The motion of atmospheric disturbances on the spherical Earth

When the perturbations of the pressure distribution due to rapidly moving cyclones are eliminated by plotting charts of the mea1;1 distribution of the pressure for a number of days, centres of larger dimensions 13,nd of a more permanent character appear, as has been shown by the work carried out by Rossby and his collaborators (7). On winter maps of the northern hemisphere, as a rule at least five of these perturbations are found: the Icelandic and the Aleutian Lows, the Azores, Asiatic and Pacific Highs. They can hardly be considered as mere perturbations of the general circulation, but must rather be regarded as important parts of it, as is evidenced by their semipermanent character. Nevertheless, they will in the following sometimes be referred to as perturbations or disturbances, since they are treated mathematically as perturbations of an undisturbed current

The motion of atmospheric disturbances

In a recent paper Rossby has discussed the effect of the latitudinal variation of the Coriolis force on the propagation of oceanic and atmospheric disturbances (2). He showed that the velocity c of a disturbance in an incompressible atmosphere on a plane earth when only the effect of the latitudinal variation of the Coriolis force is considered is given with sufficient accuracy by the formula..

Vertical distribution of temperature and humidity over the Caribbean Sea

The observations presented and discussed in this paper were obtained as part of a research project conducted under contract NObs-2083 with the Bureau of Ships of the U. S. Navy by the Woods Hole Oceanographic Institution. The observations and their original reduction were carried out under the direction of Jeffries Wyman. The airplane soundings were undertaken by Kenneth McCasland and Alfred Woodcock. The sea surface temperature was measured on the surface ships by David F. Barnes and Roger Patterson. The necessary airplane (PBY-SA) and surface boats (PC's) were made available by the U. S. Navy. All observations were made during the spring of 1946 at about 19.5°N latitude, 66°W longitude, north of San Juan, Puerto Rico, and at about lO°N latitude, 79.5°W longitude, north of Coco Solo, Panama. An extensive preliminary report on the results of the expedition with a limited circulation was prepared by Wyman and his collaborators during the summer of 1946. The present paper deals with certain phases of the work in a more detailed fashion. Special attention is given to the temperature and humidity distributions in the vertical and to their interpretation in the light of meteorological principles. A discussion of atmospheric turbulence based on airplane measurements has already been published elsewhere (Langwell, 1948), and an application of the airplane soundings to the theory of cumulus clouds has been studied by Stommel (1947). The second and third chapters of this publication deal with the description of observational techniques used by the expedition, with the methods of reduction and present the data on which the later discussion is based. It has been thought desirable to publish these data in extenso because they may be of interest to other meteorologists in view of the sparsity of upper-air observations in this region. The actual preparation of Chapters II and III is largely the work of Bunker and Stommel. In order to show how the observations made off Puerto Rico fit into the general pattern of climatic and weather conditions in the Caribbean area Chapter iv presents a survey of the climate of this region and of the weather conditions during the time when the observations were taken. This Chapter was contributed by Joanne Malkus. It is pertinent to include in this general introduction the conclusion drawn in Chapter IV namely that the weather situations encountered represented, in general, a relatively undisturbed trade-wind regime of early spring. The homogeneous layer of nearly dry-adiabatic lapse-rate of temperature and almost constant mixing ratio is one of the most characteristic phenomena in the lowest atmosphere of this region. It is also of utmost importance for the energy budget of the hydrosphere and the atmosphere. Therefore, a special discussion of this layer by Bunker is given in Chapter V. Because of the nearly dry-adiabatic lapse-rate in the homogeneous layer most of the heat transfer between water and air in the trade-wind zone must be in the form of latent heat of vaporization, a conclusion whose thermodynamic implications were discussed thoroughly by Ficker (1936). For this reason the distribution of water vapor deserves special attention, and Chapter VI deals with this variable as a problem in turbulent mass exchange. The analysis presented in this chapter is due to Haurwitz and Stommel

General Relativistic Rossby-Haurwitz waves of a slowly and differentially rotating fluid shell

We show that, at first order in the angular velocity, the general relativistic description of Rossby-Haurwitz waves (the analogues of r-waves on a thin shell) can be obtained from the corresponding Newtonian one after a coordinate transformation. As an application, we show that the results recently obtained by Rezzolla and Yoshida (2001) in the analysis of Newtonian Rossby-Haurwitz waves of a slowly and differentially rotating, fluid shell apply also in General Relativity, at first order in the angular velocity.Comment: 4 pages. Comment to Class. Quantum Grav. 18(2001)L8

Rossby-Haurwitz waves of a slowly and differentially rotating fluid shell

Recent studies have raised doubts about the occurrence of r modes in Newtonian stars with a large degree of differential rotation. To assess the validity of this conjecture we have solved the eigenvalue problem for Rossby-Haurwitz waves (the analogues of r waves on a thin-shell) in the presence of differential rotation. The results obtained indicate that the eigenvalue problem is never singular and that, at least for the case of a thin-shell, the analogues of r modes can be found for arbitrarily large degrees of differential rotation. This work clarifies the puzzling results obtained in calculations of differentially rotating axi-symmetric Newtonian stars.Comment: 8pages, 3figures. Submitted to CQ

PyClaw: Accessible, Extensible, Scalable Tools for Wave Propagation Problems

Development of scientific software involves tradeoffs between ease of use, generality, and performance. We describe the design of a general hyperbolic PDE solver that can be operated with the convenience of MATLAB yet achieves efficiency near that of hand-coded Fortran and scales to the largest supercomputers. This is achieved by using Python for most of the code while employing automatically-wrapped Fortran kernels for computationally intensive routines, and using Python bindings to interface with a parallel computing library and other numerical packages. The software described here is PyClaw, a Python-based structured grid solver for general systems of hyperbolic PDEs \cite{pyclaw}. PyClaw provides a powerful and intuitive interface to the algorithms of the existing Fortran codes Clawpack and SharpClaw, simplifying code development and use while providing massive parallelism and scalable solvers via the PETSc library. The package is further augmented by use of PyWENO for generation of efficient high-order weighted essentially non-oscillatory reconstruction code. The simplicity, capability, and performance of this approach are demonstrated through application to example problems in shallow water flow, compressible flow and elasticity

Structural basis for CRISPR RNA-guided DNA recognition by Cascade

The CRISPR (clustered regularly interspaced short palindromic repeats) immune system in prokaryotes uses small guide RNAs to neutralize invading viruses and plasmids. In Escherichia coli, immunity depends on a ribonucleoprotein complex called Cascade. Here we present the composition and low-resolution structure of Cascade and show how it recognizes double-stranded DNA (dsDNA) targets in a sequence-specific manner. Cascade is a 405-kDa complex comprising five functionally essential CRISPR-associated (Cas) proteins (CasA1B2C6D1E1) and a 61-nucleotide CRISPR RNA (crRNA) with 5′-hydroxyl and 2′,3′-cyclic phosphate termini. The crRNA guides Cascade to dsDNA target sequences by forming base pairs with the complementary DNA strand while displacing the noncomplementary strand to form an R-loop. Cascade recognizes target DNA without consuming ATP, which suggests that continuous invader DNA surveillance takes place without energy investment. The structure of Cascade shows an unusual seahorse shape that undergoes conformational changes when it binds target DNA.

Possible causes of data model discrepancy in the temperature history of the last Millennium

Model simulations and proxy-based reconstructions are the main tools for quantifying pre-instrumental climate variations. For some metrics such as Northern Hemisphere mean temperatures, there is remarkable agreement between models and reconstructions. For other diagnostics, such as the regional response to volcanic eruptions, or hemispheric temperature differences, substantial disagreements between data and models have been reported. Here, we assess the potential sources of these discrepancies by comparing 1000-year hemispheric temperature reconstructions based on real-world paleoclimate proxies with climate-model-based pseudoproxies. These pseudoproxy experiments (PPE) indicate that noise inherent in proxy records and the unequal spatial distribution of proxy data are the key factors in explaining the data-model differences. For example, lower inter-hemispheric correlations in reconstructions can be fully accounted for by these factors in the PPE. Noise and data sampling also partly explain the reduced amplitude of the response to external forcing in reconstructions compared to models. For other metrics, such as inter-hemispheric differences, some, although reduced, discrepancy remains. Our results suggest that improving proxy data quality and spatial coverage is the key factor to increase the quality of future climate reconstructions, while the total number of proxy records and reconstruction methodology play a smaller role

Phage-Induced Expression of CRISPR-Associated Proteins Is Revealed by Shotgun Proteomics in Streptococcus thermophilus

The CRISPR/Cas system, comprised of clustered regularly interspaced short palindromic repeats along with their associated (Cas) proteins, protects bacteria and archaea from viral predation and invading nucleic acids. While the mechanism of action for this acquired immunity is currently under investigation, the response of Cas protein expression to phage infection has yet to be elucidated. In this study, we employed shotgun proteomics to measure the global proteome expression in a model system for studying the CRISPR/Cas response in S. thermophilus DGCC7710 infected with phage 2972. Host and viral proteins were simultaneously measured following inoculation at two different multiplicities of infection and across various time points using two-dimensional liquid chromatography tandem mass spectrometry. Thirty-seven out of forty predicted viral proteins were detected, including all proteins of the structural virome and viral effector proteins. In total, 1,013 of 2,079 predicted S. thermophilus proteins were detected, facilitating the monitoring of host protein synthesis changes in response to virus infection. Importantly, Cas proteins from all four CRISPR loci in the S. thermophilus DGCC7710 genome were detected, including loci previously thought to be inactive. Many Cas proteins were found to be constitutively expressed, but several demonstrated increased abundance following infection, including the signature Cas9 proteins from the CRISPR1 and CRISPR3 loci, which are key players in the interference phase of the CRISPR/Cas response. Altogether, these results provide novel insights into the proteomic response of S. thermophilus, specifically CRISPR-associated proteins, upon phage 2972 infection