Courseoutline

The course is organized into two, 1½-hour lectures during the morning with 3-hour practicals during the afternoon. The morning lectures discuss specific processes, and the topics of the afternoon practicals are linkedtothelectures as much as possible. A list of the lectures and practicals, with a brief summary of their topics, follows.

Day1(introductionobservations)

Lecture1a);Introductionobservations(McCreary):Overviewofthephenomena and processesdiscussed inthecourse.

Lecture1b);Observations(Shankar):OverviewofcirculationsandmajorcurrentsintheNIO,andtheirunderlyingdynamics. Remarksonthenatureofgeophysicalfluidflows.

Practical (Suprit Kumar, Girishkumar): Introduction to Ferret, followed by an application related to the morning lecture.

Day2(oceanmodelswaves)

Lecture2a);Oceanmodels(McCreary):A hierarchy of models have been used to study the ocean. The more-complex models simulate observations most realistically, whereas the simpler systems are useful for identifying specific processes. Models discussed are oceangeneralcirculation models (OGCMs), the linear, continuously stratified (LCS) model, and a variety of layer models.

Lecture2b);Waveradiation(McCreary):Typesofwaves(gravity,Kelvin,andRossbywaves), their dispersion relations, and phase and group speeds. These waves are very apparent in the NIO. Their presence means that wind forcing in one region of the NIO can affect remote regions often thousands of kilometres away.

Practical (Suprit Kumar, Girishkumar): Filtering altimeter data and model output to isolate the waves discussed in the morning lectures.

Day3(interiorocean)

Lecture3a);InteriorOceanI(McCreary):Howdoestheinterioroceanrespondtowindforcingintheinteriorocean? Topicscovered include:Ekmandrift,Ekmanpumping,radiationofRossbywaves,andadjustmenttoSverdrupbalance.

Lecture3b);InteriorOceanII(McCreary):ContinuationofPart1.

Practical (Suprit Kumar, Girishkumar): Response to interior Ekman pumping over the Bay. Run the LCS model with the coastal and equatorial response filtered out. (Arnab already has these simulations in place for a 0.1° version of the LCS model.) Students then analyze this response in the interior-ocean practical. (They can analyze the coastal and equatorial-ocean responses later in their respective practicals.)

Day4(coastalocean)

Lecture4a);CoastalOceanI(McCreary):Howdoesthecoastaloceanrespondtoalongshorewinds? In addition to gravity and Rossby waves, coastal Kelvinwaves are excited by the wind. Vertical propagation of Kelvin waves. When there is a continental shelf, shelfwaves are also generated.

Lecture4b);CoastalOceanII(McCreary,Amol):ContinuationofPart1. Observations and modelling of coastal currents.

Practical(Amol, Mukherjee):AnalysesthatillustratewavepropagationaroundtheperimeteroftheBayandalongthewestcoastofIndia. PartofthispracticalwillbeanalysisofLCSresultswithnon-coastalresponsesfilteredout. Anotherpartcouldbeanalysisoftide-gaugeandaltimeterdata.

Day5(equatorialocean)

Lecture5a);EquatorialOceanI(McCreary):Whatareequatoriallytrappedwaves, and how do they differ fromoff-equatorialwaves? In addition to gravity and Rossby waves, there is an equatorial Kelvin wave and a Yanai wave. How does the equatorial ocean respond to wind forcing? Vertical propagation of equatorial Kelvin, Yanai, and Rossby waves.

Lecture5b);EquatorialOceanII(McCreary):Continuation of Part 1.

Practical(Chatterjee,Amol):Analysesofaltimeterdataand/orLCS/MOMoutputsthatillustrateaspectsofequatorialcurrents. Possibleanalysesare:1)WyrtkiJets,showingtheirsemiannualnature;2)obtainingmeridionalsectionsthatshowverticalphasepropagationofRossby-likefeatures(theWJsappeartopartofthisverticalpropagation);and3)isolationofequatoriallyforcedcirculationsintheBayandAS.

Day6,Saturday(small-scaleinstabilitiesmixed-layerprocesses)

Lecture6a);Small-scaleinstabilities(McCreary):Small-scale instabilitiesincludeconvectiveoverturningandKelvin-Helmholtzinstability. Mile'sfamousrequirement for theexistenceofKHinstability (Ri < 0.25) is derived. These instabilitiesareimportantfor generating turbulence in thesurface mixedlayer. KH instability is also important for subsurface mixing (e.g., for the breaking of internal waves).

Lecture6b);Mixedlayer(Shankar):Thediscussionofsmall-verticalscaleinstabilitiesleadsnaturallyintomixed-layerprocessesandmodels.

Practical(Vijith):UseFerrettocontrast mixedlayers and theirvariabilityintheBayofBengalandArabianSea. WecouldanalyzeoutputfromanOGCMsolution,ordatafromCTDs,theChatterjeeetal.(2012)climatology,andmaybeArgofloats.

Day7(biophysics)

Lecture7a);BiophysicsI(McCreary):Introduction to biophysical phenomena and processes intheNIO. A major conclusion is that oceanphysicsis critical: Unless ocean physics (in particular, the mixed-layer thickness) is accurately modelled, biological activity cannot be accurately simulated.

Lecture7b);BiophysicsII(Vijith):Aspecificexampleoftheimpactofphysicsonbiology,namely,theimpactofthelarge-scaleWICContheNEASecosystem.

Practical(Vijith):DiscussionandplottingofTOPAZresults.

Day8(large-scaleinstabilitieseddiesandfronts)

Lecture8a);Large-scaleinstabilities(McCreary):Large-scale instabilitiesincludebarotropicandbaroclinicinstability. The familiar requirement for the existence of barotropic instability (Uyy–β must change sign) is derived. When these instabilities grow to finite amplitude, they generate eddies and fronts.

Lecture8b);Eddiesandfronts(Francis, Aparna): Differences between 0.1° and 1/48° OGCM solutions will be contrasted. Specific examples of the impact of eddiesandfrontson NIO circulations.

Practical(Aparna):IdentificationofSST frontsinobservationalandmodeldata.

Day 9 (overturning circulations)

Lecture 9a); Overturning circulations I (McCreary): Two prominent overturning circulations in the NIO are the Cross-equatorial Cell (CEC) and Subtropical Cell (STC). The CEC is important for the NIO as it provides most of the water that upwells in the region. The STC is important because variability in its strength (particularly, its upwelling branch) impacts climate.

Lecture 9b); Overturning circulations II (Shankar): Two other overturning cells with their descending branches in the Arabian Sea generate Persian-Gulf water (PGW) and Red-Sea water (RSW).

Practical (Amol, Suprit Kumar, and Girishkumar): Identify overturning cells in models using Ferret.

Day10(intraseasonalvariability)

Lecture 10a); Intraseasonal variability I (Jay, Amol, Mukherjee):Introduction to instraseasonal variability (ISV) in the NIO. Analyses of altimeter and ADCP data on the west and east coasts of India.

Lecture 10b); Intraseasonal variability II (Amol):Theory and model simulations of circulations along Indian coasts.

Practical (Amol, Mukherjee): Use Ferret to identify the structure of prominent intraseasonal events in the NIO. Focus will be on analyses of altimeter data, including OSCAR currents.

Day11(South Asian Monsoon)

Lecture11a);Description (Francis):General features of the South Asian Monsoon.

Lecture11b);Oceans and the Monsoon (Francis): Variability of the South Asian Monsoon, and its links to climate processes in the Indian and Pacific Oceans (EQUINOO/IOD and ENSO).

Practical: Discussionandfeedbackofthecourse.