Munoz A.G.,University of Zulia |
Munoz A.G.,Centro Internacional Para la Investigacion del Fenomeno El Nino |
Lopez P.,Agencia Estatal de Meteorologia AEMET |
Velasquez R.,Servicio de Meteorologia de la Fuerza Aerea Venezolana SEMETF AV |
And 14 more authors.
Bulletin of the American Meteorological Society | Year: 2010
Observatorio Andino (OA) was established in 2008 by The Centro de Modelado Científico (CMC) in collaboration with Climate information applied to agricultural risk management in the Andean countries (CIIFEN). The OA main goal is to provide a collaborative network that ultimately increases the efficiency of the decision-making processes, especially in terms of getting more accurate forecasts and exchanging experiences on data, information, and scientific products, all of which is done with a standardized methodology and a Web-sharing service. The Observatorio Andino follows a three level hierarchical model execution flux, with the same approach for both short-term and seasonal products. In order to facilitate the validation process, a spatial map for each time slice of interest involving the differences and/or the anomaly correlations between model output and observations, is generated. The OA makes extensive use of its wiki, webinars, and video conferences for standardizing the methodologies.
Skansi M.D.L.M.,Servicio Meteorologico Nacional |
Brunet M.,Rovira i Virgili University |
Brunet M.,University of East Anglia |
Sigro J.,Rovira i Virgili University |
And 13 more authors.
Global and Planetary Change | Year: 2013
Here we show and discuss the results of an assessment of changes in both area-averaged and station-based climate extreme indices over South America (SA) for the 1950-2010 and 1969-2009 periods using high-quality daily maximum and minimum temperature and precipitation series. A weeklong regional workshop in Guayaquil (Ecuador) provided the opportunity to extend the current picture of changes in climate extreme indices over SA.Our results provide evidence of warming and wetting across the whole SA since the mid-20th century onwards. Nighttime (minimum) temperature indices show the largest rates of warming (e.g. for tropical nights, cold and warm nights), while daytime (maximum) temperature indices also point to warming (e.g. for cold days, summer days, the annual lowest daytime temperature), but at lower rates than for minimums. Both tails of night-time temperatures have warmed by a similar magnitude, with cold days (the annual lowest nighttime and daytime temperatures) seeing reductions (increases). Trends are strong and moderate (moderate to weak) for regional-averaged (local) indices, most of them pointing to a less cold SA during the day and warmer night-time temperatures.Regionally-averaged precipitation indices show clear wetting and a signature of intensified heavy rain events over the eastern part of the continent. The annual amounts of rainfall are rising strongly over south-east SA (26.41. mm/decade) and Amazonia (16.09. mm/decade), but north-east Brazil and the western part of SA have experienced non-significant decreases. Very wet and extremely days, the annual maximum 5-day and 1-day precipitation show the largest upward trends, indicating an intensified rainfall signal for SA, particularly over Amazonia and south-east SA. Local trends for precipitation extreme indices are in general less coherent spatially, but with more general spatially coherent upward trends in extremely wet days over all SA. © 2012 Elsevier B.V.
Munoz R.C.,University of Chile |
Quintana J.,Direccion Meteorologica de Chile |
Falvey M.J.,University of Chile |
Rutllant J.A.,University of Chile |
And 2 more authors.
Journal of Climate | Year: 2016
The climatology and recent trends of low-level coastal clouds at three sites along the northern Chilean coast (18.3°-23.4°S) are documented based upon up to 45 years of hourly observations of cloud type, coverage, and heights. Consistent with the subtropical location, cloud types are dominated by stratocumuli having greatest coverage (> 7 oktas) and smaller heights (600-750 m) during the nighttime of austral winter and spring. Meridionally, nighttime cloud fraction and cloud-base heights increase from south to north. Long-term trends in mean cloud cover are observed at all sites albeit with a seasonal modulation, with increasing (decreasing) coverage in the spring (fall). Consistent trend patterns are also observed in independent sunshine hour measurements at the same sites. Cloud heights show negative trends of about 100 m decade-1 (1995-2010), although the onset time of this tendency differs between sites. The positive cloud fraction trends during the cloudy season reported here disagree with previous studies, with discrepancies attributed to differences in datasets used or to methodological differences in data analysis. The cloud-base height tendency, together with a less rapid lowering of the subsidence inversion base height, suggests a deepening of the coastal cloud layer. While consistent with the tendency toward greater low-level cloud cover and the known cooling of the marine boundary layer in this region, these tendencies are at odds with a drying trend of the near-surface air documented here as well. Assessing whether this intriguing result is caused by physical factors or by limitations of the data demands more detailed observations, some of which are currently under way. © 2016 American Meteorological Society.
Fan X.,Shanxi University |
Wang Q.,Shanxi University |
Wang M.,Shanxi University |
Jimenez C.V.,Direccion Meteorologica de Chile
PLoS ONE | Year: 2015
An analysis of the annual mean temperature (TMEAN) (1961-2010) has revealed that warming amplification (altitudinal amplification and regional amplification) is a common feature of major high-elevation regions across the globe against the background of global warming since the mid-20th century. In this study, the authors further examine whether this holds for annual mean minimum temperature (TMIN) and annual mean maximum temperature (TMAX) (1961-2010) on a global scale. The extraction method of warming component of altitude, and the paired region comparison method were used in this study. Results show that a significant altitudinal amplification trend in TMIN (TMAX) is detected in all (four) of the six highelevation regions tested, and the average magnitude of altitudinal amplification trend for TMIN (TMAX) [0.306±0.086 °C km-1(0.154±0.213 °C km-1)] is substantially larger (smaller) than TMEAN (0.230±0.073 °C km-1) during the period 1961-2010. For the five paired highand low-elevation regions available, regional amplification is detected in the four high-elevation regions for TMIN and TMAX (respectively or as a whole). Qualitatively, highly (largely) consistent results are observed for TMIN (TMAX) compared with those for TMEAN. Copyright: © 2015 Fan et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Mena-Carrasco M.,Ministerio del Medio Ambiente |
Mena-Carrasco M.,Centro FONDAP CIGIDEN |
Saide P.,University of Iowa |
Delgado R.,Direccion Meteorologica de Chile |
And 5 more authors.
Urban Climate | Year: 2014
Santiago, an emerging megacity of 7 million plus inhabitants has shown great improvement in its air quality reducing PM2.5 concentrations from 69μg/m3 in 1989 to 24μg/m3 in 2013 with a comprehensive air quality management strategy. An operational air quality forecasting model that has shown great potential in predicting air quality episodes is used to establish how the climate A1B scenario can impact the frequency of bad air days. In comparison to 2011, in 2050 extreme air quality episodes will be reduced in 20%. WRF-Chem is used to evaluate the effect of anthropogenic emissions on the regional climate including aerosol radiative feedbacks for October-November 2008. Anthropogenic emissions of sulfur and black carbon show different geographical patterns which result in local cooling (0.2-1°C) in coastal Chile, due to large sources of SO2. Central Chile, where most of the population of the country lives, shows transportation of black carbon emissions into the Andes mountain range, resulting in local warming of 0.4°C. While global forcings may cause regional heating for 2050, reducing current black carbon emissions in Central Chile can reduce anthropogenic warming with immediate benefits to the regional climate, and simultaneously reducing local air pollution. © 2014 Elsevier B.V.
Quintana J.M.,Direccion Meteorologica de Chile |
Aceituno P.,University of Chile
Atmosfera | Year: 2011
The evolution of annual rainfall along the west coast of South America from 30 to 43° S (central Chile) is analyzed for the period 1900-2007. A prevailing negative trend in annual rainfall has been documented for this region in several previous studies. Here we focus on the significant changes and fluctuations occurring at the decadal time scale, exploring the links with regional atmospheric circulation anomalies associated with large-scale oscillatory modes of the ocean-atmospheric system. In particular, the relatively dry condition that prevailed from the 1950s to the early 1970s in the northern part of central Chile (30-35° S) is consistent with an intensified subtropical anticyclone in the southeast Pacific during a period characterized by a prevailing positive phase of the Southern Oscillation (SO) and the cold phase of the Pacific Decadal Oscillation (PDO). The shift of the PDO toward the warm phase by the mid-1970s was followed by an increased frequency of the negative phase of the SO and associated El Niño episodes. Concurrent weakening of the subtropical anticyclone favored an increased frequency of wet years in this region. Further south the negative trend in annual rainfall that prevailed since the 1950s in the region from 37 to 43° S intensified by the end of the 20th century. Changes in the meridional sea level pressure gradient at mid-latitudes and high-latitudes in the southeast Pacific, which are partially connected to the Antarctic Oscillation (AAO), play a significant role in modulating the interannual rainfall variability in all central Chile, especially during the austral winter semester (April-September). Thus, an intensified (reduced) meridional pressure gradient in that region favors a southward (northward) displacement of the latitudinal band of migratory extratropical low pressure systems and associated fronts. The significant positive trend that both the AAO index and its regional counterpart in the southeast Pacific exhibit since the 1950s may partially explain the observed downward trend in annual precipitation in the southern portion of central Chile, resulting from a reduction in both the frequency of wet days and the intensity of precipitation. Most of the global and regional climate models used to assess future climate scenarios associated with an enhanced planetary greenhouse effect, also call for a reduction of rainfall in this region which is consistent with the positive trend in the AAO predicted by those models.
Cordero R.R.,University of Santiago de Chile |
Seckmeyer G.,Leibniz University of Hanover |
Damiani A.,University of Santiago de Chile |
Jorquera J.,University of Santiago de Chile |
And 5 more authors.
Atmospheric Research | Year: 2014
Santiago de Chile (33°27' S-70°41' W) is a mid-latitude city of 6 million inhabitants with a complicated surrounding topography. Aerosol extinction in Santiago is determined by the semi-arid local climate, the urban pollution, a regional subsidence thermal inversion layer, and the boundary-layer wind airflow. In this paper we report on spectral measurements of the surface irradiance (at 290-600. nm wavelength range) carried out during 2013 in the heart of the city by using a double monochromator-based spectroradiometer system. These measurements were used to assess the effect of local aerosols, paying particular attention to the ultraviolet (UV) range. We found that the aerosol optical depth (AOD) exhibited variations likely related to changes in the subsidence thermal inversion and in the boundary-layer winds. Although the AOD at 350. nm typically ranged from 0.2 to 0.3, peak values of about 0.7 were measured. The AOD diminished with the wavelength and typically ranged from 0.1 to 0.2 at 550. nm. Our AOD data were found to be consistent with measurements of the particulate matter (PM) mass concentration. © 2014 Elsevier B.V.
Barrett B.S.,U.S. Naval Academy |
Carrasco J.F.,Direccion Meteorologica de Chile |
Testino A.P.,U.S. Naval Academy
Journal of Climate | Year: 2012
The leading intraseasonal mode of tropical atmospheric variability, the Madden-Julian oscillation (MJO), has been shown to modulate precipitation and circulation on a global and regional scale. Winter precipitation in Chile has been connected to a variety of synoptic-scale forcing mechanisms. This study explored the links between the two, first examining the intraseasonal variability of Chilean precipitation from surface gauges and the Tropical Rainfall Measuring Mission (TRMM) and then examining the variability of synoptic-scale circulation. Composites of precipitation, precipitation intensity, and lower-, middle-, and upper-tropospheric circulation were created using the Real-Time Multivariate MJO index, which divides the MJO into eight longitudinally based phases. Precipitation was found to vary across MJO phases, with positive precipitation anomalies in central and south-central Chile (30°-45°S) for MJO phases 8, 1, and 2, and negative anomalies in phases 3-7. Circulation was also found to vary across phase, in good agreement with precipitation: low geopotential height and negative omega (corresponding to upward vertical motion) anomalies were found over and upstream of Chile during the rainier phases, and the anomalies reversed during the drier phases. Surface pressure and middle- and upper-tropospheric geopotential height anomalies showed a classic equivalent barotropic wave train, indicating a teleconnection response to deep convective activity in the Maritime Continent in agreement with numerous earlier observational, modeling, and theoretical studies. © 2012 American Meteorological Society.
Munoz R.C.,University of Chile |
Alcafuz R.I.,Direccion Meteorologica de Chile
Aerosol and Air Quality Research | Year: 2012
Lidar instruments have proven useful for characterizing the structure and dynamics of aerosol layers. We compare here the diurnal, seasonal and vertical variability of urban aerosols as described by a lidar ceilometer and surface particulate matter (PM 10) concentrations using 4 years of observations available at Santiago, Chile, a city having a serious PM 10 air pollution problem. Large diurnal variation of ceilometer backscatter values is observed on average up to 600 m (400 m) above the surface in spring and summer (fall and winter). The diurnal cycles of near-surface ceilometer backscatter and PM 10 concentrations show prominent morning peaks. The large PM 10 evening peak is less marked in the ceilometer backscatter values, suggesting that this significant feature of Santiago's air pollution is constrained to a shallow atmospheric layer. Daily averages of PM 10 concentrations and ceilometer backscatter have correlations of 0.5 for the full data set, and a maximum of 0.75 for April. Results are supplemented with recently available observations gathered with a 355 nm elastic lidar. While the smaller blind region of the ceilometer provides a more complete picture of the aerosol layer dynamics, the higher resolution of the lidar allows a better definition of the aerosol layer structure. Both instruments suggest the frequent development of complex aerosol layers appearing over Santiago during the evening transition. The lidar shows also frequent occurrence of buoyancy oscillations in the stable basin's air mass. © Taiwan Association for Aerosol Research.
PubMed | Direccion Meteorologica de Chile and Shanxi University
Type: Journal Article | Journal: PloS one | Year: 2015
An analysis of the annual mean temperature (TMEAN) (1961-2010) has revealed that warming amplification (altitudinal amplification and regional amplification) is a common feature of major high-elevation regions across the globe against the background of global warming since the mid-20th century. In this study, the authors further examine whether this holds for annual mean minimum temperature (TMIN) and annual mean maximum temperature (TMAX) (1961-2010) on a global scale. The extraction method of warming component of altitude, and the paired region comparison method were used in this study. Results show that a significant altitudinal amplification trend in TMIN (TMAX) is detected in all (four) of the six high-elevation regions tested, and the average magnitude of altitudinal amplification trend for TMIN (TMAX) [0.3060.086 C km-1(0.1540.213 C km-1)] is substantially larger (smaller) than TMEAN (0.2300.073 C km-1) during the period 1961-2010. For the five paired high- and low-elevation regions available, regional amplification is detected in the four high-elevation regions for TMIN and TMAX (respectively or as a whole). Qualitatively, highly (largely) consistent results are observed for TMIN (TMAX) compared with those for TMEAN.