Single Gauge Research Articles

Effect of rainfall variability on streamflow simulation

Three recording rain gages in a 9.7‐square‐mile basin in southern California were used with a deterministic rainfall‐runoff model to simulate flood hydrographs and peaks and to assess the effects of data errors on simulation results. Bias in the estimation of effective basin rainfall seemed to result in curve fitting parameter adjustments which compensated for the bias. The combined effects for a storm of both difference in the time distribution of rainfall at different points and spatial variability of rainfall volume over the basin limit the possible accuracy of simulation results. The use of a single rain gage on a basin with this hydrology can at best be expected to predict peak discharge with a standard error of estimate on the order of 20%.

THE EFFECTS OF EARTH LEAKAGE ON ELECTRICAL RESISTANCE STRAIN GAUGES

An attempt is made to clarify the effects and the measurement of earth leakage in a strain gauge installation. A rough basis is provided on which the seriousness of the earth leakage effects may be estimated for a single active gauge in a Wheatstone Bridge Circuit.

Evaluation of Precipitation Measurements with the WSR-57 Weather Radar

Quantitative data collected with the WSR-57 radar at Atlantic City from five rainstorms and two snow-storms are compared with precipitation data from 60 recording rain gages within 100 mi of the radar. Hourly rainfall amounts of from 0.01–0.02 inches are detected by the radar in at least 95 per cent of the cases at all radar ranges out to 70 mi. Hourly amounts of from 0.04–0.05 inches are detected in at least 95 per cent of the cases at all ranges out to 100 mi. The relationship between radar echo intensity and rainfall rate varies from storm to storm. Although the radar appears to have excellent potential for determination of area-average rainfall, reflectivity measurements provide only coarse estimates of point rainfall intensity. The radar estimates of hourly rainfall averages, over a 750 sq mi area within 60 mi of the radar, are within the confidence limits of the average of 10 gage measurements, when a best-fitting radar-rainfall relationship is used for each storm. Use of one grand average relationship for all storms provides estimates of the average areal rainfall whose accuracy corresponds to those of a single rain gage located near the area center. An analysis of errors made in transferring PPI photographs to digitized arrays and in measuring the echo intensity in steps of 6 db indicates that a reduction in the size of these errors would not substantially improve the accuracy of the radar measurements. An important unresolved problem concerns the development of techniques for quick determination, under field conditions, of the most accurate reflectivity-rainfall relationship for a particular storm. A chart based on the average relationship developed in this study is presented for converting echo intensities measured with a WSR-57 to rainfall intensities.

Measurements of the Substitution Sensitivity Factor to Propane, and Helium Gases for the Leak Hunting

The substitute sensitivity factor (φ) for the single ionization gauge method was obtained experimentally for propane and helium gas which had been used for the leak hunting at the laboratory with three fixed leaks and an oil diffusion pump system.A series of fixed leak was made by flattening an annealed copper tube with inner diameter of about 1 mm and a flattened length of all the leaks was in 14 mm. The flow rates of those leaks were stably 3.0×10-3, 2.1×10-4, and 1.3×10-5 mm.Hg·1·sec-1 for air from an atmosphere to vacuum respectively.When a probe gas was covering over the leak or removing from it, transitional changes of an ionization gauge, which electron currents was controlled automatically at a constant value by electric circuit, were recorded on an electrical self-recorder.As to the φ values of the probe gases on three fixed leaks fixed values were not obtained just as the reference showed for other gases, but these values spreaded in a wide range as follows : Probe gas leak rates of fixed leaks for air in mm Hg·l·sec-13.0×10-3 2.1×10-4 1.3×10-5Propane 2613.8 13.64.8 6.83.3Helium - (0.960.92) - (0.930.89) - (0.880.85) In order to anaiyze these experimental data, flow rates of the gases were directly measured by the constant pressure method having a small dead volume. The characteristics of flow ratio to air are given as changing from viscous flow to molecular one as the leak rate of air becomes smaller.The spread of φ is thought to be due to the fact that the pumping speed of oil diffusion pump system is unstable at transitional pressure rather than the ionization cross section of probe gases to electrons varies in the gauge.

Forecasting Summertime Shower Activity at Grand Junction, Colorado

Due to the lack of a dense network of reporting stations in the Grand Junction, Colorado area and the inadequate representation of shower activity by observations of rain at a single rain gage, certain arbitrary criteria were set up to define a “shower” day at Grand Junction. Relationships of a number of meteorological variables to shower activity were determined and the four variables which showed the strongest relationships were combined graphically to form an objective forecast aid for determining the probability of shower activity at Grand Junction during the 18-hour period 1130MST to 0530MST. Tests on independent data confirm the relationship found in the developmental data.

Single versus multiple cage occupancy and convulsion frequency in C3H mice.

ConclusionsC3H male mice, singly housed and fed ordinary diets, show a high incidence of convulsions, associated chiefly with cage changing and weighing. When housed in pairs or larger groups the incidence of convulsions is low and the mortality negligible.

Accuracy of determination of annual precipitation over a given area

The limits within which the total precipitation as measured by a single gage represents the total precipitation over the surrounding area is a subject of great interest to hydrologists and meteorologists. The lack of adequate data from large areas has made detailed analytical studies impossible. The precipitation‐gage network established during the period from 1935 to 1940 in the Muskingum River Watershed in Ohio by the U.S. Soil Conservation Service provides data for limited studies for a 8038‐sq mi area. Records from 230 gages for a full year beginning October 1, 1939; are available. The data from these stations have been used by the authors to analyze the effect of gage spacing on the accuracy of determination of the amount of annual precipitation for areas in Ohio ranging in size from a few square miles to 8000 sq mi.

Differential methods of leak detection

An experimental investigation of the differential method of detecting leaks in high vacuum systems has shown that it is possible to attain a sensitivity 20 times greater than that of the corresponding single gauge method. The differential pressure change may be produced either by differential condensation of gases such as butane or by chemical absorption of carbon dioxide. With the latter method, using extremely simple equipment, a sensitivity of 10-3 lμ/sec may be obtained. With differential condensation and ionization gauges the sensitivity is only a factor 10 less than that of the mass spectrometer leak detector.

Bakerian lecture.—On the law of the pressure of gases between 75 and 150 millimetres of mercury

The observations here recorded were intended to bridge over in some degree the gap between the very low pressures (below 1·5 mm.) dealt with in a recent paper and pressures approaching the atmospheric for which the usual mercury column and cathetometer method is adequate. The principal novelty consists in the use of two similar manometric gauges. Pressures in the ratio of 1 : 2 are obtained by the use first of a single gauge and secondly of the two gauges connected in series.