A preliminary description of climatology in the western United States

We describe the climatology of the western United States as seen from two 1-month perspectives, January and July 1988, of the National Meteorological Center large-scale global analysis, the Colorado State University Regional Atmospheric Modeling System (RAMS), and various station observation sets. An advantage of the NMC analysis and the RAMS is that they provide a continuous field interpolation of the meteorological variables. It is more difficult to describe spatial meteorological fields from the available sparse station networks. We assess accuracy of the NMC analysis and RAMS by finding differences between the analysis, the model, and station values at the stations. From these comparisons, we find that RAMS has much more well-developed mesoscale circulation, especially in the surface wind field. However, RAMS climatological and transient fields do not appear to be substantially closer than the larger-scale analysis to the station observations. The RAMS model does provide other meteorological variables, such as precipitation, which are not readily available from the archives of the global analysis. Thus, RAMS could, at the least, be a tool to augment the NMC large-scale analyses.

Bering Sea FOCI Final Report

To develop an understanding of stock structure and recruitment variation in Bering Sea pollock, the Coastal Ocean Program of the National Oceanic and Atmospheric Administration (NOAA) funded an 7-year (1991-1997), interdisciplinary project named Bering Sea Fisheries-Oceanography Coordinated Investigations (BS FOCI; Schumacher and Kendall, 1995) for which NOAA and academic researchers were selected through a competitive process (Macklin, this report). The project goals, based on recommendations from an international symposium on pollock (Aron and Balsiger, 1989) were to (1) determine stock structure in the Bering Sea and its potential relationship to physical oceanography, and (2) examine recruitment processes in the eastern Bering Sea. Both of these have direct implication to management. An integrated set of field, laboratory, and modeling studies were established to accomplish these goals. To address the first goal, project objectives were to establish details of oceanic circulation relevant to larval dispersal and separation of stocks, and determine if unique chemical or genetic indicators existed for different stocks. The recruitment component of BS FOCI, addressing the second goal, focused on understanding causes of variable mortality of pollock larvae in the different habitats of the eastern Bering Sea. The emphasis of recruitment studies was to determine the dominant physical oceanographic features (turbulence, temperature, and transport) that could influence survival of pollock larvae, and investigate factors controlling food production for the larvae. A later component contrasted juvenile habitat in three hydrographic regimes around the Pribilof Islands (Brodeur, this report).

Change in Pacific Northwest coastal ecosystems. Proceedings of the Pacific Northwest Coastal Ecosystems Regional Study Workshop, August 73-14, 1996, Troutdale, Oregon

Over the past one hundred and fifty years, the landscape and ecosystems of the Pacific Northwest coastal region, already subject to many variable natural forces, have been profoundly affected by human activities. In virtually every coastal watershed from the Strait of Juan de Fuca to Cape Mendocino, settlement, exploitation and development of resou?-ces have altered natural ecosystems. Vast, complex forests that once covered the region have been largely replaced by tree plantations or converted to non-forest conditions. Narrow coastal valleys, once filled with wetlands and braided streams that tempered storm runoff and provided salmon habitat, were drained, filled, or have otherwise been altered to create land for agriculture and other uses. Tideflats and saltmarshes in both large and small estuaries were filled for industrial, commercial, and other urban uses. Many estuaries, including that of the Columbia River, have been channeled, deepened, and jettied to provide for safe, reliable navigation. The prodigious rainfall in the region, once buffered by dense vegetation and complex river and stream habitat, now surges down sirfiplified stream channels laden with increased burdens of sediment and debris. Although these and many other changes have occurred incrementally over time and in widely separated areas, their sum can now be seen to have significantly affected the natural productivity of the region and, as a consequence, changed the economic structure of its human communities. This activity has taken place in a region already shaped by many interacting and dynamic natural forces. Large-scale ocean circulation patterns, which vary over long time periods, determine the strength and location of currents along the coast, and thus affect conditions in the nearshore ocean and estuaries throughout the region. Periodic seasonal differences in the weather and ocean act on shorter time scales; winters are typically wet with storms from the southwest while summers tend to be dry with winds from the northwest. Some phenomena are episodic, such as El Nifio events, which alter weather, marine habitats, and the distribution and survival of marine organisms. Other oceanic and atmospheric changes operate more slowly; over time scales of decades, centuries, and longer. Episodic geologic events also punctuate the region, such as volcanic eruptions that discharge widespread blankets of ash, frequent minor earthquakes, and major subduction zone earthquakes each 300 to 500 years that release accumulated tectonic strain, dropping stretches of ocean shoreline, inundating estuaries and coastal valleys, and triggering landslides that reshape stream profiles. While these many natural processes have altered, sometimes dramatically, the Pacific Northwest coastal region, these same processes have formed productive marine and coastal ecosystems, and many of the species in these systems have adapted to the variable environmental conditions of the region to ensure their long-term survival.

Atmospheric nutrient input to coastal areas: reducing the uncertainties

A significant fraction of the total nitrogen entering coastal and estuarine ecosystems along the eastern U.S. coast arises from atmospheric deposition; however, the exact role of atmospherically derived nitrogen in the decline of the health of coastal, estuarine, and inland waters is still uncertain. From the perspective of coastal ecosystem eutrophication, nitrogen compounds from the air, along with nitrogen from sewage, industrial effluent, and fertilizers, become a source of nutrients to the receiving ecosystem. Eutrophication, however, is only one of the detrimental impacts of the emission of nitrogen containing compounds to the atmosphere. Other adverse effects include the production of tropospheric ozone, acid deposition, and decreased visibility (photochemical smog). Assessments of the coastal eutrophication problem indicate that the atmospheric deposition loading is most important in the region extending from Albemarle/Parnlico Sounds to the Gulf of Maine; however, these assessments are based on model outputs supported by a meager amount of actual data. The data shortage is severe. The National Research Council specifically mentions the atmospheric role in its recent publication for the Committee on Environmental and Natural Resources, Priorities for Coastal Ecosystem Science (1994). It states that, "Problems associated with changes in the quantity and quality of inputs to coastal environments from runoff and atmospheric deposition are particularly important [to coastal ecosystem integrity]. These include nutrient loading from agriculture and fossil fuel combustion, habitat losses from eutrophication, widespread contamination by toxic materials, changes in riverborne sediment, and alteration of coastal hydrodynamics. "

Atmospheric carbon dioxide and the climatic record

This paper is an attempt to provide a summary review of conclusions from previous studies on this subject. They have been organized under the following subject headings: Conceptualization of the greenhouse effect; The climatic effect of doubled carbon dioxide; Interpretation of the climatic record; Diagnosis of apparent and possible model deficiencies; The paleoclimatic record.

The annual course of precipitation over much of the United States: observed versus GCM simulation

General Circulation Models (GCMs) may be useful in estimating the ecological impacts of global climatic change. We analyzed seasonal weather patterns over the conterminous United States and determined that regional patterns of rainfall seasonality appear to control the distributions of the Nation's major biomes. These regional patterns were compared to the output from three GCMs for validation. The models appear to simulate the appropriate seasonal climates in the northern tier of states. However, the spatial extent of these regions is distorted. None of the models accurately portrayed rainfall seasonalities in the southern tier of states, where biomes are primarily influenced by the Bermuda High.

Uncovering North American temperature and precipitation patterns associated with the Southern Oscillation

The extreme phases of the Southern Oscillation (SO) have been linked to fairly persistent classes of circulation anomalies over the North Pacific and parts of North America. It has been more difficult to uncover correspondingly consistent patterns of surface temperature and precipitation over much of the continent. The few regions that appear to have consistent SO-related patterns of temperature and precipitation anomalies are identified and discussed. Also discussed are regions that appear to have strong SO-related surface anomalies whose sign varies from episode to episode.

Strong, low frequency (decadal) environmental fluctuations during the 20th century in the North Pacific Ocean, on the Washington coast, and in Puget Sound

At decadal period (10-20 years), dynamic linkage was evident between atmospheric low pressure systems over the North Pacific Ocean and circulation in a Pacific Northwest fjord (Puget Sound). As the Aleutian low pressure center shifts, storms arriving from the North Pacific Ocean deposit varying amounts of precipitation in the mountains draining into the estuarine system; in turn, the fluctuating addition of fresh water changes the density distribution near the fjord basin entrance sill, thereby constraining the fjord's vertical velocity structure. This linkage was examined using time series of 21 environmental parameters from 1899 to 1987. Covariation in the time series was evident because of the strong decadal cycles compared with long-term averages, interannual variability, and seasonal cycles.

GCM-data intercomparison: the good news and the bad

EXTRACT (SEE PDF FOR FULL ABSTRACT): General circulation models (GCMs) are probably the most sophisticated theoretical tools we have to simulate possible climatic effects of increasing carbon dioxide and other greenhouse gases. ... As will be illustrated here using a variety of examples, although the models do simulate "reality" very well on the "grand" scale (e.g., global, hemispheric, zonal), substantial differences are more apparent as the scale is reduced to areas particularly relevant to regional planners. It is particularly important that workers more clearly recognize the potential dangers in relying too heavily on simple summary statistics such as averages estimated over large regional scales. Many shortcomings are apparent in the model simulations of the present climate, indicating that further model improvements are needed to achieve reliable regional and seasonal projections of the future climatic conditions.

Skill of monthly forecasts during the Northern Hemisphere summer

We have performed GCM experiments using the National Meteorological Center's Medium Range Forecasting (MRF) model to study the skill of monthly forecasts during the Northern Hemisphere summer and to test the impact of sea surface temperature anomalies (SSTAs) on such forecasts. The daily skill varies a great deal. The skillful daily forecasts last from 5 to 8 days for the Southern Hemisphere and from 6 to 8 days for the Northern Hemisphere. SSTAs have positive impact on the forecasts in the tropics and surface variables, but the impact of tropical SSTAs on the extra-tropical circulation is, in general, positive but small. Overall, the initial conditions play a more important role than SSTAs in determining the forecast skill.

The relationship of western Pacific monsoon and tropical cyclone activity to North Pacific and North American climate anomalies

This present study investigates the influence of western Pacific tropical cyclone activity as possible centers of anomalous tropical heating on the large-scale circulation over the Pacific region. The characterization of tropical cyclone activity via an index based on anomalous 700 mb zonal wind is described first. Patterns of anomalous large-scale extratropical circulation anomalies based on composites of similar periods of tropical cyclone activity are then presented, followed by general conclusions.

A numerical simulation of cool/wet and warm/wet episodes in the western United States

Wintertime precipitation in the mountains of the western United States during a warm or cool period has a pronounced influence on streamflow. During a warm year, streamflow at intermediate elevations responds more immediately to precipitation events; during a cold year, much of the discharge is delayed until the snow melts in spring and summer. Previous efforts at studying these extremes have been hampered by a limited number and length of observational analyses. In this study, we augment this limited observational record by analyzing a simplified general circulation model.

Satellite passive microwave observations of the upper Colorado River snowpack

Seasonal snow cover in the mountains of the Upper Colorado River Basin is a major source of water for a large portion of the southwestern United States. The extent and amount of this snowpack not only reflects changes in weather patterns and climate but also influences the general circulation through modification of the energy exchange between land and atmosphere. ... Satellite observations and remote sensing techniques can enhance the standard snowpack observations to provide the temporal and spatial measurements required for understanding the role of snow in the surface energy balance and improving the management of water resources.

Near and distant connection of atmospheric systems to ocean temperature change in the coastal California Current region

In studying hydrosphere, atmosphere, and biosphere interactions, it is useful to focus on specific subsystem processes and energy exchanges (forcing). Since subsystem scales range over ten orders of magnitude, it may be difficult to focus research on scales that will yield useful results in terms of establishing causal and predictive connections between more easily and less easily observed subsystems. In an effort to find pertinent scales, we have begun empirical investigations into relationships between atmospheric, oceanic, and biological systems having spatial scales exceeding 10^3 kilometers and temporal scales of six months or more.