Content Meter Research Articles

Calibrations of Johnson-Williams Liquid Water Content Meters in a High-Speed Icing Tunnel

Abstract Wind tunnel tests have provided calibrations and intercomparisons of 14 Johnson-Williams (J–W) cloud liquid water content (LWC) measuring devices with 23 sensor heads from 10 research organizations. The absolute tunnel LWC was deduced using a rotating icing cylinder technique accurate to ∼5%. A significant fraction of the systems arrived at the tunnel with nonfunctional shell or strut heaters, which can degrade measurements below 0°C. Several sensor heads exhibited airspeed dependencies. Switching heads sometimes produced calibration changes. At −15°C an instrument problem was discovered associated with icing of the compensating wire posts, which resulted in mild to severe measurement errors in 75% of the sensor heads at 103 m s−1. Calibrations at −5°C revealed that J-W measurements usually varied linearly with tunnel LWC, but sometimes with a slope differing from unity, implying that the system dummy head did not always define the correct conversion from J-W output voltage to grams per cubic met...

油分濃度計測のための試料水配管系について

In monitoring the oil contents of ballast water being discharged from tankers, sample mixtures extracted from the effluent should be pumped up to oil content meters through the long piping system.Two tankers, existing and newly constructed, are investigated about specifications of the piping systems both for sample mixtures and over board discharge. While, the effects of the specifications on the errors in measuring the oil contents are studied experimentally with a simulating apparatus of the systems.The fluctuations in oil concentration at the outlet of the apparatus rise to 10-200% of the mean concentrations at the inlet especially for highly viscous oils. Measures to reduce the errors being caused by the fluctuations are shown as follows:(1) Increase of the flow velocity through the piping system.(2) Increase of the temperature of the sample mixture.(3) Elimination of stagnant flow, such as that in large strainer, from the system and frequent flushing with fresh water.

Errors in measuring water content of materials containing hydrogen with NMR content meters

Errors in measuring water content of materials containing hydrogen with NMR content meters

Precipitation Initiation Mechanisms and Droplet Characteristics of Some Convective Cloud Cores

Samplings of the unmixed cores and the mixed edges of convective clouds at various heights were made in an aircraft using standard instrumentation and a Continuous Particle Collector (CPC). The unmixed cores are defined as regions where constant values are indicated on the hot wire type, liquid water content meter. The various correction factors relating these CPC replicas to the true droplet and drop situation in the cloud are not well established, but the observations are nevertheless sufficiently accurate 1) to give some useful data on the relative size distributions of small droplets, and 2) to show that drizzle-size drops can develop quickly within the cloud core. The evolution of the distributions of small droplets (<40μ diameter) with height is shown. Droplet concentrations are of the order of 1000 cm−3 near cloud base, and some correlation between concentration and upcurrent strength at cloud base is noted. The large droplets from which drizzle-size drops evolve can be present, even at cloud base, in concentrations of about 20 liter−1. Possible sources of these large droplets are discussed. Graupel was encountered at −5 and −6 C, mostly outside the convective cores, presumably resulting from the freezing and riming of the larger liquid drops at relatively warm temperatures.

Cloud physics at the meteorological research flight

A review is given of the aircraft instrumentation used for cloud physics investigations. Below the cumuliform cloud the nature of the convection is examined by means of rapidly acting thermometers, hygrometers, hot wire anemometers and aircraft accelerometers. In the lowest 1000 feet where the lapse-rate is slightly super-adiabatic, continuously turbulent conditions are found. Above this bubbles or pulses 300–600 feet across rise sporadically in an environment whose lapse-rate is approximately dryadiabatic. Just below the cloud base the lapse-rate is usually stable and long wave fluctuations of temperature in the horizontal are found. Within the cloud temperatures are difficult to measure accurately. Attempts to use vortex thermometers for this purpose have been unsuccessful. Vertical currents can be estimated roughly from aircraft displacements. Water content in cumuliform cloud probably attains local values of about 5 g/m3 for short periods, but up to the present none of the instruments developed have been capable of measuring amounts of this magnitude. The progress made so far in developing hot wire water content meters and refrigerated icing disc meters is described. Cloud particles can readily be sampled from aircraft when they are small but satisfactory methods have not yet been developed for the larger particles (e.g. hail, snow and rain). Droplet sampling over England has shown the presence of large droplets (100 microns diameter or more) in moderate sized cumulus clouds. Examples are shown of rain being produced by stratiform warm sector clouds with tops well below the freezing level and precipitation in large cumulus clouds apparently preceeding the ice crystal stage. A comparison between average cloud top temperatures for clouds which produce rain and for those whose tops are composed of ice crystals rather than supercooled droplets suggests that rainfall in England may often be produced in clouds in which theBergeron mechanism does not operate.