APPLICATION OF REMOTE SENSING IN THE STUDY OF MONSOON ENERGETICS OVER BAY OF BENGAL DURING SUMMER MONSOON

IIAR ~ , rR;\CT All attempt has been made 10 slUd )' tho roon soon c ne rgeucs over Bil)' of Hengal by stu, lying th ecloud and monsoon depression field s during sum mer monsoon using 11 ROS ·N sa telli te ima ge ri es . Th e i UU h Pakinetic ft amn-s. ,-.g . vergen ce. vortic ity and vertical vclochics fur Hfcw selected ph ases in th e Ray ufHen gal .luring 27JUll("-6 Allgn ..l l Q"7lj within the 10° X Ill o grid box (it" . IS-!5 °N & ~5 0 95 ° E ) wt're computed. Next. th e kinematicIeamres o f n rypi cul disturbed phase (5-7 Jul y 1979) we re studied in a Lagrangian frame by using drop wind so n' lednm of 1 S n"!'ic;lr..: h ai rcrutt. The data profiles II a nd I' him:' been drawn 10 idemit'y the evolutiona ry femll~ ." of finassociau- I 111 1111 snnn depression.Fol lr wing Such ruau rr 111 ( I ~77) and the cln ud d lls l" r ~ltJ.t ics of (jnsw:uui t." nt , (I 'J9U): th l"wo plausible lIlod elsof Il1ntt s tlon dL'p lr ..."i n l1 hil\"l' been posmhued in lerms of C lusl er ClJ ~ l eSl.:e n ..:e Theory (CCn and Ginn! e lu slernl ~lr)· (( iCl"!The '(" nl en l 1l1 11. ~' d rClllntiuns 'Ailhin an ll a ruun,t Ihe lllunsuon d lopres..,iol1 wcn.- inl l.-ne,l hy making ll ~e ofGt }F.S im a!:l' l·l ·il-" Th " kinemal ic stud ies have rew ala l that th e h ighe r vH lues of \'ertical veloci ties , posi ti\ 'c \·.. r1icilylind \'t'll.l' C" '11.'1' c n lT,,~p h ll d w jlll lhe max imuUl cooncct in ' cloud ..:o\'e rllge 1';SoO-\'; .f fClnuing and mntu re stages ormo nSllllll d C")lll' , !, icl11

Decomposition of Vertical Velocity for Nutrient Transport in the Upper Ocean

Within the pycnocline, where diapycnal mixing is suppressed, both the vertical movement (uplift) of isopycnal surfaces and upward motion along sloping isopycnals supply nutrients to the euphotic layer, but the relative importance of each of these mechanisms is unknown. We present a method for decomposing vertical velocity w into two components in a Lagrangian frame: vertical velocity along sloping isopycnal surfaces and the adiabatic vertical velocity of isopycnal surfaces . We show that , where is the isopycnal slope and is the geometric aspect ratio of the flow, and that accounts for 10%–25% of the total vertical velocity w for isopycnal slopes representative of the midlatitude pycnocline. We perform the decomposition of w in a process study model of a midlatitude eddying flow field generated with a range of isopycnal slopes. A spectral decomposition of the velocity components shows that while is the largest contributor to vertical velocity, is of comparable magnitude at horizontal scales less than about 10 km, that is, at submesoscales. Increasing the horizontal grid resolution of models is known to increase vertical velocity; this increase is disproportionately due to better resolution of , as is shown here by comparing 1- and 4-km resolution model runs. Along-isopycnal vertical transport can be an important contributor to the vertical flux of tracers, including oxygen, nutrients, and chlorophyll, although we find weak covariance between vertical velocity and nutrient anomaly in our model.

Tracing the evolution of radiation-MHD simulations of solar and stellar atmospheres in the Lagrangian frame

Context. Radiation magnetohydrodynamics (radiation-MHD) simulations have become a standard tool for investigating the physics of solar and stellar atmospheres. Aims. The aim of this paper is to present a method that allows the efficient and accurate analysis of flows in such simulations in the Lagrangian frame. Methods. This paper presents a method that allows the construction of pathlines given a seed point that can be chosen freely at any location and at any time during the simulation where the simulation state is stored. The method is based on passive tracer particles. Through injection of particles in expanding regions the occurrence of particle-free volumes is avoided, even in the case of strongly compressive flows. Results. The method was implemented in the solar and stellar atmosphere simulation code Bifrost. It is efficient and accurate. As examples I present an analysis of a gas parcel in the convection zone and a particle in the solar transition region.

The genesis of Hurricane Nate and its interaction with a nearby environment of very dry air

The interaction of a tropical disturbance with its environment is thought to play an important role in whether a disturbance will develop or not. Most developing disturbances are somewhat protected from the intrusion of environmental dry air at mid-levels. For African easterly wave (AEW) disturbances, the protective boundary is approximated by closed streamlines in the wave-relative frame, and their interior is called the wave pouch. The dynamic and thermodynamic processes of spin-up occur inside the pouch. In this study, we define the kinematic boundaries for a non-AEW disturbance in the Bay of Campeche that originated along a sharp frontal boundary in a confluent region of low pressure. We examine these boundaries during the genesis of Hurricane Nate (2011) to show how a pouch boundary on isobaric levels in the Lagrangian frame may allow for some transport into the pouch along the frontal boundary while still protecting the innermost development region. This result illustrates a generic property of weakly unsteady flows, including the time-dependent critical layer of AEWs, that lateral exchange of air occurs along a segment of the boundary formed by the instantaneous, closed translating streamlines. Transport in the Lagrangian frame is simplest when measured with respect to the stable and unstable manifolds of a hyperbolic trajectory, which are topologically invariant. In this framework, an exact analysis of vorticity transport identifies the primary source as the advection of vorticity through the entrainment and expulsion of bounded material regions called lobes. We also show how these Lagrangian boundaries impact the concentration of moisture, influence convection, and contribute to the pouch vertical structure.

The genesis of Hurricane Nate and its interaction with a nearby environment of very dry air

The interaction of a tropical disturbance with its environment is thought to play an important role in whether a disturbance will develop of not. Most developing disturbances are somewhat protected from the intrusion of environmental dry air at mid-levels. For African easterly wave (AEW) disturbances, the protective boundary is approximated by closed streamlines in the wave-relative frame, and their interior is called the wave-pouch. The dynamic and thermodynamic processes of spin-up occur inside the pouch. In this study we define the kinematic boundaries for a non-AEW disturbance in the Bay of Campeche that originated along a sharp frontal boundary in a confluent region of low pressure. We examine these boundaries during the genesis of Hurricane Nate (2011) to show how a layer-wise pouch boundary in the Lagrangian frame may allow for some transport into the pouch along the frontal boundary while still protecting the innermost development region. This result illustrates a generic property of weakly unsteady flows, including the time-dependent critical-layer of AEWs, that lateral exchange of air occurs along a segment of the boundary formed by the instantaneous, closed translating streamlines. Transport in the Lagrangian frame is simplest when measured with respect to the stable and unstable manifolds of a hyperbolic trajectory, which are topologically invariant. In this framework, an exact analysis of vorticity transport identifies two sources; i) the advection of vorticity through the entrainment and expulsion of bounded material regions called lobes, and ii) the baroclinic contribution of vorticity transport through the tilting mechanism across the Lagrangian boundary. We also show how these Lagrangian boundaries impact the concentration of moisture, influence convection, and contribute to the pouch vertical structure.

Modeling erosion in a centrifugal pump in an Eulerian-Lagrangian frame using OpenFOAM®

Erosion induced by solid particle impingement is a very commonwear mechanism in turbomachinery and Computational Fluid Dynamics is one of the most widely used tools for its prediction. In this article, erosion is modeled in one of the channels of a centrifugal pump using OpenFOAM®,which is an Open Source CFD package. A review of some of the most commonly used erosion models is carried out in an Eulerian-Lagrangian frame along with a comparative study of the erosion rates obtained with each model. Results yielded some disparities between models due to the different factors taken into consideration. The mesh is then deformed to obtain the resulting eroded geometry.