Extratropical signature of the quasi-biennial oscillation

Using the assimilated data from the National Centers for Environmental Prediction (NCEP) reanalysis, we show that the extratropical signature of the tropical quasi-biennial oscillation (QBO) is seen mostly in the North Annular Mode (NAM) of atmospheric variability. To understand the extratropical manifestation of the QBO, we discuss two effects that have been suggested earlier: (1) The extratropical circulation is driven by the QBO modulation of the planetary wave flux, and (2) the extratropical circulation is driven by the QBO-induced meridional circulation. We found that the first effect is seen in wave 1 in the beginning of winter and in wave 2 in the end of winter. The QBO-induced circulation affects midlatitude regions over the entire winter. To investigate the QBO-NAM coupling, we use an equation that relates the stream function of the meridional circulation and the polar cap averaged temperature, which is a proxy for the NAM index. In addition to the annual Ω_a and the QBO frequency Ω_Q the spectrum of its solutions indicates the satellite frequencies at Ω_a ± Ω_Q

Climate Stability and the Origin of Agriculture

Although modern man had developed long before the migration from Africa began ∼ 55,000 years ago, no agricultural societies developed until about ∼ 10,000 years ago. But in the next 5000 years, agricultures developed in several unrelated regions of the world. It was not a chance occurrence that new agricultures independently appeared in the same 5000 years. The question is what inhibited agriculture worldwide for 44,000 years and what changed ∼ 10,000 years ago? We suggest that a major factor influencing the development of agricultural societies was climate stability. From the experience of several independent cultures, we estimate that the development of agriculture needed about 2000 years of climate free from significant climate variations on time scales of a few centuries

A Simulated Spectrum of Convectively Generated Gravity Waves: Propagation from the Tropopause to the Mesopause and Effects on the Middle Atmosphere

This work evaluates the interaction of a simulated spectrum of convectively generated gravity waves with realistic middle atmosphere mean winds. The wave spectrum is derived from the nonlinear convection model described by Alexander et al. [1995] that simulated a two-dimensional midlatitude squall line. This spectrum becomes input to a linear ray tracing model for evaluation of wave propagation as a function of height through climatological background wind and buoyancy frequency profiles. The energy defined by the spectrum as a function of wavenumber and frequency is distributed spatially and temporally into wave packets for the purpose of estimating wave amplitudes at the lower boundary of the ray tracing model. A wavelet analysis provides an estimate of these wave packet widths in space and time. Without this redistribution of energies into wave packets the Fourier analysis alone inaccurately assumes the energy is evenly distributed throughout the storm model domain. The growth with height of wave amplitudes is derived from wave action flux conservation coupled to a convective instability saturation condition. Mean flow accelerations and wave energy dissipation profiles are derived from this analysis and compared to parameterized estimates of gravity wave forcing, providing a measure of the importance of the storm source to global gravity wave forcing. The results suggest that a single large convective storm system like the simulated squall line could provide a significant fraction of the zonal mean gravity wave forcing at some levels, particularly in the mesosphere. The vertical distributions of mean flow acceleration and energy dissipation do not much resemble the parameterized profiles in form because of the peculiarities of the spectral properties of the waves from the storm source. The ray tracing model developed herein provides a tool for examining the role of convectively generated waves in middle atmosphere physics

Bordoni Receives 2009 James R. Holton Junior Scientist Award

Simona Bordoni received the 2009 James R. Holton Junior Scientist Award at the 2009 AGU Fall Meeting, held 14–18 December in San Francisco, Calif. The award recognizes outstanding research contributions by a junior atmospheric scientist within 3 years of his or her Ph.D

The Effectiveness of Facilitated Business-to-Business Word-of Mouth Marketing Strategies on Target Participants’ Information Sharing Behavior

This study examines the impact of facilitated business-to-business (B2B) word-of-mouth (WOM) on participants' information transmission decisions. We also examine characteristics of WOM participants and determine the types of participants who spread information. Understanding WOM participants' information sharing decisions is extremely important to agribusinesses using WOM in their marketing mix. For an expendable crop input, the most important factor in determining whether producers share WOM initiative information with peers is how often they are asked for advice by their peers. In contrast, for an expendable companion animal product the most important factor in determining whether veterinarians share WOM initiative information with peers is whether they had a satisfactory experience in the WOM initiative.facilitated B2B WOM, effectiveness of facilitated B2B WOM, indirect impact of facilitated B2B WOM, agribusiness firms’ information sharing decisions, Agribusiness, Industrial Organization, Marketing, Teaching/Communication/Extension/Profession, Q10, Q13,

What Do Private Firms Look like?

Private firms in the U.S. are not subject to public reporting requirements, so relatively little is known about their characteristics and behavior – until now. This Data Appendix describes a new database on private U.S. firms, created by Sageworks Inc. in cooperation with hundreds of accounting firms. The contents of the Sageworks database mirror Compustat, the standard database for public U.S. firms. It contains balance sheet and income statement data for 95,297 private firms covering 250,507 firms-years over the period 2002 to 2007. We compare this database to the joint Compustat-CRSP database of public firms and to the Federal Reserve’s 2003 National Survey of Small Business Finances

Is solar variability reflected in the Nile River?

We investigate the possibility that solar variability influences North African climate by using annual records of the water level of the Nile collected in 622–1470 A.D. The time series of these records are nonstationary, in that the amplitudes and frequencies of the quasi-periodic variations are time-dependent. We apply the Empirical Mode Decomposition technique especially designed to deal with such time series. We identify two characteristic timescales in the records that may be linked to solar variability: a period of about 88 years and one exceeding 200 years. We show that these timescales are present in the number of auroras reported per decade in the Northern Hemisphere at the same time. The 11-year cycle is seen in the Nile's high-water level variations, but it is damped in the low-water anomalies. We suggest a possible physical link between solar variability and the low-frequency variations of the Nile water level. This link involves the influence of solar variability on the atmospheric Northern Annual Mode and on its North Atlantic Ocean and Indian Ocean patterns that affect the rainfall over the sources of the Nile in eastern equatorial Africa

Gravity wave momentum flux in the lower stratosphere over convection

This work describes a method for estimating vertical fluxes of horizontal momentum carried by short horizontal scale gravity waves (lambda(sub x) = 10-100 km) using aircraft measured winds in the lower stratosphere. We utilize in situ wind vector and pressure altitude measurements provided by the Meteorological Measurement System (MMS) on board the ER-2 aircraft to compute the momentum flux vectors at the flight level above deep convection during the tropical experiment of the Stratosphere Troposphere Exchange Project (STEP-Tropical). Data from Flight 9 are presented here for illustration. The vertical flux of horizontal momentum these observations points in opposite directions on either side of the location of a strong convective updraft in the cloud shield. This property of internal gravity waves propagating from a central source compares favorably with previously described model results