Atmósfera (Journal)
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Temperature-humidity index (THI) 1917-2008 and future scenarios of livestock comfort in Veracruz, México
Get PDFResults of the analysis of combined temperature (ºC) and relative humidity (RH) data are presented in order to obtain the temperature-humidity index (THI) in livestock for the region of Veracruz, México, in order to make climate comparisons in different study periods (1917-1960, 1961-1990, 1991-2008), as well as future scenarios for 2020, 2050 and 2080. The results indicate that the possibilities for animal comfort are scarce. For the past periods a growing THI has been found: 83, 85 and 86, respectively, considering the maximum temperatures for the month of May. For the future, the obtained THI were obtained from IPCC emissions scenarios A2 and B2 for the GFDL 2020 (80.87), 2050 (81.58), 2080 (82.82); ECHAM 2020 (81.27), 2050 (82.74), 2080 (83.95) and PRECIS HADCM2 2020 (81.24), 2050 (82.65), 2080 (83.95) models, whose resultsare in the category of dangerous.Se presentan resultados del análisis de datos de temperaturas (ºC) y humedad relativa (RH) combinados, para obtener el índice de temperatura y humedad (THI por sus siglas en inglés) en ganado para la región de Veracruz, México, con el propósito de hacer comparaciones climáticas en diferentes periodos de estudio (1917-1960, 1961-1990, 1991-2008), así como futuros escenarios a 2020, 2050 y 2080. Los resultados indican que las posibilidades de confort animal son reducidas. Para los periodos pasados se encuentra un THI creciente: 83, 85 y 86, respectivamente, considerando las temperaturas máximas para el mes de mayo. Para el futuro los THI fueron obtenidos a partir de los escenarios de emisiones A2 y B2 del IPCC para los modelos GFDL 2020 (80.87), 2050 (81.58), 2080 (82.82); ECHAM 2020 (81.27), 2050 (82.74), 2080 (83.95) y PRECIS HADCM2 2020 (81.24), 2050 (82.65), 2080 (83.95), que resultan en la categoría de peligrosos
May the NAO index be used to forecast rain in Spain?
Get PDFThis paper studies the influence of the North Atlantic Oscillation (NAO) on monthly, seasonal and annual precipitation regimes in continental Spain. The data used for this study include the monthly rain series of 325 meteorological stations distributed homogeneously over the study zone, and the monthly NAO indices from 1961 to 1998. A total of 5525 rain series were employed for the analysis. Simple and multiple linear correlations were established between these variables in different combinations. The main aim was to check whether monthly, seasonal or annual precipitation data could be predicted using earlier precipitation data and the NAO index. The geographical areas where the stations have shown a statistically significant correlation have been represented on maps. The results differ depending on the correlation, but, in general, the best results have been found in the fall and winter months. Finally, a practical application of the method was carried out in the Ebro Valley and it was observed that the combination of the NAO index for spring and summer and the precipitation registered in those two seasons may be useful to forecast rain in the fall
Variability of the standardized precipitation index over México under the A2 climate change scenario
Get PDFThe 12-month Standardized Precipitation Index (SPI) is used to identify and assess drought severity in México during the 1949-2098 period under the A2 emissions scenario of the Intergovernmental Panel on Climate Change (IPCC). The analysis indicates more frequent and severe drought events in México, shown by a negative trend of the 12-month projected SPI time series. Furthermore, this study concludes that projected future drought events would surpass the time-length, magnitude and frequency of those modelled during the second half of the 20th Century
A study on certain aspects of kinetic energy associated with western disturbances over northwest India
Get PDFThe winter precipitation in western Himalayas, particularly over Jammu and Kashmir, Himachal Pradesh, Uttaranchal and neighborhood is important from the point of view of agriculture, horticulture, transport, logistics and glacier basins that feed the rivers of north India. The precipitation is due to the large-scale interaction between the mid latitude and the tropical air masses. The interaction process leads to the formation or intensification of synoptic systems known as western disturbances that move from west to east. In this paper, kinetic energy budget terms for an intense western disturbance that occurred over northwest India have been analyzed. An intense western disturbance, that gave widespread precipitation over the northwestern parts of the country, moved across the region from 19 to 21 January 1997. The data required for the study was extracted from National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis datasets. The results indicate that the strong flux convergence and adiabatic production of kinetic energy takes place during the passage of western disturbance over north India. It is found that the meridional component of kinetic energy contributes for the generation, whereas, the zonal component of kinetic energy contributes for the destruction in the adaibatic generation of kinetic energy along the track of the western disturbance
Volcanic activity parameters and volcanism-climate relationships within the recent centuries
Get PDFThe ejecta ofvolcanism, including gas-to-particle conversions, form atmospheric aerosol layers which influence the radiation processes and in consequence the climate. Thereby, the major explosive eruptions are of predominant interest. They cause stratospheric warmings whereas the atmospheric boundary layer near surface is cooled. In order to study these effects, focussed on air temperature variations within the recent centuries (stratosphere only since 1958) a new volcanic activity index "SVI" is denned based on the Smithsonian volcano chronology. This parameter is compared with other similar parameters and used for an stratosphere-troposphere analysis of volcanic forcing. A long-term statistical analysis uses correlation and coherence techniques "integrated" and moving with time, considering the annual and 10 yr low-pass filtered data. The air temperature time series refer to the Northern Hemisphere and Arctic mean as well as to the stations Philadelphia (USA) and Hohenpeissenberg (FRG). In general, the long-term volcanism-climate relationships may be more pronounced than singular events. Finally, a moving signal analysis is performed where the volcanic signals in climate and the signal-to-noise ratios exceed the 95% confidence level in some cases
Numerical simulation of wind gusts in intense convective weather and terrain-disrupted airflow
Get PDFWind gust is an important element in weather forecasting. Gusts associated with squalls in intense convective weather may bring about injuries to the public. In aviation meteorology, the aircraft may not attempt to land on the runway in gusty crosswinds, which could disrupt air traffic and adversely affect airport efficiency. The conventional method of gust forecasting is mainly based on climatological information of wind excess due to gust on top of the mean wind for different synoptic and mesoscale conditions (e.g. subtropical squall line, monsoonal flow, tropical cyclone situation, etc.). This paper uses a physical approach to wind gust estimate in meso to microscale numerical weather prediction (NWP), namely, based on turbulent kinetic energy and vertical air motion as applied to Regional Atmospheric Modelling System (RAMS) version 4.4, and examines its performance in different conditions of gusty winds at the Hong Kong International Airport (HKIA). For the typical gusty wind events considered in the paper, the performance of the wind gust estimate is found to be satisfactory in comparison with actual wind measurements at the airport (yes-yes case, viz. the actual gusty winds are captured by the wind gust estimate method). To demonstrate that the method does not over-estimate the gust (null-null case, viz. the less gusty winds are not exaggerated in the estimate), an ordinary, moderate wind event with the winds crossing the mountains at the airport is also studied, and the estimated gust is reasonably close to the actual data. Gust estimate is apparently affected by the treatment of turbulence in the NWP model. As such, a sensitively study is also conducted on the impact of selecting different turbulence parameterization schemes available in RAMS 4.4 on the estimation of wind gusts for a case of terrain-disrupted airflow
Regional climate change scenarios for México
Get PDFIn this paper we present the regional climate change scenarios that were used for the assessment of the potential impacts in México on agriculture, livestock, forestry, hydrological resources as well as on human settlements and biodiversity. Those studies were developed for the Fourth Communication of México for the United Nations Framework Convention on Climate Change and coordinated by the Centro de Ciencias de la Atmósfera. The climate change scenarios were generated combining the models presented in the Fourth Assessment Report of Intergovernmental Panel on Climate Change and the criteria established by the IPCC’s Task Group on Data and Scenario Support for Impact and Climate Analysis. Specifically, climate change scenarios for México for the time horizons 2030 and 2050 were generated using the outputs from ECHAM5, HADGEM1 and GFDL CM2.0 models. The variables considered were monthly temperature and precipitation and the emissions scenarios A1B, A2, B2 and B1. These scenarios were generated using two spatial resolutions: low (2.5º x 2.5º), and high (5´x 5´). The corresponding databases and maps are available at the webpage: www.atmosfera.unam.mx.En este trabajo se presentan los escenarios de cambio climático regionales empleados en los estudios de impactos potenciales en México en los sectores de agricultura, ganadería, forestal, recursos hídricos y en los de asentamientos humanos y de biodiversidad. Estos estudios se realizaron dentro de los trabajos para la Cuarta Comunicación de México ante la Convención Marco de Cambio Climático, coordinados por el Centro de Ciencias de la Atmósfera. Para la generación de estos escenarios se emplearon los modelos presentados por el Panel Intergubernamental sobre el Cambio Climático en su último Reporte de Evaluación y los criterios establecidos por el Grupo de Trabajo sobre Datos y Escenarios para el Análisis de Impactos y Clima. Específicamente, los escenarios de cambio climático fueron generados para la República Mexicana utilizando las salidas de los modelos ECHAM5, HADGEM1 y GFDL CM2.0, para la temperatura y precipitación mensuales, para los horizontes 2030 y 2050, y para los escenarios de emisiones A1B, A2, B2 y B1. Estos escenarios fueron generados utilizando dos resoluciones espaciales: baja (2.5º x 2.5º), y alta (5’ x 5’). Las bases de datos y los mapas correspondientes se encuentran disponibles en la página: www.atmosfera.unam.m
Ensemble spread and systematic errors in the medium-range predictions during the Indian summer monsoon
Get PDFFor preparing medium range weather forecasts, two global coarse resolution models at different resolutions were used at the National Centre for Medium Range Weather Forecasting (NCMRWF), India. In order to improve the forecasting skill, an ensemble prediction system (EPS) was implemented on experimental basis. For generating initial perturbations a breeding method was implemented. Experimental forecast runs with 8-member ensemble were carried out and results are analyzed for a monsoon season. The ensemble mean of rainfall forecasts shows that over the broad region of Gangetic Plains, the EPS brings out the monsoon activity (active and weak spell) reasonably well six days in advance. However, over the eastern parts of India, the ensemble mean rainfall is good only in short-range. The ensemble spread becomes quite large from about day-4 forecast and beyond. An examination of the rainfall pattern from day-1 to day-6 forecasts by the model and the ensemble spread shows there is no linearity in the increase of spread with the rainfall amount. The model has a systematic tendency to enhance rainfall activity over the central Bay of Bengal and eastern parts of India as the length of forecast is increased. At the same time, the model tends to dry up over the equatorial Indian Ocean region, however, in the high-resolution model, the same tendency is not seen. In circulation fields, the model also has large systematic errors. These results suggest that to obtain maximum benefit from the ensemble prediction system, the systematic biases in the model must be reduced as the breeding method only takes care of the uncertainties in the initial conditions
Water availability as a limiting factor and optimization of hydropower generation as an adaptation strategy to climate change in the Sinú-Caribe river basin
Get PDFThe Water Evaluation and Planning Model (WEAP) 2.1 was applied to the Sinú-Caribe river basin in Colombia to create several baseline and adaptation strategy scenarios for water supply, use and demand, and to make projections for the future including the potential impacts of climate change. The analysis of water availability as a limiting factor in the supply-demand balance of the productive sectors and activities in the Sinú-Caribe river basin in Colombia shows that the supply requirement would increase and thus unmet demand would increase more quickly under climate change conditions. The scarcity indexes define the critical points in this balance by the years 2074 under current or baseline conditions and 2066 with climate change. Optimization scenarios for hydropower generation for the critical months of the year were also generated and show how water resources management strategies can mitigate the adverse effects of climate change
Local wind and air pollution interaction in the Mexico basin
Get PDFComponents of the thermotopographic wind regime in the Mexico City basin are examined in their interaction with the heat island induced centripetal circulation. The resulting wind regime is such that convergent surface flow over the city is predominant mainly during the night and early morning. The low-level convergence of air flow into the city, although weakened by turbulence and up-slope valley winds is still evident on daytime mean maps of resultant winds from a network of 9 stations. The position of the maximum SO2 isolines is almost coincident with the corresponding position of the heat island. It is concluded that, for the period examined, the local thermally generated winds in Mexico City tend to restrict the ventilation of the polluted air near the surface