Toward a rule-based biome model

EXTRACT (SEE PDF FOR FULL ABSTRACT): Current projections of the response of the biosphere to global climatic change indicate as much as 50 to 90% spatial displacement of extratropical biomes. The mechanism of spatial shift could be dominated either by competitive displacement of northern biomes by southern biomes or by drought-induced dieback of areas susceptible to change. The current suite of global biosphere models cannot distinguish between these two processes, hence the need for a mechanistically based biome model. The first steps have been taken toward development of a rule-based, mechanistic model of regional biomes at a continental scale. ... The model is in an early stage of development and will require several enhancements, including: explicit simulation of potential evapotranspiration, extension to boreal and tropical biomes, a shift from steady-state to transient dynamics, and validation on other continents.

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.

Wind climate trends in the Pacific Northwest and the implications to renewable energy supply

EXTRACT (SEE PDF FOR FULL ABSTRACT): This paper examines the influence of wind climate variations on new Pacific Northwest renewable energy sources. Wind represents a potentially valuable supplemental source of energy in the region. ... The recent period of weaker winds may be associated with a stronger North Pacific Low in the last decade. This would result in winter storms more often being deflected farther north, to Canada. Also, in the last dozen years, lower SOI values were common. Other investigators have found low SOI to be associated with drier conditions in the Pacific Northwest.

Climate variability and Crater Lake water levels

Crater Lake has fluctuated in elevation by 5 meters during the 20th Century. Reasons for these fluctuations were investigated as part of a long-term study of the Crater Lake ecosystem. Lake level changes were found to be closely related to precipitation variations. The lake can be thought of as acting as both a giant precipitation gage and as a large evaporation "pan". Winter snowfall variations are related to variations in the Southern Oscillation Index. Crater Lake offers a unique combination of simple geometry and hydrology, and a long record of supporting data, available nowhere else in the world for a caldera lake.

The influence of seasonal precipitation and temperature variations on runoff in California and southwestern Oregon

EXTRACT (SEE PDF FOR FULL ABSTRACT): There is considerable seasonal-to-interannual variability in the runoff of major watersheds in the Sierra Nevada, Coastal, and Cascade ranges of California and southwestern Oregon. This variability is reflected in both the amount and timing of runoff. This study examines that variability using long historical streamflow records and seasonal mean temperature and precipitation. ... Precipitation is the only significant predictor for both amount and timing of runoff in the low elevation basins. As elevation increases, the models rely more and more on temperature to explain amount and timing of runoff.

"Cool" vs. "warm" winter precipitation and its effect on streamflow in California

Precipitation is a difficult variable to understand and predict. In this study, monthly precipitation in California is divided into two classes according to the monthly temperature to better diagnose the atmospheric circulation that causes precipitation, and to illustrate how temperature compounds the precipitation to runoff process.

Air temperature trends in California

"Greenhouse heating" of the atmosphere due to trace gases seems apparent to those who model with averages but not to those who examine individual temperature records. Temperature trends are on the minds of all those concerned with the environmental influence of the increasing human population. The big problem remains - where and how do we take the Earth's temperature? ... In California, there are 112 temperature records for 1910 to 1989; all of them were used here to examine trends in annual temperature.

One hundred years of rainfall trends in California

This paper is an examination of precipitation trends in California for 100 years based on 96 rain records. The study resulted from an attempt to develop a wetness index for the San Francisco Bay area, where declining rainfall trends indicated a lot more rainfall in the first 50 years of the study period. A regular pattern of decline was found in California coastal stations, concurrent with an increasing trend at inland stations.

Climate forcing of Pacific herring recruitment and growth in southern British Columbia

Over the last 50 years, much of the variability in ocean climate and herring recruitment has occurred at two dominant periods centered around 5 and 16 years. Herring growth has also exhibited a dominant 5- and 18-year periodicity. A recent analysis of a number of relevant time series suggests that interannual variations in oceanic conditions off the west coast of Vancouver Island affect survival of herring and their principal predator, Pacific hake, which also exhibits a marked 16-year oscillation in abundance. Thus the dynamics of the herring stock are modulated by a combination of climate and predator forcing. Much of the interannual variation in herring growth is centered around the 5-year (moderate ENSO period) and 16-year (strong ENSO period) ocean climate oscillations and the 16-year recruitment oscillation.

Upwelling, offshore transport, and the availability of rockfish in central California

EXTRACT (SEE PDF FOR FULL ABSTRACT): We used the diet of a seabird, the common murre (Uria aalge), nesting on Southeast Farallon Island and feeding in the Gulf of the Farallones, California, as an index to abundance of juvenile rockfish, then related fish abundance to indices of turbulence and upwelling over an 18-year period, 1973-1990. Strong, persistent upwelling or downwelling led to reduced availability of fish in the study area, in contrast to great abundance when upwelling was mild or pulsed. ... On the basis of our study, one effect might be that fishes thought strong enough to resist Ekman transport could be transported out of normal areas of recruitment.

The role of direct observation in predicting climatic change

The National Oceanic and Atmospheric Administration Center for Ocean Analysis and Prediction (COAP) in Monterey, California, has assembled information to suggest how NOAA's facilities for observing the ocean and atmosphere might be applied to studies of paleoclimate. This effort resulted, indirectly, in several projects that combine direct observations of the ocean/atmosphere system with studies of past climate of the Pacific region. This article considers concepts that link the two kinds of investigations. It defines the thesis that direct observation of systems that generate paleoclimatic information is the nexus upon which understanding of climatic variability begins and upon which prediction of climate and global change depends.

Initial global perspective of climate for the last thousand years: the ice core record

Climatic and environmental records from low, middle, and high latitude ice cores greatly increase our knowledge of the course of past events. This historical perspective is essential to predict climatic oscillations, dominated as they may be by increasing greenhouse gas concentrations. Forcing factors, internal and external, that have operated in the past will continue to influence the course of events.

Snow accumulation time series and their climatic interpretation

EXTRACT (SEE PDF FOR FULL ABSTRACT): Several snow accumulation time series derived from ice cores and extending over 3 to 5 centuries are examined for spatial and temporal climatic information. ... A significant observation is the widespread depression of net snow accumulation during the latter part of the "Little Ice Age". This initially suggests sea surface temperatures were significantly depressed during the same period. However, prior to this, the available core records indicate generally higher than average precipitation rates. This also implies that influences such as shifted storm tracks or a dustier atmosphere may have been involved. Without additional spatial data coverage, these observations should properly be studied using a coupled (global) ocean/atmosphere GCM.

Coastal climate reflected in carbon-13/carbon-12 ratio of organic carbon in varved sediment from Santa Barbara basin

A 1844-1987 time-series of carbon stable isotope ratios from dated sedimentary total organic carbon from the center of the Santa Barbara basin is compared with historical climate and oceanographic records. Carbon derived from carbon-13-depleted phytoplankton and carbon-13-enriched kelp appear responsible for a large part of the isotopic variance in sedimentary total organic carbon. El Niño/Southern Oscillation events are recorded by the isotopic response of marine organic carbon in sediments.

Eastern tropical Pacific corals monitor low latitude climate of the past 400 years

EXTRACT (SEE PDF FOR FULL ABSTRACT): We have measured coral growth band thickness and skeletal stable isotopic composition through a 371-year transect (AD 1583-1954) from a massive specimen of Pavona clavus from the Galápagos Islands. ... We observe a general cooling trend during 1860-1954, corresponding to the end of the Little Ice Age, an interval characterized by general warming at many mid-latitude sites. Variance at sunspot cycle frequencies in growth rate, stable isotopic, and trace element composition implies a direct or indirect link between the solar cycle and climate modulation in the eastern Pacific.