Cristina L. Archer

Historical trends in the jet streams

[1] Jet streams, the meandering bands of fast winds located near the tropopause, are driving factors for weather in the midlatitudes. This is the first study to analyze historical trends of jet stream properties based on the ERA-40 and the NCEP/NCAR reanalysis datasets for the period 1979 to 2001. We defined jet stream properties based on mass and mass-flux weighted averages. We found that, in general, the jet streams have risen in altitude and moved poleward in both hemispheres. In the northern hemisphere, the jet stream weakened. In the southern hemisphere, the sub-tropical jet weakened, whereas the polar jet strengthened. Exceptions to this general behavior were found locally and seasonally. Further observations and analysis are needed to confidently attribute the causes of these changes to anthropogenic climate change, natural variability, or some combination of the two. Citation: Archer, C. L., and K. Caldeira (2008), Historical trends in the jet streams, Geophys. Res. Lett., 35, L08803, doi:10.1029/2008GL033614.

Spatial and temporal distributions of U.S. winds and wind power at 80 m derived from measurements

windprofilesfromthesoundings,resultedin80-mwindspeedsthatare,onaverage,1.3–1.7 m/s faster than those obtained from the most common methods previously used to obtain elevated data for U.S. wind power maps, a logarithmic law and a power law, both with constant coefficients. The results suggest that U.S. wind power at 80 m may be substantially greater than previously estimated. It was found that 24% of all stations (and 37% of all coastal/offshore stations) are characterized by mean annual speeds � 6.9 m/s at 80 m, implying that the winds over possibly one quarter of the United States are strong enough to provide electric power at a direct cost equal to that of a new natural gas or coal power plant. ThegreatestpreviouslyunchartedreservoirofwindpowerinthecontinentalUnitedStatesis offshore and nearshore along the southeastern and southern coasts. When multiple wind sites are considered, the number of days with no wind power and the standard deviation of the wind speed, integrated across all sites, are substantially reduced in comparison with when one wind site is considered. Therefore a network of wind farms in locations with high annual mean wind speeds may provide a reliable and abundant source of electric power. INDEX TERMS: 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 3399 Meteorology and Atmospheric Dynamics: General or miscellaneous; 9350 Information Related to Geographic Region: North America;KEYWORDS:U.S. wind power, least squares, global warming, air pollution, energy, wind speed Citation: Archer, C. L., and M. Z. Jacobson, Spatial and temporal distributions of U.S. winds and wind power at 80 m derived from measurements, J. Geophys. Res., 108(D9), 4289, doi:10.1029/2002JD002076, 2003.

Supplying Baseload Power and Reducing Transmission Requirements by Interconnecting Wind Farms

Wind is the world’s fastest growing electric energy source. Because it is intermittent, though, wind is not used to supply baseload electric power today. Interconnecting wind farms through the transmission grid is a simple and effective way of reducing deliverable wind power swings caused by wind intermittency. As more farms are interconnected in an array, wind speed correlation among sites decreases and so does the probability that all sites experience the same wind regime at the same time. The array consequently behaves more and more similarly to a single farm with steady wind speed and thus steady deliverable wind power. In this study, benefits of interconnecting wind farms were evaluated for 19 sites, located in the midwestern United States, with annual average wind speeds at 80 m above ground, the hub height of modern wind turbines, greater than 6.9 m s 1 (class 3 or greater). It was found that an average of 33% and a maximum of 47% of yearly averaged wind power from interconnected farms can be used as reliable, baseload electric power. Equally significant, interconnecting multiple wind farms to a common point and then connecting that point to a far-away city can allow the long-distance portion of transmission capacity to be reduced, for example, by 20% with only a 1.6% loss of energy. Although most parameters, such as intermittency, improved less than linearly as the number of interconnected sites increased, no saturation of the benefits was found. Thus, the benefits of interconnection continue to increase with more and more interconnected sites.

Saturation wind power potential and its implications for wind energy

Wind turbines convert kinetic to electrical energy, which returns to the atmosphere as heat to regenerate some potential and kinetic energy. As the number of wind turbines increases over large geographic regions, power extraction first increases linearly, but then converges to a saturation potential not identified previously from physical principles or turbine properties. These saturation potentials are >250 terawatts (TW) at 100 m globally, approximately 80 TW at 100 m over land plus coastal ocean outside Antarctica, and approximately 380 TW at 10 km in the jet streams. Thus, there is no fundamental barrier to obtaining half (approximately 5.75 TW) or several times the world’s all-purpose power from wind in a 2030 clean-energy economy.

Energy Resources and Potentials

Executive Summary An energy resource is the first step in the chain that supplies energy services (for a definition of energy services, see Chapter 1). Energy services are largely ignorant of the particular resource that supplies them; however, often the infrastructures, technologies, and fuels along the delivery chain are highly dependent on a particular type of resource. The availability and costs of bringing energy resources to the market place are key determinants to affordable and accessible energy services. Energy resources pose no inherent limitation to meeting the rapidly growing global energy demand as long as adequate upstream investment is forthcoming – for exhaustible resources in exploration, production technology, and capacity (mining and field development) and, by analogy, for renewables in conversion technologies. Hydrocarbons and Nuclear Occurrences of hydrocarbons and fissile materials in the Earths crust are plentiful – yet they are finite. The extent of the ultimately recoverable oil, natural gas, coal, or uranium is the subject of numerous reviews, yet still the range of values in the literature is large (Table 7.1). For example, the range for conventional oil is between 4900 exajoules (EJ) for reserves to 13,700 EJ (reserves plus resources) – a range that sustains continued debate and controversy. The large range is the result of varying boundaries of what is included in the analysis of a finite stock of an exhaustible resource, e.g., conventional oil only or conventional oil plus unconventional occurrences, such as oil shale, tar sands, and extra-heavy oils.

Meteorology for Coastal/Offshore Wind Energy in the United States: Recommendations and Research Needs for the Next 10 Years

This document is a supplement to “Metorology for Coastal/Offshore Wind Energy in the United States: Recommendations and Research Needs for the Next 10 Years,” by Cristina L. Archer, Brian A. Colle, Luca Delle Monache, Michael J. Dvorak, Julie Lundquist, Bruce H. Bailey, Philippe Beaucage, Matthew J. Churchfield, Anna C. Fitch, Branko Kosovic, Sang Lee, Patrick J. Moriarty, Hugo Simao, Richard J. A. M. Stevens, Dana Veron, and John Zack (Bull. Amer. Meteor. Soc., 95, 515–519) • ©2014 American Meteorological Society • Corresponding author: Cristina L. Archer, University of Delaware, College of Earth, Ocean, and Environment, Newark, Delaware 19716 • E-mail: carcher@udel.edu • DOI:10.1175/BAMS-D-13-00108.2 METEOROLOGY FOR COASTAL/OFFSHORE WIND ENERGY IN THE UNITED STATES Recommendations and Research Needs for the Next 10 Years

Where is the ideal location for a US East Coast offshore grid

This paper identifies the location of an “ideal” offshore wind energy (OWE) grid on the U.S. East Coast. The ideal location would provide the highest overall and peak-time summer capacity factor, use bottom-mounted turbine foundations (depth ≤50 m), connect regional transmissions grids from New England to the Mid-Atlantic, and finally, have a smoothed power output, reduced hourly ramp rates and hours of zero power. Hourly, high-resolution mesoscale weather model data from 2006–2010 were used to approximate wind farm output. The offshore grid was located in the waters from Long Island, New York to the Georges Bank, ≈450 km east. Twelve candidate 500 MW wind farms were located randomly throughout that region. Four wind farms (2000 MW total capacity) were selected for their synergistic meteorological characteristics that reduced offshore grid variability. Sites which were likely to have sea breezes helped increase the grid capacity factor during peak time in the spring and summer months. Sites far offshore, dominated by powerful synoptic-scale storms, were included for their generally higher but more variable power output. By interconnecting all 4 farms via an offshore grid versus 4 individual interconnections, power was smoothed, the no-power events were reduced from 9% to 4%, and the combined capacity factor was 48% (gross). By interconnecting offshore wind energy farms ≈450 km apart, in regions with offshore wind energy resources driven by both synoptic-scale storms and mesoscale sea breezes, substantial reductions in low/no-power hours and hourly ramp rates can be made.

An Introduction to Meteorology for Airborne Wind Energy

Airborne wind energy systems (AWES) are devices that effectively extract energy from the air flow, more specifically kinetic energy, and convert it to electricity. Wind is the manifestation of the kinetic energy present in the atmosphere. Understanding wind, its properties and power, as well as other atmospheric properties that can affect AWES, is the goal of this chapter.

The Santa Cruz Eddy. Part I: Observations and Statistics

A shallow cyclonic circulation that occurs in the summertime over the Monterey Bay (California) is investigated. Since it is often centered offshore from the city of Santa Cruz and has never been studied in detail before, it is named the Santa Cruz eddy (SCE) in this study. Its horizontal size is 10–40 km, and its vertical extent is 100–500 m. The SCE is important for local weather because it causes surface winds along the Santa Cruz coast to blow from the east instead of from the northwest, the latter being the climatological summer pattern for this area. As a consequence of the eddy, cool and moist air is advected from the south and southeast into the Santa Cruz area, bringing both relief from the heat and fog to the city. The SCE is unique in its high frequency of occurrence. Most vortices along the western American coast form only during unusual weather events, whereas the SCE forms 78%–79% of the days during the summer. The SCE frequency was determined after analyzing two years of data with empirical orthogonal functions (EOFs) from a limited observational network and satellite imagery. An explanation of the formation mechanism of the SCE will be provided in Part II of this study.

Correction to “Spatial and temporal distributions of U.S. winds and wind power at 80 m derived from measurements”

[1] In the paper ‘‘Spatial and temporal distributions of U.S. winds and wind power at 80 m derived from measurements’’ by C. L. Archer and M. Z. Jacobson (Journal of Geophysical Research, 108(D9), 4289, doi:10.1029/2002JD002076, 2003), three errors in the methodology introduced have been identified. In addition, since publication of the article, data from an additional 179 stations have become available. The errors found have little effect on the main conclusions of the paper but result in slight modifications of some figures and tables. Below, the corrections and updates are described. [2] The first error was in the equation for the amplitude A of the r function, given in paragraph 26. The correct formula is