scholarly journals Three-Dimensional Structure and Dynamics of African Easterly Waves. Part I: Observations

2006 ◽  
Vol 63 (9) ◽  
pp. 2212-2230 ◽  
Author(s):  
George N. Kiladis ◽  
Chris D. Thorncroft ◽  
Nicholas M. J. Hall
Keyword(s):  
West Africa ◽  
Three Dimensional ◽  
Companion Paper ◽  
Radiosonde Data ◽  
Dimensional Structure ◽  
African Easterly Waves ◽  
Three Dimensional Structure ◽  
Easterly Waves ◽  
The Mean ◽  
The Waves

Abstract The mean structure of African easterly waves (AEWs) over West Africa and the adjacent Atlantic is isolated by projecting dynamical fields from reanalysis and radiosonde data onto space–time-filtered satellite-derived outgoing longwave radiation. These results are compared with previous studies and an idealized modeling study in a companion paper, which provides evidence that the waves bear a close structural resemblance to the fastest-growing linear normal mode of the summertime basic-state flow over Africa. There is a significant evolution in the three-dimensional structure of AEWs as they propagate along 10°N across West Africa. At this latitude, convection occurs in northerly flow to the east of the Greenwich meridian, then shifts into the wave trough, and finally into southerly flow as the waves propagate offshore into the Atlantic ITCZ. In contrast, to the north of the African easterly jet along 15°N convection remains in southerly flow throughout the waves’ trajectory. Along 10°N over West Africa, the location of convection is consistent with the adiabatic dynamical forcing implied by the advection of perturbation vorticity by the mean thermal wind in the zonal direction, as in the companion paper. Offshore, and along 15°N, the relationship between the convection and dynamics is more complex, and not as easily explained in terms of dynamical forcing alone.

scholarly journals Three-Dimensional Structure and Dynamics of African Easterly Waves. Part II: Dynamical Modes

2006 ◽  
Vol 63 (9) ◽  
pp. 2231-2245 ◽  
Author(s):  
Nicholas M. J. Hall ◽  
George N. Kiladis ◽  
Chris D. Thorncroft
Keyword(s):  
Baroclinic Instability ◽  
Initial Perturbation ◽  
Three Dimensional ◽  
Normal Modes ◽  
Phase Relationship ◽  
Companion Paper ◽  
Dimensional Structure ◽  
African Easterly Waves ◽  
Easterly Waves ◽  
Basic States

Abstract A primitive equation model is used to study the linear normal modes of the African easterly jet (AEJ). Reanalysis data from the summertime mean (June–September; JJAS) flow is used to provide zonally uniform and wavy basic states. The structure and growth rates of modes that grow over West Africa on these basic states are analyzed. For zonally uniform basic states, the modes resemble African easterly waves (AEWs) as in many previous studies, but they are quite baroclinic and surface intensified. For wavy basic states the modes have a longitudinal structure determined by the AEJ. They have a surface-intensified baroclinic structure upstream and a deep barotropic structure downstream, as confirmed by energy conversion diagnostics. These modes look remarkably similar to the composite easterly wave structures found by the authors in a companion paper. The similarity extends to the phase relationship of vertical velocity with streamfunction, which resembles OLR composites, suggesting a dynamical influence on convection. Without damping, the mode for the wavy basic state has a growth rate of 0.253 day−1. With a reasonable amount of low-level damping this mode is neutralized. It has a period of 5.5 days and a wavelength of about 3500 km. Further results with monthly mean basic states show slight variations, as the wave packet essentially follows displacements of the jet core. Experiments focused on specific active and passive years for easterly waves (1988 and 1990) do not yield significantly different results for the modes. These results, and in particular, the stability of the system, lead to the conclusion that barotropic–baroclinic instability alone cannot explain the initiation and intermittence of AEWs, and a finite-amplitude initial perturbation is required.

scholarly journals 5-Bromo-1-methylindoline-2,3-dione

IUCrData ◽  
2016 ◽  
Vol 1 (5) ◽  
Author(s):  
Yassine Kharbach ◽  
Amal Haoudi ◽  
Frédéric Capet ◽  
Ahmed Mazzah ◽  
Lahcen El Ammari
Keyword(s):  
Hydrogen Bonds ◽  
Title Compound ◽  
Three Dimensional ◽  
Ring System ◽  
Dimensional Structure ◽  
Three Dimensional Structure ◽  
Π Interactions ◽  
Compound C ◽  
Centroid Distance ◽  
The Mean

In the title compound, C9H6BrNO2, the indoline ring system, the two ketone O atoms and the Br atom are nearly coplanar, with the largest deviation from the mean plane being −0.1025 (4) Å. In the crystal, molecules are linked by two weak C—H...O hydrogen bonds and π–π interactions [inter-centroid distance = 3.510 (2) Å], forming a three-dimensional structure.

scholarly journals 8-Hydroxy-3,4-bis(4-methoxyphenyl)-1H-isochromen-1-one

IUCrData ◽  
2017 ◽  
Vol 2 (4) ◽  
Author(s):  
Sivakalai Mayakrishnan ◽  
Y. Arun ◽  
Narayanan Uma Maheswari
Keyword(s):  
Hydrogen Bonds ◽  
Title Compound ◽  
Three Dimensional ◽  
Ring System ◽  
Dimensional Structure ◽  
Three Dimensional Structure ◽  
Π Interactions ◽  
Compound C ◽  
Benzene Rings ◽  
The Mean

In the title compound, C23H18O5, the two methoxy-substituted benzene rings are inclined to one another by 67.0 (2)° and to the mean plane of the 1H-isochromene ring system by 67.21 (16) and 27.61 (17)°. There is an intramolecular C—H...π interaction present involving the two 4-methoxyphenyl rings. In the crystal, molecules are linked by O—H...O hydrogen bonds, forming chains propagating along the [301] direction. The chains are linked by a number of C—H...π interactions, forming a three-dimensional structure.

scholarly journals 5-Chloro-2-(2-fluorophenyl)-7-methyl-3-methylsulfinyl-1-benzofuran

2014 ◽  
Vol 70 (6) ◽  
pp. o706-o706
Author(s):  
Hong Dae Choi ◽  
Uk Lee
Keyword(s):  
Hydrogen Bonds ◽  
Dihedral Angle ◽  
Title Compound ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Three Dimensional Structure ◽  
Π Interactions ◽  
Compound C ◽  
The Mean

In the title compound, C16H12ClFO2S, the dihedral angle between the mean planes of the benzofuran and 2-fluorophenyl rings is 34.85 (6)°. In the crystal, molecules are linkedviapairs of C—H...O hydrogen bonds, forming zigzag chains along [001]. The chains are linked by C—H...π interactions, forming a three-dimensional structure.

scholarly journals Crystal structure of dimethomorph

2015 ◽  
Vol 71 (9) ◽  
pp. o654-o654
Author(s):  
Gihaeng Kang ◽  
Jineun Kim ◽  
Eunjin Kwon ◽  
Tae Ho Kim
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Dihedral Angles ◽  
Three Dimensional Structure ◽  
Π Interactions ◽  
Compound C ◽  
The Mean

In the title compound, C21H22ClNO4[systematic name: (E)-3-(4-chlorophenyl)-3-(3,4-dimethoxyphenyl)-1-(morpholin-4-yl)prop-2-en-1-one], which is the morpholine fungicide dimethomorph, the dihedral angles between the mean planes of the central chlorophenyl and the terminal benzene and morpholine (r.m.s. deviation = 0.2233 Å) rings are 71.74 (6) and 63.65 (7)°, respectively. In the crystal, molecules are linkedviaC—H...O hydrogen bonds and weak Cl...π interactions [3.8539 (11) Å], forming a three-dimensional structure.

scholarly journals Crystal structure of a photobiologically active furanocoumarin fromArtemisia reticulata

2016 ◽  
Vol 72 (4) ◽  
pp. 463-466
Author(s):  
A. K. Bauri ◽  
Sabine Foro ◽  
Nhu Quynh Nguyen Do
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Torsion Angle ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Asymmetric Unit ◽  
Three Dimensional Structure ◽  
Π Interactions ◽  
The Mean ◽  
Independent Molecules

The title furanocoumarin, C14H12O4[systematic name: 9-hydroxy-2-(prop-1-en-2-yl)-2,3-dihydro-7H-furo[3,2-g]chromen-7-one], crystallizes with two independent molecules (AandB) in the asymmetric unit. The two molecules differ essentially in the orientation of the propenyl group with respect to the mean plane of the furanocoumarin moiety; the O—C(H)—C=C torsion angle is 122.2 (7)° in moleculeAand −10.8 (11)° in moleculeB. In the crystal, theAandBmolecules are linkedviaO—H...O hydrogen bonds, forming zigzag –A–B–A–B– chains propagating along [001]. The chains are reinforced by bifurcated C—H...(O,O) hydrogen bonds, forming ribbons which are linkedviaC—H...π and π–π interactions [intercentroid distance = 3.602 (2) Å], forming a three-dimensional structure.

scholarly journals Crystal structures of 2-methoxyisoindoline-1,3-dione, 1,3-dioxoisoindolin-2-yl methyl carbonate and 1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-2-yl methyl carbonate: three anticonvulsant compounds

2014 ◽  
Vol 70 (12) ◽  
pp. 456-461
Author(s):  
Fortune Ezemobi ◽  
Henry North ◽  
Kenneth R. Scott ◽  
Anthohy K. Wutoh ◽  
Ray J. Butcher
Keyword(s):  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Dihedral Angles ◽  
Three Dimensional Structure ◽  
Π Interactions ◽  
Centroid Distance ◽  
Methyl Carbonate ◽  
The Mean ◽  
Isoquinoline Derivative

The title compounds, C9H7NO3, (1), C10H7NO5, (2), and C14H9NO5, (3), are three potentially anticonvulsant compounds. Compounds (1) and (2) are isoindoline derivatives and (3) is an isoquinoline derivative. Compounds (2) and (3) crystallize with two independent molecules (AandB) in their asymmetric units. In all three cases, the isoindoline and benzoisoquinoline moieties are planar [r.m.s. deviations are 0.021 Å for (1), 0.04 and 0.018 Å for (2), and 0.033 and 0.041 Å for (3)]. The substituents attached to the N atom are almost perpendicular to the mean planes of the heterocycles, with dihedral angles of 89.7 (3)° for the N—O—Cmethylgroup in (1), 71.01 (4) and 80.00 (4)° for the N—O—C(=O)O—Cmethylgroups in (2), and 75.62 (14) and 74.13 (4)° for the same groups in (3). In the crystal of (1), there are unusual intermolecular C=O...C contacts of 2.794 (1) and 2.873 (1) Å present in moleculesAandB, respectively. There are also C—H...O hydrogen bonds and π–π interactions [inter-centroid distance = 3.407 (3) Å] present, forming slabs lying parallel to (001). In the crystal of (2), theAandBmolecules are linked by C—H...O hydrogen bonds, forming slabs parallel to (10-1), which are in turn linkedviaa number of π–π interactions [the most significant centroid–centroid distances are 3.4202 (7) and 3.5445 (7) Å], forming a three-dimensional structure. In the crystal of (3), theAandBmolecules are linkedviaC—H...O hydrogen bonds, forming a three-dimensional structure, which is consolidated by π–π interactions [the most significant inter-centroid distances are 3.575 (3) and 3.578 (3) Å].

scholarly journals Crystal structure of ethyl 2-({[(4Z)-3,5-dioxo-1-phenylpyrazolidin-4-ylidene]methyl}amino)acetate

2014 ◽  
Vol 70 (9) ◽  
pp. o938-o939
Author(s):  
Shaaban K. Mohamed ◽  
Mehmet Akkurt ◽  
Joel T. Mague ◽  
Eman A. Ahmed ◽  
Mustafa R. Albayati
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Dihedral Angle ◽  
Title Compound ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Side Chain ◽  
Three Dimensional Structure ◽  
Compound C ◽  
The Mean

The title compound, C14H15N3O4, is nearly planar, the dihedral angle between the planes of the phenyl and pyrazolidine rings being 1.13 (7) Å, and that between the plane of the pyrazolidine ring and the mean plane of the side chain [C—N—C–C(=O)—O; r.m.s. deviation = 0.024 Å] being 2.52 (7)°. This is due in large part to the presence of the intramolecular N—H...O and C—H...O hydrogen bonds. In the crystal, pairwise N—H...O hydrogen bonds form inversion dimers, which are further associated into layers, lying very close to plane (-120),viapairwise C—H...O hydrogen bonds. The layers are then weakly connected through C—H...O hydrogen bonds, forming a three-dimensional structure.

scholarly journals Crystal structures of two new isocoumarin derivatives: 8-amino-6-methyl-3,4-diphenyl-1H-isochromen-1-one and 8-amino-3,4-diethyl-6-methyl-1H-isochromen-1-one

2019 ◽  
Vol 75 (8) ◽  
pp. 1117-1122
Author(s):  
S. Syed Abuthahir ◽  
M. NizamMohideen ◽  
S. Mayakrishnan ◽  
N. Uma Maheswari ◽  
V. Viswanathan
Keyword(s):  
Three Dimensional ◽  
Ring System ◽  
Dimensional Structure ◽  
Asymmetric Unit ◽  
Three Dimensional Structure ◽  
Π Interactions ◽  
Phenyl Rings ◽  
The Mean ◽  
Independent Molecules ◽  
Compound Ii

The title compounds, 8-amino-6-methyl-3,4-diphenyl-1H-isochromen-1-one, C22H17NO2, (I), and 8-amino-3,4-diethyl-6-methyl-1H-isochromen-1-one, C14H17NO2, (II), are new isocoumarin derivatives in which the isochromene ring systems are planar. Compound II crystallizes with two independent molecules (A and B) in the asymmetric unit. In I, the two phenyl rings are inclined to each other by 56.41 (7)° and to the mean plane of the 1H-isochromene ring system by 67.64 (6) and 44.92 (6)°. In both compounds, there is an intramolecular N—H...O hydrogen bond present forming an S(6) ring motif. In the crystal of I, molecules are linked by N—H...π interactions, forming chains along the b-axis direction. A C—H...π interaction links the chains to form layers parallel to (100). The layers are then linked by a second C—H...π interaction, forming a three-dimensional structure. In the crystal of II, the two independent molecules (A and B) are linked by N—H...O hydrogen bonds, forming –A–B–A–B– chains along the [101] direction. The chains are linked into ribbons by C—H...π interactions involving inversion-related A molecules. The latter are linked by offset π–π interactions [intercentroid distances vary from 3.506 (1) to 3.870 (2) Å], forming a three-dimensional structure.

scholarly journals Three-Dimensional Structure and Dynamics of African Easterly Waves. Part III: Genesis

2008 ◽  
Vol 65 (11) ◽  
pp. 3596-3607 ◽  
Author(s):  
Chris D. Thorncroft ◽  
Nicholas M. J. Hall ◽  
George N. Kiladis
Keyword(s):  
Three Dimensional ◽  
Lower Troposphere ◽  
Finite Amplitude ◽  
Entrance Region ◽  
Dimensional Structure ◽  
Latent Heating ◽  
African Easterly Waves ◽  
Shallow Convection ◽  
Easterly Waves ◽  
Heating Profile

Abstract This paper promotes the view that African easterly waves (AEWs) are triggered by localized forcing, most likely associated with latent heating upstream of the region of observed AEW growth. A primitive equation model is used to show that AEWs can be triggered by finite-amplitude transient and localized latent heating on a zonally varying basic state that is linearly stable. Heating close to the entrance region of the African easterly jet (AEJ) is shown to initiate AEWs downstream. The heating leads to an initial trough that reaches the West African coast about 5–7 days later, depending on the nature of the heating profile. After this, a structure that projects strongly onto the leading linear normal mode of the basic state becomes established, characterized by a number of westward-propagating disturbances that strongly resemble AEWs. The sensitivity of the forced AEWs to the nature and location of the heating profile is examined. AEWs are most efficiently triggered by heating profiles that establish lower tropospheric circulations close to the entrance region of the AEJ. In the present study, this was best achieved by lower tropospheric heating from shallow convection or upper-level heating and lower-level cooling from a stratiform precipitation profile. Both profiles have significant heating gradients in the vertical in the mid-to-lower troposphere. This triggering paradigm for the genesis of AEWs has consequences for the variability and predictability of AEWs at weather and climate time scales. In addition to the nature of the AEJ, often emphasized, it is crucial to consider the nature and variability of upstream heating triggers.

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