Inadvertent Weather Research Articles

Nonlocal Inadvertent Weather Modification Associated with Wind Farms in the Central United States

Local effects of inadvertent weather changes within and near wind farms have been well documented by a number of modeling studies and observational campaigns; however, the broader nonlocal atmospheric effects of wind farms are much less clear. The goal of this study is to determine whether wind farm-induced perturbations are able to evolve over periods of days, and over areas of thousands of square kilometers, to modify specific atmospheric features that have large impacts on society and the environment, specifically midlatitude and tropical cyclones. Here, an ensemble modeling approach is utilized with a wind farm parameterization to quantify the sensitivity of meteorological variables to the presence of wind farms. The results show that perturbations to nonlocal midlatitude cyclones caused by a wind farm are statistically significant, with magnitudes of roughly 1 hPa for mean sea-level pressure, 4 m/s for surface wind speed, and 15 mm for maximum 30-minute accumulated precipitation. Cyclone perturbation magnitude is also found to be dependent on wind farm size and location relative to the midlatitude cyclone genesis region and track.

Experimental, Observational, and Numerical Research on Intentional and Inadvertent Weather Modification

Experimental, Observational, and Numerical Research on Intentional and Inadvertent Weather Modification

Acidic Cloud Episodes in the Northern Colorado Rockies: Inadvertent Weather Modification?

Acidic cloud episodes were detected in January 1998 and January 2000 at Storm Peak Laboratory (SPL) in the northern Colorado Rockies. The episodes were characterized by increased concentrations of small droplets and condensation nucleus concentrations and reduced liquid water contents, snowfall rates and sub-cloud relative humidities. The trajectories of the air parcels arriving at SPL before, during and after the episodes were studied. The parcels arriving during the episodes encountered the least precipitation during their journey to SPL, suggesting little cloud and precipitation scavenging of aerosol particles. Further, much of the difference in acidity can be explained by dilution of the cloud droplets. Thus, the episodes may be primarily a natural phenomenon.

Characteristics of Recent Severe Haze Events in Korea and Possible Inadvertent Weather Modification

Characteristics of Recent Severe Haze Events in Korea and Possible Inadvertent Weather Modification

A Critical Assessment of Hygroscopic Seeding of Convective Clouds for Rainfall Enhancement

During the past decade, statistically positive results have been reported for four major, randomized hygroscopic seeding experiments, each in a different part of the world. Experiments on cold convective clouds using hygroscopic flares were carried out in South Africa and Mexico. Experiments on warm convective clouds using hygroscopic particles were carried out in Thailand and India. The scientific evidence for enhancing rainfall from convective clouds by hygroscopic seeding from these four randomized experiments is examined and critically assessed. The assessment uses, as a measure of proof of concept, the criteria for success of any cloud seeding activity that were recommended in the Scientific Background for the 1998 AMS Policy Statement on Planned and Inadvertent Weather Modifications, criteria that required both statistical and physical evidence. Based on a critical examination of the results of these four major, randomized hygroscopic seeding experiments, it has been concluded that they have not yet provided either the statistical or physical evidence required to establish that the effectiveness of hygroscopic seeding of convective clouds to increase precipitation is scientifically proven. The impressive statistical results from these experiments must be viewed with caution because, according to the proof-of-concept criteria, credibility of the results depends on the physical plausibility of the seeding conceptual model that forms the basis for anticipating seeding-induced increases in rainfall. The credibility of the hygroscopic seeding for microphysical effects hypothesis has been seriously undermined because it cannot explain the magnitude and timing of the statistically significant increases in precipitation that were observed. Theories suggesting that the microphysical effects of seeding-enhanced downdraft circulations to produce longer-lived clouds have been advanced; however, in the absence of any supporting physical or model evidence, they must be considered to be in the realm of speculation. These results do not alter this author's basic position; cloud seeding is advocated in situations where it is scientifically and operationally appropriate, and it is strongly recommended that an independent evaluation accompany each research or operational project in order that the science of weather modification benefit from the experience.

Intense Convective Storms with Little or No Lightning over Central Arizona: A Case of Inadvertent Weather Modification?

Abstract On 20/21 August 1993, deep convective storms occurred across much of Arizona, except for the southwestern quarter of the state. Several storms were quite severe, producing downbursts and extensive wind damage in the greater Phoenix area during the late afternoon and evening. The most severe convective storms occurred from 0000 to 0230 UTC 21 August and were noteworthy in that, except for the first reported severe thunderstorm, there was almost no cloud-to-ground (CG) lightning observed during their life cycles. Other intense storms on this day, particularly early storms to the south of Phoenix and those occurring over mountainous terrain to the north and east of Phoenix, were prolific producers of CG lightning. Radar data for an 8-h period (2000 UTC 20 August–0400 UTC 21 August) indicated that 88 convective cells having maximum reflectivities greater than 55 dBZ and persisting longer than 25 min occurred within a 200-km range of Phoenix. Of these cells, 30 were identified as “low-lightning” storm...

Atmospheric Sciences at the Illinois State Water Survey: Five Decades of Diverse Activities and Achievements

During a 50-yr history of diverse scientific endeavors, the Illinois State Water Survey's weather group has constantly shifted to meet new challenges as the nation's only sizable atmospheric research and services group housed in a state agency. The hundreds of projects encompass basic and applied research; data collection, evaluation, and storage; field projects; instrument design, development, and testing; and a services program in response to the needs of the public and specialized users of weather and climate information. Areas of major achievements include development of numerous meteorological instruments and data systems including the CHILL radar; participation in several national field projects, including the Metropolitan Meteorological Experiment (METROMEX); and pioneering research in radar meteorology, weather impacts, planned weather modification, inadvertent urban weather and climate change, applied climatology, and hydrometeorology.

Comments on “Planned and Inadvertent Weather Modification,” a policy statement of the American Meteorological Society

Comments on “Planned and Inadvertent Weather Modification,” a policy statement of the American Meteorological Society

Planned and Inadvertent Weather Modification

Planned and Inadvertent Weather Modification

Coalescence Enhancement in large Multicell Storms Caused by the Emissions from a Kraft Paper Mill

While conducting a randomized seeding experiment, a storm was selected whose microphysical characteristics were so far from what was expected, given the existing thermodynamic environment, that some explanation was needed to account for the apparent errant behavior of this storm. More than a decade of sampling at −10°C using the project Lear jet has led to a simple classification technique, based on cloud-base temperature and buoyancy, which predicts the absence or presence, and to some extent the degree of coalescence (coalescence-freezing) precipitation growth in local convective storms. The unusual nature of this storm was recognized against this extensive microphysical database. The probable cause is attributed to emissions from a Kraft paper mill 10 km south of the storm's position. The mill had recently undergone an expansion program that had quadrupled its output of paper products. Using the radar characteristics of this unusual storm as a guide, a search of one season of radar data revealed the existence of five other similar storms, all within about 30 km of the paper win. These records indicated that the storms apparently modified by the paper mill tended to last longer, grow taller, and rain harder than any other storms recorded on that day. The new awareness of this apparent inadvertent weather modification by the paper mill led to launching missions to intercept clouds growing in the vicinity of the mill. Storms, apparently altered by the mill, were sampled and compared to other nearby storms. The most singular feature of the modified storms was the appearance of lame (>4 mm) drops at the most common sampling level (−10°C), indicating an accelerated or enhanced coalescence precipitation formation process. Measurements in a field of cumuli indicated a broadening of the cloud-base droplet spectra in clouds affected by the emission of the mill. It is the addition of this “long tail” to the cloud-base droplet spectra that is apparently turning on or at least enhancing coalescence in affected storms.

Dust devils at White Sands Missile Range, New Mexico: 1. Temporal and spatial distributions

From May 13, through August 21, 1986, and again from April 3, through May 28, 1987, a dust devil census was conducted at the Permanent High Explosive Test Site on White Sands Missile Range, New Mexico. In a 260‐km2 observation area, a total of 3134 dust devils were counted on 97 days (out of 112 observing days). Within the observation area, the dust devils were concentrated in a relatively small area and showed strong correlation with roadways and other cleared areas. However, from the summer of 1986 to the spring of 1987, the center of activity shifted from a relatively undisturbed region to an area whose surface had been recently modified. This shift is attributed to changes in soil moisture and surface thermal properties. It is suggested that the co‐location of the center of activity in 1987 with the modified surface is an example of inadvertent weather modification on a very local scale. The dust devils had a daily distribution very similar to that found by Sinclair (1969) in comparable terrain in the vicinity of Tucson, Arizona. The time of the first observed dust devil was very regular on days with dry surface conditions at sunrise and clear skies through the morning. The time of the first dust devil was delayed and the degree of activity reduced if precipitation had occurred on a previous day in the observation area. The production of dust devils often ended abruptly with the onset of an afternoon thundershower in the observation area.

Planned and Inadvertent Weather Modification

Planned and Inadvertent Weather Modification

Planned and Inadvertent Weather Modification

Planned and Inadvertent Weather Modification

PURPOSEFUL AND ACCIDENTAL WEATHER MODIFICATION: OUR CURRENT UNDERSTANDING

The fields of planned and inadvertent weather are reviewed. The history, major problems, current scientific status, and research needs are assessed. Planned weather modification has been plagued by groups with conflicting interests and views, and most of the major U.S. experiments have failed owing to various problems. Basic research in cloud physics and dynamics is needed but the field now has the expertise and instrumentation to make major advances. Inadvertent weather modification studies have defined many of the urban influences but studies of regional-scale effects from irrigation and aircraft contrails need to be pursued. Studies are recommended to define better the social and environmental impacts from altered weather.

Atmospheric Issues Identified in State Water Resource Planning

Abstract Illinois is completing a comprehensive statewide water plan. The plan selects three atmospheric issues, among the 11 identified as key issues facing the state's water resources. The issues selected include climate change and prediction, inadvertent weather and climate modification, and planned weather modification. Each atmospheric issue presents major resource or policy problems, with capabilities needed to enhance the quality and/or quantity of the state's waters. The identification of these atmospheric issues reveals awareness at the policy level of their importance. Policy and programmatic needs found to be common to each issue include 1) collection of more data and continued research (with an increasing state role; 2) coordinated policy development around atmospheric expertise from several agencies and universities; and 3) an expanded public information program. A Climate Detection and Assistance Board is to be established in Illinois to provide the planning, coordination, and assistance nee...

Policy statement of the American Meteorological Society on planned and inadvertent weather modification

policy statement of the American Meteorological Society on planned and inadvertent weather modification

The Rationael for Future Weather Modification Research

A new national effort dealing with planned and inadvertent weather modification has been recommended. The contention is that this readiness stems from finally learning important facts about how to properly design and conduct difficult experimentations; the need to study and understand ever growing inadvertent weather modification; the development of complex instrumentation and growing expertise; and more awareness of the impacts of changing the weather. Most importantly, awareness has come that progress can be made only through great attention to resolving many of the complex unknowns in the areas of cloud physics and dynamics. The potential benefits of an uncertain technology are difficult to specify, but appear sufficient to justify the research and development costs many have recommended. Either a better research program should be developed or we should essentially stop weather modification research.

Is Your Weather Being Modified?

Most atmospheric modification that exists in the United States is occurring accidentally as a result of man's land-use changes. Cities, power plants, and certain agricultural activities modify the weather, often dramatically, on local and regional scales. These unintentional changes are so important and widespread that study of their scale and nature is essential in many design and policy areas. Knowing more about inadvertent weather modification has become a part of wise planning for hydrologic, agricultural, transportation systems, and activities. Furthermore, regional weather changes due to man's use of land may reduce or enhance the effectiveness of efforts to purposefully modify the weather.

Impact of man upon local and regional weather

The 1975–1978 period has brought new realization that considerable atmospheric modification exists in the United States as a result of man's land use change [Weather Modification Advisory Board, 1978]. Cities, power plants, and certain agricultural activities modify the weather, often dramatically, on local and regional scales. Concern over these unintentional changes has grown nationally, making study of their nature and magnitude essential in many design and policy areas. Awareness of inadvertent weather modification has only recently become a part of wise planning for hydrologic, agricultural, transportation systems, and human activities.

Rocket Effluent: Its Ice Nucleation Activity and Related Properties

To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager 1 and 2 launches. The aerosol's morphology, concentration, and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. Ice nucleus concentration was measured with a thermal diffusion chamber. The particles' physical and chemical properties were related to their ice nucleation activity. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce active ice nuclei and modify local weather in suitable meteorological conditions.