Showing papers on "Precipitation published in 1988"

A Satellite Infrared Technique to Estimate Tropical Convective and Stratiform Rainfall

Abstract: This paper describes a new method of estimating both tropical convective precipitation and stratiform precipitation (produced under the anvils of mature and decaying convective systems) from satellite infrared data. The method, denoted CST (Convective-stratiform Technique) locates, in an array of infrared data, all local minima in the brightness temperature field (Tmin. After an empirical screening to eliminate cirrus, these points are assumed to be convective centers. Rainrate and rain area are assigned to each minimum point as a function of its Tmin, based on one-dimensional cloud model results. A stratiform rain algorithm, using a brightness temperature threshold based on the mode temperature of thunderstorm anvils, completes the convective/stratiform rain estimation. Individual CST rain fields wore spatially most similar to the radar for young, isolated storms, and most dissimilar in capturing linear features such as squall lines. Some convective features were missed, while others (generally ...

The influence of potential evaporation on the variabilities of simulated soil wetness and climate

Abstract: An atmospheric general circulation model with prescribed sea surface temperature and cloudiness was integrated for 50 years in order to study atmosphere-land surface interactions. The temporal variability of model soil moisture and precipitation have been studied in an effort to understand the interactions of these variables with other components of the climate system. Temporal variability analysis has shown that the spectra of monthly mean precipitation over land are close to white at all latitudes, with total variance decreasing poleward. In contrasts, the spectra of soil moisture are red, and become more red with increasing latitude. As a measure of this redness, half of the total variance of a composite tropical soil moisture spectrum occurs at periods longer than nine months, while at high latitudes, half of the total variance of a composite soil moisture spectrum occurs at periods longer than 22 months. The spectra of soil moisture also exhibit marked longitudinal variations. These spectral...

Modeling dust emission caused by wind erosion

Abstract: A model for the estimation of total dust production for the United States is discussed. Its primary use will be in the inventory of alkaline elements for use in acid/base balance studies of atmospheric precipitation by the National Acid Precipitation Assessment Program (NAPAP). The model is a summation of the expected dust production caused by wind erosion for individual sampling units of the detailed soil and land use inventory of the National Resources Inventory, compiled by the U.S. Department of Agriculture. The model is based on a dust emission function derived theoretically and verified by experiment. An extremely important parameter is the threshold velocity for dust production; this parameter is dependent on effects of vegetative residue, roughness of the soil, live standing plants, soil texture and the effect of atmospheric precipitation. Experimentation has supplied values of this parameter for the calculation. Wind data used in the model were obtained from the Wind Energy Resource Information System (WERIS). The model was calibrated with dust emission data for the area, including the panhandles of Texas and Oklahoma.

The climate of China

Abstract: 1 Introduction.- 1.1 Aims and Concept of the Study.- 1.2 Climate Data.- 1.3 Review of Climate Studies on China.- 2 Controlling Factors of the Climate.- 2.1 Latitude, Longitude and Location.- 2.2 Topography and Landforms.- 2.3 Distribution of Land and Sea and Nature of the Underlying Ground.- 2.4 Seasons.- 3 Circulation.- 3.1 Seasonal Pressure Distribution at Sea Level.- 3.2 Seasonally Prevailing Winds and Air Masses.- 3.3 Winter and Summer Monsoon.- 3.3.1 Characteristics of the Monsoon in General.- 3.3.2 Onset and Duration of the Winter Monsoon.- 3.3.3 Periods of Active and Weak Winter Monsoon.- 3.3.4 Damage Due to Strong Cold Outbreaks of Winter Monsoon.- 3.3.5 Onset and Duration of the Summer Monsoon.- 3.3.6 Some Characteristics of the Summer Monsoon.- 3.4 Frontology.- 3.4.1 Mean Front Position in January and July.- 3.4.2 The Stationary Fronts in February and March as well as in the Pre-Typhoon Season in South China.- 3.4.3 Some Characteristics of the Mei-Yu Front.- 3.5 The Transient Disturbances.- 3.5.1 The Upper Westerly Troughs in the Westerlies.- 3.5.2 Extratropical Cyclones and Anticyclones.- 3.5.3 Typhoons.- 4 Temperature.- 4.1 Mean Annual Air Temperature Distribution.- 4.2 Mean Seasonal Temperature Distribution.- 4.3 Annual Range and Annual Variation of Temperature.- 4.4 Onset and End of Certain Limited Temperatures and Their Duration.- 4.4.1 Mean Daily Air Temperature ? 0 C.- 4.4.2 Mean Daily Air Temperature ? 10 C.- 4.4.3 Maximum Daily Air Temperature ? 35 C.- 4.4.4 Other Extreme Limited Temperatures.- 4.5 Vertical Distribution of Temperature.- 4.6 Comparison of Temperature at the Same Latitude.- 4.7 Diurnal Range of Temperature.- 4.8 Interannual Variability of Temperature.- 4.8.1 Variability of Annual Mean Temperature.- 4.8.2 Variability of Monthly Mean Temperatures.- 4.9 Historical-Climatic Change of Temperature During the last 5,000, 500 and 100 Years.- 5 Precipitation.- 5.1 Mean Annual Precipitation Distribution.- 5.2 Mean Seasonal Precipitation Distribution.- 5.3 Annual Variation of Precipitation.- 5.3.1 Specific Precipitation Types and Their Distribution.- 5.3.2 Variation of Wet and Dry Months over Space and Time.- 5.3.3 Summer Precipitation.- 5.4 Interannual Precipitation Variability.- 5.4.1 Variability of Annual Precipitation.- 5.4.2 Variability of Monthly Precipitation.- 5.4.3 Variability of Annual and Monthly Precipitation at Beijing.- 5.5 Precipitation Frequency Expressed in Rainy Days.- 5.6 Precipitation Intensity.- 5.7 Rainstorms and Certain Events of Heavy Rainfall.- 5.8 Diurnal Variation of Precipitation.- 5.9 Influence of Topography and Elevation on Precipitation.- 5.9.1 Influence of the Exposition of Slopes on Precipitation.- 5.9.2 Effect of Elevation on Prefipitation.- 5.10 Historical Change of Precipitation.- 5.11 Snow.- 5.11.1 Mean Length of Snow Cover Period.- 5.11.2 Number of Snowfall Days.- 5.11.3 Maximum Depth of Snow.- 5.11.4 Altitude of the Snow Line.- 6 Cloudiness and Sunshine.- 6.1 Mean Annual Cloudiness and January and July Amount.- 6.2 Sunshine.- 6.2.1 Annual Sunshine Duration.- 6.2.2 Sunshine Duration in January and July and Annual Variation.- 6.3 Global Radiation.- 6.4 Fog.- 7 Surface Wind.- 7.1 Mean and Extreme Wind Velocities.- 7.2 Local Wind Systems.- 7.2.1 Mountain and Valley Breezes.- 7.2.2 Land and Sea Breezes, Lake Breeze.- 7.2.3 Plateau Monsoon.- 7.2.4 Local Dry and Hot Winds.- 8 Climate Classification and Division of China.- 8.1 General Objectives and Fundamentals of Climate Regionalization.- 8.2 China Within Global Climate Classifications.- 8.3 National Climate Classifications of China.- 8.4 Climate Division of China According to Huang Bing-wei (1986).- 9 Climate Zones of China.- 9.1 Cold Temperate Zone (I).- 9.2 Middle Temperate Zone (II).- 9.3 Warm Temperate Zone (III).- 9.4 Northern Subtropical Zone (IV).- 9.5 Middle Subtropical Zone (V).- 9.6 Southern Subtropical Zone (VI).- 9.7 Peripheral Tropical Zone (VII).- 9.8 Middle Tropical Zone (VIII).- 9.9 Southern Tropical Zone (IX).- 9.10 Alpine Plateau Zone (H0).- 9.11 Subalpine Plateau tone (HI).- 9.12 Temperate Plateau Zone (HII).- Appendix: Climate Tables.- References.

Seasonal and intraseasonal climatology of summer monsoon rainfall over East Asia

Abstract: This paper presents a documentation of the seasonal and intraseasonal rainfall climatology of summer monsoon rainfall over East Asia, using monthly and 10-d precipitation data from East Asian stations. These data are then related to satellite measurements of longwave radiation and large-scale circulation field. Major rainfall regimes and multiple monsoon onsets are identified, indicating that, in general, monsoon rainfall over East Asia evolves with wavelike progression from north to south from April to September. Abrupt changes in the major rainbands are related to the phase-locking between intraseasonal oscillations found in this study, such as the 40-d and 20-d rainfall fluctuations, and the seasonal monsoon cycle.

Relationships between seasonal rainfall in East Africa and the Southern Oscillation

Abstract: Teleconnections between the Southern Oscillation and seasonal rainfall over East Africa during the period 1923–1984 were investigated using correlation methods. The results from the study indicated significant negative zero lag correlations between Southern Oscillation and seasonal rainfall over parts of East Africa during the months of October—December. Maximum correlations were concentrated along the coast and over some western parts. Peak values in the range — 0.6 were, however, centred along central and northern coastal regions. During the months of July—September significant positive zero lag correlations in the range of 0.5 were observed over some western parts. Low zero lag correlations were, however, obtained over most of the regions with the January—May and annual rainfall records. The computed lagged correlation values displayed characteristics similar to those observed from the zero lag correlations. Highest month to month persistences were again centred within October/November when significant lag correlations persisted for time lags greater than 2 months at some locations. It was, however, noted that although there were some relationships between the Southern Oscillation and seasonal rainfall over parts of East Africa, some of the extreme wet and dry episodes were not related to the Southern Oscillation.

The influence of North Pacific atmospheric circulation on streamflow in the West [abstract]

Abstract: EXTRACT (SEE PDF FOR FULL ABSTRACT): The annual cycle and non-seasonal variability of streamflow over a network of stations in western North America and Hawaii is studied in terms of atmospheric forcing elements. The phase lag between the annual cycle of streamflow and precipitation varies considerably over this network, as does the persistence of monthly streamflow anomalies. This lag effect appears to be largely a function of the relative amount of snow laid down in a particular basin. In addition to the rather strong annual cycle that exists in mean streamflow and its variance at most of the stations, there is also a distinct annual cycle in the autocorrelation of streamflow anomalies that is related to the interplay between the temperature and precipitation annual cycles; of particular importance is the existence of stored water in the form of a snow pack.

Influence of land surface roughness on atmospheric circulation and precipitation - A sensitivity study with a general circulation model

Abstract: The influence of land surface roughness on the large scale atmospheric circulation and rainfall is examined by comparing three sets of simulations made with a general circulation model in which the land surface roughness length, z(0), was reduced from 45 cm to 0.02 cm. It is found that the reduced surface roughness produced a two-fold increase in the boundary layer wind speed, a two-fold decrease in the magnitude of the surface stress, and almost no change in the surface evaporation and surface sensible heat flux. It is suggested that the height of the earth's vegetation cover has a large influence on the boundary layer water vapor transport convergence and the rainfall distribution.

The Effect of Variations in Surface Moisture on Mesoscale Circulation

Abstract: A two-dimensional numerical Model with moist physics is used to simulate circulations induced by horizontal variations in surface-moisture availability. The model contains prognostic equations for water vapor, cloud water, and rain water, with a simple parameterization of cloud microphysical processes. Four geometric variations of surface-moisture availability are examined: 1) an edge geometry which includes a land-water contrast (classic sea breeze) and moist land adjacent to dry land (inland sea breeze), 2) a single strip of moist land surrounded by dry land 3) alternating bands of moist and dry land, and 4) a single strip of dry land surrounded by moist land. For convectively unstable initial conditions with a relative humidity of 50%, lifting associated with the sea-breeze front induces a precipitation system which propagates inland from the coast. The sea-breeze circulation associated with dry land is considerably stronger than that produced by moist land; however, the evaporation over land ...

Precipitation Variability over the Caribbean and Tropical Americas Associated with the Southern Oscillation

Abstract: Seasonal and annual (July through June) precipitation data for up to 197 stations are used to analyze variability in the High/Dry (H/D) and Low/Wet (L/W or warm event) modes of the Southern Oscillation (SO) over the tropical Americas and the Caribbean Islands to 30°S latitude. Precipitation is significantly higher during H/D events than during L/W in northern summer, autumn and winter at most stations in the southern Caribbean and northern South America including the northern Andes and Amazon River basin. Precipitation is, in general, significantly higher in L/W than in H/D modes at higher subtropical latitudes of both hemispheres, especially in northern autumn and winter over the southern United States, Cuba and Mexico, and in spring and autumn over southern Brazil, Paraguay and Argentina. A similar pattern of spatial precipitation variability occurs in the July–June data and significant H/D minus L/W precipitation differences are found at one-third of the stations. Although drought occurs in No...

The Supercooled Warm Rain Process and the Specification of Freezing Precipitation

Abstract: About 30% of freezing precipitation cases are observed to occur in a subfreezing atmosphere (contrary to the classical melting ice model). We explain these cases with the concept of the “supercolled warm rain process” (SWRP): the warm rain process can yield liquid hydrometeors at subfreezing temperatures whenever too few ice nuclei are available to create solid hydrometeors. We find that all of the freezing precipitation cases in a subfreezing atmosphere show a rapid decrease of moisture content in the zone above the inferred cloud top (decreasing from liquid to ice saturation in lm than 20 mb), at temperatures ranging from 0° to −10°C. Additionally, this structure prevails among freezing cases (43%) much more than among solid or liquid cases (10% and 15%, respectivelly). Regression experiments demonstrated that freezing precipitation was best described when (discretized) predictors were combined to describe particular physical processes, such as the SWRP. Besides the SWRP, the usual melting ice ...

Sensitivity of 30-Day Dynamical Forecasts to Continental Snow cover

Abstract: Several series of 30-day simulations with a global simulation model are used to evaluate the sensitivities to continental snow cover over North America and Eurasia. The model is initialized with National Meteorological Center analyses for specific dates during the winter of 1976/77 through 1983/84, and snow cover in each case is prescribed according to 1) the distribution derived from observational data; and 2) the distribution containing a corresponding anomaly of the opposite sign. In ten pairs of midwinter forecasts, the major effect of extensive snow cover in eastern North America is a reduction of the near-surface air temperature in the vicinity of the snow anomaly. When snow cover is extensive, sea level pressures are somewhat lower and precipitation amounts somewhat higher offshore of the East Coast; sea level pressures are generally higher inland. In a set of six March cases, positive anomalies of Eurasian snow cover reduce the air temperatures by at least several degrees ceisius througho...

Changes in precipitation conditions in the western mediterranean over the last century

Abstract: A study of precipitation variations over the western Mediterranean is given, for a period of 95 years (1891 to 1985), based on the use of Principal Component Analysis. The curves for the scores are traced and then analyzed for annual as well as seasonal precipitation. Two principal moist periods are found (1901 to 1921 and 1930 to 1941) and two principal dry periods (1922 to 1929 and 1942 to 1954). A comparison of variations in precipitation and zonal indices (ZIa) indicates that with a meridional circulation dominating over the western Mediterranean, we have an increase in precipitation; with a zonal circulation dominating we have a decrease in precipitation.

Numerical study of orographic-convective precipitation over the eastern Arabian Sea and the Ghat Mountains during the summer monsoon

Abstract: When the western coast of India lies in the path of the low-level west-southwest wind crossing the Arabian Sea during the summer monsoon season, deep convection frequently develops over the ocean off the coast. In such a situation, the maximum rainfall occurs near the coast, not over the Western Ghats. In order to study the physics underlying orographic-convective precipitation over this area, a two-dimensional compressible moist cloud model is applied. The model is written in terrain-following coordinates and includes the Coriolis force and a planetary boundary layer parameterization. The initial fields of thermodynamic variables are specified using observed data gathered upstream of the offshore precipitating systems over the Arabian Sea. Two wind profiles are considered: vertically uniform and nonuniform flows. The latter profile represents a monsoonal westerly jet at low levels and easterlies in the layer above 5 km. Three cases are considered for each wind profile by including or omitting mo...

Acid deposition at high elevation sites

Abstract: I Modelling Cloud Chemistry and Deposition.- Atmospheric Chemistry at Elevated Sites - A Discussion of the Processes Involved and the Limits of Current Understanding.- Meteorological and Chemical Factors Influencing Cloud-Water Composition in a Non-Precipitating, Liquid- Water Updraft.- Photochemical Production of Carboxylic Acids in a Remote Continental Atmosphere.- Sulphur Scavenging in a Mesoscale Model with Quasi-Spectral Microphysics.- II Cloud and Rain Chemistry: Process Studies.- Physical Influences of Altitude on the Chemical Properties of Clouds and of Water Deposited From the Troposphere.- Measurements of the Short-Term Variability of Aqueous-Phase Mass Concentrations in Cloud Droplets.- Processes Determining Cloudwater Composition: Inferences from Field Measurements.- Cloud Microphysical Processes Relevant to Cloud Chemistry.- Modelling Wet Deposition Onto Elevated Topography.- Cloud Chemistry Research at Great Dun Fell.- Measurements of Ambient SO2 And H2O2 At Great Dun Fell and Evidence of Their Reaction in Cloud.- Wet Deposition and Altitude, The Role of Orographic Cloud.- Time Resolution in Precipitation and Cloud Sampling.- Controlled Chemical Kinetic Experiments in Cloud: A Review of the CERL/UMIST Great Dun Fell Project.- Physics of Cloudwater Deposition and Evaporation at Castlelaw, S.E. Scotland.- A Comparison of Methods for Estimating Cloud Water Deposition To A New Hampshire (USA) Subalpine Forest.- III Cloud and Rain Chemistry: Monitoring Studies.- A Comparison of Atmospheric Exposure Conditions at High-and Low-Elevation Forests in the Southern Appalachian Mountain Range.- Chemical Concentrations in Cloud Water from Four Sites in the Eastern United States.- Measurements of the Properties of High Elevation Fog in Quebec, Canada.- Experiment Alsdan (1985): Some Preliminary Results of Height Resolved Measurements of Trace Gases, Aerosol Composition, Cloud- and Precipitation Water.- Chemistry of Cloud Water and Precipitation at an Alpine Mountain Station.- Measurements of the Chemical Composition in Cloud and Fogwater.- Chemical Composition of Wet Deposition in he Eastern Alpine Region.- Concentration Gradients in Atmospheric Precipitation in Areas of High Annual Precipitation.- Fog Chemistry and Deposition in the Po Valley, Italy.- IV Dry, Wet and Occult Deposition.- Particles in Orographic Cloud and the Implications of Their Transfer to Plant Surfaces.- High Efficiency Annular Denuders for the Determination of Species Responsible For Atmospheric Acidity.- A Fog Chamber and Wind Tunnel Facility for Calibration of Cloud Water Collectors.- Chemical Composition of Bulk Atmospheric Deposition to Snow at Col De Le Brenva (MT Blanc Area).- Chemical Composition of the Seasonal Snowcover at a Southern French Alps Site: Some Preliminary Results.- Chemical Composition of Snow in the Remote Scottish Highlands.- Measuring and Modelling Dry Deposition in Mountainous Areas.- Numerical Simulation of SO2 Concentration and Dry Deposition Fields in the Tulla Experiment.- A New Instrument for SO2 Eddy Flux Measurements.- Gaseous Deposition of SO2, NOx and O3 to a Spruce Stand in the National Park "Bayerischer Wald".- V Processes at the Surface.- Deposition Rates of Airborne Substances to Forest Canopies in Relation to Surface Structure.- A Simple and Appropriate Method for the Assessment of Total Atmospheric Deposition in Forest Ecosystem Monitoring.- Observations on Wet and Dry Deposition to Foliage at a High Elevation Site.- Chemical Interactions Between Cloud Droplets and Trees.- Chemical and Physical Processes in Acid Rain Drops on Leaf Surfaces.- Author Index.

Forcing Mechanisms and Other Characteristics of Significant Summertime Precipitation

Abstract: Satellite, radar, surface, and upper-air data from the June–August periods of 1982–83 are examined to determine the mechanisms, and their relative contributions, for producing warm-season precipitation in the United States. Only areas where rainfall equaled or exceeded 12.7 mm during the 24-h period ending at 1200 UTC were considered. Rainfall associated with extratropical cyclones accounted for about half of the warm-season precipitation. Most of the remaining precipitation was produced by mesoscale forcing mechanisms acting independently from the traveling extratropical cyclones. Nearly all the warm-season precipitation was convective; over 80% of the total was directly or indirectly associated with thunderstorms. Nearly three-fourths of the precipitation that occurred between the Rockies and the Mississippi Valley was nocturnal. Conversely, about three-fourths of the precipitation east of the Mississippi Valley fell during the daylight hours. During the 1983 July-August drought, the area of pr...

The Sensitivity of a Simulated Extratropical Mesoscale Convective System to Longwave Radiation and Ice-Phase Microphysics

Abstract: A two-dimensional, nonhydrostatic version of the Colorado State University Regional Atmospheric Modeling System (RAMS) was applied to the simulation of a midlatitude, continental mesoscale convective system. A control simulation was established that exhibited many features in common with observed MCSs. The sensitivity experiments revealed that the mesoscale circulations in the stratiform region were quite sensitive to longwave radiative cooling at stratiform anvil cloud top and heating at cloud base, and the presence of ice-phase precipitation processes and thermodynamics. Surface precipitation was little affected by radiational heating, however. Turning off melting of ice particles had little influence on the strength of simulated mesoscale and convective-scale downdrafts and the strength of the middle-level, rear-to-front flow. Melting had the greatest impact on the strength of the convective scale updrafts. These numerical experiments suggest that the strength of the middle-level, rear-to-fron...

Numerical Simulation of the 1981 Sichuan Flood. Part I: Evolution of a Mesoscale Southwest Vortex

Abstract: During the period 11–15 July 1981, heavy rainfall occurred over the Sichuan Basin in China, resulting in severe floods that took a large toll in human life and property damage. Mesoscale analyses by Kuo, Cheng and Anthes have shown that the flood was directly related to the development of a long-lived mesoscale southwest (SW) vortex over the basin. In this paper we present the results of numerical experiments aimed at 1) testing the capability of a limited-area mesoscale model to predict the evolution of the SW vortex and the accompanying heavy precipitation, 2) examining the structure of the simulated vortex using the model data, and 3) elucidating the role of various physical processes in the evolution of the SW vortex. Principal findings are: 1) The control experiment, which utilized an 80-km grid spacing and simple physical parameterizations, was able to simulate the evolution of the mesoscale SW vortex and the accompanying heavy precipitation. The simulation captured many observed features a...

Estimates of Thunderstorm Precipitation Efficiency from Field Measurements in CCOPE

Abstract: The precipitation efficiency (the ratio of surface rainfall to water vapor inflow) of a small sample of thunderstorms observed in the Cooperative Convective Precipitation Experiment is calculated using surface and cloud-base airflow and moisture measurements and subcloud rainout based on radar reflectivity factor. Highly-resolved vertical flux measurements from aircraft indicate that a significant amount of water vapor inflow may have been overlooked in past work of this kind, resulting in overestimates in precipitation efficiency. Trends in the mass of water vapor influx resolved at intervals of 10 to 30 min are corroborated by the evolution of water vapor flux convergence computed at 5-min intervals from objectively analyzed surface mesonetwork observations. Fluxes of water vapor inflow and precipitated rainwater are integrated over periods exceeding an hour to obtain precipitation efficiencies applicable to the mature storm phase. Precipitated rainwater estimates from radar reflectivity-rainra...

A GCM Simulation Study of the Influence of Saharan Evapotranspiration and Surface-Albedo Anomalies on July Circulation and Rainfall

Abstract: The influence of surface albedo and evapotranspiration anomalies that could result from the hypothetical semiarid vegetation over North Africa on its July circulation and rainfall is examined using the Goddard Laboratory for Atmospheres GCM. It is shown that increased soil moisture and its dependent evapotranspiration produces a cooler and moister PBL over North Africa that is able to support enhanced moist convection and rainfall in Sahel and southern Sahara. It is found that lower surface albedo yields even higher moist static energy in the PBL and enhances the local moist convection and rainfall. Modifying the rain-evaporation parameterization in the model produces changes in the hydrological cycle and rainfall anomalies in distant regions. The effects of different falling rain parameterizations are discussed.

Evaporation of rain falling from convective clouds as derived from radar measurements

Abstract: A computerized method developed by Rosenfeld (1987) is used to track the three-dimensional structure of the rainshafts of about 3000 summer afternoon convective rain cells in the semiarid region of central South Africa. By assuming a fixed relationship between the radar reflectivity factor and the rain intensity, time- and area-integrated rain volumes of each individual rainshaft are obtained at the cloudbase level and at a lower level. These results are used to obtain the cumulative fractional evaporation of the falling rain. This permits the cumulative evaporation of the falling rain to be obtained in a quantitative way as a function of the fall distance from the cloud base level and the rain intensity at the cloud base.

Simulation of regional soil moisture deficits on a European scale

Abstract: A simple deterministic simulation model for landscape-scale soil water deficits has been developed. Standard weather station data are used to estimate ‘daily’ precipitation and actual (regional) evapotranspiration (AET). The balance is added to soil moisture, which is accounted by a simple bucket model. AET is the daily integral of the lesser of supply and demand: supply is governed by current soil moisture, demand by estimated net radiation and temperature. The model estimates geographical patterns of soil water deficit at a scale suitable for comparison with the distributions of plant species and vegetation types. The model provides a way of quantifying soil moisture stress in biogeographical research.

Variability of mean monthly temperatures and semi‐annual precipitation totals in Europe in relation to hemispheric circulation patterns

Abstract: The influence of general hemispheric circulation on European temperature and precipitation was investigated. Data from the period 1901–1976 were utilized: the monthly frequencies of occurrence of W, E, C circulation pattern types according to the Wangenheim-Girs classification, monthly values of pressure differences between 35° an 65°N (zonal index), mean temperatures of January and July at 30 stations in both the warm season (May-October) and the cold season (November-April) and semi-annual precipitation totals for 21 stations in Europe. The correlation coefficients between the circulation characteristics and climate elements indicated above in Europe were calculated. Maps of these correlation coefficients have been produced, with the areas of their statistical significance. The results show that variability of temperature, and also partly of precipitation in Europe are significantly correlated with changes of circulation pattern types. January temperature also depends on the zonal index. If it is assumed that in future, until the end of this century, an increase of W type frequency and a decrease of C circulation pattern types will take place—it may be expected that temperature and precipitation will undergo appropriate changes in certain parts of Europe. Northern and some central areas of Europe are likely to change from continental to oceanic climate as regards temperature; precipitation is likely to increase in northern Europe.