Showing papers on "Precipitation published in 1985"

Does the ocean–atmosphere system have more than one stable mode of operation?

Abstract: The climate record obtained from two long Greenland ice cores reveals several brief climate oscillations during glacial time The most recent of these oscillations, also found in continental pollen records, has greatest impact in the area under the meteorological influence of the northern Atlantic, but none in the United States This suggests that these oscillations are caused by fluctuations in the formation rate of deep water in the northern Atlantic As the present production of deep water in this area is driven by an excess of evaporation over precipitation and continental runoff, atmospheric water transport may be an important element in climate change Changes in the production rate of deep water in this sector of the ocean may push the climate system from one quasi-stable mode of operation to another

Meteorology Today: An Introduction to Weather, Climate, and the Environment

Abstract: 1. Earth and Its Atmosphere. 2. Energy: Warming the Earth and the Atmosphere. 3. Seasonal and Daily Temperatures. 4. Atmospheric Humidity. 5. Condensation: Dew, Fog, and Clouds. 6. Stability and Cloud Development. 7. Precipitation. 8. Air Pressure and Winds. 9. Wind: Small-Scale and Local Systems. 10. Wind: Global Systems. 11. Air Masses and Fronts. 12. Middle-Latitude Cyclones. 13. Weather Forecasting. 14. Thunderstorms. 15. Tornadoes. 16. Hurricanes. 17. Earth's Changing Climate. 18. Global Climate. 19. Air Pollution. 20. Light, Color, and Atmospheric Optics.

A 1500-year record of tropical precipitation in ice cores from the quelccaya ice cap, peru.

Abstract: Two ice cores, covering 1500 years of climatic information, from the summit (5670 meters) of the tropical Quelccaya ice cap, in the Andes of southern Peru, provide information on general environmental conditions including droughts, volcanic activity, moisture sources, temperature, and glacier net balance. The net balance record reconstructed from these cores reflects major precipitation trends for the southern Andes of Peru. These records indicate extended dry periods between 1720 and 1860, 1250 and 1310, and 570 and 610; wet conditions prevailed between 1500 and 1720. Establishing a tropical precipitation record may help explain climatic fluctuations since the tropical evaporation-precipitation cycle is a principal mechanism driving the atmospheric circulation.

Influences of precipitation changes and direct CO2 effects on streamflow

Abstract: Increasing atmospheric carbon dioxide concentrations are expected1 to cause major changes in the world's climate over the next 50–100 yr. The impact of such changes on water resources, through changing precipitation and evaporation, will, however, be complicated by the direct effects of increasing CO2 on vegetation. In controlled environment experiments, higher CO2 levels cause the stomata of plants to close down, decreasing their rate of transpiration and increasing their water use efficiency2. Reduced evapotranspiration would make more water available as runoff and could tend to offset the effects of any CO2-induced reductions in precipitation or enhance the effects of precipitation increases. We consider here, in a simple but revealing analysis, the relative sensitivity of runoff to these two processes, changes in precipitation and changes in evapotranspiration. We show that, for low runoff ratios, small changes in precipitation may cause large changes in runoff. The magnitude and direction of these changes is, however, strongly dependent on the magnitude of the direct CO2 effect on plant evapotranspiration.

Sulphate and nitrate concentrations in snow from South Greenland 1895–1978

Abstract: An understanding of the phenomenon of acid rain requires the identification of the sources of the species affecting the pH of rainwater, both natural and anthropogenic, and their temporal and spatial development. The scant data concerning the historical development of the acidity in precipitation are from urban regions or their vicinity, where local effects dominate and obscure the hemispherical pattern1. The Greenland ice sheet allows us to trace the evolution of the acid rain in a remote location that is free from local effects. Sulphuric and nitric acids are the two species that dominate the acidity in precipitation2–4. We report here measurements of [SO42−] and [NO3−] in firn samples spanning the period 1895–1978. Samples, each covering 1 yr, were taken from a 70-m core drilled at Dye 3, South Greenland; [NO3−] and [SO42−] both increased by a factor of ˜2 during the period. By comparing the recent concentrations of nitrate and sulphate with those resulting from natural sources, we conclude that anthropogenic emissions of the precursors (NOx, SO2) had already surpassed natural sources in the late 1950s.

Some Empirical Evidence for the Influence of Snow Cover on Temperature and Precipitation

Abstract: A case study is made of the effect of snow cover or lack of snow cover on the surface temperature and precipitation in the coterminous United States during winter 1983/1984. Extensive snow occurred in the eastern half of the country early in December 1983; this snow cover appears to have produced substantial reduction in the observed surface temperature, especially during January 1984. This diminution was especially pronounced in the daytime maximum temperatures, presumably due to increase surface albedo. The effect involving anomalous snow cover also shows up in the Great Basin area during February 1984. A quantitative evaluation of the net effect of snow cover is made using errors of temperature specifications from 700 mb patterns formed from stepwise multiple regression equations. Temperature differences as great as 5°C were found over the temperature expected from the large-scale circulation alone. The concomitant effect of increased static stability near the surface may have played a role in...

Influences of snow cover and soil moisture on monthly air temperature

Abstract: A series of objective specification experiments are performed with monthly 700 mb heights and surface station temperatures for the United States during 1947–80. The errors in these specifications are used in conjunction with observed snow cover and a computed soil moisture index to assess the impacts of a variable surface state on monthly surface air temperature. Over the eastern and central United States, the mean errors of the temperature specifications for the winter months vary by 1–2°C according to the sign of the anomaly of snow cover. Lag results suggest that snow cover can make a modest contribution to the skill of temperature predictions near the snow boundary. The summer specifications are evaluated in terms of a soil moisture index computed from monthly temperatures and precipitation amounts using a modified Thornthwaite/Nappo parameterization scheme. This index varies seasonally in a realistic manner, while the corresponding mean annual runoff is shown to agree well with runoff amount...

Seasonal relationships between indian summer monsoon rainfall and the southern oscillation

Abstract: Association between the all-India summer monsoon (June to September) rainfall and an index of the Southern Oscillation (SO) is studied in relation to the vagaries of the monsoon rainfall and the seasonal characteristics of the SO. The SOI values of different months and standard seasons show opposite tendencies during deficient and excess years of all-India monsoon rainfall. The correlation coefficients between the all-India monsoon rainfall series and the SOIs of summer monsoon, autumn and winter minus spring seasons are significant at the 1 per cent level.

Scavenging ratios, wet deposition, and in‐cloud oxidation: An application to the oxides of sulphur and nitrogen

Abstract: With special regard to the class of substances in precipitation that potentially originate from both gaseous and particulate precursors, the process of precipitation scavenging is discussed. A model relating daily average ground level scavenging ratios (W) to nucleation scavenging and in-cloud chemical transformation is introduced and is used as guidance in the regression analysis of 3 years of SO4= and NO3− scavenging-ratio observations made at six locations in eastern Canada. It was found that W of SO4=-, NO3−-, and SO4=-bearing particles is inversely proportional to the one-third power of the precipitation amount in the event. The best regression model explained 41% of the variance in log W for SO4=. It included the effects of location, precipitation amount, precipitation type, and in-cloud SO2 oxidation. The last effect accounted for 50% of the variance explained. The analysis predicts that, on average, in-cloud SO2 oxidation accounts for 42–79% of the SO4= observed in rain and with the exception of one site, less than 20% of the SO4= observed in snow. These results are consistent with a mechanism of SO2 oxidation involving photochemically produced H2O2. A similar analysis for NO3− supports the hypothesis that throughout the year much of the NO3− in precipitation originates from in-cloud NO2 oxidation. It suggests that, depending on location, oxidation of 0.5–1.2 ppbv of NO2 is sufficient to explain observations. One possible mechanism of oxidation is the reaction with O3 to form NO3 and hence soluble N2O5. These results, combined with observations in the eastern United States, indicate that in eastern North America SO2 oxidation within a rain storm becomes an increasingly important source of rain SO4= as latitude increases. Scavenging ratios are useful tools for investigating in-cloud conversion and for parameterizing precipitation removal. However, they are limited to describing the average characteristic of an ensemble of storms. They cannot be used with confidence to analyze individual events.

The Diurnal Variation of Deep Convection and Inferred Precipitation in the Central Tropical Pacific During January–February 1979

Abstract: Infrared satellite data are used to determine the diurnal variation of deep convection and inferred rainfall in the central tropical Pacific during January-February 1979. The parameter employed to characterize the convection is the percent coverage of 1.5° latitude-longitude squares by clouds with tops colder than various specified equivalent blackbody temperatures. Rainfall estimates are based on an empirical relationship between precipitation rate and fractional coverage by cold clouds derived from measurements taken during the GARP Atlantic Tropical Experiment (GATE). In addition, the diurnal variation of vertical motion, determined kinematically from level III-b gridded wind analyses of the European Centre for Medium Range Weather Forecasts, is examined. Principal conclusions are: A pronounced diurnal variation of deep convection occurred throughout the region of study. At certain hours fractional coverage by clouds colder than −36°C deviated by as much as 40% from the daily mean. The variati...

Caldep: A Regional Model For Soil Caco3 (caliche) Deposition In Southwestern Deserts

Abstract: Our objective was to develop and validate a regional model for CaCO3 deposition in desert soils of the southwestern United States. There were five major components in the simulation model: a stochastic precipitation model, an evapotranspiration model, chemical thermodynamic relationships, soil parameterization, and a soil water and CaCO3 flux model. For the present climate, a cold-dry Pleistocene climate, and a cool-wet (summer) Pleistocene climate, the model predicted a shallower depth for the calcic horizon than was found in field soils. However, the model was compatible with field soils if one assumed that most pedogenic carbonate formed during a cool-wet (winter) Pleistocene climate. The model was highly sensitive to the frequency of extreme precipitation events and to soil water-holding capacity. The biotic factor played an important role in CaCO3 deposition through its control of soil CO2 concentrations and evapotranspiration rates. The range in predicted CaCO3 deposition rates agreed with the rates for most field studies (1 to 5 g/m2/yr); also, the model predicted an increasing rate of CaCO3 deposition with increasing precipitation, which agreed with field studies. The model is a valuable research tool for evaluating the role of state factors on soil CaCO3 deposition.

The separate contributions of line squalls, thunderstorms and the monsoon to the total rainfall in nigeria

Abstract: Using thunderstorm and rainfall information from five Nigerian stations for a five year period, the separate contributions of line squalls, thunderstorms and ordinary monsoons to the total rainfall and their variations with latitude are investigated. Total and thunderstorm rainfall decreases with increasing latitude but monsoon precipitation decreases exponentially while line squall rainfall is at a maximum around 9°N. Rainfall from thunderstorms shows a single annual peak in July/August at stations north of about 8°N whereas line squall precipitation exhibits a double maximum for all stations south of 12°N. It is also shown that, in the mean, line squalls are the most important rain producing systems, giving 47-6 per cent of the mean total annual precipitation compared with 39 per cent and 13-4 per cent from thunderstorms and ordinary monsoon rain, respectively.

Synoptic Climatology of Precipitation in Iran

Abstract: The uplift mechanisms associated with 24-hour precipitation receipts of 0.1 mm or greater in Iran were investigated. Based on a subjective analysis of daily surface and 500 mb weather charts, we systematically attributed all precipitation at 40 stations for the period 1965–69 to upper tropospheric mechanisms, surface disturbances, marine influence, or instability due primarily to surface heating. These mechanisms together explained 84 percent of all precipitation days. Upper-level disturbances alone explained over 50 percent; when combined with recognizable surface disturbances, this uplift mechanism collectively accounted for over 70 percent of all precipitation days. Surface disturbances were more frequent in the north, but upper-level disturbances alone attained greater relative importance in the south where precipitation was lower. Marine influence was important only near the Caspian Sea and surface heating was a minor trigger in summer only.

Simulating Interception Loss Using Standard Meteorological Data

Abstract: A model was derived to calculate interception loss from a forest canopy on the basis of thrice daily observations of air temperature and relative humidity, daily means of wind run, daily totals of precipitation and the number of rainy hours and of bright sunshine. The forest canopy was characterized by mean tree height, crown density and water storage capacity. The model was calibrated and tested on four separate data sets obtained during 1964, 1965, 1980 and 1981 in the pine forest of the lysimeter station near Castricum, the Netherlands. Model sensitivity was demonstrated for roughness length, the above canopy wind correction factor and relative humidity during rain. Simulated net precipitation explained at least 92 percent of the observed net precipitation, suggesting a good predictive model.

The Relationship between Height and Precipitation Characteristics of Summertime Convective Cells in South Florida.

Abstract: Radar volume scan studies employed two radars simultaneously to measure heights and other echo characteristics of convective cells. Maps produced from the date were used to identify and track cells, whose properties were then related to one another by regression analysis, with the following conclusions: 1) Cell rainfall and area are strongly related. 2) Rainfall intensity, maximum precipitation area, duration and rate of precipitation, and total rain volume are strongly dependent on cell-echo height. Equations defining these relationships are shown to take the form of power laws. 3) Times taken for cells to attain maximum lifetime properties are shown to be interrelated and to be proportional to other basic properties of the cells.

The June 22 tropical squall line observed during COPT 81 experiment: Electrical signature associated with dynamical structure and precipitation

Abstract: The tropical convection experiment COPT 81 (Convection Profonde Tropicale) was carried out near Korhogo (Northern Ivory Coast) during May and June 1981. The June 22 squall line was observed using meteorological and electrical equipment. The frontal part was characterized by a heavy precipitation core associated with strong convection. It was followed by a region of weak precipitation and a wide area of stratiform rain. The characteristic of this squall line resides in the two-dimensional structure of the observed three-dimensional wind fields, with intense convection ahead of the heavy precipitation core. Electrical measurements indicate that electrostatic field changes, at ground level, occurred in the weak precipitation zone and in the stratiform precipitation region. No particular electrical activity was observed in the most convective but shallow part of the squall line. A classical dipole structure appeared within the stratiform area. The stationary electrical structure was coherent with the stationary dynamics and precipitation pattern of the squall line.

Response of vegetation of the Northern Great Plains to precipitation amount and grazing intensity.

Abstract: Changes in basal cover of vegetation were predicted in response to variation in precipitation and grazing intensity. Multiple regression analysis was used with basal cover as a dependent variable and precipitation parameters as independent variables to develop predictive equations. Predicted cover values were used to develop three dimensional response surfaces which describe individual species responses to fluctuating precipitation and different grazing intensities. Results indicate that each species reacts to precipitation regimes and grazing pressure in a unique manner. Continual changes in basal cover can be expected in the plant community as the precipitation regime changes. Moderate grazing intensity, approximately 0.92 ha (2.3 acres) per AUM, appears to be most conducive for maintaining vegetative cover that is desirable for livestock production. However, stocking rate changes need to be anticipated and planned to coincide with available forage because of large fluctuations in cover due to varying precipitation. Climate appears to be the major factor controlling plant growth in the Great Plains. Whitman et al. (1943) stated that drought is the primary influence of vegetational change. Reed and Peterson (1961) Hurtt (1951) and Clark et al. (1943) stated that major trends in vegetation are primarily determined by fluctuations in climatic conditions, and that changes within these major trends are influenced by grazing intensity. Authors are former graduate student, Department of Animal and Range Sciences, Montana State University. Bozeman 597 17; research plant physiologist, USDA-ARS. Livestockand Range Research Station, Route. I Box 2021, MilesCity, Mont. 59301; and assistant professor. Department of Animal and Range Sciences. Montana State University, Bozeman 59717, respectively. The research is a contribution from the Western Region. USDA-ARS, Livestock and Range Research Station and the Montana Agricultural Experiment Station, Journal Series No. J-1445. Manuscript accepted January 2. 1985. JOURNAL OF RANGE MANAGEMENT 38(4), July 1985 There is a close relationship between time and amount of precipitation and plant growth (Albertson et al. 1953). One wet or dry year will affect production, but 2 or more wet or dry years are required to change the basal cover (Johnson 1981). Abrupt and fundamental changes in the amount and kind of living plant crown area may result from severe drought and last longer than anticipated (Reed and Peterson 1961). Both frequency and duration of drought are important in determining the severity of effects of climate on vegetation (Cook and Sims 1975, Herbel et al. 1972). Native vegetation has developed under conditions of wide climatic variation (Albertson et al. 1957). Marked changes in botanical composition occur, but plant populations are seldom completely destroyed by climatic fluctuation (Cook and Sims 1975). These changes are slow, whether for better or worse (Sarvis 1941). Native grass species will remain dominant in prairies unless they are severely grazed or buried by dust (Cook and Sims 1975, Schumacher 1974, Albertson et al. 1957). A more comprehensive understanding of the responses of range ecosystems to weather and grazing is desirable for good management (Reed and Peterson 1961). Drought cannot be controlled, but its impact can be moderated by proper livestock management. To do this, changes in plant communities need to be better defined so that effects of both drought and above average precipitation can be anticipated on the range. There are general ideas of the influence of precipitation and grazing intensity on rangeland plant communities, but only limited effort has been made to predict the responses within plant communities to fluctuating precipitation regimes and different grazing intensities. Models have been developed to predict forage production at different levels of precipitation (Smoliak 1956, Sneva and Hyder 1962, Abel et al. 1962) but similar endeavors that evaluate plant cover response to fluctuating precipitation

A Statistical Analysis of Precipitation Frequency in the Conterminous United States, Including Comparisons with Precipitation Totals

Abstract: An alternative measure of time-aggregated precipitation for use in short-term climate studies is developed. This measure, precipitation frequency, is defined as the number of days per month or season with total amounts ≥ 2.54 mm (0.10 inch). Newly created data sets for the period 1951–80 are used as a basis for describing large-scale spatial and temporal features of precipitation frequency for the mainland United States. Comparisons between precipitation frequency and the conventional statistic, total precipitation, indicate that frequency is more normally distributed and more spatially coherent than total precipitation. Factor analysis and an orthogonal rotation to the varimax criterion are used to identify synoptic-scale, spatially coherent regions of precipitation frequency. The regions are generally consistent with previously documented cyclone trajectories.

Hydrology of low latitude Southern Hemisphere land masses

Abstract: Low latitude southern continental areas are characterized by exposure to high solar radiation and the climatic influence of southward moving warm ocean currents along their eastern coasts together with cool, northward-moving currents on their west coasts. Steep climatic gradients exist from the generally wet eastern coasts to the semi-arid and desert regions of the west. The variability of annual rainfall in both time and space increases with increasing aridity, due to the decrease in influence of reliable precipitation mechanisms and an increased reliance on convective rainfall producing mechanisms. Groundwater resources are more limited and greater reliance must be placed on surface waters for urban, industrial and agricultural purposes. Irrigation is the major water use, thereby adding to the load placed on limited surface resources and accelerating depletion rates. Surface runoff per unit area falls with increase in aridity due to the combined effects of lowered volume and raised rainfall variability plus increases in evaporation from both land surfaces and vegetation. Typically, river flows vary over a wide range from year to year, and in desert areas from hour to hour.

Warm season nocturnal precipitation in the Great Plains of the United States.

Abstract: This paper identifies temporal and spatial patterns in the diurnal cycle of hourly warm season precipitation events over the Great Plains of the United States. Results from 30 years of hourly precipitation records from 515 stations indicate that over 60% of all warm season rainfall (≥0.25 mm) occurs at night from southern Nebraska to panhandle Oklahoma and portions of northern Texas. The larger precipitation events (≥2.54 mm) display a much larger region where 60% of the warm season precipitation occurs at night. Harmonic analysis reveals a remarkably uniform longitudinal gradient in the timing of maximum rainfall frequencies across much of the Great Plains. The more precise identification of these spatial and temporal patterns should be particularly useful in 1) assessing the many theories of nocturnal precipitation in the central United States, 2) verifying numerical precipitation models for the region, and 3) generating rainfall forecasts for various times of the day.

Measuring the Global Distribution of Intense Convection over Land with Passive Microwave Radiometry

Abstract: The global distribution of intense convective activity over land is shown to be measurable with satellite passive-microwave methods through a comparison of an empirical rain rate algorithm with a climatology of thunderstorm days for the months of June-August. With the 18 and 37 GHz channels of the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR), the strong volume scattering effects of precipitation can be measured. Even though a single frequency (37 GHz) is responsive to the scattering signature, two frequencies are needed to remove most of the effect that variations in thermometric temperatures and soil moisture have on the brightness temperatures. Because snow cover is also a volume scatterer of microwave energy at these microwavelengths, a discrimination procedure involving four of the SMMR channels is employed to separate the rain and snow classes, based upon their differences in average thermometric temperature.

Diurnal Variability of Precipitation in the Northeastern United States

Abstract: The diurnal and semidiurnal variations of precipitation over the northeastern United States (New England, New York, New Jersey and Pennsylvania) are investigated using 25 years of hourly precipitation data for 271 stations. The hourly data were harmonically analyzed for all measurable precipitation events ranging upwards to amounts < 10.0 mm. Additionally, a regional probability of precipitation analysis was performed for homogeneously grouped stations. The winter season (November–March) displays a general early-to-midmorning diurnal maximum for all measurable precipitation events across the Northeast with a shift to just before noon southward into Pennsylvania. For heavier precipitation events, much of the region retains the morning maximum, a notable exception being the northern mountains of New York and New England, where there is a late-evening maximum. The spring (April–May) season is quite similar to winter, although the diurnal amplitudes become weaker everywhere except from southeastern P...

The Integrated Lake-Watershed Acidification Study: Atmospheric Inputs

Abstract: Atmospheric inputs to Woods, Panther, and Sagamore Lake-Watersheds in the Adirondack Mountains of New York State were measured on a daily basis from March 1978 through December 1981. Precipitation quality was nearly identical at all sites on monthly and yearly bases; ion loadings to each watershed were principally controlled by the amount of precipitation. No yearly trend was evident for any ion concentration in wet deposition. Annual precipitation quantities showed little deviation from long-term averages for this region. Throughfall measured under various species of trees showed enrichment in most base cations and acid anions. Deciduous trees were found to increase the pH of incident precipitation, while coniferous canopies tended to decrease pH.

Wet deposition due to fog in the Po Valley, Italy

Abstract: Wet deposition due to radiation fog is examined in this paper. The area where the reported measurements were performed, the Po Valley, northern Italy, is characterized by both a high fog occurrence during the fall-winter months and fog water solutions of high ionic concentration and acidity. Estimated wet deposition for NH 4 + , NO inf3 sup- and SO inf4 sup2- ions due to fog droplet settling to the ground accounts for 13.2, 12.1 and 5.3 percent with respect to bulk precipitations over the same period: January–March and October–December (fog season). Fog deposition rates show that this process can be an important pathway of trace gases and particles loss from the air. First indicative results of fog removal efficiency with respect to air particulate matter are presented. Dry deposition parameters should be taken into account in evaluating the potential effect of fog droplet deposition on vegetation.

The chemical characteristics of snow cover in a northern boreal forest during the spring run-off period

Abstract: An intensive snow-cover survey at Lake Laflamme, Quebec, during the spring of 1983 showed that wet deposition in the form of rain, which was a dominant phenomenon during the 1983 melt season, gave rise, according to the intensity and chemical quality of the precipitation, to both losses and gains of ion loads (meq m−2) in the snowpack. Mean values for the daily wet deposition loadings (meq m−2 d−1) of ionic species associated with atmospheric aerosols (H+, , ) were of approximately the same magnitude as the daily changes in gains recorded in the snow cover during the melt period. In contrast, the mean value for the contribution by wet deposition to the total loads of K+ and in the snow cover was far outweighed by the gains which were observed at the same time. The expected losses for the snowpack, calculated from the sum of the total loads stocked in the pack at the beginning of the melt period and the total loads in precipitation during the melt period, were lower than the sum of the actual losses observed for all ionic species except H+. The increases (%) in the loads for the major anions Cl−, and were comparable (25 to 32%). The results suggested that dry deposition either directly by aerosol interaction with the snow cover or indirectly by adsorption on organic material followed by leaching during the melt period, or by a combination of both, was a major factor in the increases observed. The values for the increases in loads for Ca2+, , Mg2+ and Na+ (50 to 287%) probably represented, in addition to leaching of local debris, the exudates of cellular material from the cell plasmolysis of detrital organic debris. High rates of in-pack production, however, were characteristic of Al3+. Mn2+, K+ and which showed substantial increases in pack loads (480 to 750%). These increases cannot be accounted for by any local phenomena other than the dissolution or microbiological degradation of organic debris. It is suggested that ion exchange capacity of both particulate and soluble organic material led to a decrease in pack acidity; this phenomenon should thus be considered as a major factor in all attempts to model acid rain fluxes through boreal forest systems.