Optical properties of stratospheric aerosols and cirrus clouds and their radiative effects are currently important subjects of research worldwide. Those investigations are typical of developed countries, conducted by several highly specialized groups dedicated separately to instrumental observations, their interpretation in the context of the weather and climate, and the numerical simulation of their radiative effects. In Camagüey, Cuba, the Grupo de Óptica Atmosférica de Camagüey [Optics Atmospheric Group of Camagüey (GOAC)] has been conducting all those research projects together for a little more than 20 years, following a self-designed long-term strategy. The results of the strategy applied by GOAC demonstrates that, even in the conditions of an underdeveloped country, it is possible to build local scientific and technical capacities for conducting state-of-the-art research for the benefit of society, both locally and worldwide.
INITIAL STAGE: COOPERATION WITH THE SOVIET UNION (1988–91).
A strong research team developed in Camagüey, Cuba, by pursuing clear and precisely defined capacity building and research goals with the help of international cooperation.
From the early 1980s to the early 1990s, the Camagüey Meteorological Center (CMC) was the experimental site for the Joint Cuban– Soviet Laboratory for Tropical Meteorology. CMC (21.4°N, 77.9°W) belongs to the Cuban Meteorological Institute [Instituto de Meteorología de Cuba (INSMET)], located in the city of Camagüey, about 500 km east of Havana. The site was equipped with aerological sounding, meteorological radar, as well as a network of six surface meteorological stations. Soviet and Cuban scientists jointly conducted cloud seeding experiments and associated research during that period (Medveded et al. 1986).
By the end of 1988, a Maket-2 lidar instrument for stratospheric aerosol (SA) measurements was installed at CMC (Fig. 1), which was afterward known as the Camagüey Lidar Station (CLS). The main parameters of the instruments appear in Table 1. The Soviet team in charge of the lidar was led by Professor Sergey Khmelevtsov, from the Institute of Experimental Meteorology (IEM), Obninsk, Russia. IEM sent engineers and physicists to Camagüey, Cuba, at the end of 1988 and early 1989 to set up the lidar and to share knowledge of how to use the lidar system with us, their Cuban counterparts: specifically, an engineer for maintenance and repair; and the lead author, who learned operation, data quality control, and processing. In 1989, both of us received one month of specialized training at the IEM in Obninsk.
Because of technical problems, we conducted only a few measurements of background conditions in the stratospheric aerosol layer in 1990. During 1991 the lidar was inoperative, but the Soviets upgraded the instrument and it became operative in January 1992 (Antuña and Sorochinski 1995). This coincided with the disintegration of the Soviet Union, interrupting the scientific cooperation, so we took charge of the project, assuming fully the operation, maintenance and repair of the instrument; meanwhile, the eruption of the Mount Pinatubo on 15 June 1991 challenged us to make the lidar measurements, despite these enormous operational obstacles.
Before 1992, while the lidar was mainly inoperative, we dedicated ourselves to intense study and self-preparation in, among other subjects, lidar technique, its measurement principles, processing and quality control; and SA and cirrus cloud (CC) properties, formation, and evolution as well as their climatic effects (Antuña 1996; Antuña et al. 1994). The local monthly mean sounding was derived for calculating the lidar molecular backscattering with the highest possible precision (J. C. Antuña et al. 1991, unpublished manuscript). We also conducted measurements to characterize the local tropopause because of its connection to SA and to some CCs (J. C. Antuña et al. 1992, unpublished manuscript).
THE ISOLATION PERIOD (1992–95).
The following years of hardships are known in Cuba as the “Special Period,” but the Cuban scientific authorities continued supporting the researchers' salaries. In early 1991 despite limited resources, Dr. Rosa Elena Simeon who was the head of the Cuban Ministry of Science, Technology and Environment at that time, assigned a 286 personal computer (PC) to the CLS to replace the outdated “Elektronika 60” Soviet minicomputer that was no longer in service. The new PC was based on the Intel 80286 processor, and would become CMC's most advanced PC. At that time the very few IBM Personal Computer XTs (PC XTs) at the CMC (and in the whole country) worked all day around the clock. The demand for access to the 286 made the lidar room a computer center during the day, when the lidar was not measuring. To end that situation, we exchanged the 286 with a less powerful XT, on the condition that the CLS team had exclusive use of the XT. The Cuban government's commitment at that time was to preserve the scientific and technical capacity already built, with the intention of utilizing it again fully upon the recovery of the economy. In those years we had only one source of spare parts: the dismantling of decommissioned Soviet computers and instruments. This approach, combined with the sustained effort of the CLS personnel and other colleagues of the CMC, allowed the lidar to stay in operation until late 1998, when no more spare parts were available.
With Soviet cooperation interrupted, several engineers from the Radar Group at the CMC provided highly valuable engineering support to CLS. Their inventive work was decisive in maintaining the lidar for so long.
In 1994, in the middle of those difficult years, the second author was assigned to work full time at the CLS. This assignment had noticeable consequences for CLS and the subsequent research unit formed from it. The second author, a high school graduate, after he finished serving in the military, began to work at CMC in 1989 in the security team. He showed enthusiasm for studying and, even before his incorporation into CMC, attended courses to become a meteorological observer and a meteorological technician, graduating in 1990. He was interested in the lidar technique, and he began to participate in the lidar measurements during his free time. Because of his dedication and seriousness, the lead author designed for him an informal but rigorous plan of professional education to pursue in parallel with his work. Through regular study of papers, all then in English, he learned the physics of stratospheric aerosols, the physics and technology of the lidar technique, and English. From 1998 to 2003, he studied electrical engineering at the University of Camagüey without abandoning his daily work at CLS (Estevan et al. 1998). Then he began graduate studies under the supervision of the lead author, receiving his doctoral degree early in 2010 (Estevan 2010). His career is a vivid example of how far a person can progress professionally based on personal effort and taking advantage of the educational facilities in Cuba.
At the same time we were continuing with measurements, data processing, quality control, and analysis, we began working on other tasks with other, long-term perspectives. Our Soviet colleagues had provided the software code for processing the lidar measurements, and for retrieving the profiles of stratospheric aerosol extinction, but not the binary data format of the files containing the photon counting profiles. By applying reverse engineering, we retrieved the binary format, allowing us several years later to produce our own processing software, with an updated algorithm, to retrieve SA and CC extinction profiles from the lidar photon counting profiles (BSPA 2004).
Another decisive development for CLS was widening our access to scientific literature. Our Soviet colleagues had provided literature in Russian about lidar and SA, which was very useful initially. Further learning, however, was blocked by the lack of Western literature; INSMET did not have the financial resources to subscribe to scientific journals. But with a little creativity, this situation was overcome. From the references in the available Russian literature, we could identify non-Russian researchers and their refereed papers on lidar and SA. Using whatever means possible (other than e-mail, which was only available to us at Camagüey several years later), we searched for the addresses of those researchers and sent letters requesting reprints of their papers, including an additional request for more recent papers of which we were not aware. After a little more than a year of literature requests, a cascade effect took place. The information, reprints, reports, chapters of books, and conference papers we began to receive provided new references to find more scientists in the field. From the few letters per month we were sending by the early 1989, the search expanded to a dozen of letters per week by 1992. That volume of specialized scientific information guaranteed the necessary information for us to increase our capabilities. By late 1993 we began to have access to e-mail in Camagüey. It was a great step, allowing more efficient communication with scientists worldwide and making the request of scientific information easier and faster.
After the CLS began to measure SA from Mount Pinatubo, the requests of literature were accompanied by information about the measurements we were conducting. As result, the research we were conducting began to be known by scientists all over the world. Among the many people we contacted at that time were two scientists who were going to play a decisive role in our efforts to get in regular contact with the scientific community in our field and to gain access to scientific knowledge.
Dr. Rumen Bojkov, then advisor to the World Meteorological Organization (WMO) secretary general, visited Cuba in early 1994 to inaugurate an ozone measurement facility in Pinar del Rio in western Cuba. He was aware of our SA lidar measurements because we had written to him requesting literature. Upon his request, the Cuban scientific authorities brought him to Camagüey to visit CLS in January 1994. During the few hours visit to the CLS, a fruitful exchange took place. He was impressed by the Mount Pinatubo SA lidar dataset we were able to compile. He offered to make arrangements for the leading author to present the CLS results at a conference on Mount Pinatubo that would take place later that year. The presentation to the North Atlantic Treaty Organization (NATO) Advanced Research Workshop on the effects of the Mount Pinatubo eruption on the atmosphere and climate, held in Rome on 26–30 September 1994, was a success (Antuña 1996). Attending the conference allowed fruitful exchanges with the attendees, who provided valuable information about the state of science about the SA in general and about the Mount Pinatubo eruption in particular. Many ideas were discussed, and several attendees committed to holding a workshop on lidar measurements in Latin America the following year. Although that workshop was never held, it was the germ of what are today the workshops on lidar measurements in Latin America (Antuña et al. 2010). Another result was the donation of a PC to the CLS. By the middle of 1995, the WMO secretary general made the long-term loan of a 386 PC for the CLS, providing a powerful tool for processing and analyzing the lidar measurements.
But the most important result of attending the NATO Advanced Research Workshop was meeting in person Professor Alan Robock of the University of Maryland (currently of Rutgers University), and arranging all the details for the lead author to apply for graduate studies in the United States. Professor Robock had earlier, on request, provided plenty of reprints of his papers on SA climatic effects. Those papers were the basis for our initial studies of the local climatic effects of the SA cited above. His scientific and personal contributions over the years were among the main reasons that CLS evolved into what is today the Grupo de Óptica Atmosférica de Camagüey (GOAC).
As result of our lidar measurements between 1988 and 1997, we collected two unique datasets in the tropical zone. The first one consists of the vertical profiles of SA lidar backscattering, covering the 15 July Mount Pinatubo volcano eruption. These data were collected beginning in January 1992 until the complete decay of the volcanic aerosol presence, shown in Fig. 2, and include SA background conditions before and after the eruption. The second dataset features vertical profiles of CC lidar backscattering. In some cases the SA lidar measurements, conducted at night, were affected by the presence of CCs. Those measurements, originally discarded by the Soviet colleagues, were preserved by the Cuban team. In those cases, several more measurements were conducted, with fewer laser shots than for the SA but with higher vertical resolution. The amount of SA and CC measurements conducted by the CLS is listed in Table 2. The former datasets have been broadly used by the CLS/GOAC team as well as by several reserachers abroad (Stenchikov et al 1998, Stevermer et al. 2000, and Torres et al. 1998).
INTERNATIONAL COOPERATION PERIOD (1996 TO THE PRESENT).
The core of the CLS team was completed with the incorporation of the third author in 1996. Then a fourth-year student of physics at the University of Oriente, he was assigned to CLS for his graduation thesis, fulfilling it successfully. Upon obtaining a bachelor's degree, he formally began work at CLS the following year. While working full time at CLS, he earned his master of science degree in optics by 2003 and began doctoral studies under the supervision of the lead author in 2004, completing it by the end of 2010 (Barja 2010). The Optical Society of America awarded Barja a share of the prize for best student presentation (for a method of obtaining the lidar ratio for subvisible CC) at the Third Workshop on Lidar Measurements in Latin America (Antuña and Barja 2006).
The leading author's master of science (1996–98) and doctoral (1999–2002) studies in the United States under Professor Robock's supervision granted access to state-of-the-art knowledge in the field. Working with Professor Robock provided contact with the higher standards of scientific methodology, expertise, and ethics for conducting scientific research. It also opened doors to contact with scientists all over the world. It should also be acknowledged the enormous personal commitment and effort made by Robock from the beginning and to the completion of the leading author's graduate studies. The U.S. government blockade against Cuba represents a serious obstacle to the scientific and academic exchange between scientists from both countries. Moreover, because the leading author's wife and son were denied U.S. visas to accompany him during his studies, he traveled every year to Cuba to visit them. Each time the difficult process for obtaining a new U.S. visa began again. Professor Robock systematically and firmly supported each one of the annual processes for getting the visa, many times contacting the U.S. Department of State and his congressman to support the application. The doctoral dissertation of the leading author allowed validation of the SA measurements of the 1991 Mount Pinatubo eruption made by the Stratospheric Aerosol and Gas Experiment II (SAGE II) satellite instrument with surface lidar measurements (Antuña et al. 2002) and the first determination of the spatial and temporal variability of the SA produced by a volcanic eruption (Antuña et al. 2003). The former characterization was conducted using SAGE II space coincident (±1° in latitude and ±5° in longitude) sunrise and sunset measurements in a 12-h window. Figure 3 shows the average percent differences between the pairs of sunset and sunrise coincident extinction profiles at 1.02 μm for the periods before (January–March 1991), during (July 1991–March 1992), and after (July 1992–July 1993) the most intense presence of the Mount Pinatubo SA. Below 25 km, where the bulk of Pinatubo aerosols were located, there was a noticeable increase in the average percentage differences from values around 15%–25% for the periods January–March 1991 and July 1992–July 1993 to values ranging between 40% and 60% during the period July 1991–March 1992. As result of this comparison, it was estimated that the aerosol extinction variability in the core of the cloud in the tropical region for the period of approximately six months following the Mount Pinatubo eruption ranged between 20% and 40% at the same point over the Earth's surface in a time lapse of 12 hours. After the lead author completed his doctoral degree and returned to Camagüey, mutual working visits to Rutgers and from Professor Robock to Camagüey have maintained active exchanges and cooperation up to the present.
As a result of the multiple exchanges facilitated by Antuña's graduate studies in the United States, a proposal for conducting research of the SA was submitted to the Program to Expand Scientific Capacity in the Americas (PESCA), in response to a call for proposals made by the Inter-American Institute for Global Change Research (IAI) in 1999. The project was accepted and funded. The principal investigator (PI) was Dr. Pablo Canziani, then in the Department of Atmospheric Sciences at the University of Buenos Aires, Argentina. Antuña was the co-PI, and CLS personnel in Cuba and Professor Robock were also participants. The research results were presented at several international meetings and conferences. An important result of the project was the implementation of a joint initiative of the CLS team and Professsor Robock—the First Workshop on Lidar Measurements in Latin America, hosted by the CLS team in Camagüey, Cuba, on 6–8 March 2001 (Robock and Antuña 2001a,b). That initiative developed into a still-active series of regular workshops every two years (Antuña et al. 2010). The leadership of the CLS team in building up of the lidar community in Latin America has been an important contribution to the development of this emerging field in the atmospheric sciences in our region and in the world.
The cited project also allowed the training of the second author on SAGE II measurement interpretation and use at Rutgers. The know-how acquired in that training was applied a few years later for characterizing the upper tropososphere (UT) and lower stratosphere (LS) aerosols in the wider Caribbean under SA background conditions (Antuña et al. 2005); updating and validating the CLS lidar measurements of SA (Estevan and Antuña 2006); and characterizing the physical and spatiotemporal features of CCs in the wider Caribbean area (Barja and Antuña 2010). For the CLS it was the first international project after the end of the Soviet cooperation. Since that time the CLS team has prepared and submitted to multiple international funding agencies a total of 17 research projects, resulting in 5 approved and funded projects, including the one described above.
Between 2005 and 2006, a research project supported by the Program of Scientific Cooperation between Argentina and Cuba was conducted between the División de Radares Láser del Centro de Investigaciones en Láseres y Aplicaciones (CEILAP), Argentina, and the CLS team. The project addressed the measurements of SA and CCs, both in Argentina and Cuba. The main results of the project were the demonstration that certain CEILAP lidar tropospheric aerosol measurements could be also processed for deriving SA extinction profiles; those lidar SA extinction profiles were compared with SAGE II coincident SA extinction profiles (Estevan et al. 2008). Also, a combination of methods to derive the optical and geometrical properties of CCs were implemented; the preliminary results showed very encouraging performances for measurements of CCs conducted by both CEILAP in Argentina and CLS in Cuba (Lavorato et al. 2008).
During Antuña's visit, in the late 2005, to the Grupo de Óptica Atmosférica (Optics Atmospheric Group) at the University of Valladolid (GOA-UVA), Spain, a letter of agreement was signed with Dr. Angel de Frutos-Baraja, chair of GOA-UVA. The goal was to establish cooperation for aerosols research between both institutions, by installing a sun photometer and a particle impactor at Camagüey, under CLS responsibility. In November 2007, after further negotiation, the international cooperation agreement between the University of Valladolid, Spain, and the Institute of Meteorology, Cuba, was signed in Camagüey. Under that agreement a low-volume particulate impactor, Dekati PM10, and a CIMEL-318 sun photometer were installed at CMC in 2008 (Fig. 4). Further, two joint research projects have been conducted, one of them still running, and a third one is in the process of gaining approval by scientific authorities of both countries. The impactor allows us to determine the particulate matter mass concentration with aerodynamic diameter <10 μm (PM10) and <1 μm (PM1) fractions. Some of the impactor measurements of the first eight months were also the subject of chemical analysis. The analysis of the PM10 and PM1 fractions and chemical composition during that period showed the highest concentration of PM between May and August, with coarse and fine modes in almost the same proportion. High concentrations of Cl−, Na+, NO3−, and SO42− were found in the coarse mode; in the fine mode, the higher concentrations belong to SO42− and NH4+ (Barja et al. 2011a).
The sun photometer is operated and replaced annually, following the protocols of the Aerosol Robotic Network (AERONET). The measurements are contributed by the Red Ibérica de Medida Fotométrica de Aerosoles (RIMA) and AERONET. Thus, this is the first and only Cuban sun photometer contribution to such a National Aeronautics and Space Administration (NASA) program. The study of the first year of the measurements of the aerosol's optical properties at Camagüey showed a maritime mixed environment—results that agree with other studies for similar sites in the Atlantic Ocean. The arrival of Saharan dust to Camagüey, Cuba, was demonstrated during multiple events in July 2009, assessed by backtrajectory analysis using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model (Estevan et al. 2011).
In June 2010 AERONET began implementing the measurements in “cloud mode” at several selected stations, including Camagüey. Those measurements are conducted when no aerosol measurements are possible because of clouds, allowing instead the calculation of the cloud optical depth (COD). Preliminary comparison of those COD measurements with hourly cloud reports from the actinometrical station operating at Camagüey reveals good agreement with the natural behavior of the clouds in our region, with a value of 15 for the maximum frequency of occurrence of the COD (Barja et al. 2011b).
Because of the cooperative engagements by CLS, the leading author was invited in late 2001 to participate in the Stratosphere–Troposphere Processes and their Role in Climate (SPARC) Assessment of Stratospheric Aerosols Properties' kickoff meeting. The CLS team participated over the years in the scientific exchanges conducted by the panel. It contributed in particular to chapters 3 and 4 of the assessment as well as to the whole report published several years later (Thomason and Peter 2006).
Also the Global Change System for Analysis, Research, and Training (START) Visiting Scientist Award Program supported in 2004 a one-month visit by the lead author to the department of Earth Physics II of the Complutense University of Madrid, Spain. Dr. Ricardo Garcia-Herrera and his team provided full scientific support to help us learn meteorological data rescue principles and techniques. The fruitful exchanges with Dr. Garcia-Herrera and members of his team and the ongoing communication maintained over the years allowed the CLS team to rescue more than 40 years of the solar radiation dataset from the Camagüey meteorological station, resulting in the first paper ever published in the BAMS by Cuban scientists (Antuña et al. 2008). The rescued dataset has been fully reprocessed and quality controlled by properly designed computer software, and it has proven useful in both research and services. Research applications include the calculation of the frequencies of clear-sky conditions and of the broadband aerosol optical depth (Fonte and Antuña 2011); the evaluation of the tropospheric aerosols' radiative effects; and the evaluation of a radiative transfer model adjustment to the climatic conditions of Camagüey (Fonte 2011). Service applications are provided online at GOAC (2011), which contains both hourly observations in real time and historical values of solar radiation variables for the period 1981–2007. The solar radiation data rescue process as well as the derived applications and results are completely new for Cuba and for the Caribbean (Antuña et al. 2011).
Our efforts first to rebuild the old lidar and then to get a new one have not achieved results, however. Having a lidar system again working at Camagüey is still a goal integrated with our broader goals of research and services. The GOAC maintains an active cooperation with the lidar community in Latin America and all over the world. We have shared our expertise in processing and analyzing lidar aerosol and cloud measurements with several teams in the region and have facilitated contacts between these new lidar teams and the rest of the lidar community. Also, we participate actively in the implementation of the Global Atmosphere Watch (GAW) Aerosol Lidar Observation Network (GALION), representing and promoting the lidar groups in Latin America (Bösenberg et al. 2007).
TRANSITION FROM CLS TO GOAC.
After the lead author returned from his doctoral studies in 2002, he shared what he learned in the United States with the rest of the team. To make possible the doctoral work by the second and third authors (on the radiative effects of SA and CC, respectively), the Geophysical Fluid Dynamics Laboratory column radiative transfer code (Freidenreich and Ramaswamy 2005) was adapted for use on the PCs and for the local conditions at Camagüey. SA and CC extinction profiles derived from lidar and SAGE II measurements were used for characterizing their physical properties and also for feeding the radiative code. The radiative effects of SA and CC were determined and subject to analysis, producing interesting and valuable results.
In the case of the CC radiative effects, a noticeable result (to the author's knowledge, not reported in the literature before) was the finding of a double maximum in the diurnal cycle of the solar CC radiative forcing around noon at the CC base height for the thin and opaque CCs, shown in Fig. 5. An explanation for such a feature was proposed based on the different magnitudes of the contribution to the solar irradiance increase during the day, both by the cirrus cloud atmospheric optical path and the elevation of the sun (Barja and Antuña 2011). Another example was the numerical simulation of the vertical distribution of the heating rate produced by the SA from the Mount Pinatubo eruption over the Caribbean for the year 1992, depicted in Fig. 6. Although the values of the heating rate are low compared to the reports from other authors (because of the lack of longwave radiation in the model we used), the effects produced by SA plus some of the components of the atmosphere, such as ozone and water vapor, are evident. At the level of maximum concentration of SA (~24 km) the maximum heating rate is achieved, with positive values above that maximum and negative below in the troposphere (Estevan and Antuña 2010).
In this way, 2002–09 was the most intense capacity building period for the team. By the end of 2009, the team was in a new stage. Two doctoral students were ready to make their defenses the following year and two new technicians—students in the third year of a bachelor of science degree in meteorology—were integrated into the team. Professors and students from the computer sciences department at Camagüey University began to cooperate with us in both upgrading existing software and developing new ones.
The scientific “critical mass” and the attendant results further facilitate the consolidation and evolution of the team. Given our general goal, the study of radiative transfer processes in the atmosphere in the conditions of our country, and its implications in our long-term strategy, we decided to become the GOAC (Fig. 7). The second author assumed management of the team, and the lead author concentrated on scientific advising and on promoting cooperation. It was natural to begin allowing a new postdoctoral associate with so much work experience to develop his management skills.
The setup of the lidar at Camagüey in the late 1980s was envisaged even then by the lead author as a unique opportunity for creating a local scientific team for radiative transfer studies with a high level of independence from the standpoint of its scientific and technical capabilities. Thus, we took advantage of the Soviet researchers sharing technology and know-how on lidar SA measurements. Making the project sustainable as a full-time professional research facility was based on several principles: complete personal dedication and engagement of the members of the team, professional quality research, and ongoing international cooperation for accessing state-of-the-art scientific knowledge and tools, together with an intense effort for developing local scientific expertise. There has also been a practical flexibility in exploiting opportunities when they appear. Also central to this enterprise has been the ability to combine in a small team the diverse investigations that typically are conducted by several highly specialized groups.
For a little more than 20 years, this work has demanded an intense effort by each one of the team members, facilitated in no small part by making decisions by consensus.
The work involved international cooperation combined with local scientific capacities to guarantee the sustainability of a self-sufficient research team in the face of severe local economic limitations, the collapse of the Soviet Union, and the initial lack of local and regional expertise.
Ours is not a unique experience in Cuba. There is, for example, the modernization of the Cuban meteorological radar network, conducted by the radar group of the CMC (Peña et al. 2000; Rodríguez et al. 2005). Several other research teams in Cuba have overcome difficulties and achieved notable scientific results. They all combine strong personal commitment, clear definition of its goals, and effective strategies for reaching them. Those experiences could serve as examples for research teams in underdeveloped countries facing similar difficulties and obstacles. We are convinced, however, that there is not just one recipe for developing scientific teams in undeveloped countries. Each case should take into account the particular conditions of each country and the availability of international cooperation.