Earth is the only planet known in the solar system to support life. Life on Earth is critically dependent upon the cycling of water back and forth among the various reservoirs (ocean, land, and atmosphere) in the Earth system, which is referred to as the hydrologic (water) cycle. Both natural and human–induced climate variations manifest themselves in the global water cycle. In fact, the most obvious signals to humans of climate change in the Earth system will likely be changes in the hydrologic cycle, particularly regional precipitation regimes, and the exacerbation of extreme hydrological events, such as floods, droughts, and hurricanes. The hydrologic cycle also affects and interacts with other components of the climate system. Consequently, any significant perturbations to the hydrologic cycle, whether they are caused by aerosols or other factors, are of paramount concern.

Clouds are known to play a major role in climate through their direct interactions with solar radiation; they can either reflect (albedo) or absorb incoming solar radiation. Aerosols serving as cloud condensation nuclei (CCN) and/or ice nuclei (IN) influence cloud microphysics, including the formation of precipitating particles and subsequent cloud lifetime, as well as cloud radiative properties, particularly cloud albedo and emission. As a consequence, these properties influence the local radiation budget, atmospheric temperatures, land surface, and ocean temperatures. Aerosols can therefore affect regional cloud properties and may affect precipitation amounts.

In the hydrologic cycle, water molecules evaporate from the oceans, seas, rivers, soils, and plants, condense to form clouds, and return to earth mainly by precipitation. Since precipitation from clouds is the only mechanism that replenishes ground water and completes the hydrologic cycle, small changes in cloud and precipitation properties may result in a spatial and temporal redistribution of rainfall, which can have a dramatic effect on climate and society. Such changes in rainfall distribution could mean drought in some regions (especially in arid regions) or flooding in others.

There is growing evidence that human activities (e.g. anthropogenic aerosols) can alter atmospheric processes, such as the hydrologic cycle, on scales ranging from local precipitation patterns to global climate. Research and documentation of anthropogenic effects on precipitation processes strengthen the physical basis for deliberate attempts to alter clouds (i.e., weather modification via cloud seeding) with the goal of enhancing precipitation or mitigating severe weather. The potential for such man–made increases in precipitation or mitigation of severe weather is strongly dependent on the natural microphysics and dynamics of the clouds that are to be seeded. HAP scientists are involved with a variety of projects around the world related to aerosol–cloud interactions and weather modification (cloud seeding), including efforts in Australia, Saudi Arabia, West Africa, Turkey, India and the state of Wyoming. RAL's role has been to scientifically evaluate the potential for cloud seeding to enhance rainfall (or snowpack in the case of the Wyoming project), as well as to conduct basic research on the impact of ambient and seeding aerosols on cloud and precipitation processes through field measurements and modeling.

Southeast Queensland | Cloud Seeding Research Program
Saudi Arabia | Assessment of Rainfall Augmentation
West Africa | Monsoon and Rainfall Enhancement
Turkey | Cloud and Aerosol Research in Istanbul
Mexico | Program for the Augmentation of Rainfall in Coahuila (PARC)
Italy | Precipitation Enhancement in Puglia, Italy
United Arab Emirates | Feasibility Study
Wyoming | Wyoming Weather Modification Pilot Project (WWMPP)
North Dakota | 2nd Polarimetric Radar Analysis of Convective Clouds (POLCAST2)
India | Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX)

Southeast Queensland | Cloud Seeding Research Program

The Southeast Queensland Cloud Seeding Research Program (CSRP) is sponsored by the Queensland Government and took place over two summer seasons between December 2007–March 2008 and November 2008–February 2009. The field research operations were based out of Brisbane, Queensland and were the result of a combined effort between NCAR and several collaborating institutions including the Queensland Climate Change Centre of Excellence (QCCCE), the Centre for Australian Weather and Climate Research (CAWCR), the Australian Bureau of Meteorology (BoM), Monash University, the University of Southern Queensland (USQ), MIPD Pty Ltd, the University of Witwatersrand (WITS) from South Africa, Weather Modification Inc. (WMI) of Fargo, North Dakota, Texas A&M University (TAMU), and Arizona State University (ASU). During the field projects, unprecedented physical measurements related to cloud and precipitation processes were collected using an extensive suite of airborne instrumentation and a large network of weather radars, which included dual–polarization and dual–Doppler radar capabilities. Additionally, statistical hygroscopic cloud seeding trials were conducted in a randomized seeding experiment.

Figure 1. a) Map of back trajectories from three measurements
taken by the research aircraft at cloud base height and b) Cloud
Condensation Nuclei (CCN) concentration measurements for those
three measurements taken at cloud base at varying
supersaturation (click to enlarge)

The primary objective of the project is to assess the feasibility of cloud seeding to enhance rainfall in the region, which includes efforts to quantify the climatology of rainfall in the region, characterize the aerosol and cloud microphysical processes, and understand the physical impacts of cloud seeding on precipitation formation processes. The Southeast Queensland coastal region experiences a variety of convective rainfall regimes, some with maritime influences and some with more continental influences (see Figure 1).

Figure 2. Time–height of mean differential reflectivity (ZDR)
overlaid on mean radar reflectivity (Z) for a seeded
Queensland cloud observed from the CP2 dual–polarization
radar (click to enlarge)

This large natural variability makes it challenging to isolate the effects of cloud seeding in our analyses. Therefore, our analyses also focus on understanding the physical processes that are impacted by hygroscopic seeding on rain formation, in addition to conducting statistical analyses of the effects of seeding on the radar–observed clouds in the randomized hygroscopic seeding experiment. Dual–polarization radar and dual–Doppler radar studies will also be used to help characterize the rain formation processes and how they may be altered by hygroscopic seeding (Figure 2).

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Saudi Arabia | Assessment of Rainfall Augmentation

Fig 1:. Results of self–organizing map (SOM) analysis in
the southwest region of Saudi Arabia. Panel (a) shows
the spatial distribution of the nine regions identified on
the SOM analysis. Panel (b) shows the seasonal distribution
of rainfall based on the SOM categorization.
(click to enlarge)

The program focused on a combination of field observation work (aircraft, radar, and surface observations) in Saudi Arabia, data analysis observations, mesoscale modeling, and training of Saudi Arabian scientists. This project was initiated in 2006 by government officials in the Kingdom of Saudi Arabia who were interested in a feasibility study to assess the possibility of augmenting rainfall in response to the growing scarcity of freshwater.

Fig 2:. Diurnal cycle of storm cell count (left panel) and
distribution of storm cells in the Southwest Region of
Saudi Arabia. (click to enlarge)

NCAR collaborated with Texas A&M University (TAMU), Arizona State University (ASU), University of Witwatersrand (WITS), South Africa, and Weather Modification Inc. of Fargo, North Dakota (WMI) and with Presidency of Meteorology and the Environment (PME) to address the following scientific objective: Determine if cloud seeding in Saudi Arabia can increase rainfall at the surface. If a positive effect is observed, future grand questions will be addressed with the project: what is the magnitude of the increase attainable over a region, and is the technology cost–effective in serving the water resource needs of Saudi Arabia?

Fig 3:. Example of the microphysical data collected from
the aircraft on 11 August 2009 for cloud penetrations P1,
P2 and P3. The top figures show the PSDs from the CDP,
FSSP, CIP and 2D–S averaged over the period identified in
the top of the figure. The middle figures shows a subset of
CIP images collected during the cloud penetration. The
2D–S images are shown below the CIP images. The first 50
particles from the 2DSH (excluding end rejects) for the
specified time period are shown. The bottom figures show a
schematic of the cloud penetration.
(click to enlarge)

The project recently focused on the Southwest region of Saudi Arabia, where there are adequate clouds to study. Figures 1 – 4 highlight the some of the observations from this region. Figure 1 shows the precipitation distribution, which is categorized into nine unique sub–regions. Figure 2 provides insight on the diurnal cycle for the different regions and the spatial distribution of cells along the escarpment. Figure 3 provides an example of the microphysics observed in the clouds in Saudi Arabia. Figure 4 highlights the distribution of aerosols observed from the surface. The future design plan included a randomized cloud seeding component to determine and quantify seeding effects along with airborne studies to examine the precipitation growth processes in both seeded and unseeded clouds.

Fig 4:. August–averaged number (left) and volume
(right) size distributions. The shaded envelopes
include +/– 1 standard deviation.
(click to enlarge)

All the cloud and precipitation studies are supported by aerosol properties and atmospheric observations to better understand the dynamic and thermodynamic conditions influencing clouds and precipitation generation in Saudi Arabia. As part of this program, a six–month training program was conducted for visiting Saudi scientists at NCAR to provide them specific training in areas such as radar, cloud microphysics, modeling, and data integration.

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West Africa | Monsoon and Rainfall Enhancement

Figure 1. Examples of the convection observed during
the randomized cloud seeding study conducted in
September – October 2008. Each panel represents an
example for each randomized seeding day (September
22, 23, 24, 25, 29, October 1, 5, 6, 8) (click to enlarge)

This airborne and radar evaluation project was conducted over a three-year (2006–2008) period in an effort to evaluate the operational cloud seeding program in Mali. The goals of this study were to determine if the frequency of cloud occurrence is sufficient to warrant the investment in a cloud seeding program and to determine if clouds are amenable to hygroscopic and/or glaciogenic seeding. To address the goals, the field programs have focused on documenting the microphysics of both natural and seeded clouds and the aerosols present using an instrumented aircraft. In 2008, an exploratory, randomized seeding experiment was implemented in an effort to determine the impacts of cloud seeding on rainfall augmentation in Mali.

Figure 2. Diurnal cycle of cell initiation for the 2006
(blue), 2007 (green), and 2008 (red) wet seasons in Mali

Figure 1 shows example of the convective storms during the randomized program. The analysis shows a tremendous variability in aerosol and cloud characteristics. Figure 2 shows diurnal variability over the three year period of study. Based on our initial assessment, cloud seeding has the potential to be successful under certain conditions (onset/retreat of the West African monsoon). However, because of the natural variability, the detection of a cloud seeding signature may be difficult to determine.

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Turkey | Cloud and Aerosol Research in Istanbul

In the winter and spring of 2008, RAL conducted the Cloud and Aerosol Research in Istanbul program. Two 6–week intensive observation periods were planned between February 2008 and June 2008. Aerosol and cloud physics measurements were done with a research aircraft to characterize the properties of the aerosols and clouds in the region of Istanbul. The aircraft was equipped with instrumentation for the characterization of atmospheric constituents (gas and aerosols) and cloud particles in addition to measuring atmospheric dynamic and thermodynamic properties. A total of 92 flights with 350 flight hours were carried out during the project. The data analysis effort was completed in May 2009.

The results of this study provide a broad perspective on the cloud and precipitation formation processes in Istanbul. High aerosol loading resulting from air pollution in the region of Istanbul was measured, which may modify the physical properties of the cloud particles, increase the number concentration of cloud droplets, and inhibit the formation of large droplets by the collision–coalescence process. Aircraft measurements documented the high levels of pollution aerosols around the Istanbul area and the effect that these may have on the cloud droplet concentrations and size distributions. In some cases a cloud modification effect was measured that may be attributed to higher concentrations of aerosols when compared to an area with lower concentration of aerosols. Although this effect is not well understood, cloud modeling studies can be useful in understanding such complex cloud modification effects.

This work was conducted in collaboration with Seeding Operations and Atmospheric Research (SOAR) and Texas A&M University (TAMU).

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Mexico | Program for the Augmentation of Rainfall in Coahuila (PARC)

During the summers of 1997 and 1998, the Program for the Augmentation of Rainfall in Coahuila (PARC) field project focused on a randomized seeding experiment as well as continuing to collect meteorological data for further evaluation of the randomized experiment and other physical studies. Over the course of two years, a total of 94 valid cases were collected: 43 seeded cases and 51 non–seeded cases. The results provide an indication of a positive effect of seeding, in terms of precipitation flux, rain mass above 6 km, rain area, lifetimes of the storms, the integrated area of precipitation, and the total precipitation. These results are very similar to those found in the South African experiment (Mather et al., 1997). This fact is encouraging, especially because the timing as well as the magnitude of the seeding effects corresponds well to the South African results. It is important to note that the number of cases (94 cases) is still marginal for any statistical analysis. The South African experiment consisted of approximately 150 cases. The PARC program was planned for four years and the fourth year would probably have provided a sufficient number of cases. However, due to funding problems the fourth year of the experiment could not be completed. Therefore, caution should be exercised in interpreting the results as unambiguous proof of success.

In order to transfer the knowledge and technology associated with hygroscopic cloud seeding, PARC was organized to create training opportunities for graduate students, their professors, and other scientists both within Coahuila and throughout México. A number of students (or asistentes) were trained in field operations over the three years of PARC, with a few of them continuing their formal education in meteorology or computer sciences. Other significant interactions with the Mexican scientific community included joint precipitation studies with hydrologists from the Instituto Mexicano de Tecnologia del Agua and the Servicio Meteorologico Nacional, cooperative data exchanges with the regional office of the Comision Nacional del Agua (CNA–Saltillo), and collaborations with agrometeorologists at the local university and with the faculty of the Centro de Ciencias de la Atmosfera program at the Universidad Nacional Autonoma de México in Mexico City.

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Italy | Precipitation Enhancement in Puglia, Italy

During the winter of 2004–2005, scientists from the Research Applications Laboratory (RAL) of the National Center for Atmospheric Research (NCAR), in collaboration with AEROTECH SA, conducted a preliminary one–year feasibility study on the design and execution of a rainfall enhancement experiment via cloud seeding in the Puglia region of Italy. Aerotech continued operations and data collection during the 2005–2006 winter season. Weather modification research requires a multi–faceted approach due to the large range of scales and their interactions that must be addressed. The goal of our investigations in the Puglia region was to condense the overwhelming number of potential influences down to tractable studies that address the most important aspects. Therefore our emphasis during the 2004–2005 season (1 November 2004 to 31 March 2005) was on studying natural clouds – their frequency and precipitation characteristics – and on assessing their suitability for seeding based on observations and numerical modeling. During the 2005–2006 field project, this assessment continued as limited observations of both natural clouds and seeded clouds were collected during field operations performed by Aerotech personnel, who had been trained in the most important aspects of cloud seeding operations during the previous winter season.

One of the unique aspects of the Puglia study was implementing a seeding module into the microphysics parameterization of a mesoscale model. The model results indicated that seeding material needs to be directly injected into regions of substantial amounts of SLW at temperatures between –5° and –15°C. Otherwise, seeding will not have a significant effect on precipitation in winter frontal stratiform–type cloud systems. The results also indicate that mixing of the seeding material in these cloud systems is very limited and that neither cloud–base nor cloud–top seeding is likely to be effective. Nonetheless, the modeling work verifies that AgI can produce significant amounts of cloud ice and precipitation. These results emphasize the point that seeding in the future should be done according to the original design of the Puglia seeding mission as put forth in the Operations Plan prepared for the 2004–2005 season.

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United Arab Emirates | Feasibility Study

Example of Winter Westerlies

Example of Summer Easterlies

In late 2000, the government of the UAE, through the newly established Department of Water Resources Studies (DWRS) of the Office of His Highness the President, approached NCAR about developing and applying the technology of cloud seeding in the UAE.

A preliminary assessment identified some key areas of study required for assessing the efficacy and potential benefits of rainfall enhancement via hygroscopic seeding, including:

1. Collating existing data and collecting specific data on clouds and rainfall
2. Establishing the natural background and variability of aerosols in the region
3. Adapting and developing numerical models for simulating UAE clouds
4. Understanding the UAE hydrology sufficiently to assess the impact of rainfall on groundwater resources

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Wyoming | Wyoming Weather Modification Pilot Project (WWMPP)

The Wyoming Weather Modification Five–Year Pilot Project (WWMPP) is funded by the State of Wyoming through the Wyoming Water Development Commission (WWDC). The main purposes of the WWMPP are to establish an orographic cloud seeding program in three target areas (the Medicine Bow Range, Sierra Madre Range and Wind River Range) and evaluate the feasibility and effectiveness of the cloud seeding.

The first two winter seasons of the program (2005–06, 2006–07) involved performing exploratory studies to develop the evaluation plan, permitting activities, installing equipment, and peer review of the scientific experimental design. The final design, accepted at the end of 2007, established the two southern ranges as targets for the randomized seeding experiment to be conducted using ground–based seeding from 15 November through 15 April. High–resolution precipitation gauges were deployed for the snowfall measurement, along with auxiliary instruments to assist in determining seeding conditions. Seeding under operational–like conditions is taking place in the Wind River Range, and will be evaluated using current instrumentation (e.g., SNOTEL data, special observations from other area projects, etc.) and numerical modeling studies.

A total of 54 cases have been called over two seeding seasons, one of which was abbreviated while waiting on approval of the final design. While the initial studies relied on historic data to estimate the number of cases likely to be gathered in a season and the total number of cases needed for statistical significance (given some assumptions), data collected during actual cases have begun to refine those original estimates. Although 54 cases are not nearly enough for any definitive results, the trend in the analysis to date suggests a precipitation increase for seeded cases within the expected range. The stability of the results, including the precipitation variance, the correlation between ranges, and the trend toward increases, should improve as more cases are collected.

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North Dakota | Polarimetric Cloud Analysis and Seeding Test (POLCAST)

Figure 1. PPI image of randomized case observed on 09 July 2008

The Polarimetric Cloud Analysis and Seeding Test (POLCAST) is an ongoing field and research program located in Eastern North Dakota, centered on Grand Forks, ND. The field programs are conducted every other summer. The last field program was conducted in the summer of 2010 (21 June 2010 through 23 July 2010). The previous field experiment was conducted from 09 June through 11 July 2008. The original field program took place in August–September 2006. The experiment utilizes the University of North Dakota (UNDs) polarimetric C–Band Doppler weather radar, Weather Modification Incorporated (WMIs) instrumented Cessna 340 aircraft, and the University of North Dakota Citation II research aircraft. The POLCAST studies are supported through the North Dakota Atmospheric Resource Board (NDARB) and are collaborative efforts between the National Center for Atmospheric Research (NCAR), NDARB, University of North Dakota (UND), and Weather Modification Incorporated (WMI).

Figure 2. Reflectivity (top panels) and hydrometeor retrieval
(bottom panels) PPI images for elevation tilt of 2.4° (left panels)
and 8.0° (right panels) for storm observed around 2040 UTC 09
July 2008 (click to enlarge)

The main objective of the POLCAST studies is to better understand the effects of hygroscopic seeding at cloud base on convective clouds in Eastern North Dakota. Specifically, the focus of the POLCAST is to determine identifiable signatures of hygroscopic seeding in polarimetric observables or derived fields; characterize the effects of hygroscopic seeding at base in cloud base which was stratified by ambient distributions of aerosol and cloud condensation nuclei (CCN) in the atmosphere. All the cases are randomized to characterize cloud droplet distributions above cloud base for seeded and non–seeded clouds to confirm inferences observed in the polarimetric Doppler weather radar fields.

Figure 3. Distribution of hydrometeors observed at 2040 UTC 09
July 2008 (click to enlarge)

For the second POLCAST field campaign in 2008 (POLCAST2), the seeding aircraft flew 13 randomized events. During 2010 (POLCAST3), a total of 14 randomized events were collected. The plan is to conduct the fourth field campaign in summer 2012 in an effort to increase the sample size of randomized cases.

An example of results obtained from POLCAST is shown in Figures 1–3. Figure 1 shows a radar snapshot of an event that was targeted on 09 July 2008 between 2013 and 2025 UTC. The aircraft targeted feeder cells on the western side of the storm for this case. Figure 2 shows an example of the spatial distribution of hydrometeors retrieved using the NCAR polarimetric hydrometeor identification (HID) analysis. Figure 3 shows the distribution of hydrometeors from the HID retrieval of the storm shown in Figure 2.

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India | Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX)

Following the flurry of operational weather modification programs in India over the last decade, the Indian Institute of Tropical Meteorology (IITM) implemented a multi–year program to study cloud–aerosol interactions and cloud seeding. An Indian research program called "Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX)" was implemented in 2008. CAIPEEX is a national program with participation from different research and governmental organizations in India. During Phase I in May to September 2009 aerosol and cloud microphysics observations were collected over different meteorological regimes and at different locations over India. In 2010, Phase II was conducted during an intensive observation period (IOP) from August to November.

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When a cloud forms, moisture in the form of water vapor is carried into the cloud until it condenses on particles into liquid water, thus forming cloud droplets (see Figure 1, part 1). The cloud droplets are very small, however, and cannot readily fall out of the cloud, and therefore other processes must occur to grow the liquid cloud droplets large enough to fall as rain. One such process is called collision and coalescence, in which cloud droplets of a variety of sizes (which therefore fall at different speeds to one another) collide with each other and coalesce into a combined larger drop (Figure 1, part 2). This process continues until drops are large enough to overcome the updraft speed within the cloud and fall as rain.

Figure 1: Hygroscopic seeding conceptual model diagram.

However, in addition to processes that help the droplets grow, there are factors that can deplete the liquid water from eventually becoming rain on the ground, such as evaporation of the droplets or the freezing of small droplets (that were carried to the sub–freezing cloud top by the updraft) into small ice crystals that are unable to fall as precipitation (this process is known as cloud glaciation). Thus, the amount of water vapor that enters a cloud never all falls to the ground as rain. The precipitation efficiency (or the percent of incoming cloud water vapor that falls as rain) varies from cloud to cloud, and cloud seeding technologies aim to convert more of the water vapor processed in the cloud to more rainfall at the ground thereby increasing the cloud's precipitation efficiency.

Cloud seeding is a science–based technology that aims to add particles to a cloud that will help precipitation develop more efficiently, thus hopefully yielding more rainfall. The type of particle added to the cloud depends on the characteristics of the clouds that will be seeded. Deep clouds that have portions growing in sub–freezing temperatures may be seeded with silver iodide (AgI), a material whose properties are very similar to an ice crystal and thus serve as good surfaces on which ice can form (also called ice nuclei). Supercooled liquid water (liquid water that has been carried into suba–freezing temperatures, but has yet to freeze) can freeze on these AgI particles and initiate and enhance ice–based precipitation formation processes at key levels in the cloud, and prevent loss of that water to glaciation aloft. Other clouds may be seeded with hygroscopic materials (particles that take on water easily, such as salts) in the updraft region of the cloud just below the cloud base (Figure 1, part 3). These hygroscopic particles are then carried into the cloud by the updraft and water vapor condenses on them to form additional liquid cloud droplets, whose size depends on the size of the hygroscopic particles introduced in the cloud. Adding additional particles of larger sizes may help enhance collision and coalescence processes that are responsible for rain formation and convert more of the cloud water to rainfall. In essence, a more efficient collision and coalescence rain formation process yields more rainfall at the ground (Figure 1, part 4).

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Freud E., D. Rosenfeld, D. Axisa, and J. R. Kulkarni, 2011: Resolving both entrainment-mixing and number of activated CCN in deep convective clouds. Atmos. Chem. Phys. Discuss., 11, 9673–9703, doi:10.5194/acpd-11-9673-2011

Garstang, M., R. Bruintjes, R. Serafin, H. Orville, B. Boe, W. Cotton, and J. Warburton, 2005: Weather Modification: Finding Common Ground. Bull. Amer. Meteor. Soc, 86, 647–655.

Grant, D. D., J. D. Fuentes, M. S. DeLonge, S. Chan, E. Joseph, P. A. Kucera, S. A. Ndiaye, and A. T. Gaye, 2008: Ozone transport by mesoscale convective storms in western Senegal. Atmos. Environ, 42, 7104–7114.

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Lamptey, B. L., R. E. Pandya, T. T. Warner, R. Boger, R. T. Bruintjes, P. A. Kucera, A. Laing, M. W. Moncrieff, M. K. Ramamurthy, and T. C. Spangler, 2009: INTERNATIONAL RELATIONS: The UCAR Africa Initiative. Bull. Amer. Meteor. Soc, 90, 299–303.

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Ross, K.E., S.J. Piketh, R.T. Bruintjes, R.P. Burger, R.J. Swap and H.J. Annegarn, 2003: Spatial and seasonal variations in the distribution of cloud condensation nuclei and the aerosol–cloud condensation nuclei relationship over Southern Africa. J. Geophys. Res, 108 (D13), 8481, doi:10.1029/2002JD002384.

Stroud, C.A., A. Nenes, J.L. Jimenez, P.F. DeCarlo, J.A. Huffman, R. Bruintjes, E. Nemitz, A.E. Delia, D.W. Toohey, A.B. Guenther, and S. Nandi, 2007: Cloud Activating Properties of Aerosol Observed during CELTIC. J. Atmos. Sci, 64, 441–459.

Tessendorf, S.A., R. Bruintjes, C. Weeks, M. Dixon, M. Pocernich, J. Wilson, R. Roberts, E. Brandes, K. Ikeda, C. Knight, L. Wilson, J. Peter, and N. Torosin, 2010: Overview of the Queensland Cloud Seeding Research Program. J. Wea. Modification, 42, 33–48.

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Wise, M.E., T.A. Semenluk, R. Bruintjes, S.T. Martin, L.M. Russell, and P.R. Buseck, 2007: Hygroscopic behavior of NaCl–bearing natural aerosol particles using environmental transmission electron microscopy. J. Geophys. Res, 112, D10224, doi:10.1029/2006JD007678.

Note: full phone: 303 - 497 - XXXX | email addresses end in "@ucar.edu"

Primary Contacts

• BRUINTJES, Roelof | PROJ SCIENTIST III | ph: 8909 | email: roelof
• BREED, Dan | PROJ SCIENTIST II | ph: 8933 | email: breed
• KUCERA, Paul | PROJ SCIENTIST II | ph: 2807 | email: pkucera
• TESSENDORF, Sarah | PROJ SCIENTIST I | ph: 2708 | email: saraht
• AXISA, Duncan: | ASSOC SCIENTIST III | ph: 2843 | email: duncan