Un sistema automatizado de pronóstico de dispersión de cenizas y su monitoreo en tiempo real para el volcán Popocatépetl

El volcán Popocatépetl ha estado muy activo desde el 21 de diciembre de 1994. Su actividad, a lo largo de los casi 30 años de actividad eruptiva ha sido de carácter explosivo (principalmente de tipo vulcaniano), alternado con actividad efusiva (construcción de domos de lava). La actividad explosiva ha producido columnas de cenizas con diferentes tamaños, de hasta ~20 km de altitud y con una dispersión que ha llegado hasta los EUA. Sin embargo, la lluvia de cenizas importante se ha restringido a los ~65 km alrededor del cráter con evidencias de caída de cenizas en las ciudades de México y Puebla principalmente. El monitoreo de la actividad eruptiva ha sido llevado a cabo por el Centro Nacional de Prevención de Desastres, conjuntamente con investigadores de la Universidad Nacional Autónoma de México, principalmente del Instituto de Geofísica, durante los años que lleva en actividad el volcán. Este monitoreo ha consistido principalmente en la vigilancia sísmica, la deformación, las emisiones de gases volcánicos y el monitoreo de aguas de manantiales cercanos, entre otras líneas de trabajo

Measurement report: Evolution and distribution of NH3_3 over Mexico City from ground-based and satellite infrared spectroscopic measurements

Ammonia (NH$_3$) is the most abundant alkaline compound in the atmosphere, with consequences for the environment, human health, and radiative forcing. In urban environments, it is known to play a key role in the formation of secondary aerosols through its reactions with nitric and sulfuric acids. However, there are only a few studies about NH$_3$ in Mexico City. In this work, atmospheric NH$_3$ was measured over Mexico City between 2012 and 2020 by means of ground based solar absorption spectroscopy using Fourier transform infrared (FTIR) spectrometers at two sites (urban and remote). Total columns of NH$_3$ were retrieved from the FTIR spectra and compared with data obtained from the Infrared Atmospheric Sounding Interferometer (IASI) satellite instrument. The diurnal variability of NH$_3$ differs between the two FTIR stations and is strongly influenced by the urban sources. Most of the NH$_3$ measured at the urban station is from local sources, while the NH$_3$ observed at the remote site is most likely transported from the city and surrounding areas. The evolution of the boundary layer and the temperature play a significant role in the recorded seasonal and diurnal patterns of NH$_3$. Although the vertical columns of NH$_3$ are much larger at the urban station, the observed annual cycles are similar for both stations, with the largest values in the warm months, such as April and May. The IASI measurements underestimate the FTIR NH$_3$ total columns by an average of 32.2 ± 27.5 % but exhibit similar temporal variability. The NH$_3$ spatial distribution from IASI shows the largest columns in the northeast part of the city. In general, NH$_3$ total columns over Mexico City measured at the FTIR stations exhibited an average annual increase of 92 ± 3.9 × 10$^{13}$ molecules cm$^{−2}$ yr$^{−1}$ (urban, from 2012 to 2019) and 8.4 ± 1.4 × 10$^{13}$ molecules cm$^{−2}$ yr$^{−1}$ (re- mote, from 2012 to 2020), while IASI data within 20 km of the urban station exhibited an average annual increase of 38 ± 7.6 × 10$^{13}$ molecules cm$^{−2}$ yr$^{−1}$ from 2008 to 2018

Monitoring holopelagic Sargassum spp. along the Mexican Caribbean coast: understanding and addressing user requirements for satellite remote sensing

Massive influxes of holopelagic Sargassum spp. (Sargassum natans and S. fluitans) have been causing major economic, environmental and ecological problems along the Caribbean coast of Mexico. Predicting the arrival of the sargassum as an aid to addressing these problems is a priority for the government, coastal communities and the society; both mitigating the impacts and providing opportunities for its use. Lack of data concerning precise locations and times of sargassum beachings means that public and private funds are being spent inefficiently and most actions are reactive. The dynamic nature of sargassum beachings/influxes render conventional ground-based monitoring insufficient. Earth observation and cloud-based processing services offer tools to track, quantify and understand sargassum beaching remotely in a frequent, systematic and reliable manner with the temporal and spatial resolutions required for its management. In order to find the right solutions to address this problem, in this paper the needs and requirements of stakeholders are taken into consideration for the development of an Earth observation-based service to monitor sargassum along the Mexican Caribbean coast. Routine monitoring of sargassum over a large area will be cost effective and help mitigate the negative effects of sargassum influxes. The combination of imagery from Planet, specifically their SuperDove systems that provide daily data at 3 m spatial resolutions, with the freely available EU Copernicus data would be useful for many different stakeholders and potential users. A prototype of the service is presented, based on the main user requirements. The system would enable public and private organizations to allocate resources appropriately in affected areas quickly and efficiently, thereby minimizing economic, social and environmental impacts and enhancing the resilience of local communities. It would also assist the sargassum industry in the collection of fresh algae for onward processing. The system could easily be implemented for similar types of environmental monitoring in the Greater Caribbean and beyond

Effects of anomalous propagation conditions on weather radar observations

In this chapter our objective is to provide an overview of the effects of anomalous propagation conditions on weather radar observations, based mostly on studies performed by the authors during the last decade, summarizing results from recent publications, presentations, or unpublished material. We believe this chapter may be useful as an introductory text for graduate students, or researchers and practitioners dealing with this topic. Throughout the text a spherical symmetric atmosphere is assumed and the focus is on the occurrence of ground and sea clutter and subsequent problems for weather radar applications. Other related topics such as long-path, over-the-horizon propagation and detection of radar targets (either clutter or weather systems) at long ranges is not considered here; however readers should be aware of the potential problems these phenomena may have as range aliasing may cause these echoes appear nearer than they are ¿ for more details see the discussion about second trip echoes by Zrnic, this volume

Assessing Nowcast Models in the Central Mexico Region Using Radar and GOES-16 Satellite Data

In this study, the nowcast models provided by the Python pySTEPS library were evaluated using radar derived rain rate data and the satellite product Split-Window Difference (SWD) based on GOES-16 data, focusing on central Mexico. Initially, we obtained a characterization of the rainfall that occurred in the region using the radar rain rate and the SWD. Subsequently the nowcasts were evaluated using both variables. Two nowcast models were employed from pySTEPS: Extrapolation and S-PROG. The results indicate that average SWD is below 2.5 K, 90 min before the onset of rainfall events, and, on average, the SWD is 2 K during rainfall events. The results from both nowcast models were accurate and produced similar results. The nowcasts performed better when SWD data were used as input, having an average Probability of Detection (PoD) above 70% and a False Alarm Rate (FAR) reaching 40% for the 15-min prediction. The nowcasts were less accurate using the radar rain rate as input for the 15-min forecast, where the PoD was maximum 70% and FAR reaching 40%. However, these nowcasts were more reliable during well-organized precipitation events. In this work, it was determined that the nowcast models provided by pySTEPS can provide valuable rain forecasts using GOES-16 satellite and radar data for the central Mexico region

Effects of anomalous propagation conditions on weather radar observations

In this chapter our objective is to provide an overview of the effects of anomalous propagation conditions on weather radar observations, based mostly on studies performed by the authors during the last decade, summarizing results from recent publications, presentations, or unpublished material. We believe this chapter may be useful as an introductory text for graduate students, or researchers and practitioners dealing with this topic. Throughout the text a spherical symmetric atmosphere is assumed and the focus is on the occurrence of ground and sea clutter and subsequent problems for weather radar applications. Other related topics such as long-path, over-the-horizon propagation and detection of radar targets (either clutter or weather systems) at long ranges is not considered here; however readers should be aware of the potential problems these phenomena may have as range aliasing may cause these echoes appear nearer than they are ¿ for more details see the discussion about second trip echoes by Zrnic, this volume

Distribution and variability of NH₃ in Mexico City from ground-based FTIR and space-based IASI measurements

International audienceThe most abundant alkaline compound in the atmosphere is ammonia (NH3). This key gas is involved in several chemical reactions, especially those to neutralize acids. NH3 also contributes to aerosol formation and particulate matter, with potential consequences to the environment, human health, and radiative forcing. NH3 is primarily emitted by agricultural sources; however, it is also present in urban environments like Mexico City, one of North America’s biggest cities with a high population density and major pollution episodes. This work investigates the temporal and spatial variability of NH3, including some enhancement events, to address the lack of information available in this region. Using solar absorption ground-based measurements from two Fourier transform infrared (FTIR) spectrometers located in urban and rural areas of Mexico City, total columns NH3 were retrieved using the PROFFIT9 algorithm. These measurements were complemented by satellite data products over the Mexico City area from the Infrared Atmospheric Sounding Interferometer (IASI) instrument on board the MetOp-A platform.The ground-based results reveal similarities in the seasonal variability of NH3 between the urban and rural sites and exhibit temperature dependence, with the highest columns during the warmest months and the lowest columns during the cold and rainy seasons. In contrast, the diurnal pattern of NH3 present remarked differences due to the meteorology and the surrounding urban sources. Both sites showed an increasing trend of NH3 through the most recent years. The IASI total columns of NH3 are smaller than the urban FTIR columns (using coincidence criteria of 20 km and 80 min), but exhibit similar seasonal variability and provide information about the spatial distribution of NH3 around the Mexico City region, identifying the highest concentrations in the northeast area. Back-trajectory analysis was used to confirm the influence of this area in the observed NH3 enhancement events. These findings provide insight into atmospheric processes involving NH3 and can be used to improve air quality models

Influence of spatial resolution in mesoscale modeling to reproduce wind power production in southern Mexico

Understanding near-surface wind variability is crucial to support wind power penetration on national electrical grids. High-resolution numerical simulations are often proposed as the best solution to study the fluctuation of wind resources. We compare Weather Research and Forecasting (WRF) and Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) bias-corrected wind speeds at hub height at different spatial resolutions and transform them to wind power production using a logistic power curve fitted to wind power measurements; the comparisons are based on error statistics and time series spectral analysis. The results show that numerical models reproduce observed wind speeds with correlations higher than 0.9 for WRF and 0.8 for MERRA-2. Moreover, annual observed wind power is reproduced with a maximum difference from observations of 0.011. However, each resolution reproduces the magnitudes of high-resolution periodicities differently so that there is a clear relationship between grid size and signal variance at high frequencies, as variance is indirectly proportional to frequency. This relationship is expected for wind speed, but based on results, it can be associated also for capacity factor sampled at hourly intervals. Therefore, the main benefit of high spatial resolution lies in the added variance in frequencies at sub-daily time scales. The study of the added value of high-resolution simulations in this region contributes to current efforts to develop reliable forecasting tools and strategies to support the development of wind power as a reliable energy source

Boundary Layer Height Characteristics in Mexico City from Two Remote Sensing Techniques

The Atmospheric Boundary Layer (ABL) height is a key parameter in air quality research as well as for numerical simulations and forecasts. The identification of thermally stable layers, often with radiosondes, has been a common approach for estimating ABL height, though with limited temporal coverage. Remote sensing techniques offer essentially continuous measurements. Nevertheless, ABL height retrievals from different methods can vary greatly when compared, which is particularly notable for topographically complex terrains, such as that surrounding Mexico City. This study, employing one year of data in Mexico City, reveals that the daytime convective boundary layer height (retrieved from Doppler lidar data) is typically lower than the aerosol layer height (retrieved from ceilometer data). Although both estimated heights evolved diurnally, the more elevated aerosol layer decays more slowly, suggesting that the mechanisms that elevate aerosols are not limited to convective motions. Additionally, both diurnal and seasonal variability are investigated, comparing remotely sensed-retrieved heights with thermally stable layers estimated from radiosonde data. Multiple stable layers often develop, those at higher levels have similar values to the ceilometer-retrieved heights, while stable layers at lower heights are similar to Doppler lidar height retrievals. The present research constitutes the first detailed analysis of ceilometer backscatter and Doppler lidar thresholding methods for estimating ABL height over Mexico City, and our results illustrate the complexity of mixing mechanisms on the ABL in this region of complex orography