Showing papers on "Precipitation published in 1982"
TL;DR: In an East Mediterranean marine core, the upper sapropel begins soon after the start of a global event, a very heavy precipitation which occurred in the equatorial latitudes during the late Glacial-early Holocene as discussed by the authors.
Abstract: In an East Mediterranean marine core, the upper sapropel begins soon after the start of a global event—a very heavy precipitation which occurred in the equatorial latitudes during the late Glacial–early Holocene. This heavy precipitation in Africa, channelled by the Nile River across 35° of latitude, produced a low-salinity surface layer in the East Mediterranean. In this confined basin, with high bottom salinity, the steep salinity gradient stratified the water column. The stagnant bottom waters triggered the sapropel formation. Cretaceous sapropels in the tropical oceans may result from the same chain of events in warm, humid climates, with contrasting wet-and-dry seasonal rhythm.
588 citations
TL;DR: The remarkable short response time of Bouteloua gracilis to a rainfall stimulus enables this species to utilize small events and may influence its persistence as a dominant species in the steppe region.
Abstract: Small precipitation events account for a large proportion of the precipitation received in semiarid regions, and their potential ecological importance has previously been ignored. We investigated the effect of a small rainfall event (5 mm) upon Bouteloua gracilis, the dominant grass species of the central and southern Great Plains of North America. An effect of a small event on leaf water potential and leaf conductance to water vapor was observed in less than 12 h and lasted for up to two days.
500 citations
TL;DR: In this article, an intensified monsoon circulation was simulated for Northern Hemisphere summer and the annual and global average land surface temperature and precipitation were the same for the simulated 9000 years B.P. climate and the present climate.
Abstract: The earth's orbital parameters, precession, obliquity and eccentricity, produce solar radiation differences (compared to present) of ∼7% at the solstices 9000 years before present (B.P.): more radiation in June-July-August, less in December-January-February. When this amplified seasonal cycle of solar radiation is used to drive a low-resolution general circulation model, an intensified monsoon circulation is simulated for Northern Hemisphere summer. The annual- and global-average land surface temperature and the annual- and global-average precipitation are the same for the simulated 9000 years B.P. climate and the present climate. Certain features of the simulated monsoon climate from this orbital-parameter sensitivity experiment agree with the paleoclimatic evidence.
366 citations
TL;DR: In this paper, the seasonal and spatial variations of stable isotope ratios in present day European precipitation are simulated with a simple multibox model of the mean west-east horizontal transport of the atmospheric water vapour across the European continent.
Abstract: The seasonal and spatial variations of stable isotope ratios in present day European precipitation are simulated with a simple multibox model of the mean west-east horizontal transport of the atmospheric water vapour across the European continent. Isotope fractionation during the formation of precipitation leads to an increasing depletion of heavy isotopes in the residual air moisture as it moves towards the centre of the continent. This isotopic depletion is partly compensated, particularly in summer, by evapotranspiration, which is assumed to transfer soil water into the atmosphere without isotope fractionation. The model estimates are based on horizontal water vapour flux data, varying seasonally between 88 and 130 kg m -1 s -1 for the Atlantic coast region, and on the monthly precipitation, evapotranspiration and surface air temperature data available for various locations in Europe. Both continental and seasonal temperature effects observed in the stable isotope composition of European precipitation are fairly well reproduced by the model. The calculations show that the isotopic composition of local precipitation is primarily controlled by regional scale processes, i.e. by the water vapour transport patterns into the continent, and by the average precipitation-evapotranspiration history of the air masses precipitating at a given place. Local parameters such as the surface and/or cloud base temperature or the amount of precipitation modify the isotope ratios only slightly. Implications of the model predictions for the interpretation of stable isotope ratios in earlier periods as they are preserved in ice cores and in groundwater are also discussed. DOI: 10.1111/j.2153-3490.1982.tb01801.x
255 citations
TL;DR: In this paper, the authors provide an overview of the organization and structure of precipitating cloud systems, which contribute the bulk of precipitation over the Earth, and provide a detailed analysis of the mesoscale features of these systems.
Abstract: Publisher Summary This chapter provides an overview of the organization and structure of precipitating cloud systems. The emphasis is on precipitating cloud systems, which contribute the bulk of precipitation over the Earth. Most precipitation occurs in storms that are 20–2000 km in horizontal dimension. Small showers may greatly outnumber larger precipitating cloud systems, but these do not contribute significantly to total precipitation. The cloud systems considered in this chapter are all in the mesoscale size range. Precipitation occurs over the globe in three major latitude belts. The midlatitude maxima of the Northern and Southern Hemispheres are essentially mirror images of each other and are accounted for by cloud systems associated with extratropical frontal cyclones and midlatitude thunderstorms. The equatorial maximum is accounted for mainly by rainfall from tropical cloud clusters and, to some extent, by hurricanes and smaller scale convection. This chapter explains the major precipitating cloud systems of each latitude belt and extratropical cyclones and describes midlatitude convective systems, and tropical cloud systems. Information about the mesoscale features is presented. Details are also provided about air motions within the rainband, the substructure of the rainband, the precipitation-producing mechanisms, and the dynamic processes responsible for the formation of the band.
180 citations
TL;DR: In this article, the effects of industrial atmospheric emissions of lead in the northern hemisphere westerlies which have overwhelmed prehistoric natural fluxes of lead to the oceans have been revealed, showing that present rates of atmospheric lead inputs are 10-fold greater than prehistoric outputs.
Abstract: A total atmospheric Pb input flux of 7 ng Pb cm^−2 yr^−1 was measured in the North Pacific Easterlies at Enewetak. Parameters used to measure this flux were ratio of dry deposition flux to precipitation flux; Pb/^(210)Pb in precipitation and seawater; ^(210)Pb flux; washout factor; and Pb concentrations in air, rain, and dry deposition deposits. Relations among these parameters established at Enewetak were used to recompute and confirm previous estimates of lead fluxes to the oceans (ng Pb cm^−2 yr^−1) at the following locations: North Atlantic Westerlies, 170; North Pacific Westerlies, 50; and South Pacific Easterlies, 3. Prehistoric lead output fluxes to sediments (ng Pb cm^−2 yr^−1) at these locations have been previously measured and were 4 (Enewetak); 30 North Atlantic Westerlies; 3 North Pacific Westerlies; 4 South Pacific Easterlies. These data show that the rates of atmospheric inputs of lead to the oceans vary directly with variations in rates of upwind emissions of industrial lead from urban complexes on land. In the North Pacific and North Atlantic, present rates of atmospheric lead inputs are 10-fold greater than prehistoric outputs. In equatorial regions, present inputs and past outputs are more nearly equal. These observations disclose the effects of intense industrial atmospheric emissions of lead in the northern hemisphere westerlies which have overwhelmed prehistoric natural fluxes of lead to the oceans. The average concentration of lead in marine air at Enewetak is 170 pg m−3 and varies less than a factor of 2 from that mean. One to 15% of this lead comes from seaspray, while the remainder comes from sources on land. About 90% of the seaspray lead is industrial, while 80 to 99% of that originating from land sources is industrial. Concentrations of lead in rain at Enewetak range from 6 to 63 pg/g with a mean value of 28. The mean precipitation flux, corrected for recycled lead in sea salts, measured by four different methods, was 6 ng Pb cm^−2 yr^−1, while the net dry deposition flux measured on horizontal plastic plates was 0.6 ng Pb cm^−2 yr^−1. The total dry deposition flux measured was 6 ng cm^−2 yr^−1, but 90% of this lead came from recycled seaspray. Lead isotope tracers show that Japan is the major source of industrial lead at Enewetak during the dry season, while the United States is the major source during the wet season.
172 citations
TL;DR: The organization and structure of a narrow cold-frontal rainband (NCFR) on the small mesoscale and the microscale have been investigated through quantitative radar reflectivity, Doppler radar observations, airborne observations and surface measurements.
Abstract: The organization and structure of a narrow cold-frontal rainband (NCFR) on the small mesoscale and the microscale have been investigated through quantitative radar reflectivity, Doppler radar observations, airborne observations and surface measurements. The NCFR was composed of small mesoscale regions of heavy precipitation called “precipitation cores” (PCs) oriented at an angle to the synoptic-scale cold front; in horizontal cross section the PCs were roughly elliptical in shape. Areas of lighter precipitation called “gap regions” (GRs) separated the PCs. The PCs were so oriented that their loading edges were regions of strong low-level convergence. The weather associated with the passage of a PC resembled that of a squall-line gust front, with concurrent windshifts and pressure checks occurring ∼5 min before heavy precipitation and a fall in temperature. The changes in surface weather that accompanied the passage of a GR were more variable but tended to be less marked than for PCs. Thus, the se...
140 citations
TL;DR: In this paper, a new general circulation model, developed to run on a coarse grid (8 x 10 deg resolution) at the Goddard institute for Space Studies, was employed to investigate the potential use of ground moisture anomalies for seasonal climate prediction.
Abstract: A new general circulation model, developed to run on a coarse grid (8 x 10 deg resolution) at the Goddard institute for Space Studies is employed to investigate the potential use of ground moisture anomalies for seasonal climate prediction. For three different summertime simulations, the ground moisture on 1 June over the United States is reduced to 1/4 of its value in the control run. The results show that the subsequent surface air temperature is significantly higher throughout most of the summer, while the precipitation decreases, especially in June and July. Knowledge of late spring ground moisture anomalies should thus be an aid in predicting summertime climate.
129 citations
TL;DR: In this paper, the authors show that fog drip could have added 882 mm of water to total precipitation during a year when precipitation measured 2160 mm in a rain gage in a nearby clearing.
Abstract: Net precipitation under old growth Douglas fir forest in the Bull Run Municipal Watershed (Portland, Oregon) totaled 1739 mm during a 4Cbweek period, 387 mm more than in adjacent clearcut areas. Expressing data on a full water year basis and adjusting gross precipitation for losses due to rainfall interception suggest fog drip could have added 882 mm (35 in) of water to total precipitation during a year when precipitation measured 2160 mm in a rain gage in a nearby clearing. Standard rain gages installed in open areas where fog is common may be collecting up to 30 percent less precipitation than would be collected in the forest. Long term forest management (Le., timber harvest) in the watershed could reduce annual water yield and, more importantly, summer stream flow by reducing fog drip.
128 citations
TL;DR: In this paper, it was shown that the principal factors which determine the 3H content of the fracture fluids are the U, Th, Li and B contents of the rock and its matrix porosity.
Abstract: Natural tritium production by the reaction, 63Li(n, α)31H, may in some circumstances lead to 3H contents in the fracture fluids of a granite, which are significantly above the present natural 3H content (0.5 tritium units, TU) of pre-bomb precipitation. We show here that the principal factors which determine the 3H content of the fracture fluids are the U, Th, Li and B contents of the rock and its matrix porosity. Granites with high U, Th and Li contents; low B content and a low matrix porosity may have a naturally maintained 3H content of up to about 2.5 TU in water within the matrix. This has important implications for the interpretation of groundwater flow patterns from their 3H contents. Whereas it has generally been assumed that ground-waters with 3H contents greater than 0.5 TU have a proportion of post-1954 recharge present, this may not always be a valid conclusion.
109 citations
TL;DR: In this article, observations of rain cells in the remains of a decaying tropical storm were made by Airborne Microwave Radiometers at 19.35,92 and three frequencies near 183 GHz.
Abstract: Observations of rain cells in the remains of a decaying tropical storm were made by Airborne Microwave Radiometers at 19.35,92 and three frequencies near 183 GHz. Extremely low brightness temperatures, as low as 140 K were noted in the 92 and 183 GHz observations. These can be accounted for by the ice often associated with raindrop formation. Further, 183 GHz observations can be interpreted in terms of the height of the ice. The brightness temperatures observed suggest the presence of precipitation sized ice as high as 9 km or more.
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TL;DR: The acidity of precipitation due to combustion of fossil fuels has been well documented for both the eastern USA1 and Canada2 The SO2 and NOx emitted by the burning of coal, natural gas, fuel oil and petrol are oxidized in the atmosphere to sulphuric and nitric acids which subsequently give rise to acid precipitation.
Abstract: Increased acidity of precipitation due to combustion of fossil fuels has been well documented for both the eastern USA1 and Canada2 The SO2 and NOxemitted by the burning of coal, natural gas, fuel oil and petrol are oxidized in the atmosphere to sulphuric and nitric acids which subsequently give rise to acid precipitation1 However, the SO2 and NOx emitted, and their oxidation products, are not all removed by atmospheric deposition over the North American continent; a large fraction is advected east out of North America3 In a study between 1 May 1980 and 30 April 1981, we have detected acid precipitation (pH<56) on the island of Bermuda, which is ∼1,000 km east of the Atlantic seaboard of the USA We report here that the acidity of such precipitation is eight times greater on a volume-weighted annual average than rainwater in natural atmospheric equilibrium, and that the acids present are almost wholly sulphuric with a small nitric acid contribution There is a strong correlation between the presence of these strong acids and the meteorological back trajectory of Bermuda storm systems to the North American continent, which suggests long-range atmospheric transport of acid rain precursors to Bermuda, these having similar anthropogenic origins (that is, from remote fossil fuel combustion) to acid rain precursors on the continent
TL;DR: In this paper, a mesoscale anvil is characterized by a nearly continuous stratiform cloud, referred to here as a Mesoscale Anvil, of ∼ 100-500 km dimension extending from the mid-troposphere to near the tropopause (∼ 17 km).
Abstract: During the December 1978 field phase of the International Winter Monsoon Experiment (Winter MONEX), a regular diurnal cycle of deep convective activity occurred over the South China Sea immediately to the north of Borneo. The convection was initiated during the late night hours by convergence of the low-level northeast monsoon flow with the land breeze along Borneo's north coast. The precipitation feature that developed was characterized during its mature stage by a nearly continuous stratiform cloud, referred to here as a mesoscale anvil, of ∼ 100–500 km dimension extending from the mid-troposphere (∼5 km) to near the tropopause (∼ 17 km). Using rawinsonde data from the sounding network, thermodynamic and Circulation characteristics of the convection are documented. Mesoscale upward motion is found to within the anvils, with a MCSOMC downdraft below producing a warm, dry region over a lame area just above the boundary layer. Air flow relative to the anvil on both its leading and trailing edges i...
TL;DR: This article measured the deuterium-to-hydrogen ratios (D/H) of precipitation at Mohonk Lake, New York, from individual storms over a 2-yr period, July 1977-June 1979.
Abstract: The isotopic content of precipitation falling at a point provides information of potential importance concerning atmospheric circulation and climate change1–6. The isotopic content of precipitation, however, is controlled by the particular meteorological processes acting at a given time and place and is subject to considerable variation. We have measured the deuterium-to-hydrogen ratios (D/H) of precipitation at Mohonk Lake, New York, from individual storms over a 2-yr period, July 1977–June 1979. These ratios varied systematically with the locus of the paths followed by the storms: the more seawards (and southerly) the paths and the colder the temperatures at Mohonk, the lower were the D/H ratios.
TL;DR: In this paper, the authors derived wet removal coefficients for rain and snow for regional or mesoscale models and are meant to apply for soluble particles that are incorporated into the cloud liquid water via nucleation.
TL;DR: In this paper, the time function of bomb tritium concentrations in river runoff to the Arctic Ocean has been reconstructed from published data on trinium in precipitation 1959-1975, which indicates the average age of the freshwater component to be 11±1 years in the Nansen Basin and the outflow and somewhat higher in the Canada Basin.
Abstract: The time function of bomb tritium concentrations in river runoff to the Arctic Ocean has been reconstructed from published data on tritium in precipitation 1959–1975. Tritium measurements on oceanic samples through the halocline exhibit strong linear relationships between tritium concentrations (TU values) and salinity. These waters thus look like binary mixtures of Atlantic source water and freshwater runoff. Combining these data, the vintage of the freshwater component in the Arctic Basin has been determined assuming no other major tritium source. The relation indicates the average age of the freshwater component to be 11±1 years in the Nansen Basin and the outflow and somewhat higher in the Canada Basin. According to tritium/salinity data, a surface layer of 10–60 m is affected by sea ice melting and freezing in the Nansen Basin, and the thickness of this layer increases to 150–170 m toward the Canada Basin. There is tritium also in the deeper waters, the unmixed Atlantic water, which points at residence times for that water not to exceed 17 years.
The appendix is available with the entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document J81-012; $1.00, payment must accompany order.
TL;DR: In this article, a quasi-Lagrangian reference frame centered with respect to the moving surface cyclone for several storm volumes is used to calculate the moisture, vorticity and kinetic energy budgets.
Abstract: Moisture, vorticity and kinetic energy budgets are constructed to diagnose the transformation of tropical storm Agnes (June 1972) into an extratropical cyclone in this second of two papers on Agnes. The vertical motions and divergent wind components used in the computations are taken from the solution of the nonlinear balance model described in Part I [DiMego and Bosart (1982)]. The budget equations are formulated in a quasi-Lagrangian reference frame centered with respect to the moving surface cyclone for several storm volumes. The results are displayed spatially as well as in time-section format. Synoptic-scale transport and moisture convergence dominate the moisture budget and all terms together define well the areas of observed precipitation. Both budget and model-computed precipitation, particularly the latter, underestimate the observed precipitation. The discrepancy is attributed to the sub-grid scale convective processes and model underestimation of the divergent wind components. Advectio...
TL;DR: In this article, a simple quantitative model has been developed which predicts that a parametric correlation between the isotopic composition of precipitation and precipitation intensity can exist as a consequence of the condensation process when certain conditions are met.
Abstract: A simple quantitative model has been developed which predicts that a parametric correlation between the isotopic composition of precipitation and precipitation intensity can exist as a consequence of the condensation process when certain conditions are met. These conditions include the following: (1) approximate constancy, from one sampling interval to the next, of the initial isotopic composition of the water vapor in precipitation-producing air masses; (2) approximate constancy of the initial condensation temperature; (3) approximate constancy of the rate of vertical ascent of the precipitating air mass; and (4) approximate constancy of the ratio of condensed water to water vapor. Such conditions are probably rare in nature for the short collection intervals represented by existing samples. However, with the probable exception of condition 3, tropical oceanic islands may satisfy the preceding conditions on the month-to-month time scale for which precipitation samples have generally been collected for isotopic analysis. Precipitation samples from Wake and Johnston islands that plot on the meteoric water line were used to compare monthly δD values with corresponding precipitation intensity. In general, there appears to be a convergence of the data at high values of δD (low intensity) and a divergence at low values of δD (high intensity). Such behavior is predicted by the isotopeintensity model largely in terms of variation in the vertical rate of ascent. For Wake Island this divergence of the data appears to be bimodal in character. However, for Johnston Island, there is considerable scatter in the data. This scatter is roughly constrained by the envelope defined by two vertical ascent rates that approximately characterize the presumably bimodal Wake Island trends. Thus much of the scatter in the Johnston Island data may be explained by month-to-variability in vertical ascent rates. The data for these two islands suggest that a simple precipitation δD versus intensity correlation is unlikely for monthly sample intervals. However, the issue remains unresolved for longer time scales.
TL;DR: The daily input of plant macro-nutrients in bulk precipitation was measured over a 16-month period at Siguatepeque, Honduras as mentioned in this paper, where most of the annual influx of each element taking place on only a few rain days.
Abstract: The daily input of plant macro-nutrients in bulk precipitation was measured over a 16-month period at Siguatepeque, Honduras. Total annual inputs of all elements were small relative to those recorded elsewhere in the tropics, a difference which is attributed to the low rainfall of the area, its elevation, and its remoteness from the ocean. Input patterns were highly irregular with most of the annual influx of each element taking place on only a few rain days. A major influx of all elements was recorded at the start of each wet season, and one period of exceptionally high cation input during the wet season is tentatively attributed to volcanic activity. Despite the irregularity of nutrient influx, calculation of a daily water balance for the area shows that a large proportion of elements received can normally be retained temporarily in soil-moisture storage. However, effective capture of these by ecosystems probably requires rapid plant uptake. We suggest that plants occupying infertile tropical soils may be strongly selected for the ability to absorb irregular pulses of atmospheric nutrients.
TL;DR: In this article, an analysis of hourly sequential precipitation samples collected at Brookhaven National Laboratory over a 4-y period shows systematic relationships between amounts of chemicals deposited in precipitation and meteorological conditions.
01 Jan 1982
TL;DR: In this paper, a linear relation between the surface air temperature and the percentage of occurrences of snowfall to all the cases of precipitation was obtained from the observations at the station (4958 m) near Glacier AX010 in Shorong Himal.
Abstract: Precipitation phenomena during some summer monsoon seasons were observed in high-mountain areas of the Nepal Himalaya. The main results obtained from these observations are as follows. (a) Precipitation along the main valley of Dudh Kosi decreases with altitude in the range from 2800 m to 4500 m a.m.s.l. (b) The total amount of precipitation around peaks and ridges is 4 or 5 times larger than that around valley bottoms. (c) The frequency and amount of precipitation around peaks and ridges are concentrated during the day-time when cumulus convection is predominant, while those around valley bottoms are concentrated during the evening up to midnight. (d) A linear relation between the surface air temperature and the percentage of occurrences of snowfall to all the cases of precipitation was obtained from the observations at the station (4958 m) near Glacier AX010 in Shorong Himal.
TL;DR: The seasonal and year-to-year variation of bulk precipitation as a source of total N, nitrate and ammonia was reported for a 7-year period at the Rhode River, a subestuary of Chesapeake Bay, U.S.A.
Abstract: The seasonal and year-to-year variation of bulk precipitation as a source of total N, nitrate and ammonia is reported for a 7-year period at the Rhode River, a subestuary of Chesapeake Bay, U.S.A. These values are placed in perspective by comparison with analogous nitrogen loading due to watershed discharges. Although year-to-year variations were important, in an average year about the same amount of readily available nitrogen entered the system via precipitation as entered in land runoff and, during the summer and fall, precipitation was the largest source.
TL;DR: In this article, the authors measured lead concentrations in rain selected for least influence by local sources of contamination at several tropical and subtropical islands (Enewetak, Pigeon Key, Florida; and American Samoa) and shipboard stations (near Bermuda and Tahiti).
Abstract: Concentrations of lead, ^(210)Pb, and ^(210)Po were measured in rain selected for least influence by local sources of contamination at several tropical and subtropical islands (Enewetak; Pigeon Key, Florida; and American Samoa) and shipboard stations (near Bermuda and Tahiti). Ratios expressed as ng Pb/dpm ^(210)Pb in rain were 250–900 for Pigeon Key (assuming 12% adsorption for ^(210)Pb and no adsorption for lead), depending on whether the air masses containing the analyzed rain came from the Caribbean or from the continent, respectively; about 390 for the northern Sargasso Sea downwind from emissions of industrial lead in North America; 65 for Enewetak, remote from continental emissions of industrial lead in the northern hemisphere; and 14 near Tahiti, a remote location in the southern hemisphere where industrial lead emissions to the atmosphere are much less than in the northern hemisphere. (The American Samoa sample yielded a higher ratio than Tahiti; the reason for this is not clear but may be due to local Pb sources.) The corresponding fluxes of lead to the oceans, based on measured or modeled ^(210)Pb precipitation fluxes, are about 4 ng Pb/cm^2y for Tahiti, 10 for Enewetak, and 270 for the Sargasso Sea site, and between 110 to 390 at Pigeon Key.
TL;DR: Results show that 20 to 30 percent of the sulfates in rain and snow at Argonne, Illinois, are of primary origin, which is significantly higher than that of sulfates formed from sulfur dioxide after emission.
Abstract: The relative amounts of primary and secondary sulfates in atmospheric aerosols and precipitation can be estimated from measurements of the stable oxygen isotope ratios. The oxygen-18 content of sulfates formed in power plant stack gases before emission into the atmosphere is significantly higher than that of sulfates formed from sulfur dioxide after emission. Results show that 20 to 30 percent of the sulfates in rain and snow at Argonne, Illinois, are of primary origin.
TL;DR: In this paper, an aerodynamic approach was applied to compute the annual mean value of E-P over the Mediterranean Sea using upper air data collected during the 5-year period 1968-1973.
Abstract: Previous studies of the water balance of the Mediterranean have relied on estimating evaporation (E) and precipitation (P) rates separately over the basin. An independent approach is to obtain the net difference between these rates by evaluating the divergence of the atmospheric flux of water vapor over the region. We apply this aerological approach to compute the annual mean value of E-P over the Sea using upper air data collected during the 5-year period 1968–1973. Our result is in general agreement with those obtained by the more classical methods. In addition we present maps of the two-dimensional fields of precipitable water, of the vertically integrated water vapor flux vector, and of the divergence of water vapor over the region. These analyses are discussed in light of various climatological and hydrological considerations.
TL;DR: In this paper, the authors examined the consistency of sampling and chemical analysis methods used, and in relation to earlier European work, they found that the historical data are of insufficient quality and quantity to support any long-term trends in precipitation acidity change in the eastern United States.
TL;DR: In this article, a numerical model of cumculonimbus allowing a simulation of the growth of the electric field is described, and two possibilities are considered: an inductive method, in which hail particles are polarized in the local electric field, and a non-inductive ice-ice method, where charge transfer is attributed to a difference in surface potential of the ice particles in contact.
Abstract: A numerical model of cumculonimbus allowing a simulation of the growth of the electric field is described. The cloud model is three dimensional and includes a representation of the ice phase. The charge generating mechanism is assumed to arise from the collision of rimed hail particles with smaller ice crystals. Two possibilities are considered: an inductive method, in which hail particles are polarized in the local electric field, and a non-inductive ice-ice method, where charge transfer is attributed to a difference in surface potential of the ice particles in contact.
These mechanisms are compared for a test cloud displaying the rainfall characteristics of a typical, small maritime thunderstorm and their sensitivity to the assumed form of the hail size spectrum examined. A cloud of relatively small size is chosen to constitute a more severe criterion of the strength of the electrification mechanisms than is possible in large thunderstorms where weaker modes of charge transfer could also produce a lightning discharge. Hence the comparison of mechanisms presented is specifically for a small thunderstorm. The results indicate that the electric field can reach a breakdown threshold within half an hour of the appearance of precipitation with the inductive method, providing that the hail size spectrum represents relatively small particles and that the effect of multiple collisions of any ice crystal with more than one hail particle is discounted, i.e. when it is assumed that ice crystals are uncharged before impact. It is found that the non-inductive ice-ice mechanism can lead to lightning within a similar time providing that the product of ice particle concentration and charge separation per collision exceeds 7 pC per litre.
TL;DR: In this article, the 18-year precipitation record from the dense gage network on the Reynolds Creek Experimental Watershed located in southwest Idaho was used to determine the spatial distribution of annual and monthly precipitation on a mountainous watershed.
Abstract: The 18-year precipitation record from the dense gage network on the Reynolds Creek Experimental Watershed located in southwest Idaho was used to determine the spatial distribution of annual and monthly precipitation on a mountainous watershed. Analyses of these data showed a linear relationship between annual amounts and elevation. This relationship was best when the gages were grouped into downwind and upwind sites. This grouping was appropriate because most of the winter storms moved over the watershed from the west and southwest, and the heaviest precipitation was on the west (downwind) side of the watershed. Gage sites along the western and southern watershed borders were most representative of the upwind gages on the east side, because they measured the precipitation from the air moving upwind onto the watershed. The maximum annual precipitation on the watershed was just leeward of the western watershed boundary.
The monthly precipitation and elevation relationship was also best represented by grouping the gage sites into upwind and downwind sites. However, during the summer when there are only small amounts of pre cipitation and thunderstorms are the source of most precipitation, one equation can be used to represent the elevation relationship. This study also showed that the log-normal distribution could be used to generate the annual synthetic series, and the cube-root-normal distribution could be used to generate monthly synthetic series for all locations on the watershed.
TL;DR: In this article, empirical orthogonal function analysis is used to synthesize precipitation data at seven stations along the west coast of North America, dating back to 1851 at some stations, and characteristics of runs of generally wet and generally dry conditions are quantified.
Abstract: Precipitation data at seven stations along the west coast of North America, dating back to 1851 at some stations, are synthesized by means of empirical orthogonal function analysis. Characteristics of runs of generally wet and generally dry conditions are quantified. A significant change in precipitation regime, lasting 41 yrs, occurred in the middle of this century and could return in the future. Drought occurrences, similar to midwestern United States episodes, appear in the data, but are not statistically verifiable.
TL;DR: In this paper, the authors defined the start of the rains as the first day or two-day rain spell, in which greater than a specified total amount of rain occurs, and used a Markov chain model of the daily precipitation.
Abstract: The start of the rains is defined to be the first day, or two-day rain spell, in which greater than a specified total amount of rain occurs. A method of calculating the probability distribution of the start of the rains from a Markov chain model of the daily precipitation is given. The application of this method is illustrated with data from Samaru, Nigeria.