Arturo I. Quintanar

Impacts of land use/land cover change on climate and future research priorities.

Several recommendations have been proposed for detecting land use and land cover change (LULCC) on the environment from, observed climatic records and to modeling to improve its understanding and its impacts on climate. Researchers need to detect LULCCs accurately at appropriate scales within a specified time period to better understand their impacts on climate and provide improved estimates of future climate. The US Climate Reference Network (USCRN) can be helpful in monitoring impacts of LULCC on near-surface atmospheric conditions, including temperature. The USCRN measures temperature, precipitation, solar radiation, and ground or skin temperature. It is recommended that the National Climatic Data Center (NCDC) and other climate monitoring agencies develop plans and seek funds to address any monitoring biases that are identified and for which detailed analyses have not been completed.

An air quality emission inventory of offshore operations for the exploration and production of petroleum by the Mexican oil industry

Abstract An air quality screening study was performed to assess the impacts of emissions from the offshore operations of the oil and gas exploration and production by Mexican industry in the Campeche Sound, which includes the states of Tabasco and Campeche in southeast Mexico. The major goal of this study was the compilation of an emission inventory (EI) for elevated, boom and ground level flares, processes, internal combustion engines and fugitive emissions. This inventory is so far the most comprehensive emission register that has ever been developed for the Mexican petroleum industry in this area. The EI considered 174 offshore platforms, the compression station at Atasta, and the Maritime Ports at Dos Bocas and Cayo Arcas. The offshore facilities identified as potential emitters in the area were the following: (1) trans-shipment stations, (2) a maritime floating port terminal, (3) drilling platforms, (4) crude oil recovering platforms, (5) crude oil production platforms, (6) linking platforms, (7) water injection platforms, (8) pumping platforms, (9) shelter platforms, (10) telecommunication platforms, (11) crude oil measurement platforms, and (12) flaring platforms. Crude oil storage tanks, helicopters and marine ship tankers were also considered to have an EI accurate enough for air quality regulations and mesoscale modeling of atmospheric pollutants. Historical ambient data measure at two onshore petroleum facilities were analyzed to measure air quality impacts on nearby inhabited coastal areas, and a source–receptor relationship for flares at the Ixtoc marine complex was performed to investigate health-based standards for offshore workers. A preliminary air quality model simulation was performed to observe the transport and dispersion patterns of SO 2 , which is the main pollutant emitted from the offshore platforms. The meteorological wind and temperature fields were generated with CALMET, a diagnostic meteorological model that used surface observations and upper air soundings from a 4-day field campaign conducted in February of 1999. The CALMET meteorological output and the generated EI drove the transport and dispersion model, CALPUFF. Model results were compared with SO 2 measurements taken from the monitoring network at Dos Bocas.

A Coupled MM5-NOAH Land Surface Model-based Assessment of Sensitivity of Planetary Boundary Layer Variables to Anomalous Soil Moisture Conditions

The sensitivity of the near-surface weather variables and small-scale convection to soil moisture for Western Kentucky was investigated with the aide of the MM5 Penn State/NCAR mesoscale atmospheric model for three different synoptic conditions in June 2006. The model was initialized with FNL reanalysis from NCEP containing soil moisture data calculated with the Noah land surface model. Dry and wet experiments were performed in order to find the influence of soil moisture specification on boundary layer atmospheric variables. Dry experiments showed less available atmospheric moisture (between 2 and 6 g kg-1) at near-surface levels during all synoptic events consistent with slightly deeper boundary layers, higher lifting condensation levels and a larger Bowen ratio. As expected, precipitation rates were generally smaller than those of the control simulation. However, during a moderately strong synoptic event in early June, the dry experiments displayed larger precipitation rates compared to the control experiment (up to 5 mm in 3 hr) as the soil volumetric fraction was decreased from 0.05 to 0.15 (m3 m-3) with respect to the control simulation. Precipitation rates in wet experiments were also modulated by characteristics of synoptic conditions. In early June, precipitation rates slightly were larger than the control run (from 0.2 mm 3 h-1 to 1.4 mm 3 h-1) while in the other periods precipitation was reduced significantly. Both dry and wet anomaly experiments experienced reduced precipitation for different reasons. It was found, lifting condensation level, CAPE and low Bowen ratio were not sensitive markers of changes in soil moisture. Equivalent potential temperature was a better indicator of precipitation changes among all experiments. The controlling factor in these responses was the soil moisture content forcing vertical velocities. Thermodynamic conditions such as local stability played a less substantial role in controlling the precipitation processes. It was found that the response of planetary boundary layer variables under a variety of soil moisture conditions can be modified due to degree of synoptic forcing. Weak-to-moderate forcing favored convection while strong synoptic forcing tended to suppress it under dry soil moisture conditions. Wetter soils did not produce a response in horizontal wind fields as large as under the drier soils.

A mesoscale modeling study of wind blown dust on the Mexico City Basin

Abstract The latest phase of the program to improve the air quality in the Valley of Mexico, also known, as Pro Aire is about to go into effect for the next 10 years. Pro Aire puts emphasis on agricultural wind erosion and associated dust emissions impacting downwind air quality. The main objective of this investigation was to use an empirical USEPA erosion model coupled to a meteorological/transport-dispersion prediction model, CALMET/CALPUFF, to estimate dust emissions and concentrations in the Mexico City Basin. The model simulations for particulate matter (PM 10 ) are validated against observations taken at the most recent research field study, the IMADA–AVER field campaign, conducted during the spring of 1997 to provide information about high ozone, particulate matter concentrations and visibility impairment. The spatial and temporal PM distribution in the region is presented for a specific wind blown dust event consisting of two IMADA days, in order to understand how soil dust emissions from agricultural fallow land affect downwind areas during the dry season. Results show good agreement with the main spatial features of the local wind circulation and wind blown dust concentrations. A correlation coefficient of nearly 0.8 between predictions and observations for a modeled day suggests that an important portion of the total measured concentration had geological origin. This work constitutes an essential advancement on the mesoscale air quality problem on the MCMA due to wind erosion.

Ensemble forecast spread induced by soil moisture changes over mid-south and neighbouring mid-western region of the USA

ABSTRACT This study investigated the potential impact of soil moisture perturbations on the statistical spread of an ensemble forecast for three different synoptic events during the summer of 2006. Soil moisture was perturbed from a control simulation to generate a 12 member ensemble with six drier and six moister soils. The impacts on the near-surface atmospheric conditions and on precipitation were analysed. It was found, as previous studies have confirmed, that soil moisture can change the spatial and temporal distribution of precipitation and of the overlying circulation. It was found that regardless of the conditions in synoptic forcing, temperature, relative humidity and horizontal wind field exhibited a spatial correlation coefficient (R) close to one with respect to the control simulation. Vertical velocity, however, showed a marked decrease in R down to 0.4 as the precipitation activity increased. For vertical velocity, however, this quantity grew to near 1.0 consistent with R near zero and standard deviations very close to that of the control. These results suggested a more complex picture in which soil moisture perturbations played a major role in modifying precipitation and the near-surface circulation but did not broaden the statistical spread of trajectories in phase space of all variables.

Influence of Karst Landscape on Planetary Boundary Layer Atmosphere: A Weather Research and Forecasting (WRF) Model–Based Investigation

AbstractKarst hydrology provides a unique set of surface and subsurface hydrological components that affect soil moisture variability. Over karst topography, surface moisture moves rapidly below ground via sink holes, vertical shafts, and sinking streams, reducing surface runoff and moisture infiltration into the soil. In addition, subsurface cave blockage or rapid snowmelt over karst can lead to surface flooding. Moreover, regions dominated by karst may exhibit either drier or wetter soils when compared to nonkarst landscape. However, because of the lack of both observational soil moisture datasets to initialize simulations and regional land surface models (LSMs) that include explicit karst hydrological processes, the impact of karst on atmospheric processes is not fully understood. Therefore, the purpose of this study was to investigate the importance of karst hydrology on planetary boundary layer (PBL) atmosphere using the Weather Research and Forecasting Model (WRF). This research is a first attempt t...

Mexican GPS Tracks Convection From North American Monsoon

The North American monsoon (NAM) is a dominant feature of the climate of northwest Mexico and the southwest United States. The annual monsoon, which usually lasts from July to September, contributes more than half of the yearly precipitation for much of the region. Thunderstorms brought on by the monsoon are routinely responsible for severe weather, including flooding, hail, wind, dust storms, and lightning. Tropical storms and hurricanes during the NAM season can also wreak havoc on a much larger scale.

A comparison of the MM5 and the Regional Atmospheric Modeling System simulations for land-atmosphere interactions under varying soil moisture

A comparison between two mesoscale models, Colorado State University Regional Atmospheric Modeling System (RAMS) version 4.4 coupled with the Land-Ecosystem–Atmosphere Feedback Model (LEAF2) and Penn State/NCARs Mesoscale Model (MM5) coupled with NOAH Land Surface Model, was conducted in order to assess the sensitivity of forecasted planetary boundary layer (PBL) variables to anomalous initial volumetric soil moisture conditions. The experiments were conducted using three synoptic events: June 11, 17 and 22, 2006. For each event, one control run and six additional simulations were completed using RAMS and MM5. In each of the events, initial volumetric soil moisture was increased and decreased by 0.05, 0.10 and 0.15 m3m−3. Each of the events was individually analysed. Precipitation generally increased and decreased with enhanced and reduced soil moisture, respectively. Overall, RAMS simulations presented a greater sensitivity and variability in precipitation and PBL parameters. It was found that equivalent potential temperature, vertical wind velocities, and latent and sensible heat flux were helpful in explaining precipitation accumulation and distribution.

Changes in Intense Precipitation Events in Mexico City

AbstractThe authors analyzed an extensive precipitation dataset available for the Mexico City basin that included hourly precipitation in various sectors of the city from 1993 to 2007. Observations indicated that significant changes occurred in the timing and number of intense events (precipitation rate >20 mm h−1) over this time period. Alternative hypotheses that changes in the emission of aerosol pollutants or in the land use can result in the observed variations are tested. The Weather Research and Forecasting Model was used to simulate September precipitation from 2002 to 2011 at the peak of the wet season. Changes were introduced to the microphysical scheme as a proxy for differences in the aerosol population and the droplet activation spectra. Simulations were also performed with the land use of the urban areas set up to represent older and more current conditions. Results indicate that increased pollution (decreased urban area) led to an average precipitation decrease over the mountain areas of 20...

Application of the NARCM model to high-resolution aerosol simulations: Case study of Mexico City basin during the Investigación sobre Materia Particulada y Deterioro Atmosférico-Aerosol and Visibility Research measurements campaign

The Northern Aerosol Regional Climate Model (NARCM) is used to study the visibility and three-dimensional (3-D) evolution of aerosol distributions within the Mexico City basin. NARCM simulates transport, diffusion, deposition, and size distributions of sulphur aerosol particles in the region. The model assumes only simple sulphur oxidation, not taking explicitly into account the urban air chemistry. Rather, it focuses on detailed aerosol microphysics and 3-D optical properties. The simulation performance is compared with upper air and ground-based observations for the following specific days of intensive measurement: 2, 4, and 14 March 1997. Time series at Mexico City airport shows lower values of visibility in the morning due to a shallow mixed layer and higher values in the afternoon following the evolution of the mixed layer depth. Modeled visibility shows large dependence on cardinal direction and size distribution of particles. It is found that better resolution of particle size leads to better representation of coagulation processes and to realistic size distributions which show a characteristic accumulation mode around 0.3 μm. As a result, visibility simulations are closer to those observed at the airport location. Comparing visibility is a stringent test for the model because it requires an accurate representation of 3-D meteorological fields together with a realistic aerosol simulation.