The climatology of synoptic-scale ascent over Western North America: a perspective on storm tracks

pre-printThe position and variability of storm tracks across western North America are examined during the October-April cool seasons spanning 1989-2010. The location and intensity of storms are represented by strong synoptic-scale ascent, which is diagnosed by the alternative balance omega equation applied to ECMWF Re-Analysis Interim data. This dynamically filtered method removes poorly resolved updrafts arising from subsynoptic-scale phenomena such as convection and mountain waves. The resulting vertical motions are illustrated for the case of a strong storm traversing the western United States. Summary statistics of synoptic-scale ascent are compiled over months, seasons, and the entire 21-yr period. Locations exhibiting high mean values of ascent are deemed to represent storm tracks. The climatological-mean storm track exhibits a sinusoidal shape across the eastern Pacific and western North America. The composite evolution of strong storms moving along specific segments of the storm track show regional differences (e.g., storms poleward of 508N tend to result from progressive low-amplitude troughs progressing through the mean planetary ridge, while storms over the western United States are initiated by digging troughs that temporarily suppress the mean ridge). Seasonal shifts in the storm track are pronounced and exhibit coherent regional patterns. Interannual variations in synoptic-scale ascent indicate meridional shifts in position as well as changes in the degree of amplification within the dominant sinusoidal storm track. These changes in structure are related to the phase of ENSO: El Nin˜ o (La Nin˜ a) winters favor zonal (amplified) and southern (northern) storm tracks

Observing snow and wind: using the environment to engage students in science and engineering

posterThis study focused on the effectiveness of new curriculum that was integrated with hands on environmental instrumentation and student learning. The goals of this study were to increase student proficiency with environmental instrumentation, as well as enhance student confidence to use technologies to observe the environment and solve real-world problems. A description of activities used and feedback received are included

Idealized large-eddy simulations of sea and lake breezes: sensitivity to lake diameter, heat flux and stability

ManuscriptIdealized large-eddy simulations of lake and sea breezes are conducted to deter mine the sensitivity of these thermally-driven circulations to variations in the land-surface sensible heat flux and initial atmospheric stability. The lake-breeze and sea-breeze metrics of horizontal wind speed, horizontal extent, and depth are assessed. Modelled asymmetries about the coastline in the horizontal extent of the low-level onshore flow are found to vary as a function of the heat flux and stability. Small lake breezes develop similarly to sea breezes in the morning, but have a significantly weaker horizontal wind speed component and a smaller horizontal extent than sea breezes in the afternoon

Summer Ozone Concentrations in the Vicinity of the Great Salt Lake

Residents near the Great Salt Lake in northern Utah, USA have been exposed to ozone levels during recent summers exceeding the current United States National Ambient Air Quality Standard. Accurately forecasting those exceedances has been difficult as a result of the complex meteorological and photochemical processes fostering them. To help improve such forecasts, a low-cost field study was conducted during summer 2015 to provide comprehensive observations of boundary-layer ozone concentrations in the context of the prevailing meteorological conditions. A network of surface ozone sensors was supplemented by sensors mounted on vehicles, a public transit light-rail car, news helicopter, tethered sonde, and unmanned aerial vehicle. The temporal and spatial evolution of boundary-layer ozone concentrations were compared with the prevailing regional and local meteorological conditions on the basis of gridded operational analyses, surface weather stations, and additional sensors deployed for the field study. High ozone concentrations during June 2015 resulted primarily from local processes while smoke transported from distant wildfires contributed to elevated ozone concentrations during August. The Great Salt Lake influenced ozone concentrations along the Wasatch Front through several mechanisms, most importantly its impact on local wind circulations. The highest ozone concentrations were often found in a narrow zone between the Great Salt Lake and the urban regions to its south and east. Observations from multiple fixed site and mobile platforms during 18–19 August illustrate the complex variations in ozone concentrations as a function of elevation at the surface as well as vertically through the deep boundary layer

Operational Water Forecast Ability of the HRRR-iSnobal Combination: An Evaluation to Adapt into Production Environments

Operational water-resource forecasters, such as the Colorado Basin River Forecast Center (CBRFC) in the Western United States, currently rely on historical records to calibrate the temperature-index models used for snowmelt runoff predictions. This data dependence is increasingly challenged, with global and regional climatological factors changing the seasonal snowpack dynamics in mountain watersheds. To evaluate and improve the CBRFC modeling options, this work ran the physically based snow energy balance iSnobal model, forced with outputs from the High-Resolution Rapid Refresh (HRRR) numerical weather prediction model across 4 years in a Colorado River Basin forecast region. Compared to in situ, remotely sensed, and the current operational CBRFC model data, the HRRR-iSnobal combination showed well-reconstructed snow depth patterns and magnitudes until peak accumulation. Once snowmelt set in, HRRR-iSnobal showed slower simulated snowmelt relative to observations, depleting snow on average up to 34 d later. The melting period is a critical component for water forecasting. Based on the results, there is a need for revised forcing data input preparation (shortwave radiation) required by iSnobal, which is a recommended future improvement to the model. Nevertheless, the presented performance and architecture make HRRR-iSnobal a promising combination for the CBRFC production needs, where there is a demonstrated change to the seasonal snow in the mountain ranges around the Colorado River Basin. The long-term goal is to introduce the HRRR-iSnobal combination in day-to-day CBRFC operations, and this work created the foundation to expand and evaluate larger CBRFC domains

Intelligent Systems for Geosciences: An Essential Research Agenda

A research agenda for intelligent systems that will result in fundamental new capabilities for understanding the Earth system. Many aspects of geosciences pose novel problems for intelligent systems research. Geoscience data is challenging because it tends to be uncertain, intermittent, sparse, multiresolution, and multiscale. Geosciences processes and objects often have amorphous spatiotemporal boundaries. The lack of ground truth makes model evaluation, testing, and comparison difficult. Overcoming these challenges requires breakthroughs that would significantly transform intelligent systems, while greatly benefitting the geosciences in turn

Association between neighborhood need and spatial access to food stores and fast food restaurants in neighborhoods of Colonias

Objective To determine the extent to which neighborhood needs (socioeconomic deprivation and vehicle availability) are associated with two criteria of food environment access: 1) distance to the nearest food store and fast food restaurant and 2) coverage (number) of food stores and fast food restaurants within a specified network distance of neighborhood areas of colonias, using ground-truthed methods. Methods Data included locational points for 315 food stores and 204 fast food restaurants, and neighborhood characteristics from the 2000 U.S. Census for the 197 census block group (CBG) study area. Neighborhood deprivation and vehicle availability were calculated for each CBG. Minimum distance was determined by calculating network distance from the population-weighted center of each CBG to the nearest supercenter, supermarket, grocery, convenience store, dollar store, mass merchandiser, and fast food restaurant. Coverage was determined by calculating the number of each type of food store and fast food restaurant within a network distance of 1, 3, and 5 miles of each population-weighted CBG center. Neighborhood need and access were examined using Spearman ranked correlations, spatial autocorrelation, and multivariate regression models that adjusted for population density. Results Overall, neighborhoods had best access to convenience stores, fast food restaurants, and dollar stores. After adjusting for population density, residents in neighborhoods with increased deprivation had to travel a significantly greater distance to the nearest supercenter or supermarket, grocery store, mass merchandiser, dollar store, and pharmacy for food items. The results were quite different for association of need with the number of stores within 1 mile. Deprivation was only associated with fast food restaurants; greater deprivation was associated with fewer fast food restaurants within 1 mile. CBG with greater lack of vehicle availability had slightly better access to more supercenters or supermarkets, grocery stores, or fast food restaurants. Increasing deprivation was associated with decreasing numbers of grocery stores, mass merchandisers, dollar stores, and fast food restaurants within 3 miles. Conclusion It is important to understand not only the distance that people must travel to the nearest store to make a purchase, but also how many shopping opportunities they have in order to compare price, quality, and selection. Future research should examine how spatial access to the food environment influences the utilization of food stores and fast food restaurants, and the strategies used by low-income families to obtain food for the household

Sensitivity of Wasatch Snowpack to Temperature Changes

Potential changes to snowpack in the Wasatch Mountains resulting from global warming are examined. Since global climate simulations are unable to resolve narrow mountain ranges such as the Wasatch, limited confidence is generally ascribed to model estimates of precipitation changes in Utah due to global warming. The observed sensitivity of high elevation precipitation to temperature during each storm within the past 25-30 years is proposed as a proxy metric to estimate the potential impact of increased temperature during the winter. The methodology follows from that applied for other regions; Casola et al. (2008) suggest that a 1o C increase in winter seasonal temperature could lead to reductions in spring snowpack of order 20% for the lower elevation Cascades. NRCS daily precipitation records at Ben Lomond Peak and the nearby lower elevation site at Ben Lomond Trail provide a relatively unique opportunity to examine the elevational dependence of precipitation to temperature. Two approaches are used: (1) histograms of daily precipitation as a function of estimated temperature at the station elevation and (2) simple estimates of the amount of precipitation falling as rain or snow along the east slope of the Wasatch as a function of the temperature profile. Both of these approaches yield reductions in winter season precipitation of order 10% per 1o C increase in winter seasonal temperature. The smaller potential reduction due to increasing temperature for the Wasatch relative to the Cascades is not too surprising given the higher base elevation of the Wasatch. Our plans for using such proxy indicators to examine climate simulations of current and future climate scenarios will be discussed

An Overview of Weather and Climate Interactions with the Great Salt Lake

The hydrology of the Great Salt Lake depends on complex interactions between net precipitation within its basin, surface and subsurface runoff into the lake, and evaporation from its surface. In turn, the level and temperature of the lake influence the intensity and frequency of lake-breeze fronts and lake-effect snowstorms that affect the populace and water resources of northern Utah. Current capabilities to monitor weather and climate variations in the vicinity of the Great Salt Lake will be reviewed