modelling “top-down” mechanisms, whereby stratospheric changes influence the underlying troposphere, offer promising explanations of the observed phenomena. In contrast, the suggested modulation of low-altitude clouds by galactic cosmic rays provides an increasingly inadequate explanation of observations.  相似文献   

4.
Seven winters of analyses and forecasts from the operational archives of the European Centre for Medium Range Weather Forecast had been previously analyzed to assess the performance of the model in forecasting blocking events. This work updates some of this previous diagnostic work to the last five winters, from 1987/88 to 1991/92. The data set therefore covers all winter seasons (DJF) from 1980/81 to 1991/92, and consists of daily northern hemisphere 500 hPa geopotential height analyses and of the ten corresponding forecasts verifying on the same day (“Lorenz data”). Local blocking and sector blocking have been defined, using different modifications of the original Lejenas and Økland index. The comparison between the first seven and the last five winters, within the restrictions imposed by limited length of the data set, suggests a much improved situation as far as model climatology of blocking is concerned, especially over the Euro-Atlantic region. Operational predictability of blocking as an initial value problem is also shown to be measurably improved, in both Atlantic and Pacific sectors. All such improvements are shown to have taken place together with a considerable reduction of the model systematic error. Nevertheless, forecasting blocking in the medium range remains a difficult task for the model. More work is needed to understand whether the improvements are to be ascribed to the increased model resolution or to better physical parametrisations.  相似文献   

5.
Afroosa  M.  Rohith  B.  Paul  Arya  Durand  Fabien  Bourdallé-Badie  Romain  Joseph  Sudheer  Prerna  S.  Shenoi  S. S. C. 《Ocean Dynamics》2022,72(7):523-538
Ocean Dynamics - An intraseasonal see-saw has been observed in the Indo-Pacific barotropic sea level anomaly during boreal winters. This see-saw carries a significant amount of energy and is...  相似文献   

6.
All existing data (6 years) on gravity wave activity, inferred from the nighttime A3 (oblique incidence on the ionosphere) radio wave absorption measurements in the lower ionosphere on 270 kHz at Prhonice in Central Europe, have been exploited to get information on the effects of QBO phases and the Mt. Pinatubo volcanic eruption on the gravity wave activity in the winter half of the year. There appears to be an enhancement of gravity wave activity in the two winters just after the strong volcanic eruption of Mt. Pinatubo. This enhancement is remarkable for long-period waves (T=2–3 hours). No clear effect of the phase of QBO on the level of gravity wave activity has been found; a possible effect of QBO on the correlations between gravity wave activities in individual period bands is indicated. The results are limited by a relatively short data series; however, no more data will he available.  相似文献   

7.
A three-dimensional transport model has been used to compare and contrast the extent of processing by polar stratospheric clouds during the northern hemisphere winters of 1991/1992 and 1992/1993. The model has also been used to compare the potential for ozone loss between these two winters. The TOMCAT off-line model is forced using meteorological analyses from the ECMWF. During winter 1992/1993 polar stratospheric clouds (PSCs) in the model persisted into late February/early March, which is much later than in 1991/1992. This persistence of PSCs should have resulted in much more ozone loss in the later winter. Interestingly, however, the extent of PSC processing and ozone loss was greater in January 1992 than January 1993. In January 1992 PSCs occurred at the edge of a distorted polar vortex whilst in January 1993 the PSCs were located at the centre of a much more zonally symmetrical vortex. In March 1993, distortions of the vortex led to the tearing off of vortex air and its mixing into midlatitudes.  相似文献   

8.
Geomagnetism and Aeronomy - The results of microwave radiometry studies of the ozone-content dynamics in the middle atmosphere above Peterhof during stratospheric warmings of two winters,...  相似文献   

9.
Summary The results of the winter anomaly observations at the Panská Ves Observatory on 2775 kHz and 2614 kHz (A3 method, feq1 and 0.8 MHz) are studied for the winters of 1971/72 and 1972/73. Ionospheric responses to minor (1972) and major stratospheric warmings are found to be different and relatively small. A regular winter-anomaly background absorption increase with a maximum in January was observed during both winters studied. Magnetic storms are found to play an insignificant, if any, role in the winter-anomaly phenomenon. The relation between magnetic activity and ionospheric absorption seems to be better in non-anomalous periods.  相似文献   

10.
Air quality has been deteriorated seriously in urban areas as a result of increasing anthropogenic activities. Meteorological conditions affect air pollution levels in the urban atmosphere significantly due to their important role in transport and dilution of the pollutants. This paper aims to investigate usability of some promising statistical methods for examining the impacts of metrological factors on SO2 and PM10 levels. Data were collected from city centre of Kocaeli in winter periods from 2007 to 2010 as pollutant concentrations increase in winters due to expanding combustion facilities. Results of bivariate correlation analysis showed that humidity and rainfall have remarkable negative correlations with the pollutants. Multiple linear regression models and artificial neural network (ANN) models were used to predict next day's PM10 and SO2 levels. In regression models calculated R2 values were 0.89 and 0.75 for PM10 and SO2, respectively. Among the various architectures, single layer networks provided better performance in ANN applications. Highest R2 values were obtained as 0.89 and 0.69 for PM10 and SO2, respectively, by using appropriate networks.  相似文献   

11.
Effects of Arctic Sea Ice Decline on Weather and Climate: A Review   总被引：7，自引：0，他引：7  
The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction in sea ice cover has increased the heat flux from the ocean to atmosphere in autumn and early winter. This has locally increased air temperature, moisture, and cloud cover and reduced the static stability in the lower troposphere. Several studies based on observations, atmospheric reanalyses, and model experiments suggest that the sea ice decline, together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the North Atlantic Oscillation and Arctic Oscillation. The suggested large-scale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western and a low over the eastern North America have also been suggested, favouring advection of Arctic air masses to North America. Mid-latitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions. Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half of the twenty-first century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia.  相似文献   

12.
The unsteady-state process of deep-water convection in the Gulf of Lion has been observed and investigated in recent decades. However, the mechanisms of the uncertainty and irregularity of the deep-water convection in this region have not yet been fully understood. In this study, the effects of time variation of the surface buoyancy flux on the formation of the deep-water convection are examined. Numerical simulations using the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) with the NRL Coastal Ocean Model (NCOM) as an oceanic component were conducted for the period from October 1998 to September 2000 to cover two winters, 1998–1999 and 1999–2000, over the Gulf of Lion region. The results show large differences in the deep-water convection between the two winters, even though the total surface heat fluxes during the two winter seasons are similar. The differences are related to the time variation of the surface buoyancy flux that causes large differences in the preconditioning and mixing stages of the convection.  相似文献   

13.
Comprehensive fog field observations were conducted during the winters of 2006–2009 at the Nanjing University of Information Science and Technology to study the macro and micro-physical structures and the physical–chemical processes of dense fogs in the area. The observations included features of the fog boundary layer, characteristics of fog water, the particle spectrum, the chemical composition of atmospheric aerosols, radiation and heat components, turbulence, meteorological elements (air temperature, pressure, wind speed, wind direction), and environmental monitoring. The fogs observed were divided into four types: radiation fog, advection–radiation fog, advection fog, and precipitation fog, according to the mechanisms and primary factors of the fog processes. Fog boundary-layer structures of different types and their corresponding characteristics were then studied. Fog boundary-layer features, temperature structures, wind fields, and fog maintenance are discussed. The results show that radiation fog had remarkable diurnal variation and formed mostly at sunset or midnight, and lifted after sunrise or at noon, and that advection–radiation fog and advection fog were of very long duration. Extremely dense fogs occurred only in radiation-related cases. Inversion in radiation fog was short-lived, disappearing 1 or 2 hours after sunrise or at noon, faster than that in advection–radiation fog. When wind direction reversed from easterly to westerly or from southerly to northerly, the fog became an extremely dense fog. Low-level jet at times impeded fog development, whereas at other times it encouraged fog continuance. The deep inversion was merely an essential condition for a thick fog layer; sufficient vapor supply was advantageous to the formation and maintenance of a deep fog layer.  相似文献   

14.
The high-precision observational data on water temperature obtained during seven winters in a small boreal lake are considered. The spectral analysis revealed that the oscillations with a period of about 27 min prevailed in a water column. This period is close to the theoretical estimate of the first mode of the longitudinal barotropic seiche. The variability of temperature oscillations, vertical velocity, and displacement of isotherms suggest the presence of short internal waves along with seiches. The amplitude of the internal waves is an order of magnitude greater than that of seiches, and the length of internal waves is two orders of magnitude less than the linear extent of the lake.  相似文献   

15.
A northern hemisphere thermodynamic climate model is used to compute the effect of the insolation anomalies due to orbital variations in the climates for the next 4000 years. Bergers mean monthly anomalies of insolation are used in the computations, which are carried out for 1000, 2000, 3000 and 4000 years after present (kyears AP). The numerical simulations show that in the climates of the next 4000 years, due to the effect of the orbital variations, springs and summers will be increasingly dryer and falls and winters wetter than the present climate.  相似文献   

16.
北极海冰的急剧消融在近年来欧亚大陆频发的低温事件中扮演着关键角色.秋季北极海冰的偏少对应着冬季欧亚大陆的低温天气,然而二者的联系在年代际和年际两种时间尺度上存在显著区别.本文运用1979—2012年哈德莱中心第一套海冰覆盖率(HadISST1)、欧洲中心(ERA_Interim)的2m温度、风场、海平面气压场、高度场等资料,分别研究了年代际和年际时间尺度上前期秋季北极海冰与欧亚冬季气温的联系.结果表明,欧亚和北极地区(0°—160°E,15°N—90°N)的冬季气温具有显著的年代际和年际变化.在年代际尺度上,温度异常分布在21世纪初由北极冷-大陆暖转为北极暖-大陆冷.这一年代际转折与前期秋季整个北极地区的海冰年代际减少联系密切.秋季北极全区海冰年代际偏少对应冬季欧亚大陆中高纬地区的高压异常,有利于北大西洋的暖湿气流北上和北极的冷空气南侵,造成北极暖-大陆冷的温度分布;在年际时间尺度上,温度异常分布主要由第一模态的年际变化部分和第二模态组成,且第一模态包含的年际变率信号也存在显著的年代际变化.年际尺度上全区北极海冰对欧亚冬季气温的影响远不及位于北冰洋西南边缘的巴伦支海、喀拉海和拉普捷夫海西部(30°E—120°E,75°N—85°N)的关键区海冰影响显著.关键区内海冰的偏少会引发冬季的北大西洋涛动负位相,导致北大西洋吹往欧亚大陆的暖湿气流减弱和欧亚大陆中高纬地区的气温偏低.  相似文献   

17.
Uruguay has stimulated the development of its forest sector since the promulgation of Forest Law N° 15 939 in December of 1987. Nevertheless, the substitution of natural grasslands with forest plantations for industrial use has raised concerns regarding hydrological processes of groundwater recharge and water consumption involving evapotranspiration. The purpose of this study is to assess the effects of this substitution approach on water resources. Input data were collected from two small experimental watersheds of roughly 100–200 hectares located in western Uruguay. The watersheds are characterized by Eucalyptus Globulus ssp. Maidenni and natural grasslands for cattle use. Total rainfall, stream discharge, rainfall redistribution, soil water content and groundwater level data were collected. Groundwater recharge was estimated from water table fluctuations and from groundwater contributions to base flows. Seasonal and annual water budgets were computed from October of 2006 to September of 2014 to evaluate changes in the hydrological processes. The data show a decrease in annual specific discharge of roughly 17% for mean hydrological years and no conclusive effects on annual groundwater recharge in the forested watershed relative to the reference pasture watershed. Reduced annual specific discharge is equivalent to the mean annual interception. The computed actual annual evapotranspiration is consistent with international catchment measurements. Reduction rates vary seasonally and according to accumulated rainfall and its temporary distribution. The degree of specific discharge decline is particularly high for drier autumns and winters (32 to 28%) when the corresponding rainfall varies from 275 to 400 mm. These results are of relevance for water resources management efforts, as water uses downstream can be affected. These findings, based on a study period dominated by anomalous wet springs and summers and by dry autumns and winters, oppose earlier results based on 34 years of rainfall and discharge data drawn from Uruguayan large basins. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

18.
The distribution of controlling pressure formations, occurring in the Northern Hemisphere during the winters (January and February) of the years 1952 – 1996, has been analysed. It was found that the deepening of the Icelandic and Aleutian pressure lows is connected not only with a particular QBO phase and level of geomagnetic activity (Bochníek et al., 1999) but also with a particular level of solar activity.  相似文献   

19.
Zusammenfassung Die aus der Erfahrung gewonnene Kenntnis vom unmittelbaren Zusammenhang zwischen dem Wettergeschehen und der Vereisung der Meere führte dazu, in der vorliegenden Arbeit, welche sich mit der Dauer des Abschmelzvorganges an den deutschen Küsten befa?t, die Lufttemperatur als eisbildenden Faktor heranzuziehen. Es wurden daher unter der Abschmelzzeit des Eises die Tage mit nichtnegativem Tagesmittel der Lufttemperatur verstanden, welche am Winterausgang beim Einsatz von Tauwetter verstreichen, bis das letzte Eis verschwunden ist. Nach Aufspaltung des Materials in normale und eisreiche Winter wurde dann für die einzelnen Eisbeobachtungsgebiete an den deutschen Küsten aus einer Reihe von Jahren eine mittlere Abschmelzzeit des Eises bestimmt und die Ergebnisse in Karten eingetragen. — Die verschieden lange Dauer des Abschmelzvorganges in der Nordsee und Ostsee ist zu einem gro?en Teil klimatologisch bedingt, zum anderen ist aber die L?nge der Abschmelzzeit von solchen Faktoren stark abh?ngig, die sich aus dem Unterschied Randmeer-Binnenmeer ergeben. Kleinr?umige Unterschiede innerhalb der beiden Meere sind meist die Folge von unterschiedlichen morphologischen und hydrographischen Verh?ltnissen. In normalen und eisreichen Wintern verhalten sich die Eisbeobachtungsgebiete der Nordsee sehr ?hnlich, jedoch weichen in der Ostsee die Werte stark voneinander ab; dieses ist bedingt durch die ausgedehnten Eisfl?chen auf offener See in eisreichen Wintern.
The melting time of the ice on the German coasts between the rivers Ems and Oder
Summary Proceeding from the experiences about the direct influence of weather conditions on ice conditions at sea, in the following paper the air temperature is dealt with as ice producing factor. Therefore the melting time of the ice is defined as the number of days with a non-negative diurnal mean air temperature which after thawing has definitely set in at the end of the winter, has elapsed until the disappearance of the last ice. After dividing the observations into two groups, viz. normal winters and winters rich in ice, from a number of years a mean melting time of ice was determined for the ice reporting areas on the German coasts, and the results plotted on charts. — The different duration of the melting process in the North Sea and the Baltic is mostly due to climatic differences, moreover, the length of the melting time depends to a large degree on the factors that result from the differences between marginal and landlocked seas. Local differences within both areas are mainly the result of different morphological and hydrographical conditions. In normal winters and in winters rich in ice the observation areas show almost similar conditions throughout the coastal regions of the North Sea. In the Baltic, however, the values greatly differ owing to the extensive ice fields in the open sea during the winters of the second group.
La durée du dégel des glaces sur les c?tes allemandes entre les fleuves Ems et Oder
Résumé Partant de l'expérience que les conditions du temps influencent immédiatement la formation des glaces en mer, l'article actuel traite la température de l'air du point de vue de sa qualité productive en formant des glaces. Par conséquent, on comprend comme durée du dégel le nombre de jours avec une température moyenne de l'air non-négative qui passe vers la fin de l'hiver depuis le commencement de la fusion des glaces jusqu'à la disparation des derniers restes des glaces. Après avoir divisé les observations en deux groupes, c'est à dire en hivers normaux et en hivers abondant en glaces, une moyenne de la durée du dégel est déduite des observations de plusieurs années dans les régions d'observations sur les c?tes allemandes; les résultats en sont dessinés sur deux cartes. Le fait que la durée du dégel des glaces est plus courte sur la mer du Nord qu'elle n'est sur la mer Baltique est d'une part d? aux différences climatiques et dépend d'autre part de tels facteurs qui résultent des différences dominantes entre des mers secondaires et des eaux continentales. Les différences locales en dedans de ces deux régions sont presque toujours causées par des différences en conditions morphologiques et hydrographiques. Sur les c?tes allemandes de la mer du Nord les régions d'observation sont d'un caractère a peu près homogène tandis que la mer Baltique est caractérisée à cet égard par de grandes différences qui sont d?es aux champs étendus des glaces sur la haute mer.
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20.
Warm winters and high precipitation in north-eastern Japan generate snow covers of more than three meters depth and densities of up to 0.55 g cm−3. Under these conditions, rain/snow ratio and snowmelt have increased significantly in the last decade under increasing warm winters. This study aims at understanding the effect of rain-on-snow and snowmelt on soil moisture under thick snow covers in mid-winter, taking into account that snowmelt in spring is an important source of water for forests and agriculture. The study combines three components of the Hydrosphere (precipitation, snow cover and soil moisture) in order to trace water mobility in winter, since soil temperatures remained positive in winter at nearly 0.3°C. The results showed that soil moisture increased after snowmelt and especially after rain-on-snow events in mid-winter 2018/2019. Rain-on-snow events were firstly buffered by fresh snow, increasing the snow water equivalent (SWE), followed by water soil infiltration once the water storage capacity of the snowpack was reached. The largest increase of soil moisture was 2.35 vol%. Early snowmelt increased soil moisture with rates between 0.02 and 0.035 vol% hr−1 while, rain-on-snow events infiltrated snow and soil faster than snowmelt and resulted in rates of up to 1.06 vol% hr−1. These results showed the strong connection of rain, snow and soil in winter and introduce possible hydrological scenarios in the forest ecosystems of the heavy snowfall regions of north-eastern Japan. Effects of rain-on-snow events and snowmelt on soil moisture were estimated for the period 2012–2018. Rain/snow ratio showed that only 30% of the total precipitation in the winter season 2011/2012 was rain events while it was 50% for the winter 2018/2019. Increasing climate warming and weakening of the Siberian winter monsoons will probably increase rain/snow ratio and the number of rain-on-snow events in the near future.  相似文献   

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