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Accumulated winter chill is decreasing in the fruit growing regions of California. Baldocchi, Dennis; Wong, Simon.
Climatic Change:
2008
Notes
We examined trends in accumulated winter chill across the fruit growing region of central California and its internal coastal valleys. We tested the hypothesis that global warming is in motion in California and is causing accumulated winter chill to decrease across the fruit and nut growing regions of California. The detection of potential trends in accumulated winter chill (between 0 and 7.2°C) was determined using two complementary climate datasets. The California Irrigation Management Information System (CIMIS) contains hourly climate data and is suitable for computing accumulated chill hours and chill degree-hours. But, its longest data records extend back only to the 1980s. The National Weather Service Coop climate record is longer, extending beyond the 1950s at many sites. But its datasets only contain information on daily maximum and minimum temperatures. To assess long term trends in winter chill accumulation, we developed an algorithm that converted information from daily maximum and minimum temperature into accumulated hours of winter chill and summations of chill-degree hours. These inferred calculations of chill hour accumulation were tested with and validated by direct measurements from hourly-based data from the CIMIS network. With the combined climate datasets, we found that the annual accumulation of winter chill hours and chill degree hours is diminishing across the fruit and nut growing regions of California. Observed trends in winter chill range between -50 and -260 chill hours per decade. We also applied our analytical algorithm to project changes in winter chill using regional climate projections of temperature for three regions in the Central Valley. Predicted rates of reduced winter chill, for the period between 1950 and 2100, are on the order of -40 h per decade. By the end of the 21st century, orchards in California are expected to experience less than 500 chill hours per winter. This chronic and steady reduction in winter chill is expected to have deleterious economic and culinary impact on fruit and nut production in California by the end of the 21st Century.
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Adaptability and adaptations of California’s water supply system to dry climate warming. Medellín-Azuara, Josué; Harou, Julien; Olivares, Marcelo; Madani, Kaveh; Lund, Jay; Howitt, Richard; Tanaka, Stacy; Jenkins, Marion; Zhu, Tingju.
Climatic Change:
2008
Notes
Economically optimal operational changes and adaptations for California’s water supply system are examined for a dry form of climate warming (GFDL CM2.1 A2) with year 2050 water demands and land use. Economically adaptive water management for this climate scenario is compared to a similar scenario with the historical climate. The effects of population growth and land use alone are developed for comparison. Compared with the historic hydrology, optimized operations for the dry climate warming scenario raise water scarcity and total operation costs by $490 million/year with year 2050 demands. Actual costs might be somewhat higher where non-economic objectives prevail in water management. The paper examines the economical mix of adaptation, technologies, policies, and operational changes available to keep water supply impacts to such modest levels. Results from this screening model suggest promising alternatives and likely responses and impacts. Optimized operations of ground and surface water storage change significantly with climate. Dry-warm climate change increases the seasonal storage range of surface reservoirs and aquifers. Surface reservoir peak storage usually occurs about a month earlier under dry-warm climate change.
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Aerosol-cloud-precipitation interactions. Part 1. The nature and sources of cloud-active aerosols. Andreae, M. O.; Rosenfeld, D..
Earth Science Reviews:
2008
DOI: 10.1016/j.earscirev.2008.03.001
Notes
Atmospheric aerosol particles serve as condensation nuclei for the formation of both, cloud droplets and atmospheric ice particles. As a result, they exert a substantial influence on the microphysical properties of water and ice clouds, which in turn affect the processes that lead to the formation of rain, snow, hail, and other forms of precipitation. In recent years, considerable progress has been made in understanding the chemical composition of aerosols, their microphysical properties, and the factors that enable them to act as cloud condensation nuclei (CCN) and ice nuclei (IN). The first part of this review article will focus on the nature and sources of CCN and IN. We discuss the fundamentals of the cloud droplet and ice nucleation processes, and the role that the chemical composition and particle size play in this process. We show that, in many instances, the influence of chemical composition can be represented by a simple parameterization, which leaves particle size as the main variable controlling CCN efficiency. Aerosol particles are produced either directly by anthropogenic and natural sources (dust, sea salt, soot, biological particles, etc.), or they are formed in the atmosphere by condensation of low-volatility compounds (e.g., sulfuric acid or oxidized organic compounds). We discuss the magnitude of these sources, and the CCN and IN characteristics of the particles they produce. In contrast to previous assessments, which focused on the aerosol mass, we are emphasizing the number of particles being produced, as this is the key variable in cloud microphysics. Large uncertainties still exist for many aerosol sources, e.g., the submicron part of the seaspray aerosol, the particles produced by the biosphere, and the secondary organic aerosol. We conclude with a discussion on what particle concentrations may have been in the pristine atmosphere, before the onset on anthropogenic pollution. Model calculations and observations in remote continental regions consistently suggest that CCN concentrations over the pristine continents were similar to those now prevailing over the remote oceans, suggesting that human activities have modified cloud microphysics more than what is reflected in conventional wisdom. The second part of this review will address the effects of changing CCN and IN abundances on precipitation processes, the water cycle, and climate. (C) 2008 Elsevier B.V. All rights reserved.
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Aerosol pollution impact on precipitation: a scientific review. Levin, Zev; Cotton, William.
Springer:
2008
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Aircraft Measurement of the Impacts of Pollution Aerosols on Clouds and Precipitation Over the Sierra Nevada. Daniel Rosenfeld.
PIER:
2008
http://www.energy.ca.gov/publications/displayOneReport.php?pubNum=CEC-500-2008-015
Notes
Reports on field studies using two research aircraft to determine how aerosols are affecting precipitation levels
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Ambient temperature predicts sex ratios and male longevity. Catalano, Ralph; Bruckner, Tim; Smith, Kirk R..
Proceedings of the National Academy of Sciences:
2008
DOI: 10.1073/pnas.0710711104
Notes
The theory that natural selection has conserved mechanisms by which women subjected to environmental stressors abort frail male fetuses implies that climate change may affect sex ratio at birth and male longevity. Using time series methods, we find that cold ambient temperatures during gestation predict lower secondary sex ratios and longer life span of males in annual birth cohorts composed of Danes, Finns, Norwegians, and Swedes born between 1878 (earliest year with complete life tables) and 1914 (last birth cohort for which male life span can be estimated). We conclude that ambient temperature affects the characteristics of human populations by influencing who survives gestation, a heretofore unrecognized effect of climate on humanity.
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An 'aerosol effect' detected but precipitation no affected. Hindman, Edward (Ward).
Weather Modification Association The 17th Joint Conference on Planned and Inadvertent Weather Modification:
2008
Notes
A 23-year record (1983/84-2005/06) of wintertime measurements at Storm Peak Laboratory (SPL) in the northern Colorado Rocky Mountains has shown, on average, condensation nucleus concentrations were directly related to cloud droplet concentrations and the droplet concentrations were inversely related to droplet mean diameters, evidence of an ‘aerosol effect'. With the removal of two outlying precipitation rate values, the droplet mean diameters were directly related to the precipitation rates; the mean diameters and precipitation rates are related through snow crystal riming. These results suggest aerosol concentrations can affect precipitation rates at SPL. However, there was no trend in either precipitation rates or in seasonal precipitation. Apparently, precipitation was governed more by meteorological factors than by aerosol concentrations.
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Analog European Heat Waves for U.S. Cities to Analyze Impacts on Heat-Related Mortality. Kalkstein, Laurence S.; Greene, J. Scott; Mills, David M.; Perrin, Alan D.; Samenow, Jason P.; Cohen, Jean-Claude.
Bulletin of the American Meteorological Society:
2008
Notes
Europe experienced an unprecedented excessive heat event (EHE) in 2003, raising the question: What if a similar EHE were experienced in U.S. cities?This study used an airmass-based meteorological method to develop analogs to the 2003 European EHE for five U.S. cities: Detroit, New York, Philadelphia, St. Louis, and Washington, D.C.; and calculated the potential excess mortality for these analogs.Analogs capture the 2003 EHE's characteristics by determining daily deviations from long-term averages for meteorological variables in Paris, France, expressed as a multiple of the standard deviation for each variable's long-term average.The 2003 daily multiples of the standard deviation measured in Paris for 12 meteorological variables, and daily maximum and minimum temperatures, were transferred to each U.S. city, and multiplied by the corresponding standard deviation calculated for each variable, to produce analog meteorological variables. With these data, an airmass calendar for each city was developed, and excess mortality was calculated using existing city-specific airmass algorithms.Results show the analog EHEs breaking all-time records for maximum and high minimum temperatures in all five cities. Excess heat-related mortality for the analog summer is 2 to over 7 times the long-term average, with New York showing the greatest increases. In all cities, calculated excess heat-related mortality for the analog summer exceeds the hottest recorded summer in 35 yr.These study results could be valuable for public health planning and a wide range of additional reliability or sensitivity analyses.
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Analysis of terrestrial water storage changes from GRACE and GLDAS. Syed, Tajdarul H.; Famiglietti, James S.; Rodell, Matthew; Chen, Jianli; Wilson, Clark R..
Water Resources Research:
2008
Notes
Since March 2002, the Gravity Recovery and Climate Experiment (GRACE) has provided first estimates of land water storage variations by monitoring the time-variable component of Earth’s gravity field. Here we characterize spatial-temporal variations in terrestrial water storage changes (TWSC) from GRACE and compare them to those simulated with the Global Land Data Assimilation System (GLDAS). Additionally, we use GLDAS simulations to infer how TWSC is partitioned into snow, canopy water and soil water components, and to understand how variations in the hydrologic fluxes act to enhance or dissipate the stores. Results quantify the range of GRACE-derived storage changes during the studied period and place them in the context of seasonal variations in global climate and hydrologic extremes including drought and flood, by impacting land memory processes. The role of the largest continental river basins as major locations for freshwater redistribution is highlighted. GRACE-based storage changes are in good agreement with those obtained from GLDAS simulations. Analysis of GLDAS-simulated TWSC illustrates several key characteristics of spatial and temporal land water storage variations. Global averages of TWSC were partitioned nearly equally between soil moisture and snow water equivalent, while zonal averages of TWSC revealed the importance of soil moisture storage at low latitudes and snow storage at high latitudes. Evapotranspiration plays a key role in dissipating globally averaged terrestrial water storage. Latitudinal averages showed how precipitation dominates TWSC variations in the tropics, evapotranspiration is most effective in the midlatitudes, and snowmelt runoff is a key dissipating flux at high latitudes. Results have implications for monitoring water storage response to climate variability and change, and for constraining land model hydrology simulations.
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An ensemble approach for attribution of hydrologic prediction uncertainty. Wood, Andrew W.; Lettenmaier, Dennis P..
Geophysical Research Letters:
2008
DOI: 10.1029/2008GL034648
Notes
Hydrologic prediction errors arise from uncertainty in initial moisture states (mainly snowpack and soil moisture), in boundary forcings (primarily future precipitation and temperature), and from model structure and parameter uncertainty. We evaluate the relative importance of initial condition and boundary forcing uncertainties using a hindcastbased framework that contrasts Ensemble Streamflow Prediction (ESP) with an approach that we term ‘‘reverse- ESP’’. In ESP, a hydrologicmodel with assumed perfect initial conditions (ICs) is forced by a forecast ensemble resampled from observed meteorological sequences; whereas reverse- ESP combines an ensemble of resampled ICs with a perfect meteorological forecast. The framework shows that in northern California, US, ICs yield streamflow prediction skill for up to 5 months during the transition between the wet and dry seasons, whereas during the reverse transition, climate forecast information is critical. In southern Colorado, IC knowledge outweighs climate predicti skill for shorter periods due to a more uniform precipitation regime.
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