Micro-scale Climate Research Articles

Evaluating the Impact of Heat Mitigation Strategies Using Added Urban Green Spaces during a Heatwave in a Medium-Sized City

Recognizing the growing trend of the urban population and the undeniable fact of global and regional climate change, it becomes increasingly important to explore how we can improve the livability of our cities not only in the distant future but also in the next few years. A critical aspect of this endeavor involves studying how we can effectively mitigate human heat load in urban areas. In our research, in the case of a medium-sized city (Szeged, Hungary), we examined the effect of surface modifications caused by vegetation on human thermal perception during the day and night of two heatwave days. To achieve this, we used the MUKLIMO_3 micro-scale climate model to simulate the thermal climate of Szeged, while the thermal load was assessed with the perceived temperature calculated by the Klima-Michel model. Our analysis also relied on the local climate zone (LCZ) system to describe the original land cover and the additional urban green spaces in the study area. We scrutinized the effects of added vegetation of different types and densities, as well as the presence of protective forests surrounding the city. Our findings revealed that the effect of the added vegetation can only be detected on the modified surfaces and in their immediate vicinity. Notably, dense urban greenery resulted in up to a 2–3 °C reduction in perceived temperature in certain areas during the daytime, highlighting the profound impact of targeted green space development. In addition, it is crucial to consider the airflow-blocking effect of woody vegetation, which can increase thermal load by 1–3 °C in the areas located in a downwind direction. Therefore, the changing regional climatic conditions (e.g., wind direction) and the development of the right type and location of urban green areas deserve special attention during modern urban planning processes.

Does the spatial configuration of urban parks matter in ameliorating extreme heat?

Extreme heat challenges the liveability of cities. Urban parks are popular as an efficient mitigative solution; however, uncertainties remain regarding whether and how the spatial configuration affects the effectiveness in practice. This paper tackles this issue by comparing the microclimatic amelioration potential of urban parks with the same green ratio in different spatial configurations. The study was conducted using microscale climate simulation in ENVI-met within three highly developed urban settings in Melbourne City, Australia, on 30th January 2009, during one of the most intense heatwave events. Hourly simulated data were extracted from all outdoor grids, encompassing nine heat-related indices, including meteorological variables, thermal comfort variables, and energy balance components. Linear mixed models were used to assess the effect of spatial configuration on improving outdoor thermal conditions. The results highlight a significant influence of spatial configuration in microclimate amelioration, and that these effects were context-specific, and no universally effective design emerged across locations, even within the same city. The findings underscore the necessity of considering other factors, such as surface cover characteristics and building configurations, and emphasise the importance of conducting site-specific simulations when introducing green infrastructure for heat mitigation.

Long-Term Assessment of Bioclimatic Conditions at Micro and Local Scales in the Cities of the Western Part of the Balkan Peninsula during the 21st Century

Thermal comfort assessments at local or micro-scales within urban areas can provide crucial insights for the urban adaptation strategies pertaining to climate-conscious urban planning and public health. However, the availability of long-term or mid-term daily or hourly meteorological data sets from urban environments remains a significant challenge even in the 21st century. Consequently, this study aimed to assess the thermal conditions in cities across the western part of the Balkan Peninsula, encompassing five countries (Slovenia, Croatia, Serbia, Bosnia and Herzegovina, and Montenegro), by utilizing the Physiological Equivalent Temperature (PET) index. Meteorological data sets, comprising air temperature, relative humidity, wind speed, and cloudiness, were collected from 32 national meteorological stations/measurement locations spanning the period from 2001 to 2020. The PET calculations were conducted based on meteorological data measured three times per day (7 a.m., 2 p.m., and 9 p.m.). Upon conducting a spatial analysis of the meteorological stations, it was observed that most of them (25 stations) were situated within built-up areas or urban suburbs, rendering them highly relevant for local or micro-scale climate and bioclimate assessments. The findings revealed that urban locations exhibited slightly higher PET heat stress levels, particularly during the summer season and at 2 p.m. Moreover, higher average PET values were observed in both urban and non-urban stations situated within a continental climate during warmer periods, such as summer. In contrast, during the colder seasons, namely winter and spring, higher PET values were prevalent in the Mediterranean region. Furthermore, the PET frequency analysis revealed a greater prevalence of extreme and severe heat stress levels in stations within continental climates, particularly those located in urban areas, as compared to stations in Mediterranean climates. In contrast, during the winter and spring seasons, monitoring stations in close proximity to the Adriatic Sea, characterized by a Mediterranean climate, exhibited significantly lower levels of cold stress compared to inland stations. Evidently, in addition to the climatic characteristics and surrounding terrain, the urban morphology significantly impacts the thermal conditions within cities.

Self-adaptive hybrid urban morphologies community (HUMC): Its shared environment and soft intervention for sustainable urban governance

Cities have entered a transitional stage from incremental development to intension existent development. Beyond demolition and reconstruction, revitalising existing functioning neighbourhoods to make them more liveable and resilient while balancing their inter-relationships is an important topic in sustainable urban planning and governance. This paper puts forward a conceptual model for a “hybrid urban morphologies community” (HUMC) and explores its collective environmental performances. Taking the Hubei HUMC as a case study site, the paper examines its diverse temporal-spatial environmental performances by adopting on-site observation and measurement, focusing on local micro-scale climate, thermal comfort, and pedestrian ventilation capacity. Results reveal that none of the eight examined morphological patterns in Hubei HUMC consistently exhibited satisfactory environmental performance across all time periods in a typical summer day. Each morphological pattern presented varied merits and drawbacks during specific time periods. These morphological patterns together create an environmental complementary and form a synergetic socio-ecological system under the shared environment mechanism, which enables residents to have continuous outdoor habitation. Correlation and regression analyses illustrated that SVF, TSF, GCR, and GSA were the most critical of the “adaptable” urban morphological indicators (UMIs) that influenced urban outdoor environmental performances. Ultimately, soft intervention is advocated through temporarily rather than permanently adjusting these “adaptable” UMIs to ameliorate spaces with unsatisfactory environmental performances during the specific time periods. The proposed HUMC provides a reference model for urban management zoning and establishment of resilient self-adaptive urban communities.

30-Year Spatial-Temporal Analysis of Air Surface Temperature as Climate Change Mitigation

Natural and anthropogenic factors, such as volcanic eruptions and land use, are indirect causes of changes in the micro-scale climate. Over the past 30 years, climate change has been detected with increased air surface temperature (AST) above 30.00C, a phenomenon of Urban Heat Island. Therefore, this study aimed to create a spatial model to see changes in AST in Bandar Lampung City from1990 to 2020. The spatial and temporal analysis uses Landsat data to produce land surface temperature (LST) and AST models. The results showed a temperature rise in the LST area, which tends to be the northern part of Bandar Lampung City, by 25.0oC and above for 30 years. Compare LST and AST from two stations between 30 years is 5.00C. In 1990, the LST concentrated on the spatial distribution of the AST model with a temperature above 30.00C, while in 2020, it diffused to the northern part of Bandar Lampung City. The results concluded that the air temperature in the city has warmed up to 0.46OC (+10C), which is in line with the findings of IPPC and various world cities. It is also in occurrence with the UHI phenomenon since 2014 that climate change is part of mitigation.

The MicroClimate Screen – A microscale climate exposure system for assessing the effect of CO2, temperature and UV on marine microalgae

Global warming and anthropogenic activities are changing the ocean, inducing profound impacts on marine life and ecosystems from changing physical and chemical factors in and above the water column. Rising surface temperatures, ocean acidification, and seasonal variations in UV radiation (UVR), modulated by water clarity and sea-ice extent, affect life cycles of the marine food-web, and directly or indirectly also the global carbon fixation. Diatoms, pelagic microalgae that are responsible for 40% of the marine productivity, have limited capability to avoid exposure to changing ocean conditions, and hence, highly relevant for model studies of the influence of climate change on growth and productivity in the marine environment. A plate-based high-throughput exposure system was constructed to assess the biological effects from relevant climate change factors on the diatom Skeletonema pseudocostatum, conducted as a chronic toxicity tests over 72 h periods. The exposure system consisted of a micro-climate unit and a light-exposure unit, enabling accurate regulation of pCO2, temperature, UVR and photosynthetic active radiation (PAR). Changes in physical factors, including pH, dissolved inorganic carbon (DIC), total alkalinity (TA), temperature and salinity in the medium, as well as reduction in growth were characterised to demonstrate performance of the micro exposure system. The results demonstrate that the exposure system successfully simulated ocean acidification and could maintain stable temperature (CV < 3%), PAR and UVR irradiance (CV < 8%). Growth inhibition responses were typically dose-dependent and verified that the micro-exposure system could be used to assess effects and adaptions to climate-relevant stressors.

Climate trend analysis for a semi-arid Borana zone in southern Ethiopia during 1981\u20132018

BackgroundUnderstanding the climate variability at local scale could help suggest local adaptation responses to manage climate associated risks. This paper analyzed the variability and trend of climate in semi-arid Borana zone of southern Ethiopia over the period 1981–2018 using Mann–Kendall (MK) test, Sen’s Slope Estimator (SEE) and inverse distance weighted (IDW) interpolation technique. Gridded (4 km * 4 km) climate data (daily precipitation, daily maximum temperature (Tmax) and minimum temperature (Tmin)) were collected from National Meteorology Agency (NMA) of Ethiopia.ResultsThe results revealed the study area received a mean monthly precipitation of 39.19 mm and a monthly mean Tmax and Tmin of 29.66 °C and 16.31 °C were observed respectively. Rainfall shows a significant increasing trend during August, October and November and extremely variable during December, January and February where CV > 100%. Tmax shows a significant warming trend during August but January, February, August and October exhibited similar trend for Tmin. Rainfall and Tmin shows a significant trend during Meher and no trend for the rest of the seasons. Mean annual rainfall shows a significant increase where no trend observed for both Tmax and Tmin at this timescale. Decadal rainfall and Tmin exhibited no trend but Tmax show significant warming trend during 2001–2010 decade. Better rainfall and cooler temperature were observed in the north central, northeastern and northwestern whereas the southeastern and southwestern regions were drier and warmer.ConclusionRainfall is highly variable than temperature both at temporal and spatial scales in Borana. The intensity of rainfall decreases from the northeastern and northwestern parts towards the southwest while temperature increased from the north central parts towards the southwest for Tmax and the southeast for Tmin. The effect of topography is substantial for the local scale variability observed in the study area. Internal variability is observed at temporal and spatial scales and therefore any adaptation responses to local climate variability should consider the microscale climate.

Importance of Microscale Climate Simulations in City Scale Overheating Assessments

This study demonstrates the importance of high-resolution climate simulations when conducting city-scale outdoor heat wave alert and indoor overheating assessments. This is done by modelling urban climate of the Ottawa and Montreal cities at 1 km and 25 km, typical for regional climate modelling respectively, over the summer of 2018 when an extreme heat event caused around 100 deaths in these cities. It is shown that urban climate characteristics (higher temperatures, lower wind speeds, lower relative humidity in the urban core than surroundings) are better simulated at 1 km than at 25 km spatial resolution. Indoor conditions are simulated for an archetype model of a single detached house using EnergyPlus software for two locations within the cities: a) city center and b) airport location. It is shown that the simulated indoor air temperature in the building is highly correlated with the outdoor air temperature. Furthermore, it is found that the maximum indoor air temperature difference of the city center and the airport can be as high as 8°C in Montreal and 9°C in Ottawa. Such intra-urban differences in overheating in buildings will be ignored if microscale simulations are not performed, highlighting their importance for building overheating assessments in cities.

Modeling impacts of super cool roofs on air temperature at pedestrian level in mesoscale and microscale climate models

Passive daytime radiative cooling is gaining increasing relevance as recent studies report that newly developed materials with very high reflectivity and emissivity could be able to effectively reduce urban heat stress, when applied as roofing material (super cool roofs). A recent microscale sensitivity study with ENVI-met modeled the impact of super cool roofs with maximum air temperature reductions of around 0.85 K at pedestrian level for an idealized model area. To verify these findings in real urban structures featuring complex building morphologies and varying meteorological conditions, we conducted climate simulations for two contrasting cities: New York City, NY, and Phoenix, AZ. (Super) cool roof's cooling impacts are compared using mesoscale and nested microscale simulations in both cities with the Weather Research and Forecasting Model (WRF) and ENVI-met, respectively. While ENVI-met predicts daytime air temperature cooling at pedestrian level of up to 0.49 K (New York) and 0.94 (Phoenix), WRF estimates maximum cooling of 2.51 K (New York) and 3.31 K (Phoenix). Despite these differences both models showed high agreement in statistical analysis of modeled pedestrian-level air temperatures and roof surface temperatures. Climatological conditions could be identified as a major driver for cooling impact differences between New York City and Phoenix.

Monitoring and Modeling Roof-Level Wind Speed in a Changing City

Results of an observational campaign and model study are presented demonstrating how the wind field at roof-level in the urban area of Vienna changed due to the construction of a new building nearby. The investigation was designed with a focus on the wind energy yield of a roof-mounted small wind turbine but the findings are also relevant for air dispersion applications. Wind speed profiles above roof top are simulated with the complex fluid dynamics (CFD) model MISKAM (Mikroskaliges Klima- und Ausbreitungsmodell, microscale climate and dispersion model). The comparison to mast measurements reveals that the model underestimates the wind speeds within the first few meters above the roof, but successfully reproduces wind conditions at 10 m above the roof top (corresponding to about 0.5 times the building height). Scenario simulations with different building configurations at the adjacent property result in an increase or decrease of wind speed above roof top depending on the flow direction at the upper boundary of the urban canopy layer (UCL). The maximum increase or decrease in wind speed caused by the alternations in building structure nearby is found to be in the order of 10%. For the energy yield of a roof-mounted small wind turbine at this site, wind speed changes of this magnitude are negligible due to the generally low prevailing wind speeds of about 3.5 m s−1. Nevertheless, wind speed changes of this order could be significant for wind energy yield in urban areas with higher mean wind speeds. This effect in any case needs to be considered in siting and conducting an urban meteorological monitoring network in order to ensure the homogeneity of observed time-series and may alter the emission and dispersion of pollutants or odor at roof level.

Influence of tectonic uplift of the Qinling Mountains on the paleoclimatic environment of surrounding areas: Insights from loess–paleosol sequences, Weihe Basin, central China

The southern edge of the Chinese Loess Plateau affected by the stepwise uplift of the Qinling Mountains is a transitional climatic area between the different climatic environments and sedimentary characteristics to the north and south sides of the Qinling Mountains. The study of different Quaternary loess deposits in this region is conducive to improving our understanding of the micro-scale climatic effects of tectonic developments. Here, we use a series of experimental methods on a well-preserved loess–paleosol sequence in the South Jingyang Plateau to obtain proxy data, including grain-size, magnetic susceptibility, loss on ignition, and geochemical elemental. Changes in grain-size, magnetic susceptibility and loss on ignition indicate that the East Asian monsoon has undergone significant changes due to the continued global cooling and mid-Pleistocene climate transition during the deposition process of XSD loess, i.e., the intensities of the winter and summer monsoons were simultaneously enhanced. Elemental correlations and factor analysis indicate the sedimentary environment and provenance of the deposits, while elemental enrichment and element ratios, including Si/Ti, Al/Ti, Rb/Sr and Zr/Rb, are consistent with changes in the intensity of pedogenic and of the East Asian monsoon as reflected by climate proxies, illustrating that XRF core scanning analysis technology has great potential in the field of Quaternary environmental changes of loess. Furthermore, the stepwise uplift of the Qinling Mountains, which has blocked the winter and summer monsoons to a certain extent, has had a significant impact on the relative degree of loess accumulation and pedogenic in the northern piedmont, southern piedmont and intermontane basin of the Qinling Mountains and also appears to have promoted settlement by early humans. Hence, the study of paleoclimate in areas of active tectonic movement has the potential to promote our understanding of micro-scale climate change in this region in the future.

Evaluating the ENVI-met microscale model for suitability in analysis of targeted urban heat mitigation strategies

Microscale atmospheric models are increasingly being used to project the thermal benefits of urban heat mitigation strategies (e.g., tree planting programs or use of high-albedo materials). However, prior to investment in specific mitigation efforts by local governments, it is desirable to test and validate the computational models used to evaluate strategies. While some prior studies have conducted limited evaluations of the ENVI-met microscale climate model for specific case studies, there has been relatively little systematic testing of the model's sensitivity to variations in model input and control parameters. This study builds on the limited foundation of past validation efforts by addressing two questions: (1) is ENVI-met grid independent; and (2) can the model adequately represent the air temperature perturbations associated with heat mitigation strategies? To test grid independence, a “flat” domain is tested with six vertical grid resolutions ranging from 0.75 to 2.0 m. To examine the second question, a control and two mitigation strategy simulations of idealized city blocks are tested. Results show a failure of grid independence in the “flat” domain simulations. Given that the mitigation strategies result in temperature changes that are an order of magnitude larger than the errors introduced by grid dependence for the flat domain, a lack of grid independence itself does not necessarily invalidate the use of ENVI-met for heat mitigation research. However, due to limitations in grid structure of the ENVI-met model, it was not possible to test grid dependence for more complicated simulations involving domains with buildings. Furthermore, it remains unclear whether existing efforts at model validation provide any assurance that the model adequately captures vertical mixing and exchange of heat from the ground to rooftop level. Thus, there remain concerns regarding the usefulness of the model for evaluating heat mitigation strategies, particularly when applied at roof level (e.g. high albedo or vegetated roofs).

Assessment of human thermal perception in the hot-humid climate of Dar es Salaam, Tanzania

Dar es Salaam, Tanzania, is a typical African city along the Indian Ocean coast, and therefore an important urban area to examine human thermal perception in the hot-humid tropical climate. Earlier research on human bioclimate at Dar es Salaam indicated that heat stress prevails during the hot season from October to March, peaking between December and February, particularly the early afternoons. In order to assess the human thermal perception and adaptation, two popular places, one at an urban park and another at a beach environment, were selected and questionnaire surveys were conducted in August-September 2013 and January 2014, concurrently with local micro-meteorological measurements at survey locations. The thermal conditions were quantified in terms of the thermal index of the physiologically equivalent temperature (PET) using the micro-scale climate model RayMan. The thermal comfort range of human thermal comfort and the local thermal adaptive capacity were determined in respect to the thermal index by binning thermal sensation votes. The thermal comfort range was found to be well above that in temperate climates at about 23-31°C of PET. The study could significantly contribute to urban planning in Dar es Salaam and other coastal cities in the tropics.

Analysis of Thermal Environment over a Small-Scale Landscape in a Densely Built-Up Asian Megacity

Many studies have found that larger parks might be needed to counteract the Urban Heat Island effects typical in densely populated Asian megacities. However, it is not easy to establish large parks to serve as urban cool islands in Asian megacities, where little space exists for large urban neighborhood parks. Officials in these cities would rather use small areas by replacing heat-absorbing artificial land cover with natural cover. The main objective of this study was to understand the cooling effect of changes in land cover on surface and air temperatures in urban micro-scale environments for supporting sustainable green-space planning and policy in densely built-up areas. This was achieved using measurements at different heights (ground surface, 0.1 m, and 1.5 m) for five land cover types (LCTs) and modeling with the micro-scale climate model ENVI-met. At all vertical measuring points, the average temperature over the entire measurement period had the same hot-to-cold order: asphalt &gt; soil &gt; grass &gt; water &gt; forest. However, the value dramatically decreased as the measuring points became higher. The intensity of hot and cool spots showed the highest value at surface by 18.2 °C, and declined with the height, showing 4.1 °C at 0.1 m and 3.1 °C at 1.5 m. The modeling results indicated that the well-known diurnal variation in surface insolation also occurred in our small domain, among the various LCTs. Based on these findings, providing small-scale green infrastructure in densely built-up areas could be an effective way to improve urban micro-scale thermal conditions.

Modeling the effective emissivity of the urban canopy using sky view factor

Surface emissivity is a critical parameter for studying city-, meso-, and micro-scale climate and energy balance. The emissivity of complex surfaces e.g. a forest or an urban canopy is an effective surface property since it depends on both surface materials and geometry. This study presents a novel methodology for estimating effective emissivity using sky view factor retrieved from airborne Lidar data, building GIS data, and land use and land cover classification data. First, a high correlation between the effective emissivity retrieved from ASTER TIR bands 10–14 and the sky view factor was observed (r2=0.93, 0.99, 0.99, 0.97, 0.97). When the sky view factor decreases, the effective emissivity tends to increase, which is mainly due to multiple scattering (cavity effect), thus increases the effective emissivity. A simplified model which assumes that reflection and scattering only occurs within a single pixel was developed. Results showed that the correlations between the modeled and the spectral (band) emissivity retrieved from the ASTER multispectral TIR data (five spectral bands) are high (r2=0.93, 0.99, 0.98, 0.93, 0.97), and with low RMSE (0.019, 0.016, 0.012, 0.003 and 0.004 from band 10–14 respectively). The emissivity derived from this simplified model, however, tends to be overestimated in band 10–12. Thus, a refined urban emissivity model based on sky view factor (UEM-SVF) which considers the scattering and reflection from adjacent pixels was developed in this study. Results show a good agreement with ASTER spectral (band) emissivity: r2=0.90, 0.98, 0.96, 0.94 and 0.96, and very low RMSE (0.006, 0.003, 0.004, 0.002 and 0.004). This study illustrates that the UEM-SVF can be useful for estimation of land surface emissivity of complex surfaces, and can further be used for accurate land surface temperature retrieval.

Optimal location of green zones in metropolitan areas to control the urban heat island

In this paper we analyze and numerically solve a problem related to the optimal location of green zones in metropolitan areas in order to mitigate the urban heat island effect. So, we consider a microscale climate model and analyze the problem within the framework of optimal control theory of partial differential equations. Finally we compute its numerical solution using the finite element method, with the help of the interior point algorithm IPOPT, interfaced with the FreeFem++ software package.

고밀도 관측자료를 이용한 야간 지면냉각과 찬공기 이동 분석 - 서울 은평구 뉴타운 사례

ABSTRACT Climate analysis is important in urban planning for human comfort. Synoptic weather conditions can only resolve the 30% of local variance of wind conditions whereas 70% of the variance arise from local terrain, buildings, and other small scale thermal conditions. Climate Analysis Seoul (CAS) was developed to resolve such micro-scale climate. The Local-scale air temperature Deviation (LD) analysis map from CAS showed the co-existence of built-up and suburban areas in the study region (CR, Cold-air analysis Region) despite its small extent. Temperature, humidity, wind speed, and wind direction were monitored in CR. Hourly observed cooling rate agreed well with LD. Cold air production, transportation, and stagnation was visualized by the observed Vertical Temperature Gradient (VTG) along the small stream in CR. VTG observed at the upper-most stream can be divided into two components: radiative cooling and cold air inflow from outside. Radiative cooling exists regardless of the wind speed whereas cold air inflow occurs only with calm wind. From the regression analyses based on the wind speed, the inflow portion was determined as 84% of radiative cooling. Climate analysis in the future will be able to characterize the changes in cold air by urban development plan to support the human comfort.KEYWORDS : Urban Planning, Urban Climate, Cold Air, Nocturnal Cooling, High Density Observation

Thermal Characteristics of Urban Surface Materials

This paper studies the influence of different urban coverings (green areas or dry cover) on the urban microclimate. Different urban structures in a small area show different microclimatic behavior, depending on the thermophysical properties of the surface materials, in particular on the presence and extent of green areas. The research has been developed in downtown Rome in the summer period. In order to evaluate the impact of different urban envelopes, a typical urban square has been considered and analyzed systematically with the microscale climate model ENVI-met. A number of simulations has been performed with various kinds of surface covers and of vegetation and their effect on the air and soil temperatures and on the surface heat fluxes has been determined.

A new zero-equation turbulence model for micro-scale climate simulation

Micro-scale climate is vital for the health and comfort of residents in urban areas. Simulation platforms being used to predict micro-scale climate usually take CFD (Computational Fluid Dynamics) as their core procedure. The popular turbulence models in practical CFD application for micro-scale climate are the k-ɛ series models. Given that the two-equation models might cost too much CPU time, they can hardly be applied at the design stage of complex urban area. Compared with the two-equation models, zero-equation turbulence models can reduce the computer load significantly. This paper proposes a new two-layer zero-equation turbulence model specific for the micro-scale climate simulations. The model assumes the turbulence viscosity as a function of velocity deformation rate and the length scale in the inner layer and function of length scale and local mean velocity in the outer layer. Validated with the wind-tunnel experiment data, this new zero-equation turbulence model can give reasonably acceptable results in micro-scale climate simulations. Besides, it costs much less CPU time and computer memory than the standard k-ɛ model does. This new zero-equation turbulence model can be an applicable alternative in micro-scale climate research.

Evidence of sexual reproduction in the hermatypic corals Pocillopora damicornis, Porites panamensis, and Pavona gigantea in Banderas Bay, Mexican Pacific

The reproductive capacity of coral communities in the Mexican Pacific is still poorly documented. One of the most abundant coral communities in this region is found in Banderas Bay, yet the reproductive patterns of the coral species have not been analyzed. In order to document the annual reproductive cycle of the three most common species of corals in the bay, samples of Pocillopora damicornis, Porites panamensis, and Pavona gigantea were collected monthly from Redonda Island from December 2001 to November 2002. Colony fragments were processed by histological techniques and analyzed under a microscope. The three species showed the presence of gametes, which was associated with an increase in sea surface temperature. Gametogenesis was first observed in P. damicornis, classified as hermaphrodite. In P. panamensis, reproductive cells were observed in May 2002, and embryos and planulae in September 2002; this species was classified as gonochoric, showing internal fertilization and a distinct reproductive behavior compared with that reported for other areas of the eastern tropical Pacific. In P. gigantea, gametogenesis started later and occurred over a short period of time; this species was classified as gonochoric and no mature gametes were evident. All three species showed reproductive potential during the summer, confirming the reproductive capacity documented for these species in adjoining areas of the Mexican Pacific. The intensity and duration of the reproductive cycle in Banderas Bay are likely regulated by periodic events like El Niño and microscale climate oscillations that modulate temperature and light patterns in the area.