Showing papers on "Precipitation published in 1980"

Sensitivity of a global climate model to an increase of CO2 concentration in the atmosphere

Abstract: This study investigates the response of a global model of the climate to the quadrupling of the CO2 concentration in the atmosphere. The model consists of (1) a general circulation model of the atmosphere, (2) a heat and water balance model of the continents, and (3) a simple mixed layer model of the oceans. It has a global computational domain and realistic geography. For the computation of radiative transfer, the seasonal variation of insolation is imposed at the top of the model atmosphere, and the fixed distribution of cloud cover is prescribed as a function of latitude and of height. It is found that with some exceptions, the model succeeds in reproducing the large-scale characteristics of seasonal and geographical variation of the observed atmospheric temperature. The climatic effect of a CO2 increase is determined by comparing statistical equilibrium states of the model atmosphere with a normal concentration and with a 4 times the normal concentration of CO2 in the air. It is found that the warming of the model atmosphere resulting from the CO2 increase has significant seasonal and latitudinal variation. Because of the absence of an albedo feedback mechanism, the warming over the Antarctic continent is somewhat less than the warming in high latitudes of the northern hemisphere. Over the Arctic Ocean and its surroundings, the warming is much larger in winter than summer, thereby reducing the amplitude of seasonal temperature variation. It is concluded that this seasonal asymmetry in the warming results from the reduction in the coverage and thickness of the sea ice. The warming of the model atmosphere results in an enrichment of the moisture content in the air and an increase in the poleward moisture transport. The additional moisture is picked up from the tropical ocean and is brought to high latitudes where both precipitation and runoff increase throughout the year. Further, the time of rapid snowmelt and maximum runoff becomes earlier.

Monthly precipitation distribution: a comparative index

Abstract: Modification of the Gibbs-Martin Index of Employment Diversification permits derivation of a precipitation concentration index (PCI) that characterizes the monthly concentration of precipitation on a scale that ranges from less than 10 for evenly distributed rainfall to 100 for extreme monthly rainfall distribution. The defined lower and upper limits of the index contrast to other statistical descriptions of precipitation distribution, which are open-ended. Mapped values of the PCI provide a good visual guide to relative monthly distribution of precipitation. Suggested applications of the index are related to both pedagogic and research applications.

Correlation of 18 O in precipitation with temperature and altitude

Abstract: The 18O/16O ratio in precipitation is correlated to climatic parameters, especially temperature. However, the meteorological processes determining the stable isotope composition of precipitation are complex and only partly understood, so that a quantitative interpretation of ancient isotope ratios in precipitation, as recorded in polar ice1 or in carbonate sediments from lakes2, has not yet been possible. For several years we have measured 18O/16O ratios on monthly precipitation samples from Switzerland and here summarize these data.

Determination of cloud water acidity at a mountain observatory in the Adirondack Mountains of New York State

Abstract: A ground-based, cloud water collection system capable of intercepting significant volumes of water from clouds has been in operation at a mountain field station in the Adirondack Mountains of New York State for three summer seasons. An analysis of cloud water pH for August–September 1977 and 1979 strongly suggests that acid input to the ecosystem due to clouds at Whiteface Mountain may be significantly more important than that due to the much-discussed phenomenon of acid precipitation. The mean pH of nonprecipitating clouds was 3.55 during 1977 and 3.50 during 1979; approximately 90% of all observations were found in the pH interval between 2.66 and 4.66. In the event that precipitation is intercepted concurrently with cloud droplets, a minimum dilution of the cloud water acidity by a factor of 60–80% can be expected. Other aspects of the collection and pH analysis of cloud water at Whiteface Mountain are also discussed.

The Mesoscale and Microscale Structure and Organization of Clouds and Precipitation in Midlatitude Cyclones. I: A Case Study of a Cold Front

Abstract: Detailed information is deduced on the mesoscale organization of precipitation, the structures of the clouds, the air flows associated with mesoscale rainbands, and the precipitation efficiencies and the mechanisms producing precipitation in the rainbands associated with a cold front. Measurements were obtained with quantitative reflectivity and Doppler radars, two instrumented aircraft, serial rawinsondes and a network of ground stations. The regions of heaviest precipitation were organized into a complex mesoscale rainband in the warm-sector air ahead of the front, a narrow band of precipitation at the surface cold front, and four wide cold-frontal rainbands. The wide cold-frontal rainbands and the smaller mesoscale areas of precipitation within them moved with the velocities of the winds between ∼3—6 km. The narrow rainband, which was produced by strong convergence and convection in the boundary layer, moved with the speed of the cold front at the surface. A coupled updraft and downdraft was p...

Scenario for a warm, high-CO2 world

Abstract: Plausible patterns for temperature and precipitation changes accompanying a general global warming, such as might occur due to a large increase in atmospheric carbon dioxide levels, are presented. The patterns are determined by comparing the five warmest years in the period 1925–74 with the five coldest in this period. Temperature increases are indicated for most regions, with maximum warming over northern Asia. A few isolated regions show cooling. Precipitation changes are fairly evenly distributed between increases and decreases; the most important features being an increase over India, and decreases in central and south-central USA and over much of Europe and Russia. The latter decreases, should they occur, could have considerable agricultural impact.

The Objective Use of Upper Air Soundings to Specify Precipitation Type

Abstract: Linear screening regression is used to derive relationships between parameters computed from observed upper air soundings (RAOBS) and concurrent observations of precipitation type. Precipitation type is defined as three categories: liquid (rain or drizzle), freezing (freezing rain or freezing drizzle) and frozen (snow or ice pellets). Statistical screening results indicate that of the parameters tried the following are important: the mean temperature in the surface–1000 m and 500–2500 m layers; the depth of the warm layer (temperature >0°C), if one exists; the area between the temperature profile and the 0°C isotherm in the warm layer, the depth of the surface-based cold layer, if one exists, with respect to the wet-bulb temperature profile; and the area between the wet-bulb temperature profile and the 0°C isotherm in the surface-based cold layer. Verification of the specification equations on both developmental and independent data samples indicates that the scores are generally stable. The equa...

New Zealand Climate: I. Precipitation Patterns

Abstract: New Zealand is a country with high relief that protrudes into the southern westerly circulation. Precipitation patterns are identified by two different methods: correlation of precipitation time series at stations with the time series of circulation indices and principal component analysis. Components were rotated to give more definite patterns. Examination of synoptic events and surface pressure anomalies in key months allowed the identification of the synoptic cause of each component pattern. The link between the components and circulation indices was investigated. The first method shows that precipitation is anomalously high on the windward side of the country to any airflow, and low on the leeward side. Component analysis revealed eight distinct patterns. All am related to synoptic events and surface pressure anomalies where humid air advects over a windward coast. Confirmation is provided by the patterns of correlations of precipitation associated with the circulation indices. These bear a c...

Simulation of Daily Weather Data Using Theoretical Probability Distributions

Abstract: A computer simulation model was constructed to supply daily weather data to a plant disease management model for potato late blight. In the weather model Monte Carlo techniques were employed to generate daily values of precipitation, maximum temperature, minimum temperature, minimum relative humidity and total solar radiation. Each weather variable is described by a known theoretical probability distribution but the values of the parameters describing each distribution are dependent on the occurrence of rainfall. Precipitation occurrence is described by a first-order Markov chain. The amount of rain, given that rain has occurred, is described by a gamma probability distribution. Maximum and minimum temperature are simulated with a trivariate normal probability distribution involving maximum temperature on the previous day, maximum temperature on the current day and minimum temperature on the current day. Parameter values for this distribution are dependent on the occurrence of rain on the previou...

Coastal-inland distributions of summer air temperature and precipitation in northern alaska

Abstract: Using data from summer air temperature stations from the inland tundra to the immediate coastal area, regression analyses of the air temperature data from 1975 to 1978 were used to predict temperature values across the Alaskan Arctic Coastal Plain based upon latitude and longitude. This provides the best approximation of average values based on exist

Evidence of Urban and Lake Influences on Precipitation in the Chicago Area

Abstract: A study of summer precipitation conditions in the Chicago area sought to discern evidence of urban influences on precipitation processes and rainfall magnitude by investigating cloud, radar echo, rainfall and thunderstorm data. The rainfall studies identified an area of 15% greater rainfall in central Chicago, considered largely a result of urban influences. The degree of change is less than found at St. Louis, possibly a result of the inhibiting lake influences at Chicago. With respect to the placement of the rain change, the synoptic weather conditions when rain changes occur (squall lines and zones), and the tendency for rain changes to exist in heavier rainfall conditions, the Chicago findings reveal good agreement with those at St. Louis. Limited causative studies suggest an urban enhancement of convective clouds over Chicago and southern Lake Michigan during late afternoon, and case studies of radar echo behavior showed maximum echo intensification repeatedly occurred over the city and at h...

Quaternary temperatures and precipitation for the north-west coast of North America

Abstract: Palynologists utilize present-day pollen rain to interpret the climatic setting of pollen records from Quaternary deposits. Analogues are sought which relate the present with the past. Because climatic conditions at mid-latitudes during the Quaternary were diverse, often ranging from a tundra type at one extreme to a closed forest type at the other, a modern data set should cover the extremes of vegetation and climate expected during this time. For interpreting climatic parameters from Quaternary pollen in land and marine cores, we calculated a pair of regression equations relating modern pollen rain from the Pacific coastal forest and tundra to mean July temperature and mean annual precipitation at a series of sites from the Aleutian Islands to northern California. We describe here how application of these equations to Quaternary pollen profiles from western Washington enabled us to quantify temperature and precipitation over the past ∼80,000 yr.

The Inference of GATE Convective Rainfall from SMS-1 Imagery

Abstract: Quantitative precipitation estimates have been made for the GARP (Global Atmospheric Research Program) Atlantic Tropical Experiment (GATE) from geosynchronous, infrared satellite imagery and a computer-automated technique that is described in this paper. Volumetric rain estimates were made for the GATE A scale (1.43 × 107 km2) and for a 3° square (1.10 × 105 km2) that enclosed the B scale for time frames ranging from all of GATE (27 June—20 September 1974) down to 6 h segments. The estimates for the square are compared with independent rain measurements made by four C-band digital radars that were complemented by shipboard raingages. The A-scale estimates are compared to rainfall estimates generated by NASA using Nimbus 5 microwave imagery. Other analyses presented include: 1) comparisons of the satellite rain estimates over Africa with raingage measurements, 2) maps of satellite-inferred locations and frequencies of new cumulonimbus cloud formation, mergers and dissipations, 3) latitudinal preci...

Wet deposition in the northeastern United States

Abstract: Attempts are made to examine concentration and wet deposition of pollutant material at selected stations within the northeastern United States and to characterize as many events as possible with respect to air mass origin. Further attempts are made to develop a regional pattern for the deposition of dominant ion species. MAP3S (US Multistate Atmospheric Power Production Pollution Study) data for 1977 to 1979 are used to determine concentration and deposition on an event basis from which monthly, seasonal, annual, and cumulative averages are developed. The ARL-ATAD trajectory model is used to characterize individual events as to air mass origin. Case studies are examined to illustrate variability in the chemical composition of precipitation originating from distinctly different air mass trajectories. A difference in concentration of pollution-related ions in precipitation is noted between Midwest/Ohio Valley and Great Lakes/Canadian air mass origins for carefully selected cases. Total deposition of the major ions is examined in an effort to develop a regional pattern for deposition over a period of at least one year. For that purpose, total deposition is normalized to remove the variability in precipitation amounts for inter-station comparison. No marked gradient is noted in the normalized deposition totals within the northeast ofmore » the United States. The Adirondack region exhibited the lowest normalized ion deposition value, while the Illinois station showed the highest of the MAP3S network. The data analysis suggest that the acid rain phenomena covers the entire northeast. The concept of large scale mixing emerges to account for the lack of a significant gradient in the normalized deposition.« less

Winter Storms over the San Juan Mountains. Part II: Microphysical Processes

Abstract: Airborne observations of wintertime storms in southeastern Colorado have shown that the microphysical structure of those storms evolved in close relationship to the dynamical structure. The storms evolved from deep synoptic-scale systems to shallower orographic systems, and in the course of this evolution became unstable. During early storm stages the precipitation developed primarily by diffusional growth of ice crystals, but during later storm stages accretional growth was at least as important as diffusional growth. Early storm stages were almost completely glaciated, but extensive regions of supercooled water appeared in later storm stages. Weak embedded convection also produced important regions of supercooled water in the later storm stages. Ice crystal concentrations were high, often in excess of 50 L−1. The observed ice crystal concentrations were far above the corresponding ice nucleus measurements, and the discrepancy could not be attributed to known ice multiplication processes.

Rain-Related Impacts on Selected Transportation Activities and Utility Services in the Chicago Area

Abstract: An intensive meteorological study of summer precipitation in the Chicago area during 1976–78 furnished detailed data needed to perform a study of the impacts of rain on selected transportation-related activities and on certain utility services. Degree of effect on these activities was studied on a rain day versus non-rain day basis and further on a land use basis to help infer changes in impacts due to urban-influenced increases in rain occurrences, rainfall amounts and storm activity. Added rain resulted in over 100% more vehicle accidents, particularly in the urban area, but the accident severity associated with rain was greater in the rural areas. Rainfall decreased ridership of mass transit systems by 3–5% and apparently this was disproportionately due to midday discretionary riders such as shoppers. Little relationship of rain to pleasure boat emergencies was found but more rain decreased usage of pleasure boats. The number of delays in flight departures from O'Hare Airport was highly relate...

Precipitation Patterns in West Africa

Abstract: A regional precipitation analysis from a total of 813 recording stations in 11 West African countries for the drought period 1968–75 is presented. Results illustrate the severity and extent of meteorological drought which prevailed throughout the region and reached greatest magnitude in 1973. In that year, the critical 300–400 mm zone of annual rainfall was at least 200 km south of its normal position resulting in major crop failures in several sub-Saharan countries. In Nigeria, 50-year records of rainfall from 28 stations were examined to study both temporal and spatial distributions. In the northern Sahelian zone of Nigeria, two prolonged drought periods were observed (i.e., 1940’s and 1968–76). This detailed analysis further demonstrated the strong relationship between rainfall in the Sahelian region and the position of the Intertropical Convergence Zone (ITCZ). However, there were years during which widespread below-normal rainfall occur-red throughout most of Nigeria which supports previous ...

Some Effects of Rain and Mist on Plants, with Implications for Acid Precipitation

Abstract: Rain and mist mean different things to different people To the farmer, rain means water for growth of crops, affecting the movement of nutrients from the soil into the roots To the plant pathologist, rain means a medium in which spores can germinate and grow, often with an increased incidence of disease

Hail Growth Mechanisms in a Colorado Storm: Part II: Hail Formation Processes

Abstract: Hail growth mechanisms in a Colorado multicellular hailstorm were investigated through use of dual-wavelength radar data, three-dimensional wind field data, in situ aircraft measurements and trajectory calculations. Hail production consisted of a transient, pulsating component and a weak, quasi-steady component. Peak hail production resulted when graupel particles and hailstones which grew within the updraft region of a feeder cell were advected in the wind field and fell into the main updraft region where they continued to grow. A minimum in hail production resulted when hail growth was confined to the main updraft region. Recirculation of particles within the main updraft had minor importance in the hail production mechanism. Aggregates of dendritic ice crystals probably comprised most of the hail embyros. These aggregates grew along the forward portion of the storm in a region of precipitation debris associated with decaying cumulus congestus clouds. They were introduced into developing feeder...

Mass Balance of Glacier AX010 in Shorong Himal, East Nepal during the Summer Monsoon Season

Abstract: Observation of mass balance of Glacier AX010 at the southern front of the Nepal Himalayas was made from June to September in 1978. Since much of the annual accumulation due to the monsoon. and ablation occur simultaneously in the summer, the separate measurement of the amounts of accu mulation and ablation is difficult in this area. Accumulation is estimated from the precipitation on the basis of the relation between the probability of occurrences of solid precipitation ana surface air temperature, and ablation is obtained from the difference between the accumulation and the observational results of the balance. The probability of occurrences of solid precipitation had different linear relations with the air temperature between daytime and nighttime. The relation of air temperature to the estimated ablation is expressed by a power function. Although the change of accumulation depended on air temperature, the ablation was much more sensitive to the change of air temperature. The average summer balance over the whole area of the glacier was negative, but the positive summer balance in recent years is deduced. It is concluded that the fluctuation of the summer temperature on glaciers in the Nepal Himalayas under the influence of the summer monsoon is important for the variation of mass balance.

Long‐term annual surface heat and water balances over Canada and the United States South of 60°N: Reconciliation of precipitation, run‐off and temperature fields

Abstract: The analysis compares the observed field of run‐off (assumed correct) with adjusted precipitation over North America (as amended by den Hartog and LeDrew over Canada) and derives the principal hydroclimatological ratios for each five‐degree latitude‐longitude square. The amended precipitation field yields values of the Budyko dry ness index close to values suggested by the vegetation distribution. The Priestley‐Taylor parameter, α, lies between unity (equilibrium) and potential (1.26) values over much of humid North America, but exceeds these values in the northwest Pacific squares, where advective heating may be the cause. Other regions of strong seasonal advective heating (e.g. the Great Plains) do not appear to influence the distribution strongly. A weighted convective forcing temperature is derived, varying from 298 K in the extreme south to below 285 K in the north. This function (and the Bowen ratio) achieve improbable values in northern Labrador‐ Ungava. The precipitation, run‐off and net ...

Multiple‐scattering effect on radiometric determination of rain attenuation at millimeter wavelengths

Abstract: The multiple-scattering effects in rain are negligibly small in comparison with the absorption effects when raindrop sizes are much smaller than a wavelength. This is often true for light to moderate rain below about 30 GHz, and the total atmospheric attenuation along the path may be estimated by the emission method using the usual radiometric formula. At higher frequencies and heavy rain the multiple-scattering effects cannot be ignored. This paper describes a theoretical study of the correction due to the multiple-scattering effect for the determination of the total atmospheric attenuation by the emission method. The observed temperatures at the ground both for vertical and horizontal polarizations and for various raindrop temperatures, precipitation rates, ground temperatures, ground albedos, and frequencies ranging from 30 GHz to 120 GHz are calculated on the basis of the equation of transfer, taking into account the polarizations and the Stokes parameters. The cross sections of rain droplets are calculated using the Mie solution with the Laws and Parsons drop size distribution and Saxton's formula for refractive index of water. These calculations show the differences between the total rain attenuation and the attenuation calculated from the sky temperature measurements and the assumed rain temperatures. The results are compared to some experimental data, showing a good agreement.

Seasonal patterns of soil water recharge and extraction on semidesert ranges.

Abstract: Soil water is recharged in the semidesert Southwest during the usual winter precipitation season, and again during the usual summer rainy season. The amount and depth of recharge varies widely depending primarily on the amount of precipitation, and secondarily on storm character, soil texture, vegetation cover, and evapotranspiration. Soil water depletion patterns and amounts differed among species, between plants and bare soil, and between seasons. Compared to evaporation from bare soil, plants extracted water much faster, but at more variable rates. Essentially all available soil water was used by plants or evaporated during most depletion periods. Essentially all soil water in semidesert areas is either used by plants or is evaporated from the soil surface; relatively little percolates below the reach of plant roots. Evaporation and extraction by plants are so rapid that water is seldom available for more than a few weeks at a time. The present study was undertaken to determine: (1) seasonal patterns of soil water recharge on the Santa Rita Experimental Range south of Tucson, Arizona, and (2) seasonal patterns of water extraction by seven major native and two important

The Sensitivity of Soils to Acid Precipitation

Abstract: Acid precipitation may lead to adverse effects on the soil and on the percolating water. The relative magnitude of these effects varies with the soil properties. In soils with strong buffering against acid compounds no acidification of the discharge water will occur. On the other hand, in soils with low buffering capacity, especially if the soil is shallow, the discharge water will become acidified proportionally to the infiltrating precipitation and to its acidity.

Fluoride distribution and dispersion processes about an industrial point source in a forested coastal zone

Abstract: This preliminary survey comprises a collection of fluoride concentration data for air, water, soil, vegetation and marine samples obtained both specifically for this paper, and from the hitherto unpublished results of others, in the vicinity of a large aluminum smelter operating at the head of Kitimat Arm, a typical Canadian west coast fjord with high rainfall. The significance of the fluoride distribution and dispersion processes derived from this data matrix and from special leaching tests using water, dilute acids, and aqueous sodium bicarbonate is considered in the light of prevailing temperature, wind and precipitation patterns with regard to the plant, animal, and marine life of the area. The most recent data available are further related to the time of complete installation of dry scrubber emission control devices to determine how ambient air, water, soil, and vegetation concentrations may be responding to the reduced air and water mass emissions rates.

Physical influences on east coast cyclogenesis

Abstract: Three examples of cyclogenesis off the east toast of North America are studied using an 8‐level primitive equations model. The model includes input of sensible and latent heat from the sea surface, both parameterized convective and large‐scale precipitation and release of latent heat, surface frictional drag and orography. The grid size is 190 km. Twenty‐four‐hour prognoses were made for four time periods with similar results: orography and fluxes of sensible and latent heat from the ocean were of little consequence, while the effect of the land‐water roughness contrast was significant. The lack of appreciable orographic influences is attributable to the fact that the Lows studied crossed the Appalachians south of the highest terrain. The cyclones formed along well‐developed frontal systems where the difference between air or dew‐point temperature and sea temperature in the warm sector was small or negative. Consequently fluxes of both sensible and latent heat near the Low centres during cyclogen...

Average storm duration and seasonal precipitation rates for the northeast sector of the United States

Abstract: Regional and seasonal averages of storm duration and precipitation rates for the northeast sector of the United States are needed as input variables in models aimed at describing precipitation processes relating to acid rain and other problems. Hourly precipitation data for 78 first order weather stations for four summer months and three winter months were used to calculate the regional average storm duration and average precipitation rates over the 19 northeastern states north of 36/sup 0/N latitude and east of 92/sup 0/W longitude. Average storm duration for summer (June-August), and winter (December-February) seasons are calculated based on a scheme that allows a period of up to three dry hours in summer storms, and up to six dry hours in winter storms to be included as part of the same storm. Thus, each storm consists of one or more precipitation periods or events. The arithmetic mean of event precipitation rates was used to determine the average precipitation rates for summer and winter season storms. The data suggest a preferred summer storm time duration of about three hours and a preferred winter storm time scale of about 26 hours. The summer storms typically consist of one rain event lasting about three hoursmore » with rain rates averaging 2.5 mm h/sup -1/. The 26 hour winter storm averages about three precipitation periods (or rain bands). Each period lasts about six hours and has an average precipitation rate of 0.9 mm h/sup -1/.« less

Organochlorines in Precipitation in the Great Lakes Region

Abstract: Atmospheric precipitation in the form of snow (1976) and rain (1976 and 1977) was collected from around the Canadian side of the Great Lakes as well as inland. All sites were remote from any nearby industrial or urban contamination. Rain samples were collected with a 0.36 m2 stainless steel funnel and were event related. Snow was obtained from the accumulated columns during the month of February, 1976. A total of 81 rain and 17 snow samples were examined.