bluuebunny/crossref_metadata_2025 huggingface dataset:
The acetyl co‐enzyme A synthetase genes of Kluyveromyces lactis
Authors: Zeeman A.‐M. , Steensma H. Y.
Published: December 2002

Two Kluyveromyces lactis genes encoding acetyl co‐enzyme A synthetase isoenzymes were isolated. One we named KlACS1, as it has high similarity to the ACS1 gene of Saccharomyces cerevisiae. The other gene, KlACS2, showed more similarity to S. cerevisiae ACS2 than to KlACS1 or ScACS1. This suggests that divergence of the two isogenes occurred before the evolutionary separation of the species and that the different functions have been conserved. In line with this idea is the regulation of transcription of the genes. The mode of regulation appeared to be maintained between ScACS1 and KlACS1 and between ScACS2 and KlACS2. The KlACS1 transcript was absent in glucose‐grown cells, whereas transcription levels in ethanol‐ and acetate‐grown cells were high. Disruption of the KlACS1 gene did not result in growth defects on glucose or ethanol. The growth rate on acetate, however, was reduced by a factor of two. KlACS2 was expressed at similar levels during growth on glucose and acetate, whereas expression on ethanol was slightly higher. A null mutant in this gene showed a reduced growth rate on all three carbon sources. Taken together, these data suggest that KlACS2 is used during growth on glucose and that KlACS1 is most dominant during growth on acetate. Strains in which both ACS genes are deleted could only be retrieved when a plasmid containing the ACS2 gene was present, suggesting that the double mutant is lethal. Tetrad analysis confirmed that non‐viable spores with a deduced Klacs1Klacs2 genotype germinated but could not divide further. It therefore appears that, as in S. cerevisiae, the pyruvate dehydrogenase bypass formed by the enzymes pyruvate decarboxylase, acetaldehyde dehydrogenase and acetyl co‐enzyme A synthetase is essential for growth. These results are in apparent contradiction with the growth on glucose of a strain with a disruption in the only structural pyruvate decarboxylase gene of K. lactis. Residual enzyme activity might, however, account for this discrepancy, or Acs fulfils an additional as yet unknown function, separate from its enzymatic activity. The sequences of KlACS1 and KlACS2 have been deposited in the EMBL database under Accession Nos AF061265 and AF134491, respectively. Copyright © 2002 John Wiley & Sons, Ltd.
Un théorème de rigidité non-métrique pour les variétés localement symétriques hermitiennes
Authors: Klingler B.
Published: December 2002

Let X be an irreducible Hermitian symmetric space of non-compact type of dimension greater than 1 and G be the group of biholomorphisms of X ; let

{\rm M} = \Gamma \backslash X

be a quotient of X by a torsion-free discrete subgroup

\Gamma

of G such that M is of finite volume in the canonical metric. Then, due to the G-equivariant Borel embedding of X into its compact dual Xc, the locally symmetric structure of M can be considered as a special kind of a

(G_{\Bbb C} , X_c)

-structure on M, a maximal atlas of Xc-valued charts with locally constant transition maps in the complexified group

{\rm G}_{\Bbb C}

. By Mostow's rigidity theorem the locally symmetric structure of M is unique. We prove that the

({\rm G}_{\Bbb C} , X_c)

-structure of M is the unique one compatible with its complex structure. In the rank one case this result is due to Mok and Yeung.
Transitively twisted flows of 3-manifolds
Authors: Nakayama H.
Published: December 2002

A non-singular C1 vector field X of a closed 3-manifold M generating a flow

\varphi_t

induces a flow of the bundle N X orthogonal to X. This flow further induces a flow

P \varphi_t

of the projectivized bundle of N X. In this paper, we assume that the projectivized bundle is a trivial bundle, and study the lift

\angle\varphi_t

of

P \varphi_t

to the infinite cyclic covering

M \times \mathbb{R}

. We prove that the flow

\angle\varphi_t

is not minimal, and construct an example of

\varphi_t

such that

\angle\varphi_t

has a dense orbit. If

\varphi_t

is almost periodic and minimal, then

\angle\varphi_t

is shown to be classified into three cases: (1) All the orbits of

\angle\varphi_t

are bounded. (2) All the orbits of

\angle\varphi_t

are proper. (3)

\angle\varphi_t

is transitive.
Relèvements des algèbres lisses et de leurs morphismes
Authors: Arabia A.
Published: December 2002

Let

R

be a commutative ring and let

I

be any ideal of

R

, put

{\bf\it\bar R} : = {\bf\it R} / {\bf\it I}

. We prove that for any smooth

\bf\it\bar R

-algebra

\bf\it\bar A

there exist a smooth

R

-algebra

A

such that

\bf\it\bar A

is isomorphic to

{\bf\it\bar R} \otimes_{\bf\it R} {\bf\it A}

. We also show that for any morphism of smooth

\bf\it\bar R

-algebras

{\it\bar a} : {\bf\it\bar A} \rightarrow {\bf\it\bar B}

, there exist a morphism of smooth

R

-algebras

{\it a} : {\bf\it A} \rightarrow {\bf\it B}

such that

{\bf 1} \otimes {\it a} : {\bf\it\bar R} \otimes {\bf\it A} \rightarrow {\bf\it\bar R} \otimes {\bf\it B}

is isomorphic to

{\it\bar a} : {\bf\it\bar A} \rightarrow {\bf\it\bar B}

. As a corollary, when

R

is noetherian, we show that for any smooth

\bf\it\bar R

-algebra

\bf\it\bar A

there exist a very smooth weakly complete algebra

{\bf\it A}^\dagger

over

R

such that

{\bf\it\bar R} \otimes {\bf\it A}^\dagger

is isomorphic to

\bf\it\bar A

.

Soient

R

un anneau commutatif et

I

un idéal de

R

, notons

{\bf\it\bar R} : = {\bf\it R} / {\bf\it I}

. Nous prouvons que pour toute

\bf\it\bar R

-algèbre lisse

\bf\it\bar A

, il existe une

R

-algèbre lisse

A

telle que

\bf\it\bar A

est isomorphe à

{\bf\it\bar R} \otimes_{\bf\it R} {\bf\it A}

. Nous prouvons également que pour tout morphisme de

\bf\it\bar R

-algèbres lisses

{\it\bar a} : {\bf\it\bar A} \rightarrow {\bf\it\bar B}

, il existe un morphisme de

R

-algèbres lisses

{\it a} : {\bf\it A} \rightarrow {\bf\it B}

tel que

{\bf 1} \otimes {\it a} : {\bf\it\bar R} \otimes {\bf\it A} \rightarrow {\bf\it\bar R} \otimes {\bf\it B}

est isomorphe à

{\it\bar a} : {\bf\it\bar A} \rightarrow {\bf\it\bar B}

. On en déduit, lorsque

R

est nmthérien, que pour toute

\bf\it\bar R

-algèbre lisse

\bf\it\bar A

, il existe une

R

-algèbre faiblement complète très lisse

{\bf\it A}^\dagger

telle que

{\bf\it\bar R} \otimes {\bf\it A}^\dagger

est isomorphe à

\bf\it\bar A

.
The Rost invariant has trivial kernel for quasi-split groups of low rank
Authors: Garibaldi R. S.
Published: December 2002

For G a simple simply connected algebraic group defined over a field F, Rost has shown that there exists a canonical map

R_G : H^1(F, G) \rightarrow H^3(F, \mathbb{Q} / \mathbb{Z}(2))

. This includes the Arason invariant for quadratic forms and Rost's mod 3 invariant for exceptional Jordan algebras as special cases. We show that RG has trivial kernel if G is quasi-split of type E6 or E7. A case-by-case analysis shows that it has trivial kernel whenever G is quasi-split of low rank.
Invariant measure and Lyapunov exponents for birational maps of P^2
Authors: Diller Jeffrey
Published: December 2002

In this paper we construct and study a natural invariant measure for a birational self-map of the complex projective plane. Our main hypothesis - that the birational map be "separating" - is a condition on the indeterminacy set of the map. We prove that the measure is mixing and that it has distinct Lyapunov exponents. Under a further hypothesis on the indeterminacy set we show that the measure is hyperbolic in the sense of Pesin theory. In this case, we also prove that saddle periodic points are dense in the support of the measure.
Pincement de polynômes
Authors: Haïssinsky Peter
Published: December 2002

Let

f_{0} : \mathbb{C} \to \mathbb{C}

be a semi-hyperbolic polynomial in the sense of Carleson-Jones-Yoccoz with an attracting point. The goal of this paper is to show that one can define a semi-hyperbolic deformation

(f_{t})_{t\ge 0}

such that the attracting cycle becomes parabolic for the limit polynomial

f_{\infty}

and that

f_{0}

and

f_{\infty}

are semi-conjugate. This deformation is defined by pinching curves in appropriate quotient spaces.
Harmonic forms and near-minimal singular foliations
Authors: Katz G.
Published: December 2002

For a closed 1-form

\omega

with Morse singularities, Calabi discovered a simple global criterion for the existence of a Riemannian metric in which

\omega

is harmonic. For a codimension 1 foliation

\cal {F}

, Sullivan gave a condition for the existence of a Riemannian metric in which all the leaves of

\cal {F}

are minimal hypersurfaces. The conditions of Calabi and Sullivan are strikingly similar. If a closed form

\omega

has no singularities, then both criteria are satisfied and, for an appropriate choice of metric,

\omega

is harmonic and the associated foliation

\cal {F}_\omega

is comprised of minimal leaves. However, when

\omega

has singularities, the foliation

\cal {F}_\omega

is not necessarily minimal.¶ We show that the Calabi condition enables one to find a metric in which

\omega

is harmonic and the leaves of the foliation are minimal outside a neighborhood U of the

\omega

-singular set. In fact, we prove the best possible result of this type: we construct families of metrics in which, as U shrinks to the singular set, the taut geometry of the foliation

\cal {F}_\omega

outside U remains stable. Furthermore, all compact leaves missing U are volume minimizing cycles in their homology classes. Their volumes are controlled explicitly.
On the Haefliger-Hirsch-Wu invariants for embeddings and immersions
Authors: Skopenkov A.
Published: December 2002

We prove beyond the metastable dimension the PL cases of the classical theorems due to Haefliger, Harris, Hirsch and Weber on the deleted product criteria for embeddings and immersions. The isotopy and regular homotopy versions of the above theorems are also improved. We show by examples that they cannot be improved further. These results have many interesting corollaries, e.g. 1) Any closed homologically 2-connected smooth 7-manifold smoothly embeds in

\mathbb{R}^11

. 2) If

p \leq q

and

m \geq \frac{3q}2 + p + 2

then the set of PL embeddings

S^{p} \times S^{q} \to \mathbb{R}^m

up to PL isotopy is in 1-1 correspondence with

\pi_q(V_{m-q,p+1})\oplus\pi_p(V_{m-p,q+1})

.
Relations among the lowest degree of the Jones polynomial and geometric invariants for a closed positive braid
Authors: Kawamura Takashi
Published: December 2002

By means of a result due to Fiedler, we obtain a relation between the lowest degree of the Jones polynomial and the unknotting number for any link which has a closed positive braid diagram. Furthermore, we obtain relations between the lowest degree and the slice euler characteristic or the four-dimensional clasp number.
GW invariants and invariant quotients
Authors: Halic M.
Published: December 2002

Given a complex, projective variety and a connected, reductive group acting on it, we investigate the relationship between the Gromov-Witten invariants of the variety and those of its invariant quotient for the group action. Certain so-called Hamiltonian invariants naturally appear in the context.
Kodaira dimensions and hyperbolicity of nonpositively curved compact Kähler manifolds
Authors: Zheng Fangyang
Published: December 2002

In this article, we prove that a compact Kähler manifold M n with real analytic metric and with nonpositive sectional curvature must have its Kodaira dimension, its Ricci rank and the codimension of its Euclidean de Rham factor all equal to each other. In particular, M n is of general type if and only if it is without flat de Rham factor. By using a result of Lu and Yau, we also prove that for a compact Kähler surface M 2 with nonpositive sectional curvature, if M 2 is of general type, then it is Kobayashi hyperbolic.
Closed incompressible surfaces in the complements of positive knots
Authors: Ozawa M.
Published: December 2002

We show that any closed incompressible surface in the complement of a positive knot is algebraically non-split from the knot, positive knots cannot bound non-free incompressible Seifert surfaces and that the splittability and the primeness of positive knots and links can be seen from their positive diagrams.
Some properties of locally conformal symplectic structures
Authors: Banyaga A.
Published: December 2002

We show that the

d_{\omega}

-cohomology is isomorphic to a conformally invariant usual de Rham cohomology of an appropriate cover. We also prove a Moser theorem for locally conformal symplectic (lcs) forms. We point out a connection between lcs geometry and contact geometry. Finally, we show the connections between first kind, second kind, essential, inessential, local, and global conformal symplectic structures through several invariants.
Foliations, topology and geometry of 3-manifolds: R-covered foliations and transverse pseudo-Anosov flows
Authors: Fenley Sérgio R.
Published: December 2002

We analyse the topological and geometrical behavior of foliations on 3-manifolds. We consider the transverse structure of an R-covered foliation in a 3-manifold, where R-covered means that in the universal cover the leaf space of the foliation is Hausdorff. If the manifold is aspherical we prove that either there is an incompressible torus in the manifold; or there is a transverse pseudo-Anosov flow. It follows that manifolds with R-covered foliations satisfy the weak hyperbolization conjecture.
A perturbative SU(3) Casson invariant
Authors: Cappell Sylvain , Lee R. , Miller E. Y.
Published: December 2002

A perturbative SU(3) Casson invariant

\Lambda_{SU(3)}(X)

for integral homology 3-sphere is defined. Besides being fully perturbative, it has the nice properties: (1)

4\cdot \Lambda_{SU(3)}

is an integer. (2) It is preserved under orientation change. (3) A connect sum formula. Explicit calculations of the invariant for 1/k surgery of (2, q) torus knot are presented and compared with Boden-Herald‘s different SU(3) generalization of Casson‘s invariant. For those cases computed, the invariant defined here is a quadratic polynomial in k for k > 0 and a different quadratic polynomial for k < 0.
On the dynamics of certain actions of free groups on closed real analytic manifolds
Authors: Belliart Michel
Published: December 2002

Let M be a closed connected real analytic manifold; let

\Gamma

be a free group on two generators. The set of analytic actions of

\Gamma

on M endowed with Taken‘s topology contains a nonempty open subset whose corresponding actions share three properties: (a) they have every orbit dense, (b) they leave invariant no geometric structure on M, (c) any homeomorphism conjugating two of them is analytic.
Divergence exponentielle des sous-groupes discrets en rang supérieur
Authors: Quint Jean-François
Published: December 2002

Soient G un groupe de Lie semi-simple, réel, connexe et de centre fini,

\mathfrak a

un sous-espace de Cartan de l‘algèbre de Lie de G et

\mathfrak a^{+} \subset \mathfrak a

une chambre de Weyl fermée de

\mathfrak a

. Si

\Gamma

est un sous-groupe discret Zariski dense de G, nous lui associons une fonction homogène

\psi_{\Gamma} : \mathfrak a^{+} \rightarrow \mathbb {R} \cup \{-\infty\}

qui généralise l‘exposant de convergence de

\Gamma

considéré en

\mathbb {R}

-rang 1. Nous montrons alors que cette fonction est concave. Dans un travail ultérieur, nous en déduirons des constructions de généralisations des mesures de Patterson-Sullivan. Nous démontrons aussi des analogues de nos résultats sur les corps locaux.
Artin monoids inject in their groups
Authors: Paris Luis
Published: December 2002

We prove that the natural homomorphism from an Artin monoid to its associated Artin group is always injective.
Perceived Genetic Risks for Bipolar Disorder in a Patient Population: An Exploratory Study
Authors: Quaid Kimberly A. , Aschen Sharon R. , Smiley Carrie L. , Nurnberger John I.
Published: December 2002

Thirty‐one subjects with bipolar illness completed a questionnaire about genetic risk for bipolar disorder. Subjects estimated both quantitative and qualitative genetic risk for bipolar disorder for the following categories: general population, siblings, parents, spouses, and children. Results showed that quantitative risks were inflated when compared to qualitative risks and that subjects routinely overestimated the risk for developing bipolar illness. These findings suggest that genetic counseling may be useful for this population.
Tectonic evolution of the Pacific margin of Antarctica 1. Late Cretaceous tectonic reconstructions
Authors: Larter Robert D. , Cunningham Alex P. , Barker Peter F. , Gohl Karsten , Nitsche Frank O.
Published: December 2002

We present new Late Cretaceous tectonic reconstructions of the Pacific margin of Antarctica based on constraints from marine magnetic data and regional free‐air gravity fields. Results from interpretation of new seismic reflection and gravity profiles collected in the Bellingshausen Sea are also incorporated in the reconstructions. The reconstructions show regional constraints on tectonic evolution of the Bellingshausen and Amundsen Seas following the breakup between New Zealand and West Antarctica. The breakup began at c. 90 Ma with the separation of Chatham Rise, probably accompanied by the opening of the Bounty Trough. Campbell Plateau separated from West Antarctica later, during chron 33r (83.0–79.1 Ma). A free‐air gravity lineation northeast of Chatham Rise represents the trace of a triple junction that formed as a result of fragmentation of the Phoenix plate a few million years before Chatham Rise separated from West Antarctica. Remnants of the western fragment, the Charcot plate, are preserved in the Bellingshausen Sea. Subduction of the Charcot plate stopped before 83 Ma, and part of it became coupled to the Antarctic Peninsula across the stalled subduction zone. Subsequent convergence at the western margin of this captured ocean floor produced the structures that are the main cause of the Bellingshausen gravity anomaly. Part of a spreading ridge at the western boundary of the Phoenix plate (initially Charcot–Phoenix, evolving into Marie Byrd Land–Phoenix, and eventually Bellingshausen–Phoenix (BEL–PHO)) probably subducted obliquely beneath the southern Antarctic Peninsula during the Late Cretaceous. All of the Phoenix plate ocean floor subducted at the Antarctic Peninsula margin during the Late Cretaceous was probably <14 Myr old when it reached the trench. Several observations suggest that independent Bellingshausen plate motion began near the end of chron 33n (73.6 Ma). Reconstructions in which part of the West Antarctic continental margin, including Thurston Island, is assumed to have been within the Bellingshausen plate seem more plausible than ones in which the plate is assumed to have been entirely oceanic.
Estimation of cirrus cloud effective ice crystal shapes using visible reflectances from dual‐satellite measurements
Authors: Chepfer Helene , Minnis Patrick , Young David , Nguyen Louis , Arduini Robert F.
Published: December 2002

This study develops and examines a multiangle, multisatellite method for determining effective cloud particle shapes from reflectances observed at visible wavelengths. The technique exploits the significant differences in the various cloud particle shape phase functions near the backscatter direction to infer particle shape from a combination of views from a near‐backscatter angle and a side scattering angle. Adding‐doubling calculations confirm that the optimal viewing combinations include one near‐backscatter angle and another between 60° and 150°. Sensitivity to shape increases with solar zenith angle. A total of 28 collocated, visible images from pairs of currently operating meteorological satellites with the desired viewing combinations were analyzed for particle shape. Matching reflectances from images with optimal viewing angles clearly separates water droplet from ice crystal clouds. Reflectance pairs from matched pixels containing ice crystals can be explained by the range of selected microphysical models. The most common retrieved shapes correspond to combinations of hexagonal compacts (aspect ratio of unity), hexagonal columns, and bullet rosettes. Although no single microphysical model can account for the observed variability, taken together, the models used for retrieving cloud particle size by the Clouds and the Earth's Radiant Energy System and the Moderate Resolution Imaging Spectroradiometer Projects can account for most of the reflectance variability observed in this limited data set. Additional studies are needed to assess the uncertainties in retrieved shapes due to temporal and spatial mismatches, anisotropic and bright background reflectances, and calibration errors and to validate the retrieved shapes. While applicable to a limited number of dual‐satellite viewing combinations for current research and operational meteorological satellites, this approach could be used most extensively to derive effective particle size, shape, and optical depth from a combination of an imaging satellite in an L1 orbit, like Triana, and any other lower Earth orbiting satellites.
Volatile organic compound emissions in relation to plant carbon fixation and the terrestrial carbon budget
Authors: Kesselmeier Jürgen , Ciccioli Paolo , Kuhn Uwe , Stefani Paolo , Biesenthal Thomas , Rottenberger Stefanie , Wolf Annette , Vitullo Marina , Valentini Ricardo , Nobre Antonio , Kabat Pavel , Andreae Meinrat O.
Published: December 2002

A substantial amount of carbon is emitted by terrestrial vegetation as biogenic volatile organic compounds (VOC), which contributes to the oxidative capacity of the atmosphere, to particle production and to the carbon cycle. With regard to the carbon budget of the terrestrial biosphere, a release of these carbon compounds is regarded as a loss of photosynthetically fixed carbon. The significance of this loss for the regional and global carbon cycles is controversial. We estimate the amount of VOC carbon emitted in relation to the CO2 taken up, based on our own enclosure and micrometeorological flux measurements of VOC emissions and CO2 exchange within the Mediterranean area and the tropical rainforest in Amazonia and on literature data. While VOC flux estimates are small in relation to net primary productivity and gross primary productivity, the amount of carbon lost as VOC emissions can be highly significant relative to net ecosystem productivity. In fact, VOC losses are of the same order of magnitude as net biome productivity. Although we must assume that large amounts of these reemissions are recycled within the biosphere, a substantial part can be assumed to be lost into longer‐lived oxidation products that are lost from the terrestrial biosphere by transport. However, our current knowledge does not allow a reliable estimation of this carbon loss.
Latitudinal change of remineralization ratios in the oceans and its implication for nutrient cycles
Authors: Li Yuan‐Hui , Peng Tsung‐Hung
Published: December 2002

A new three‐end‐member mixing model is introduced to obtain remineralization ratios of organic matter in the water column. Remineralization ratios (P/N/Corg/−O2) of organic matter in the deep water column change systematically from the northern Atlantic to the Southern Oceans, then to the equatorial Indian and the northern Pacific oceans, more or less along the global ocean circulation route of deep water. Average remineralization ratios of organic matter for the northern Atlantic Ocean are P/N/Corg/−O2 = 1/(16 ± 1)/(73 ± 8)/(137 ± 7), and for the Southern Oceans P/N/Corg/−O2 = 1/(15 ± 1)/(80 ± 3)/(133 ± 5). Those values are similar to the traditional Redfield ratios of P/N/Corg/−O2 = 1/16/106/138 for marine plankton, except for the low Corg/P ratio. Average remineralization ratios for the equatorial Indian Ocean are P/N/Corg/−O2 = 1/(10 ± 1)/(94 ± 5)/(130 ± 7), and for the northern Pacific Ocean P/N/Corg/−O2 = 1/(13 ± 1)/(124 ± 11)/(162 ± 11). The apparent low N/P ratio for both ocean basins suggests that organic nitrogen was converted partly into gaseous N2O and N2 by bacteria through nitrification/denitrification processes in a low‐oxygen or reducing microenvironment of organic matter throughout the oxygenated water column. The actual N/P ratio of remineralized organic matter is probably around 15 ± 1. The −O2/Corg ratio of remineralized organic matter also decreases systematically along the global ocean circulation route of deep water, indicating changes in relative proportions of biomolecules such as lipids, proteins, nucleic acids, and carbohydrates. No temporal trends of remineralization ratios are detected when comparing the results obtained by GEOSECS and WOCE data sets.
Relationship between surface reflectance in the visible and mid‐IR used in MODIS aerosol algorithm ‐ theory
Authors: Kaufman Yoram J. , Gobron Nadine , Pinty Bernard , Widlowski Jean‐Luc , Verstraete Michel M.
Published: December 2002

Data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument that flies in polar orbit on the Terra and Aqua satellites, are used to derive the aerosol optical thickness and properties over land and ocean. The relationships between visible reflectance (at blue, ρblue, and red, ρred), and mid‐infrared (at 2.1 μm, ρ2.1) are used in the MODIS aerosol retrieval algorithm to derive global distribution of aerosols over land. These relations have been established from a series of measurements indicating that ρblue ∼ 0.5 ρred ∼ 0.25 ρ2.1. Here we use a model to describe the transfer of radiation through a vegetation canopy composed of randomly oriented leaves to assess the theoretical foundations for these relationships. Calculations for a wide range of leaf area indices and vegetation fractions show that ρblue is consistently about 1/4 of ρ2.1 as used by MODIS for the whole range of analyzed cases, except for very dark soils, such as those found in burn scars. For its part, the ratio ρred/ρ2.1 varies from less than the empirically derived value of 1/2 for dense and dark vegetation, to more than 1/2 for bright mixture of soil and vegetation. This is in agreement with measurements over uniform dense vegetation, but not with measurements over mixed dark scenes. In the later case, the discrepancy could be probably mitigated by shadows due to uneven canopy and terrain on a large scale.
A simulation study of space‐based observations of gravity waves in the airglow using observed ALOHA‐93 wave parameters
Authors: Hickey M. P. , Brown J. S.
Published: December 2002

We use gravity wave parameters derived from the ALOHA‐93 campaign to model four gravity waves in airglow emissions as observed from the ground to numerically predict whether these waves could have been observed from space. In spite of encountering critical levels, some waves may still be observed in the airglow provided the critical level lies within the airglow emission region. One of the four waves experiences a critical level in the lower region of an airglow layer such that the disturbance to the volume emission rate would be effectively limited to a short distance along a satellite line of sight. The effect of this is to mitigate the effects of destructive interference in the airglow making the wave more observable from space. For this particular wave the amplitude is derived by normalizing the model‐derived airglow fluctuation amplitude to that observed from the ground during the ALOHA‐93 campaign. The model then provides momentum and energy fluxes as a function of height as well as the flux divergences, from which the mean state forcing is evaluated. The results suggest that the observed wave could provide significant mean state forcing. Therefore, we conclude that some waves experiencing critical level interactions in the airglow regions are not only likely to be important to the momentum balance of the upper mesosphere/lower thermosphere region but also are more likely to be observed from space.
Microearthquakes on the Endeavour segment of the Juan de Fuca Ridge
Authors: Wilcock William S. D. , Archer Stephen D. , Purdy G. M.
Published: December 2002

We report the results of a 55‐day microearthquake experiment on the Endeavour segment of Juan de Fuca Ridge. The network covered a 5‐km section of the ridge axis centered on the Main vent field and extended 15‐km off axis on the west flank. The ridge axis and flanks were seismically active, and 1750 earthquakes were located with a minimum of five travel time picks including at least one S wave. Over half the earthquakes occurred in swarms, and a waveform cross‐correlation technique was used to obtain relative locations. On the western flank, the hypocenters for four swarms at midcrustal depths are compatible with steeply dipping fault planes that strike at 035–050°N and oblique to the abyssal hills. Focal mechanisms determined from P wave first motions and P/S amplitude ratios are predominantly strike‐slip with north‐south compression and appear to be affected by the reorganization of the Explorer plate. Earthquakes beneath the ridge axis are concentrated in a band of intense seismicity at 1.5–3.5 km depth. To the north of High Rise vent field, the seismicity defines a plane striking parallel to the ridge axis and dipping east at 70° and the earthquakes appear to extend beneath an axial reflector previously imaged at 2.3 km depth. Farther south, the hypocenters are not compatible with a single fault plane. Focal mechanisms are characterized by subhorizontal tension axes oriented in all directions except parallel to the ridge and suggest a stress field that is about equally influenced by ridge spreading and hydrothermal cooling.
Cyclostratigraphy and rock‐magnetic investigation of the NRM signal in late Miocene palustrine‐alluvial deposits of the Librilla section (SE Spain)
Authors: Kruiver Pauline P. , Krijgsman Wout , Langereis Cor G. , Dekkers Mark J.
Published: December 2002

We constructed a high‐resolution time frame for the cyclic continental palustrine‐alluvial section of Librilla (SE Spain) which covers the onset of the Messinian salinity crisis in the marine realm. The section was dated earlier by Garcés et al. [1998], using magnetostratigraphy. We resampled part of the section that contained a reversed overprint in detail to refine the magnetostratigraphy and to investigate the behavior of the natural remanent magnetization (NRM) signal. The detailed sampling yielded a better constrained position of the upper reversal of Chron C3An.1n. By counting the number of cycles in C3An.1n and taking into account the duration of this Chron, we were able to show that the basic sedimentary cycles in Librilla reflect climatic precession. Subsequently, the sedimentary pattern was tuned to the summer insolation curve, providing a high‐resolution time. Two intervals of complex NRM behavior were identified, showing normal and reversed overprints. The reversed overprints seemed to be restricted mainly to gray palustrine layers. The analysis of coercivity components revealed no difference between samples with overprints or real NRM directions. We performed fuzzy c‐means cluster analysis on a geochemical data set to link magnetic behavior to geochemical proxies, resulting in a three‐cluster model that roughly describes lithology. Remarkably, all the samples with a normal overprint belong to one particular cluster. The reversed overprints, however, do not show any relation to the cluster partition. We favor the explanation of Garcés et al. [1998] that the reversed overprint would be related to the Messinian salinity crisis.
Parameterization of a spectral solar irradiance model for the global ocean using multiple satellite sensors
Authors: Bouvet Marc , Hoepffner Nicolas , Dowell Mark D.
Published: December 2002

Monthly and seasonal means of the spectral solar radiation at the sea surface is determined at global scale (1° × 1° grid) from satellite composite imagery. The transmittance functions of each atmospheric component have been modified from an existing clear‐sky radiative model to assimilate data sets from multiple satellite sensors, including the Sea‐viewing Wide Field‐of‐view Sensor (NASA). All satellite‐derived parameters and other climatologies were resampled at common scales in time and space, and a cloud correction scheme has been implemented by comparing two different methods based on ultraviolet reflectance from the Total Ozone Mapping Spectrometer (NASA) and cloud fraction from the Special Sensor Microwave Imager (NASA), respectively. The new “PARsat” model relies on a complete computation of the radiative transfer at each grid point, while being less dependent on some meteorological parameters that are often known at local scale only. Although PARsat is a full spectral model providing downwelling irradiance at daily scale and up, the model is applied for 1997 up to present, and only the results for 1998 are shown in this work as monthly global maps of surface photosynthetically active radiation (PAR). A comprehensive evaluation of the model is conducted through comparisons with monthly PAR values obtained globally with other well‐referenced models and with a large data set of in situ measurements. An overall uncertainty of 5.2% is obtained when the performance of the model is validated with in situ measurements collected from two array systems of moored buoys.
Comparison of POAM III ozone measurements with correlative aircraft and balloon data during SOLVE
Authors: Lumpe Jerry D. , Fromm Mike , Hoppel Karl , Bevilacqua Richard M. , Randall Cora E. , Browell Edward V. , Grant William B. , McGee Thomas , Burris John , Twigg Laurence , Richard Erik C. , Toon Geoffrey C. , Margitan James J. , Sen Bhaswar , Pfeilsticker Klaus , Boesch Hartmut , Fitzenberger Richard , Goutail Florence , Pommereau Jean‐Pierre
Published: December 2002

The Polar Ozone and Aerosol Measurement (POAM) III instrument operated continuously during the Stratospheric Aerosol and Gas Experiment (SAGE) III Ozone Loss and Validation Experiment (SOLVE) mission, making approximately 1400 ozone profile measurements at high latitudes both inside and outside the Arctic polar vortex. The wealth of ozone measurements obtained from a variety of instruments and platforms during SOLVE provided a unique opportunity to compare correlative measurements with the POAM III data set. In this paper, we validate the POAM III version 3.0 ozone against measurements from seven different instruments that operated as part of the combined SOLVE/THESEO 2000 campaign. These include the airborne UV Differential Absorption Lidar (UV DIAL) and the Airborne Raman Ozone and Temperature Lidar (AROTEL) instruments on the DC‐8, the dual‐beam UV‐Absorption Ozone Photometer on the ER‐2, the MkIV Interferometer balloon instrument, the Laboratoire de Physique Molèculaire et Applications and Differential Optical Absorption Spectroscopy (LPMA/DOAS) balloon gondola, the JPL in situ ozone instrument on the Observations of the Middle Stratosphere (OMS) balloon platform, and the Système D'Analyze par Observations Zénithales (SAOZ) balloon sonde. The resulting comparisons show a remarkable degree of consistency despite the very different measurement techniques inherent in the data sets and thus provide a strong validation of the POAM III version 3.0 ozone. This is particularly true in the primary 14–30 km region, where there are significant overlaps with all seven instruments. At these altitudes, POAM III agrees with all the data sets to within 7–10% with no detectable bias. The observed differences are within the combined errors of POAM III and the correlative measurements. Above 30 km, only a handful of SOLVE correlative measurements exist and the comparisons are highly variable. Therefore, the results are inconclusive. Below 14 km, the SOLVE comparisons also show a large amount of scatter and it is difficult to evaluate their consistency, although the number of correlative measurements is large. The UV DIAL, DOAS, and JPL/OMS comparisons show differences of up to 15% but no consistent bias. The ER‐2, MkIV, and SAOZ comparisons, on the other hand, indicate a high POAM bias of 10–20% at the lower altitudes. In general, the SOLVE validation results presented here are consistent with the validation of the POAM III version 3.0 ozone using SAGE II and Halogen Occultation Experiment (HALOE) satellite data and in situ electrochemical cell (ECC) ozonesonde data.
Seasonal variability of ozone mixing ratios and budgets in the tropical southern Pacific: A GCTM perspective
Authors: Wei C.‐F. , Kotamarthi V. R. , Ogunsola O. J. , Horowitz L. W. , Walters S. , Wuebbles D. J. , Avery M. A. , Blake D. R. , Browell E. V. , Sachse G. W.
Published: December 2002

Significant seasonal variations in the concentrations of several trace gases were observed in the southern tropical Pacific during the Pacific Exploratory Mission (PEM) TROPICS‐A (PT‐A, September/October 1996) and PEM TROPICS‐B (PT‐B, March/April 1999) campaigns. The objective of this study is to evaluate the relationship between the measured and modeled seasonal variabilities through comparisons of these observations with model calculations. A three‐dimensional (3‐D) global‐scale chemical transport model was employed to (1) evaluate the seasonal variations in ozone and CO mixing ratios; (2) calculate an ozone budget and identify its controlling factors; (3) evaluate the effectiveness of atmospheric transport barriers in the model, such as the Intertropical Convergence Zone (ITCZ); and (4) test the sensitivity of ozone over the tropical south Pacific to biomass‐burning emissions. The model reproduces the main features of the observed seasonal variation in ozone and CO. According to the model calculation, the ozone burden during the PT‐A was larger due to the transport of ozone into the central pacific middle troposphere from the west, whereas a net outflow of ozone from this region to the east resulted in a reduction of ozone burden during the PT‐B period. Transport of ozone from the Northern Hemisphere into this region was found to be much larger during the PT‐B period compared with the PT‐A period. The in situ production and loss of ozone calculated in the model agreed with that derived from measurements. The gradients in the model for selected trace gases across the ITCZ were shown to be qualitatively similar to measurements.
Comparison of ER‐2 aircraft and POAM III, MLS, and SAGE II satellite measurements during SOLVE using traditional correlative analysis and trajectory hunting technique
Authors: Danilin M. Y. , Ko M. K. W. , Bevilacqua R. M. , Lyjak L. V. , Froidevaux L. , Santee M. L. , Zawodny J. M. , Hoppel K. W. , Richard E. C. , Spackman J. R. , Weinstock E. M. , Herman R. L. , McKinney K. A. , Wennberg P. O. , Eisele F. L. , Stimpfle R. M. , Scott C. J. , Elkins J. W. , Bui T. V.
Published: December 2002

We compared the version 5 Microwave Limb Sounder (MLS), version 3 Polar Ozone and Aerosol Measurement III (POAM III), version 6.0 Stratospheric Aerosol and Gas Experiment II (SAGE II), and NASA ER‐2 aircraft measurements made in the Northern Hemisphere in January–February 2000 during the SAGE III Ozone Loss and Validation Experiment (SOLVE). This study addresses one of the key scientific objectives of the SOLVE campaign, namely, to validate multiplatform satellite measurements made in the polar stratosphere during winter. This intercomparison was performed by using a traditional correlative analysis (TCA) and a trajectory hunting technique (THT). TCA compares profiles colocated within a chosen spatial‐temporal vicinity. Launching backward and forward trajectories from the points of measurement, the THT identifies air parcels sampled at least twice within a prescribed match criterion during the course of 5 days. We found that the ozone measurements made by these four instruments agree most of the time within ±10% in the stratosphere up to 1400 K (∼35 km). The water vapor measurements from POAM III and the ER‐2 Harvard Lyman α hygrometer and Jet Propulsion Laboratory laser hygrometer agree to within ±0.5 ppmv (or about ±10%) in the lower stratosphere above 380 K. The MLS and ER‐2 ClO measurements agree within their error bars for the TCA. The MLS and ER‐2 nitric acid measurements near 17‐ to 20‐km altitude agree within their uncertainties most of the time with a hint of a positive offset by MLS according to the TCA. We also applied the Atmospheric and Environmental Research, Inc. box model constrained by the ER‐2 measurements for analysis of the ClO and HNO3 measurements using the THT. We found that: (1) the model values of ClO are smaller by about 0.3–0.4 (0.2) ppbv below (above) 400 K than those by MLS and (2) the HNO3 comparison shows a positive offset of MLS values by ∼1 and 1–2 ppbv below 400 K and near 450 K, respectively. Our study shows that, with some limitations (like HNO3 comparison under polar stratospheric cloud conditions), the THT is a more powerful tool for validation studies than the TCA, making conclusions of the comparison statistically more robust.
Effects of biomass burning, lightning, and convection on O3, CO, and NOy over the tropical Pacific and Australia in August–October 1998 and 1999
Authors: Kondo Y. , Koike M. , Kita K. , Ikeda H. , Takegawa N. , Kawakami S. , Blake D. , Liu S. C. , Ko M. , Miyazaki Y. , Irie H. , Higashi Y. , Liley B. , Nishi N. , Zhao Y. , Ogawa T.
Published: December 2002

In situ aircraft measurements of O3, CO, total reactive nitrogen (NOy), NO, and non‐methane hydrocarbons (NMHCs) were made over the western Pacific Ocean and Australia during the Biomass Burning and Lightning Experiment (BIBLE) A and B conducted in August–October 1998 and 1999. Generally, similar features were seen in the BIBLE A and B data in the latitudinal variations of these species in the troposphere from 35°N to 28°S at longitudes of 120°–150°E. The focus of this paper is to describe the characteristics of air masses sampled at 15°N–10°S (tropical Pacific) and 10°S–28°S (over Australia). With the exception of occasional enhancements in reactive nitrogen seen over New Guinea associated with lightning activities, the tropical Pacific region is distinguished from the rest of the region by smaller concentrations of these trace species. This can be explained in terms of the absence of surface sources over the ocean, lack of stratospheric intrusion, and the preclusion of midlatitude air and air from the west due to active convection throughout the troposphere. The median O3, CO, NOy, and NO mixing ratios in tropical air above 4 km were about 15–20 parts per billion by volume (ppbv), 60–75 ppbv, 20–100 parts per trillion by volume (pptv), and 5–40 pptv, respectively. Data obtained from PEM‐West A and B conducted in 1991 and 1994 showed similar latitudinal features, although the PEM‐West A values were somewhat elevated due to dominating westerly winds in the lower troposphere associated with El Niño. Over Australia, the levels of O3, CO, NOy, NO, and NMHCs were elevated throughout the troposphere over those observed in the tropical Pacific both in 1998 and 1999. The effect from biomass burning that occurred in northern Australia was limited to within the boundary layer because of strong subsidence in the period. Analyses based on 14‐day back trajectories identified free tropospheric air over Australia that originated from Indonesia, the Indian Ocean, Africa, and southern midlatitudes. The levels of O3, CO, NOy, and NMHCs in these air masses were much higher than those from the tropical Pacific due to their stronger sources from biomass burning and lightning. These values are compared with those obtained in the South Pacific during PEM‐Tropics A. Effects of biomass burning and lightning are discussed as possible sources of O3 and its precursors in these air masses.
Reactive nitrogen over the tropical western Pacific: Influence from lightning and biomass burning during BIBLE A
Authors: Koike M. , Kondo Y. , Kita K. , Nishi N. , Liu S. C. , Blake D. , Ko M. , Akutagawa D. , Kawakami S. , Takegawa N. , Zhao Y. , Ogawa T.
Published: December 2002

The Biomass Burning and Lightning Experiment phase A (BIBLE A) aircraft campaign was carried out over the tropical western Pacific in September and October 1998. During this period, biomass burning activity in Indonesia was quite weak. Mixing ratios of NOx and NOy in air masses that had crossed over the Indonesian islands within 3 days prior to the measurement (Indonesian air masses) were systematically higher than those in air masses originating from the central Pacific (tropical air masses). Sixty percent of the Indonesian air masses at 9–13 km (upper troposphere, UT) originated from the central Pacific. The differences in NOy mixing ratio between these two types of air masses were likely due to processes that occurred while air masses were over the Islands. Evidence presented in this paper suggests convection carries material from the surface, and NO is produced from lightning. At altitudes below 3 km (lower troposphere, LT), typical gradient of NOx and NOy to CO (dNOy/dCO and dNOx/dCO) was smaller than that in the biomass burning plumes and in urban areas, suggesting that neither source has a dominant influence. When the CO‐NOx and CO‐NOy relationships in the UT are compared to the reference relationships chosen for the LT, the NOx and NOy values are higher by 40–60 pptv (80% of NOx) and 70–100 pptv (50% of NOy). This difference is attributed to in situ production of NO by lightning. Analyses using air mass trajectories and geostationary meteorological satellite (GMS) derived cloud height data show that convection over land, which could be accompanied by lightning activity, increases the NOx values, while convection over the ocean generally lowers the NOx level. These processes are found to have a significant impact on the O3 production rate over the tropical western Pacific.
Soil surface CO2 flux in a boreal black spruce fire chronosequence
Authors: Wang Chuankuan , Bond‐Lamberty Ben , Gower Stith T.
Published: December 2002

Understanding the effects of wildfire on the carbon (C) cycle of boreal forests is essential to quantifying the role of boreal forests in the global carbon cycle. Soil surface CO2 flux (Rs), the second largest C flux in boreal forests, is directly and indirectly affected by fire and is hypothesized to change during forest succession following fire. The overall objective of this study was to measure and model Rs for a black spruce (Picea mariana [Mill.] BSP) postfire chronosequence in northern Manitoba, Canada. The experiment design was a nested factorial that included two soil drainage classes (well and poorly drained) × seven postfire aged stands. Specific objectives were (1) to quantify the relationship between Rs and soil temperature for different aged boreal black spruce forests in well‐drained and poorly drained soil conditions, (2) to examine Rs dynamics along postfire successional stands, and (3) to estimate annual soil surface CO2 flux for these ecosystems. Soil surface CO2 flux was significantly affected by soil drainage class (p = 0.014) and stand age (p = 0.006). Soil surface CO2 flux was positively correlated to soil temperature (R2 = 0.78, p < 0.001), but different models were required for each drainage class × aged stand combination. Soil surface CO2 flux was significantly greater at the well‐drained than the poorly drained stands (p = 0.007) during growing season. Annual soil surface CO2 flux for the 1998, 1995, 1989, 1981, 1964, 1930, and 1870 burned stands averaged 226, 412, 357, 413, 350, 274, and 244 g C m‐2 yr−1 in the well‐drained stands and 146, 380, 300, 303, 256, 233, and 264 g C m−2 yr−1 in the poorly drained stands. Soil surface CO2 flux during the winter (from 1 November to 30 April) comprised from 5 to 19% of the total annual Rs. We speculate that the smaller soil surface CO2 flux in the recently burned than the older stands is mainly caused by decreased root respiration.