1988 summer drought over the Great Plains: some causes and predictions

EXTRACT (SEE PDF FOR FULL ABSTRACT): The 1988 summer drought over much of the United States is described in terms of hemispheric mid-tropospheric flow patterns, temperature and precipitation anomalies, and sea surface temperature patterns. This drought was similar to earlier Great Plains droughts, although spatially more extensive than most. Three attempts to predict this drought from antecedent spring were moderately successful, though no one anticipated its severity and extent. ... A modified barotropic model iterating from a mean summer estimate of seasonal forcing from the May mid-tropospheric height pattern was reasonably successful in forecasting the drought. Sea surface temperature indications show that cold water (La Niña) along the equator subsequent to the 1987 El Niño, while contributory, cannot be considered a principal cause of the drought, since earlier cold water episodes did not produce drought, and other drought episodes occurred in the absence of cold equatorial waters.

Changes in mid-troposphere snow accumulation on Mt. Logan, Yukon, over the last three centuries

EXTRACT (SEE PDF FOR FULL ABSTRACT): A net snow accumulation time series is presented. It is derived from a 102.5 m ice core retrieved from Mt. Logan at an altitude of 5340 m a.s.l. Annual increments are identified using stable isotopes, trace chemistry, and beta activity. ... The resulting time series of nearly 300 years seems to indicate a lower mean accumulation from AD 1700 to the mid-19th century than after that time. The last 100 years of the series correlates significantly with certain instrumental station records at mid-northern latitudes.

Simulation and diagnosis of large-scale atmospheric moisture and surface hydrology over North America

We describe a preliminary investigation into large-scale atmospheric and surface moisture variations over North America. We compare large-scale hydrologic budgets in the Los Alamos general circulation model (GCM) to observed precipitation and vertically integrated atmospheric moisture fluxes derived from the National Meteorological Center's operational analyses. THe GCM faithfully simulates the integrated flux divergence and P-E differences. However, the integrated moisture content is too low, and precipitation and evaporation are too high. The model produces summertime soil moisture dryness, which supports previous studies showing increased droughts under warmer conditions.

Variations in northeast Asian environments over the last 350,000 years reconstructed from pollen records from the northwest Pacific Ocean

EXTRACT (SEE PDF FOR FULL ABSTRACT): Recent analyses of terrestrial (pollen) and marine microfossils (foraminifera and radiolaria) in cores V28-204 and RC14-99 from the northwest Pacific Ocean extend the continuous, chronostratigraphically-controlled records of the regional vegetation of the Pacific coast of Japan and offshore marine environments through three full glacial cycles. The high-resolution pollen time series show systematic relationships between fluctuations in Japanese vegetation and global ice volume over the last 350 kyr. ... Comparison with solar insolation at 30°N and with an index of orbital parameters suggests that variation in northeast Asian summer monsoon intensity is related to orbital forcing.

Is the California drought over?

For the 6-year period 1987 through 1992, most of California suffered the worst or near-worst drought in a recorded history of about 140 years. Based on tree ring reconstructions, it may have been the worst in more than 400 years. The purpose of this paper is to review briefly the recent drought, then talk about the water supply situation this year, with some discussion of why the California drought is over hydrologically for most people; but for some, water supply problems continue.

Inter-decadal climate variability in the Southern Hemisphere: evidence from Tasmanian tree rings over the past three millennia

EXTRACT (SEE PDF FOR FULL ABSTRACT): The characterization of inter-decadal climate variability in the Southern Hemisphere is severely constrained by the shortness of the instrumental climate records. To help relieve this constraint, we have developed and analyzed a reconstruction of warm-season (November-April) temperatures from Tasmanian tree rings that now extends back to 800 BC. A detailed analysis of this reconstruction in the time and frequency domains indicates that much of the inter-decadal variability is principally confined to four frequency bands with mean periods of 31, 57, 77, and 200 years. ... In so doing, we show how a future greenhouse warming signal over Tasmania could be masked by these natural oscillations unless they are taken into account.

Decadal hydroclimatic variability over western North America [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Variability of precipitation over North America on ENSO and decadal time scales is examined from several decades of precipitation and snow course records.

Decadal climate variability over the North Pacific and North America: dynamics and predictability [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The dynamics and predictability of decadal climate variability over the North Pacific and North America are investigated by analyzing various observational datasets and the output of a state-of-the-art coupled ocean-atmosphere general circulation model, which was integrated for 120 years.

Decadal variability over the North Pacific Ocean [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): In this study we use ocean and atmosphere datasets from observations and from an ocean general circulation model integration to examine decadal time scale variability that is centered in the Pacific basin. We know that decadal variability is likely to have a strong expression in the Pacific basin; for example, a marked "shift" of cool season climate in the mid-1970s introduced major changes in Pacific SST and atmospheric circulation, along with many other physical and biological properties.

The terrestrial paleorecord of climate change over the past thousand years in the Canadian Rockies [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): High alpine environments provide a variety of paleorecords based on physical (glaciers, glacio-lacustrine sedimentation) and biological systems (tree rings, tree-line fluctuations). These records have varying temporal resolution and contain different climate-related signals but, in concert, provide a more comprehensive reconstruction of past climates than is possible from any single archive.

Evidence for changes in large-scale upwelling in the California Current over the past 700 years [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Bidecadal radiocarbon measurements on tree rings provide a detailed series of carbon-14 activities at isotopic equilibrium with atmospheric carbon dioxide. ... Most marine environments do not permit development of a comparable series of carbon-14 ages with which to compare the terrestrial tree ring series. However, we have recently begun work on such a series using material from the varved sediments of the Santa Barbara Basin off southern California. ... We now have a nearly continuous record of carbon-14 dates representing the age of the water over the upper 100 meters. ... The ocean reservoir ages show an increase prior to 1450 and a progressive decrease with time after 1450. Although there may be other explanations, we believe this trend is principally the result of changes in large-scale upwelling of water from below 500 meters. These changes were probably also associated with changes in the intensity of the California Current.

Synoptic dendroclimatology: a process-based approach for linking tree-ring information to atmospheric circulation over the Pacific and western North America [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Synoptic dendroclimatology uses dated tree rings to study and reconstruct climate from the viewpoint of the climate's weather components and their relationship to atmospheric circulation. This approach defines a connection between large-scale circulation and ring-width variation at local sites using correlation fields, composite maps, indexing, and other circulation-based methodologies.

Multiple-proxy lacustrine record of moisture transport over western North America from 24,000 to 12,000 YBP, Lake Estancia, New Mexico [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Pluvial Lake Estancia in central New Mexico experienced large and rapid fluctuations in surface area and elevation during the build-up to and termination of the last glacial maximum (LGM). Due to continuous groundwater discharge, a minimum pool covering about 400 square kilometers was maintained in the central basin until about 12,000 years ago, ensuring a continuous depositional sequence even during low stands of the lake. ... The sensitive response to fluctuations in climate by several independent proxies at Estancia show that transport of Pacific moisture over western North America changed dramatically during the last Ice Age, perhaps comparable to the large and rapid changes in climate documented from high-latitude ice and North Atlantic marine sediments for the LCM and its transitions.

Over-wintering performance of mixed sex and monosex tilapia (Oreochromis niloticus L.) in Bangladesh

An experiment was conducted for six months in 6 experimental ponds (each size 80 of m2) to assess the over-wintering performance between mixed sex and monosex tilapia, Oreochromis niloticus. The experiment was carried out with two treatments each with three replicates. In the first treatment (T1), mixed sex tilapia were stocked in 3 ponds with a mean initial of 4.80±0.18 g. In the second treatment (T2), monosex tilapia were stocked in another 3 ponds with a mean initial weight of 4.81 ±0.20 g. Each pond was stocked with 250 fingerlings. Fish were fed at the rate of 6% of fish body weight at the beginning. The feeding rate was gradually reduced to 2% for the third month and finally increased to 3% for rest of the period. Water quality was monitored fortnightly and the ranges were: temperature17.86-29.10°C, dissolved oxygen 4.25-6.10 mg/1, pH 6.97-7.20 and transparency 24.10-36.50 cm. After 6 months of rearing monosex tilapia attained a significantly (p