Abstract: Cloud seeding is a form of weather modification, a way of changing the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud. The most common chemicals used for cloud seeding include silver iodide, potassium iodide and dry ice. Liquid propane, which expands into a gas, has also been used. Cloud seeding is used to increase precipitation in an area, to evaporate fog and clouds to keep an area dry by precipitating out, for reducing the cloud cover, to clean out the pollution, to help put out wildfire by making it rain. Cloud seeding has never been statistically proven to work but it is claimed to increase precipitation (Pelley, 2016). Since India is not very water rich, the cloud seeding technology is very closely associated with water resource management that is the major requirement for India. Under the guidelines of the Clean Water Act by the EPA, silver iodide is considered a hazardous substance, a priority pollutant and as a toxic pollutant. Chronic ingestion of iodides may produce skin rashes, running nose, headache and irritation of the mucous membranes.

Abstract: The Wyoming Weather Modification Pilot Project randomized cloud seeding experiment was a crossover statistical experiment conducted over two mountain ranges in eastern Wyoming and lasted fo...

Abstract: The sensitivity of warm and mixed-phase orographic precipitation to the aerosol background with simultaneous changes in the abundance of cloud condensation nuclei and ice nucleating particles is explored in an idealized, 2-dimensional modeling study. The concept of precipitation susceptibility d ln P / d ln N, where P is the precipitation mixing ratio and N the cloud droplet number, is adapted for orographic clouds. Precipitation susceptibility is found to be low because perturbations to different precipitation formation pathways compensate each other. For mixed-phase conditions, this in particular means a redistribution between warm and cold pathways. The compensating behavior is described as a consequence of a balance equation for the cloud water along parcel trajectories that constrains the total precipitation formation to match the drying from condensation and vapor deposition on ice-phase hydrometeors caused by the mountain flow. For an aerosol-independent condensation rate (saturation adjust...

Abstract: Targeting seedable clouds with silver iodide in complex terrain adds considerable uncertainty in weather modification studies. This study explores the geographic and temporal distribution of silver iodide associated with an active cloud seeding program in central Idaho snowpack using trace chemistry. Over 4,000 snow samples were analyzed for the presence of a cloud seeding silver iodide (AgI) signature over two winter seasons. The results indicate the following. At sites within 70 km of AgI sources, silver enrichments were detected at 88% of cases involving seeding efforts from ground generators, but none from aircraft seeded cases. Real-time snow collection methods were replicable within 0.41 ppt and confirmed seeding signatures for the entire duration of a seeded storm ( ). Sites sampled beyond 70 km of AgI sources ( ) lacked detectable seeding signatures in snow. The results of this study demonstrate some of the strengths and limitations of chemical tracers to evaluate cloud seeding operations and provide observational data that can inform numerical simulations of these processes. The results also indicate that this chemical approach can be used to help constrain the spatiotemporal distribution of silver from cloud seeding efforts.

Abstract: A model was developed for simulating the effects of airborne silver iodide (AgI) glaciogenic cloud seeding using the weather research and forecasting (WRF) model with a modified Morrison cloud microphysics scheme. This model was used to hindcast the weather conditions and effects of seeding for three airborne seeding experiments conducted in 2016. The spatial patterns of the simulated precipitation and liquid water path (LWP) qualitatively agreed with the observations. Considering the observed wind fields during the seeding, the simulated spatiotemporal distributions of the seeding materials, AgI, and snowfall enhancements were found to be reasonable. In the enhanced snowfall cases, the process by which cloud water and vapor were converted into ice particles after seeding was also reasonable. It was also noted that the AgI residence time (>1 hr) above the optimum AgI concentration (105 m−3) and high LWP (>100 g m−2) were important factors for snowfall enhancements. In the first experiment, timing of the simulated snowfall enhancement agreed with the observations, which supports the notion that the seeding of AgI resulted in enhanced snowfall in the experiment. The model developed in this study will be useful for verifying the effects of cloud seeding on precipitation.

Abstract: C-band radars were installed at Baramati and Shegaon as a part of operational cloud seeding program of Maharashtra State in the monsoon season (June–September) 2004. These provided first time a unique opportunity to study (1) characteristics of precipitating monsoon clouds (2) convection and (3) number of seedable clouds over Indian meteorological subdivisions of Madhya Maharashtra (rain-shadow) and Vidarbha (drought-hit). The monsoon season is divided into active and break periods. The cloud characteristics studied are: diurnal variation, cloud top heights and durations. Diurnal variation of cloud frequency shows maximum in the afternoon hours (10–11 UTC) and minimum in the early morning hours (3–4 UTC) in both the periods. Cloud tops show trimodal distributions with modes at 2–3, 8–9 and above 9 km. Mean cloud duration is 55 min. Congestus has been found prominent cloud type (65%) with mean top height of 6.76 km. Frequency of cumulonimbus clouds is found higher in the break periods. Cloud scale is taken as a metric for characterization of convection. Maximum frequency of cloud scale is found at C scale (mesoscale: area 100–1000 km2). Mesoscale Convective System has been found dominating convection type. The convection over the area has been shown to be hybrid type, consisting of basic oceanic type modulated by land convection. Convective clouds having maximum reflectivities between 25 and 35 dBZ, suitable for hygroscopic and glaciogenic seeding, are found in a large number. Understanding of characteristics of clouds and convection is useful for the diagnostic and precipitation enhancement studies over the rain-shadow/drought-hit regions.

Abstract: A method and device for inverting a phase change process of water vapors in cloud based on a ground-based microwave radiometer are provided. The method includes obtaining the actually measured data ofa vertical detection target area of the ground-based microwave radiometer and checking data consistency; using the actually measured data and a cloud threshold to identify a mixed phase state cloud region and to calculate an air pressure profile; using the actually measured data in combination with the calculated air pressure profile, calculating each water vapor pressure profile in the cloud; and inverting the phase change process of water vapors in cloud by using a water vapor phase change model. The method solves a problem that it is difficult for a conventional dual-polarization radar toaccurately recognize a particle phase state due to a low signal-to-noise ratio and a satellite can only recognize the phase states of the water cloud and the ice cloud on to top of the cloud, and canobtain the phase change process with time and space of water vapors in the mixed phase cloud of the target region, reflects the dynamic trends of the balance between the solid, liquid, and gaseous states of water vapors in the cloud, is particularly applicable to predicting and forecasting rainfall phase states, analyzing the evolution characteristics of cloud microphysics, and determining artificial precipitation (hail prevention) cloud seeding positions and selecting right time for the job.

Abstract: The present invention relates to a system for determining a seeding condition and an altitude for artificial snowmaking, which comprises: a seeding optimization condition determining unit which determines whether a surface air temperature and an upper air temperature are below a predetermined temperature based on surface weather observation information and vertical weather observation information of a target area or not, determines whether the highest value of cloud liquid water is larger than a predetermined value or not when the surface air temperature and the upper air temperature are below the predetermined temperature, determines whether the cloud liquid water increases at each altitude from the ground or not when the highest value of the cloud liquid water is larger than the predetermined value, decides a traditional ground seeding experiment (a ground seeding experiment in a first type) when the cloud liquid water increases at each altitude from the ground, and decides an aviation seeding experiment (or a non-traditional ground experiment) when the cloud liquid water at each altitude increases from an upper altitude apart from the ground; a ground seeding condition determining unit which determines implementation of the ground seeding experiment at the target area when the ground seeding experiment is determined; and an aviation seeding condition determining unit which determines an optimum seeding altitude when the aviation seeding experiment is determined, and implements the aviation seeding experiment at the altitude. The present invention is able to reduce economic losses caused by improper seeding design.

Abstract: In order to investigate the physical structure characteristics of the clouds and precipitation over the Tianshan Mountains in summer, the Urumqi Institute of Desert Meteorology of China Meteorological Administration (CMA) carried out an atmospheric detection experiment in Bayanbulak from 1st to 31st August 2012 by means of a wind-profiling radar and a Doppler weather radar Using the radar observation data, this paper analyzes the dynamic, thermodynamic, radar echo intensity and macro-micro structure characteristics of the 2–3 August precipitation process The results show that: (1) The radar echo intensity of this rainfall process changes within 5–38 dBZ, and the precipitation cloud system is under the height of 6500 m, with notable 0 °C level echo bright band between 1200 m and 2000 m height NCEP analysis data shows that the cloud top temperature ranges from −25 °C to −32 °C These indicate the features of typical stratiform cold cloud precipitation (2) Atmospheric motion during the precipitation process presents the multi-layer structure with wind velocity varying within the range of 30–80 m/s The temperature advection is presented with the vertical structure distribution of “cold-warm-cold”, which indicates relative stability of the atmospheric stratification (3) By retrieving and analyzing the raindrop size distributions below 0 °C level bright band within 600–1200 m height, when the precipitation evolve from early stage to its peak stage, the concentration of the tiny particle zone (D ≤ 25 mm) changes a little while the concentration of the medium particle zone (25 4 mm) increase considerably; but after peak stage the concentration in the medium particle zone and the concentration in the large particle zone decline first, then the concentration in the tiny particle zone reduces (4) Raindrop size distribution data is used to calculate the precipitation intensity and the liquid water content, whose spatial-temporal variation characteristics are the same During peak stage of the precipitation, the instantaneous precipitation intensity reaches 50 mm/h, and the liquid water content reaches 035 g/m3 This study would help deepen the understanding on the physical structure of the clouds and precipitation over the Tianshan Mountains in summer, and also provide some scientific basis for cloud seeding operation over this area

Abstract: Karnataka state in India is highly prone to drought conditions due to the high variability of rainfall. The main rainfall season is during the monsoon period of June to September. With most of the agriculture being rain-fed, the impact of deficient rainfall is very high. Most of Karnataka is in the rain shadow region due to being in the leeward side of the Western Ghats mountain range. This leads to large amounts of clouding over Karnataka with potential or sub critical potential for rainfall. The monsoon rainfall in 2017 was deficient for the entire state until mid-August and this provided a suitable occasion for taking up cloud seeding operations. Towards mitigating this adverse impact, the Government undertook a project on cloud seeding using modern techniques. The infrastructure for the project consisted of installation of the Doppler radars at three strategic locations: Bengaluru, Gadag and Shorapur to monitor clouds over the entire state. The observations were supported by Radiosonde equipment at Gadag, Bengaluru and Sholapur (closer to Shorapur). The hourly INSAT satellite data provided cloud cover, cloud top temperature, cloud motion vector and potential water content. The model forecasts for the day issued by the Indian Meteorological Department and the Indian Space Research Organisation using high resolution model runs were also utilized. All these data were analysed to prepare a potential area chart indicating areas for cloud seeding based on antecedent rainfall, cloud convection, synoptic situation and current radar observations. The final selection of the cloud system was based on aircraft observations of temperature, liquid water content and updrafts. The rainfall monitoring over the state was carried out using a calibrated dense network of automated telemetric rainguage network of 6,000 stations. The results from several case studies are presented in this paper. The quantitative results indicate positive impact of cloud seeding and a viable alternative to recurrent drought hit areas.

Abstract: To influence the weather is a long-treasured dream of mankind. Current cloud seeding technology mostly relies on chemicals such as silver iodide and hygroscopic salts, which may have negative impacts on environment and human health. Here, we present a new method for triggering macroscopic water precipitation in air. Experiments demonstrated that high-voltage generated corona discharge was able to induce rain and snow formation in atmospheric pressure air. The effect was confirmed by precipitation experiments performed in a 1- and 15 000-m3 cloud chamber, where the absolute water content was close to the actual values in natural cumulonimbus clouds. With the presence of electrical charges, the collision efficiency between the water droplets was increased by over one order of magnitude, accelerating the coalescence process and possibly leading to the rain and snow formation otherwise impossible to form. The electric-based technology presented in this paper provides an effective, inexpensive, and environmental friendly tool for triggering water precipitation, and may open up new opportunities for producing water precipitation in large open space.