Langmuir Laboratory Research Articles

Airborne and ground‐based studies of thunderstorms in the vicinity of Langmuir Laboratory

AbstractFlights through the central regions of thunderstorms were made over New Mexico on 6 and 15 August 1977 with the ONR/NMIMT Schweitzer aeroplane which carried equipment designed to measure all three components of the electric field, and the charge, Q, and diameter, d, of individual precipitation elements. On the earlier day, information was also obtained with: a rain‐gauge network surrounding Langmuir Laboratory; a 3 cm radar; an acoustic system for locating lightning channels; a ground‐based field‐change meter.The first cell on 6 August produced precipitation at the ground but no lightning. Vertical fields, Ex, of up to about 50kVm−1 and precipitation charge densities ρ of up to −0.5 C km−3 were recorded within the cloud. The second cell, which grew as the first one decayed, produced 7 lightning strokes in 9 minutes during which time the radar revealed vigorous vertical growth in a narrow zone containing precipitation.Thunder reconstructions showed the acoustic sources for the first flash of this cell to be very near the top of the cloud at an altitude of 10 km a.s.1. The subsequent flashes produced acoustic signals from progressively lower in the cloud. When the radar echo reached its maximum height lightning activity ceased. Ex values of up to about 50kVm−1 and pp values of down to −1 Ckm−3 were measured. ρp was consistently negative, individual charges being less than ±40 pC. Q values were within the inductive limit for a thundercloud at breakdown but no systematic relation between Q and d was found.Six penetrations were made through the thundercloud of 15 August, which produced only two lightning strokes. The Ex records were indicative of a (±) dipole located near the cloud top, at around –13°C. Fields of up to about 100kVm−1 and ρp values (positive and negative) of around 5Ckm−3 were measured. Q values of up to ±250 pC were recorded, with charges around ±50 pC being commonly found. No systematic Q‐d relation was revealed, and smaller precipitation particles frequently carried charges (positive or negative) in excess of the inductive limit.On both days estimated precipitation rates were of order 10mmh−1 and on most occasions the pilot reported precipitation particles to be either ‘ice’ or ‘mixed liquid water and ice’.

Airborne and ground-based studies of thunderstorms in the vicinity of Langmuir laboratory

Airborne and ground-based studies of thunderstorms in the vicinity of Langmuir laboratory

Thunderstorm on July 16, 1975, over Langmuir laboratory: A case study

The electric field along the path of an instrumented balloon was closely coupled to the wind profile and to the radar echo structure of a weak thunderstorm over Langmuir Laboratory on July 16, 1975. The balloon ascended at 3.5 m/s into the southern part of the storm, where a stable layer had stopped the cloud's vertical convection at 6.4 km above sea level. At lower altitudes, near the cloud base, the balloon rose past two nearby oppositely charged regions which were associated with a precipitation echo and with an outflow of air from the storm. When the balloon ascended into clear air through the top of the lower cloud at 6.4‐km altitude, its motion indicated a sharp change in wind direction, and its electric field meter showed an abrupt decrease in field intensity, probably from a screening layer at the cloud boundary. Above 7.5 km the balloon encountered a slanted and charged downdraft just before entering the northern part of the storm under its anvil cloud. This downdraft, which had a velocity of about 6 m/s, was a prominent and persistent feature of the cloud's circulation. It held the balloon at a nearly constant altitude of 7.7 km for 10 min while carrying it 3 km toward the center of the storm. When the electric field meter descended, after release from the balloon, it encountered the downdraft a second time, 24 min after its first encounter. Electric field measurements suggest that the downdraft was carrying a negative charge. Our measurements on this storm also contain evidence for vertical transport of horizontal momentum and for a net positive charge in the upper part of the storm.

Conjugate photoelectron excitation of O I 4368 airglow emission

Conjugate photoelectron fluxes are shown to be mainly responsible for the excitation of O I 4368 radiation observed with a grille spectrometer located at Langmuir Laboratory, New Mexico (L equals 1.7). On the basis of observations of O I 7774 and 4368 tropical emissions at Agulhas, Negras, Brazil (L equals 1.1), the contribution of radiative recombination to the New Mexico intensity is shown to be small. Conjugate photoelectron excitation at the Brazilian site has not been observed.

Electric field measurements in thunderclouds using instrumented rockets

In the summer of 1969 we launched instrumented 2.75-inch-diameter Folding Fin Aircraft Rockets from the ground through thunderclouds over Langmuir Laboratory, New Mexico, to measure electric fields. The instrument is our version of the rotating-cylinder field mill. The entire rocket is made to spin by modifying its fins; thus there are no moving parts relative to the rocket. It measures only the component of E perpendicular to the long axis of the rocket (i.e. the radial component). The instrument is not sensitive to charge on the rocket or to corona from the fins; corona from the front of the rocket is minimized by the design. The signal is transmitted by FM telemetry. With the initial flights we found that intensities of the radial electric fields in thunderclouds were commonly over 10 kv/m but seldom over 60 kv/m and that they did not change rapidly with distance. Significant changes occurred only in 500 meters or more.

Scientists to map anatomy of a thunderstorm

Scientists from several countries are participating in a study at Langmuir Laboratory, New Mexico to find out what causes thunderstorms and the associated lightning and rain. Their tools include rockets, airplanes, a laboratory in the sky, and a powerful IBM information processing system.Langmuir Laboratory, supported primarily by the National Science Foundation, is literally a laboratory in the clouds. Built atop a 10,600‐foot peak in the Magdalena Mountains west of Socorro, New Mexico, the laboratory site is unique in that thunderstorms occur almost daily during the summer and autumn, directly above and around the lab.

Seasonal Behaviour of Atmospheric Pressure Oscillations

IT is well known that the atmospheric pressure at any given point does not remain constant in time and is subject to periodic and non-periodic fluctuations. Statistical analyses have been used to establish them and many investigations have been published. This communication reports the results of a spectral density analysis performed for the barometric pressure data at the Langmuir Laboratory (33° 59′ N., 107° 11′ W., elevation 3,320 m above mean sea level), a research facility of the New Mexico Institute of Mining and Technology, and at the Institute campus at Socorro (34° 4′ N., 106° 54′ W., elevation 1,410 m above mean sea level). The Langmuir Laboratory is on a summit ridge of the Magdalena Mountains and the campus is 27 km east in the Riogrande Valley. A comparison of the results of these two stations provides an interesting example of atmospheric behaviour in a “mountain–valley” situation.

Conductivity and concentration of small ions in the lower atmosphere

The correlation between polar conductivity and the concentration of atmospheric small ions with mobilities higher than 10−4 m2 v−1 sec−1 has been investigated by means of a Gerdien conductivity meter. The apparatus has been operated in Socorro at an elevation of 4620 ft and at 10,640 ft on a nearby mountaintop at the Langmuir Laboratory. The correlation coefficient between conductivity and concentration is higher than 0.97 for positive as well as for negative ions at both locations. A least-squares analysis of the results of measurement furthermore shows that the conductivity is proportional to the concentration of small ions. The over-all average mobility has been found to be 1.6×10−4 m2 v−1 sec−1 for small positive ions and 2.0×10−4 m2 v−1 sec−1 for small negative ions. The average fair-weather negative and positive conductivities on the campus and the negative conductivity at the Langmuir Laboratory are essentially the same, having a value of 1.4×10−14(ohm-m) −1. The average positive conductivity at the mountain site is 3.2 times the other values. This is attributed to the higher atmospheric electric field, with a resultant ‘electrode’ effect.

Atmospheric physics

The Irving Langmuir Laboratory for Atmospheric Research, established last year by the New Mexico Institute of Mining and Technology, is currently engaged in a variety of research programs relating to cloud physics and thunderstorm phenomena. During the International Quiet Sun Years of 1964 and 1965, the Laboratory is cooperating with the Joint Committee on Atmospheric and Space Electricity of the International Union of Geodesy and Geophysics by making data available for use in an international effort to correlate the basic parameters of atmospheric electricity on a world‐wide scale.