Physical mechanisms involved in the development and forecast of clouds and precipitation are both quite complex and dependent on the local atmospheric environment, especially when severe weather conditions are imminent. Research aimed at understanding the environmental mechanisms favorable to the different atmospheric scenarios can help operational weather forecasters to issue warnings. This paper provides qualitative and quantitative contributions from radiosondes, radar, and numerical simulations to evaluate the formation of convective, stratiform, and nonprecipitating clouds over the metropolitan area of Rio de Janeiro, Brazil. The convective available potential energy (CAPE) and lifted index (LI), showed higher values on convective days (CAPE = 2600 J.Kg–1 and LI = –4 ºC), followed by nonprecipitating (CAPE = 1500 J.Kg–1 and LI = –2 ºC) and stratiform cloud days (CAPE = 1400 J.Kg–1 and LI = –1.5 ºC). High wind convergence was observed at low- (1000–850 hPa) and mid- (850–700 hPa) levels on convective days (–16.5 s–1 and –9.6 s–1, respectively). In contrast, wind divergence at the same levels was observed on stratiform (6.4 s–1 and 6.9 s–1) and nonprecipitating (9.7 s–1 and 7.3 s–1) days. Higher wind divergence (8.3 s–1) was observed on convective days at upper levels (300–200 hPa) compared with stratiform (3.2 s–1) and nonprecipitating (2.8 s–1) days. Results show a coupling of wind convergence, moisture and energy in the lower troposphere and divergence at upper levels on convective days. Despite moisture availability on stratiform days and thermodynamic energy on nonprecipitating days, the respective coupling between these conditions and dynamic triggers was not observed.

Emissions inventories are fundamental tools in the management and research of air pollution, climate change, and other relevant areas of knowledge. This work shows how the Mexico national emissions inventory for criteria pollutants was transferred from an Excel file to a structured and standardized one based on Extensible Markup Language (XML), following the Keyhole Markup Language (KML) standard and the United States Environmental Protection Agency consolidated emissions reporting schema using a Python script (provided as supplementary material). We also show how once in the KML format, the results are compatible with Google Earth and any Geographic Information System (GIS) platforms. The KML format may also allow emissions inventory models to interoperate with Chemical Transport Models (CTM) that would be able to read/write XML files for research and public environmental management policy. As an example, we used Google Earth to engage the point source data and the dispersion of a hypothetical release for that point source modeled using the Hybrid Single Particle Lagrangian Integrated Trajectory developed by the National Oceanic and Atmospheric Administration (HYSPLIT-NOAA), whose outputs also can be displayed on Google Earth. Finally, the KML files outputs from the inventory and HYSPLIT-NOAA model can be visualized on any computer platform and mobile applications that incorporate Google Earth.

There are significant differences in the way that researchers have defined “Etesian wind days”. An attempt is made here to establish common definitions of the various types of Etesian winds from the weather forecaster’s viewpoint. These definitions are based on objective criteria adopted from the frequency of atmospheric circulation features associated with the occurrence of the Etesian winds and their physical characteristics. The presence of fairly constant northerly winds over the Greek Seas in summer are called Etesian winds. When a new spell of Etesian winds is established with no diurnal variation of the wind direction for consecutive days (maximum of seven), these winds are called “type B” Etesian winds or “Etesian outbursts”. The atmospheric circulations associated with the occurrence, origin and evolution of the type B Etesian winds and the accompanying weather are revealed utilizing data for the period 1975-2015 and focusing on two case studies on July 21-22, 1983 and July 3-4, 2017. The presence of the Subtropical Jet Stream (SJS) over the Greek territory and its interaction with the Polar Jet Stream (PJS) are dominant factors. Large-scale atmospheric circulations are studied to identify simultaneous direct links to the Indian Summer Monsoon (ISM), El Niño-Southern Oscillation (ENSO), Madden-Julian Oscillation (JMO), deep convective activity in the Hadley circulation in the tropics, and West Africa Monsoon (WAM).

Ruminants are the main source of methane emissions from the agricultural sector. Emission inventories and mitigation strategies require reliable technics of measurement. The respiration chamber methodology is a precise approach for measuring enteric methane emissions in cattle. A set of experiments was carried out to validate two respiration chambers for measuring enteric methane emissions of cattle. The chambers were calibrated considering three main components: the methane analyzer, the air duct and air extraction system, and the chamber itself, by evaluating linearity and response time of the analyzer, plateau variability and high purity methane recoveries in chambers. Recovery test calculations carried out after releasing high purity methane into the chambers gave calibration factors of 0.95 ± 0.05 and 1.03 ± 0.03 for the complete system of respirations chambers one and two, respectively, with corresponding uncertainties of 4.87 and 2.49%. Thus, the respiration chambers for enteric methane measurements of cattle at the University of Yucatan, Mexico function with precision and accuracy. This technique can be used to establish methane inventories and methane mitigation strategies in cattle.

A rare winter thunderstorm event near Hong Kong is documented in this paper. The thunderstorm occurrence was confirmed by the observation of one of the authors and lightning location information systems (both regional and global). It developed over the frontal cloud band associated with the winter monsoon. Observing the upper air measurements, however, the thermodynamic conditions did not seem favorable to the occurrence of the thunderstorm. The convective available potential energy could not be determined in the cool and dry lower troposphere. There was only a moister layer in the middle troposphere. The weather forecaster did not anticipate the occurrence of thunder and lightning. However, some features could have changed dynamically, which suggested the possibility that a thunderstorm would take place. For instance, waves could be identified in the middle troposphere and a broad troughing flow could be analyzed in the lower troposphere. The integrated wave vapor was also of a rather high level. It is hoped that this paper can serve as a useful reference for forecasters in assessing the possibility of thunderstorms occurring during winter over subtropical latitudes in association with frontal cloud bands.

Building-induced turbulence may affect aviation safety, e.g., when the aircraft is about to land at an airport. Observations of such flow have been conducted at the Hong Kong International Airport using short-range LIDAR (SRL). Statistical analysis of the radial velocity, namely, the longitudinal structure function, is described herein. It is found that the classical Kolmogorov theory for homogeneous turbulence applies to LIDAR observations of building-disrupted airflow. Some distinctive features of the turbulent flow are also discussed, notably velocity streaks and tiny anticyclones at the hectometer scale. The potential impact on a landing aircraft is examined and compared to flight data. The results in this paper could be useful for studying building-induced turbulence at other airports around the world.

Downward longwave radiation flux is an important variable for estimating net radiation, in order to investigate the surface energy budget and carry out climatic studies. The flux is usually estimated using empirical models based on the information of meteorological parameters such as relative humidity, surface and air temperature, and water vapor pressure. This paper presents the assessment of 11 widely used empirical models for estimating downward longwave radiation using a ground-based dataset acquired from January 2016 to December 2017 at Ile-Ife, a tropical city in Nigeria. The original Idso and Niemela et al. models performed better than other models with errors less than 5.0% when compared to measured values. The performances of all the models improved greatly after calibration. The Guest model, which gave low errors (MBE = 0.65 Wm–2, RMBE = 0.15%, RMSE = 9.38 Wm–2, RRMSE = 2.14%, MAE = 7.84 Wm–2, RMAE = 1.79%), performed best followed by the Dilley and O’Brien, Idso, Prata, Brutsaert, Garratt, Niemela et al., and Ångström models. The calibrated models presented in this study can be used to estimate the flux under cloudless sky conditions at Ile-Ife and at other places with similar meteorological conditions, where this flux is not measured due to technological problems and the high cost of purchasing and maintaining the needed sensors. The proposed model for estimating the flux showed better performance with lower statistical errors than all the existing empirical models tested, and conform greatly (R2 = 0.88) to the measured data.

In this paper we assessed the association (relative risk, RR) between the exposure to PM10 and PM2.5 (as a continuous variable and as categories of low or high pollution exposure) on the incidence of pulmonary tuberculosis (PTB) in Mexicali, Baja California, Mexico. We used a weekly, lagged multiple Poisson regression model. We observed a 10-week delayed effect for PM10 and PM2.5 in all PTB cases and in male cases with PTB. An 11-week delayed effect occurred in the female PTB cases. For all the PTB cases, the RR rose by 2.4% (95% CI: 2.1, 2.6, p<0.10) for each 10 µg/m3 increase of PM10 in the continuous exposure and by 3.6% (CI: 3.3, 4.0, p<0.05) in the high pollution exposure category, and by 3.2% (CI: 2.9, 3.4, p<0.05) for each 10 µg/m3 increase of PM2.5 in the continuous exposure and by 3.9% (CI: 3.6, 4.3, p<0.05) in the high pollution exposure category. In men, the RR rose by 2.8% (CI: 2.5, 3.1, p<0.10) for each 10 µg/m3 increase of PM10 in the continuous exposure and by 4.6% (CI: 4.2, 5.0, p<0.05) in the high pollution exposure category, and by 3.4% (CI: 3.1, 3.7, p<0.05) for each 10 µg/m3 increase of PM2.5 in the continuous exposure and by 4.2% (CI: 3.8, 4.6, p<0.05) in the high pollution exposure category. In women, the RR rose by 5.1% (CI: 4.7, 5.5, p<0.05) for each 10 µg/m3 increase of PM10 in the continuous exposure and by 5.3% (CI: 4.7, 5.8, p<0.10) in the high pollution exposure category, and by 4.3% (CI: 3.8, 4.8, p<0.10) for each 10 µg/m3 increase of PM2.5 in the continuous exposure and by 5.3% (CI: 4.8, 5.9, p<0.10) in the high pollution exposure category. PM air pollution appears to associate with the incidence of PTB in the population of Mexicali.

Jet streams in the atmospheric boundary layer may lead to hazardous weather over southern China. In this paper, the jet-related low-level windshear to be encountered by an aircraft is documented. Two typical cases under the northeast monsoon regime are considered, namely, easterly jet disrupted by the mountains to the south of Hong Kong International Airport, and outbreak of monsoon surge that produces a low-level northeasterly jet. The Doppler Light Detection and Ranging (LIDAR) systems are found to capture the corresponding windshear features very well, e.g., consistent with pilot reports and flight data. They are useful in providing timely alert to the aircraft. In particular, the LIDAR captures a double jet structure in the atmospheric boundary layer for the easterly wind case, which has not been reported in the literature before. The physical mechanism for the occurrence of the double jet is yet to be revealed. Moreover, the performance of a high spatial resolution (200 m) numerical weather prediction (NWP) model in predicting the jet and the associated low-level windshear is studied. The model is found to provide reasonable prediction of the windshear features at a few hours ahead, and, for the cases studied, shows skills in providing timely alerts to the aircraft.

This paper presents a new index to determine meteorological drought conditions, the Drought Exceedance Probability Index (DEPI), derived from monthly precipitation time series. Its formulation is simple and undemanding in terms of baseline information requirements. This makes the DEPI suitable for routine application to any climate, similar to the well-known Standardized Precipitation Index (SPI). The index is based on the calculation of cumulative rainfall anomalies and their subsequent standardization, similarly to other indices. The hallmarks of the DEPI, and its main comparative advantages, are the process of accumulating anomalies and their standardization process. The paper compares the DEPI with the SPI in several different climates across the world and in all cases the results show the complementarity of both indices. The DEPI shows an excellent ability to reflect the actual severity and duration of droughts, without requiring application on different time scales, unlike the SPI. It is also valid for all types of climates, including arid and semiarid or Mediterranean, for which the literature has shown that using the SPI is problematic.

We study a regional precipitation time series built upon seven meteorological records from south-central Chile (SCC; 37º-42º S), which altogether cover the period 1900-2019. As a first objective, we investigated changes in the return period (RP) of dry (< P20) and wet (> P80) seasonal extreme events of precipitation (SEE) for each season. We observed a reduction in the RP of wet SEE during 1900-1950 in all seasons. Moreover, the dry SEE RP shows a reduction from 1950 to the present in all seasons. This phenomenon is noteworthy since 1900 for summer and winter, and since 1930 for autumn. Spring registers a constant RP value from 1990 onwards. As a second objective, we study possible relationships between seasonal precipitation variability and climate modes, such as the Southern Annular Mode (SAM) and the Tripole Index (TPI) of sea surface temperature (SST) over the Pacific Ocean. Summer and autumn precipitation showed a significant negative correlation with SAM activity at interannual and decadal scales, while winter and spring precipitation recorded a significant positive correlation with SST variability over multiple regions of the Pacific Ocean (including the tropics and New Zealand) and the Southern Ocean (Amundsen-Bellingshausen Sea). Finally, we confirm that SAM strongly modulates precipitation in SCC, especially in autumn, and that SEE variability in SCC is considerably associated with climate modes of tropical and extra-tropical origin.

The influence of El Niño Southern Oscillation (ENSO) on Colombia's hydrological variables has been shown in different studies. Most of the methodologies implemented have identified linear relationships and have associated the warm (cold) phase called El Niño (La Niña) with negative (positive) rainfall and streamflow anomalies. One of the most adverse impacts founded is the reduction in water supply during the warm phase. Therefore, it is necessary to study the linkage between ENSO and precipitation variability for efficient management of water resources.  Consequently, the present paper has two purposes. The first one is to explore nonlinear correlations of the ENSO-precipitation relationship, particularly for specific regions where the freshwater resources have been significantly reduced during El Niño events.  The second one is to identify which indices will enable in improving the predictability of hydro-climatological variables. The research was based on the wavelet coherence analysis of monthly precipitation time series from 1981-2016 and the ENSO indices for the same period.  The results show that ENSO events influence the precipitation as periods of rainfall deficit or excess.  Also, precipitation is organized in bands and that the 2–8-year scales explain most of their variance.  The most significant sectors are those that cover El Niño events. In contrast, sectors are smaller when La Niña episodes. Then impacts on precipitation tend to be greater for warm events. Results also allowed to identify that El Niño 3, Niño 3,4, ONI, and BEST indices can be good indicators for forecasting work in these specific places. The use of two kinds of data, one in situ and the other from CHIRPS program, allows to establish the feasibility of using data from satellite origin in regions without enough information; the results showed that CHIRPS data tend to report fewer anomalies than data in situ. However, the coherence structure is similar, but in periods between 36 and 48 months, there were discrepancies of  pi/4 in the phase difference, that is, between 3 and 6 months of difference in lags calculated with each database.

The Amazon region is one of the most pristine continental areas whose concentrations of atmospheric trace gases and aerosol particles are very low, mainly in the wet season. This study provides observational results of aerosol optical and radiative characteristics in situ as well as atmospheric columnar at a pristine forest in Central Amazonia. Spectral variation of the aerosol properties (aerosol optical depth [AOD], single scattering albedo [SSA], and asymmetry parameter [AP]) was evaluated using the AErosol RObotic NETwork (AERONET) data. The SSA values under natural atmospheric column conditions (AERONET) were compared to the SSA values calculated with in situ measurements. The values of shortwave aerosol radiative forcing (SWARF) on top of the atmosphere (TOA) and the surface (SUR) were estimated using the SBDART model and were validated with the AERONET values with regression analysis. SWARF had a high correlation to TOA (0.97) and SUR (0.92), including dry and wet seasons. Monthly, seasonal and annual mean values of SWARFTOA and SWARFSUR were negative while SWARFATM values were positive. SWARFTOA was –9.18 ± 2.80 W m–2 and SWARFSUR was –20.77 ± 5.04 W m–2 in the dry season, inducing a heating rate (HR) of 0.37 ± 0.13 K.day–1. This study showed that, for a long series of measurements, the effects caused by aerosols on the radiative flux in the pristine forest of Central Amazonia were of the order of SWARFTOA of –3.66 ± 1.59 W m–2 and SWARFSUR of –11.86 ± 2.35 W m–2 during the wet season.

This paper examines the interaction of tropical moisture with an atmospheric river. The analysis of this paper is focused mainly on dropsonde data collected during the fifth day of the Convective Processes Experiment (CPEX). An area of interest is chosen over the central Gulf of Mexico, where the remnant moisture of the tropical system Beatriz penetrated from the Eastern Pacific after making landfall in the western coast of Mexi-co. Results in this study show an eastward-tilting pattern of enhanced mid-level vorticity, coupled with high saturation fraction and low instability index in the predominantly stratiform regime present in the region. An inverse relation between saturation fraction and instability index, as indicated by moisture quasi-equilibrium (MQE), is found in a previously-dominant convective regime. Strong vertical shear signals that the vorticity pattern within this stratiform system is being advected poleward into mid-latitudes. Poleward-moving moisture plumes in narrow channels called atmospheric rivers (ARs) are observed during the mission. We provide insights into vorticity and MQE as conceptual tools to characterize the moisture mechanism of atmospheric rivers near the tropics, where the physical processes behind these river-like structures are less well-understood.

The following estimates analyse human bioclimatic conditions due to climate change in three time horizons, as suggested by Article 2 of the Paris Agreement. Each scenario corresponds to an increase in the global average temperature (∆T) of 1 ºC, 1.5 ºC and 2 ºC, respectively. The measurements of residential electricity consumption for air conditioning were made in 30 metropolitan areas of Mexico with at least half a million inhabitants in 2010. Bioclimatic conditions also included estimates of the effects of urban heat islands (UHI). Use of heating will decrease and, in some cases, disappear, while the need for cooling will increase. Electricity consumption due to cooling is expected to increase in Mexicali, Reynosa-Río Bravo (on the border with the United States), Cancún, Villahermosa, and Veracruz (on the shores of the Caribbean Sea and the Gulf of Mexico). Urban areas like Toluca, Pachuca, Xalapa, San Luis Potosí, and Puebla-Tlaxcala used little or no energy for cooling in the second decade of the 21st century but will need to do so halfway through the century