 So, today we are going to discuss the monsoonal regions of the world. So far we have primarily focused on the Indian monsoon, but now we should know what are the other regions of the world which also experience the monsoon. So, that is what we will look at today. In fact, the distinguishing attributes of the monsoon are the last seasonal variation in rainfall and direction of the wind. Since the monsoon is traditionally defined as a seasonal reversal of the direction of the surface wind, you remember this definition came from the fact that it was Arab sailors who coined the word monsoon. So, it was the traditional definition is in terms of seasonal reversal of direction of surface winds. So, monsoonal regions of the world are also identified on the basis of seasonal variation of the wind. Consider the monsoonal regions of the world as delineated by ramage. Now, how did he delineate these regions? He defined monsoonal regions of the world as those regions which satisfy the following criteria in terms of the wind. So, these are defined as regions marked with a last seasonal variation in the direction of winds. The prevailing wind direction shifts by at least 120 degrees between January and July. So, seasonal reversal would mean 180. So, he is saying that at least there should be a difference of 120 degrees between the direction of wind in January and July. Then the average frequency of prevailing wind directions in January and July should exceed 40 percent. You know the wind direction should not be so variable that we cannot talk that the mean wind is not representative of too many days. Therefore, he says when we talk of prevailing wind it should be wind that occurs on most of the days in those months. So, he says the average frequency of prevailing wind direction should exceed 40 percent. And there is one more condition he put in which actually is not implicit in the kind of definitions that people had used before him. And that is that mean January or July wind has to be greater than 3 meters per second. This strikes me as being slightly arbitrary although it is true that when we talk of changing of wind direction the wind has to have a certain magnitude before we can talk of changing wind direction. But whether it should be 3 meters per second or 2 meters per second or 1 meter per second is really subjective decision. So, these are the monsoonal regions of the world delineated by ramage using these criteria and in fact they come somewhat complicated. So, he then suggests that this is the box which in fact delimits the monsoonal regions of the world. Notice that India is very much at the center of the monsoonal regions of the world according to ramage and according to him monsoonal regions comprise primarily of Africa and Asia and part of West Pacific that is what according to him they include. So, these are the monsoonal regions of the world as delineated by ramage on the basis of winds. Now, let us see how they came about because what you see here is the surface streamline patterns in January and in July below and I am sorry, but the longitudes are not what they were before and India is around here and you see actually that in January the winds are from the northeast and they change completely to become from the south west here in July. So, this is the major monsoonal change which you see in this box here similarly till the winds also reverse here now he claims that the other regions are not monsoonal. The red line corresponds to the surface trough the red line that is drawn here and only problem there is that they have given a gap here over South America they do not continue the trough and in December, January, February actually there is a low created over South American region much the same way that we have a low created over the Indian region here and see over the Indian region here the trough actually is moves northward. It is south of the equator in January and it actually moves northward to lie over India in July, but they have not drawn the trough to lie over South Africa in the January case and this again is a subjective decision I believe. So, when real draws location of the surface trough in July and January what you see is this is again the picture we have seen before this is the July and this is the January and I have drawn in red boxes indicating ramages regions over that these are the monsoonal regions of the world and you can see immediately that monsoonal regions are characterized by a very large migration of the trough extending over 20 degrees in latitude. So, there is a big difference in the latitudinal location of the July trough and the January trough over monsoonal regions if you look at the other regions which are not monsoonal according to ramage then in fact you see that over most of the regions there is hardly any change less than 10 degree change between the January location and the July location of the surface trough and what I have indicated here is that had they taken the South American low into account then you would have had some kind of a substantive seasonal variation over South America as well, but they have not done. So, now, so we have seen that if we superpose monsoonal regions as determined by ramage on to the surface trough in January and July then monsoonal regions are characterized by a very large variation in the latitude of the surface trough between January and July. On the other hand over 160 west to 40 west that is to say over much of the Pacific ocean starting with 160 west. So, east of 160 west over the entire ocean and including the South American continent the trough is in the northern hemisphere in both the months and the variation is much less than 10 degrees. So, there is no seasonal variation in the direction of the wind. So, this is how ramages delineation of the monsoonal region can be reconciled with the classic picture drawn by real of how the surface trough changes. So, the two are consistent. Now, as I pointed out before we who live in the monsoonal regions of the world really are concerned with the seasonal variation in the rainfall associated with the monsoon and over Indian region for example, in common parlance monsoon means the rainy season and rainfall associated with the monsoon is also called monsoon. So, we talk of poor monsoon years in which rainfall is much below the average we talk of good monsoon years when it is above the average and so on. So, to us the monsoon is almost synonymous with the rainfall it brings. Now, so we must see how monsoonal regions based on ramages criteria for seasonal variations in the direction of wind. In fact, are they how do they relate to the variation of rainfall? See that is the most important thing to see for us and here now we have these are again ramages monsoon region in the red box and now I have made India more to the center of the plot and what you see here is the rainfall of July rainfall of January and this is the difference between July minus January. So, blue means rainfall is much more in July in the northern part here than it is in January and this means rainfall is more in January yellows means rainfall is more in the southern hemisphere here than it is then it is in July. So, what we see here is that monsoonal regions you have a large shift of the rain belt and the fact that there is a shift of the rain belt is reflected in this dipole here because this is of one sign and this is of the other sign right. This says that the rain is more in July here, this says the rain is more in January here, this suggests that the rain belt moves from here to here between January and July this is very clear. So, this north south dipole that we see here is a manifestation of the seasonal migration and what therefore ramages monsoonal regions are associated with seasonal migration of this major rain belt over a latitudinal range of at least 20 degrees or so that is what it is. Now, so ramages monsoonal regions are characterized by seasonal migration of the major rain belt which we know we have seen in the last lecture which is associated with the tropical convergence zone over a latitudinal range of at least 20 degrees extending across the southern and northern hemispheres. So, this is again can be considered as a distinguishing attribute of monsoonal regions that there is a seasonal migration of the rain belt associated with the TCC over a latitudinal range of at least 20 degrees from one hemisphere to another. Now, over the Atlantic the migration is only about 10 degrees and only in the northern hemisphere. So, we see here that over the Atlantic which is here you can say that this is a bit of a migration it has come from near the equator slightly to the north there is a migration and over the Pacific really there is no migration, but rather the systems staying more or less there, but being much weaker in January and there is a strengthening in July and that is what you see here the big blue here just means that there is a strengthening in situ strengthening of the system over the east Pacific. So, over the Atlantic the migration is only very small and only in the northern hemisphere over the east Pacific a TCC occurs only in the boreal summer around 10 degrees north. So, what do we see then that these regions again these are ramages regions here and these regions are characterized by seasonal migration of the ITCC whereas, this region is specific is characterized by summer strengthening by eastward extension of the ITCC you see. So, there is summer strengthening and eastward extension see the ITCC remains here even in the winter, but it is strengthened in the summer and extends eastward that is what is seen here. Now, note that ramages boxes never includes South America. So, although you see that over the South American longitudes you do get a shift of the rain belt. Which you can see also as a dipole here, but ramage does not consider that as a part of the monsoon region. So, monsoon is considered to be a manifestation of the response of the to the seasonal variation in the radiation from the sun. So, see the distinguishing attribute of monsoon is the seasonal variation where does that come from that is a response to the seasonal variation in the radiation from the sun. The location of the surface trough averaged over all longitudes in fact also varies and this is a picture from real. So, if you talk of the equatorial trough and you average over all the longitudes then this is the latitude of the equatorial trough and this is the latitude of the sun. And remember in September the sun crosses the equator. So, it is at 0 then it goes to the southern hemisphere then it crosses again in April and then March and then it comes to the northern hemisphere. So, this is a very simple oscillation of the latitudinal location of where the sun is overhead. And you can see that this is the topic of Capricorn and this is the topic of cancer. So, the sun is overhead at latitudes which vary from topic of Capricorn to topic of cancer over the year and this is the way it varies in a very smooth manner. And when you do all the averaging the equatorial trough also varies in a smooth manner, but notice that the amplitude of variation is much smaller than the variation of the sun because this amplitude is 47 degrees or so whereas this amplitude is of the order of 20 degrees or so from here to here. So, the amplitude of variation is much less also you notice that there is a lag. Now, this is where this sun is at the minimum or the most southern most latitude and that occurs as you know between in December end of December whereas the minimum or the southern most latitude of the equatorial trough occurs about 2 months later. Similarly, there is a lag between the peaks as well of about 2 months. So, the location of the surface trough averaged over all the longitudes is seen to vary with the season, but the amplitude of the latitudinal extent of the variation is smaller than that of the sun and also there is a lag of 2 months as you have seen. Now, if we consider the monsoonal regions to be characterized by a large amplitude of the migration between the summer hemispheres, then the east specific and Atlantic or obvious non-monsoonal because they do not even have the ITCZ in the summer hemisphere during December, January, February. So, now again we see what are the different monsoonal regions of the world and you can see what are the different regions. So, we have the east specific here and the east Atlantic here both of which are not considered monsoonal at all. Then we have the Asian-Australian monsoon which we have seen before which is this huge region here. Asian-Australian monsoon is this huge region here. Then we have the African monsoon which is this region here and you can see that both of these are very clear pole this dipole kind of a thing when we look at the difference it is very clear that there is a seasonal migration of the rain belts here. Whereas, here as we mentioned before there is a in situ strengthening, but you also see that there is a South American monsoon here where you have strengthening in the southern summer and there is a dipole signal here and you see this is the South American monsoon cleared up in DJF and you see that during JJA also towards the north there is a rain belt here. So, South American region also seems to have a seasonal migration although the amplitude is not as large as the classic Asian-Australian monsoon or the African monsoon. Now, recently it has become very fashionable to say that even the monsoon North America has a monsoon and this they claim is the North American monsoon region. And for some reason monsoon has become a very catchy word and everybody would like to have a monsoon at their own doorstep. I think partly this kind of reasoning has gone into defining this as a North American monsoon. We will get into that when we study the other monsoonal regions in greater detail, but as far as one can see it really does not satisfy the criteria of seasonal migration or anything like that. What seems to be happening is that in the summer there is some extension of the specific ITCZ to give some rain over Mexico and parts of United States, southern parts of United States and since that occurs in the summer they call it the North American monsoon. It is somewhat debatable whether it is a monsoon in the sense that the other well-known monsoonal regions of the world are. See they talk of the African monsoon, the Indian monsoon, the Asian monsoon, the Australian monsoon. Australia also you can see is part of this pole you know with shift in the rain belt very clear, but North American part you do not quite see the same thing but nevertheless it has now come into vogue. Now, let us look at how the migration actually occurs. So, now we are looking at monthly pictures at over a given longitudinal belt. So, first we look at Africa and this is 10 degrees to 40 degrees east and what it looks like I have shown you here. This is between these two red lines we are looking at we are averaging over these longitudes and asking the question where is the rain belt. So, in January you see clearly the rain belt is here the equator is here as you can see rain belt is in the southern hemisphere and then it goes to the northern hemisphere. This is a very classical picture of seasonal migration of the kind we have seen before for the Indian monsoon as well and we will see again. So, this is the African monsoon how it goes from the southern hemisphere to the northern hemisphere. Now, but we should also see I had asserted that this rain belt is associated with a tropical conversion zone. Now, this assertion requires proof and that is what we are going to look at now. This is from the European centre re-analysis and what we have here is the vertical circulation. So, this is the north south circulation and the vertical circulation. So, it is the north it is a circulation in the plain north south versus vertical plain and what you see here is this is for two months this is January and this is the average over several years and this is July and what you see here is this zone of ascent here. This is where the rain occurs and you can see that the ascent is throughout the troposphere here. So, it is very much like the tropical conversion zone or Trenberg C E O F 1 the dominant mode of divergent circulation. So, that is what is responsible for the rainfall of the African monsoon and you see that this is the July pattern again very similar ascent throughout the troposphere. So, that we can say that there are T C G's in both the hemispheres the northern hemisphere during the northern hemispheric summer, southern hemisphere during the southern hemispheric summer and there is a seasonal migration between the two. So, this is a classic case of the monsoon in which the T C G's move from one hemisphere to the other in response to the movement of the sun. Now, we look at the Asian Australian monsoon and we are going to look at a very large region average over a very large region it is 60 degrees east to 180 degrees east and when we do that again we see very nice migration here. Of course, notice that the rainfall is so much higher in the Asian Australian Australian monsoon than it is in the African monsoon. See the same shades are used, but you see this is much less and you have 6 and 8 here and here you see much higher rain occurs in the Asian Australian monsoon. Again you see very nice seasonal migration of the belt. Now, question is are that T C G's in both the hemispheres? Yes, even when we average over such a large region 60 to 180, it is very clear that you have over the in January over the southern hemisphere very nice and clean ascent right up to the upper troposphere and you see the same in the northern hemisphere in July. So, there are T C G's in both the hemispheres. Now, if we look at the Indian monsoon and now we are looking at a relatively small part of the Asian Australian monsoon. We are looking from 70 to 90 east only. It is shown here and what you see is in fact there is a seasonal migration, but you also see that there is an equatorial band persisting here and this is something we had seen and the latitudinal extent of the migration is more than 20 degrees and we know very well that actually we have the primary band which moves north and you can see that the latitudinal movement here remember the data for the southern hemisphere was not available. Otherwise it starts from around 0 or 5 south and so on and you have a very large variation in latitude and this is the seasonal migration of the primary band which is the T C G, but there is also another equatorial band which persists through the season. Now, even when you average over 70 to 90 again we see that the rain belt is associated with ascent throughout the troposphere and this you can see that there is a T C G here in January and there is a also ascent throughout the troposphere in July, but notice that the region over which it is ascending in July is much much wider than the one in January. Now, this is because if you look at the mean picture then you get ascent due to the equatorial band as well as the primary band you see everything appears here and that is why there is a huge region over which ascent is occurring. So, we note that as far as the Indian region is concerned there are T C G's in both the summers and that in July the latitudinal extent of the region with upward velocity is almost 40 degrees in latitudinal extent you can see this is almost 40 degrees in latitudinal extent whereas this is only about 15 degrees or so each of these is 10 degrees. So, you can see very clearly this is about 40 degrees in extent whereas January it is less than 15 degrees. Now, if you look at these monthly pictures what we see is actually consistent with Blanford's comment about spreading of the rainy belt with a shift of the maximum. You may recall that in the last century 1886 Blanford with the little data available had made very perceptive comments on the nature of the system that gives us rain the Indian monsoon and he did not believe that the monsoon was a manifestation of seasonal migration of the equatorial rainy belt remember he was aware that there is a rainy belt in the equatorial region. But he did not think that it is a seasonal migration rather in his view the equatorial belt of constant rainfall exists across the monsoon region and is not bodily transferred northward to India and southward to Australia with the annual march of the sun in declination is a well established fact thesis in 1886 that it is not a matter of marching with the sun and he continues saying rainfall registers of the Malay or Palago show that while in the neighborhood of the equator the season of the heaviest and most frequent rainfall is from November to January. There is no month in which the precipitation does not amount to at least 3 to 4 percent of the annual total. So, it is raining all the time in the equatorial belt which is a true statement. In fact, during the monsoon the whole region between the equator and the Himalayas is more or less one of precipitation and may be regarded rather as an extension and broadening out of the normal equatorial rainy zone which is an interesting concept. So, he says it is not as if the equatorial belt moves away it is an it becomes broader in latitude it becomes extended northward and furthermore he says with a northward transfer of its maximum. So, whereas in the winter November to January the maximum rain was in the equatorial region now the maximum rain occurs to the north. So, with a normal transfer northward transfer of the maximum and a partial concentration in northern India rather than a bodily transfer of the zone northward to southern Asia. So, this is a very interesting and perceptive remark and in fact, the monthly patterns that we saw with ascent over 40 degrees of latitude and so on and so forth is consistent with this and it is also consistent with the monthly OLR pictures that we used to see where we see that in fact, the low OLR region is a broad region with the minimum OLR around here true, but it is not as if this one has given up its right to also have a low OLR region. So, this again is very consistent. So, it is clear that the monthly pattern can be properly interpreted only when the variation on the daily scale is considered as I discussed earlier. So, earlier we had shown that only on the daily scale we saw that this monthly pattern arose because of the presence of two ITCs or tropical conversion zone and the propagations between the two equatorial region and the monsoon region. Now, we consider the South American monsoon which according to Rammage is not monsoon at all and so, we look at this region this is South America and again this is July and this is January and you can see that there is a shift of the rain belt and if we take the average over this belt what we see is in fact, a migration. Now, the question is say we are not so much bothered about wind we would be happy to call this a monsoon if in fact, we see that the rain system is akin to a TCG and indeed it is. So, we have in for January you see a broad band of rising again rising up to the upper troposphere. So, this is again the canonical tropical conversion zone that we see here and in the northern summer we see a somewhat narrower, but the same story that the ascent is throughout the troposphere. So, we have again TCG is in both the hemispheres and a seasonal migration between them and the season only thing is that the latitudinal extent of the seasonal migration is only from about 10 degrees out to 7 degree north. So, it is a little less than 20 degrees it is not as large as what we see over the Asian region or over the African region, but otherwise it seems to have the characteristics of a monsoonal region. Now, in spite of this South American region is not considered to be monsoonal by Ramesses criteria. This is because the temperature at the surface in the austral summer is not as high as over the other continents and the seasonal reversal of winds not as dramatic. See, this is what I meant when I said that the third criteria of ramage which said that the winds have to be greater than 3 meters per second wind speed may have been the one that killed the possibility of having a monsoon over the South American part. Now, you see this is the surface air temperature and you can see reds are very hot and you can see how hot it is here in the northern summer and this is the Sahara and Arthara desert and this is the Australian desert in the southern summer, but compared to that the temperature contrast is not much over South America and for that matter over Africa also. Africa also there is not that higher temperature, but they Ramesses no problem in calling this monsoonal region, but I believe there is some problem in calling this as far as Ramesses concerned, but then this has been contested in a nice paper called does a monsoon climate exist over South America by Zao and Lau and this came out in 1998 and what they showed was that although the seasonal reversal of the winds is not as spectacular as in the Indian or African monsoon, the major features that is seasonal migration of the rain belt which we see as being associated with the TCZ remember we just saw that and cross equatorial flow which is the next slide up present. Now, you have to remember that see cross equatorial flow is another important facet of the monsoon and see this is the low level flow during the thing and you can see that the air is actually coming from the other hemisphere. Now, you will remember that when the monsoon trough gets established over the Indian region, we have a very large cross equatorial flow which is particularly large near the coast of Africa and that cross equatorial flow we had seen when we looked at the Indian monsoon. Now, that occurs only when you have a well developed trough in the southern hemisphere in the summer hemisphere in that case it sucks in air from the other hemisphere that is precisely what is happening here. You have air coming in from the northern hemisphere into the southern hemisphere and returning to the northern hemisphere that is the heavy line there. So, this is what they showed that they have that they have a cross equatorial flow is there and in fact, we do see TCZ in both the season. So, I personally believe that South America is a monsoonal region since there is a clear seasonal migration of the TCZ, but the monsoon is weaker than the Asian Australian or African monsoon because the temperature gradients are not so spectacular. Now, just to complete the stories this we look at a non-monsoonal region this is the Pacific eastern east central. So, this is 170 west over to 90 west and what you see is in fact, a persistent system which strengthens in July, August and weakens afterwards, but it just hangs around the same place there is no migration and we call it monsoonal. Now, as I mentioned it weakens and we saw that and that is seen here. Now, this is January, February, March when the system is very weak and it is comparable to the you know canonical ITCZ or the ITCZ over the west Pacific only in this part only over our northern hemispheric summer. Here it is very weak, weak rain and let us see now what the vertical circulation looks like and that is very interesting. When we look at 170 west to 90 west, when we look at the summer there is no problem there is ascent through the troposphere here and descent here, but when we look at winter January case then what you see is a heat low kind of a circulation. You see that there is ascent only up to here and there is no ascent throughout the troposphere. So, that what we are seeing in January, February this little rain this little rain this that we are seeing here is actually associated not with the TCZ, but with the heat low kind of circulation. There must be an SST maximum there even in January I am sorry I this is the one this is the Pacific one and so there must be a even in January with there is rain but that rain cannot be attributed to a TCZ that is very clear the TCZ occurs only in this part in the northern summer and that is what this diagram is telling you about the Pacific. Now let us see about the North American monsoon and this is the so called North American monsoon region which is 110 west to 80 west and what you see here is in fact there is considerable rain in the summer and very little rain in our summer northern hemispheric summer and very little rain outside and this is the picture which in fact is very similar to what you saw in the East Pacific adjoining East Pacific because here again you see ascent throughout only in July and what you see in January is a heat low kind of circulation. So what you are getting is not a migration of the TCZ at all is the occurrence of a TCZ only in the northern hemispheric summer. So it is still associated with summer rains no doubt and so are monsoonal regions associated with summer rain but the point is that we believe that monsoonal regions are characterized by seasonal migration of the rain belt from the other hemisphere that does not occur for the North American monsoon. So given this constraint if people would like to call it a monsoon what is in the name but there are major problems and major differences between this and the canonical monsoonal regions of the world. So the seasonal variation of the rainfall and the vertical circulation pattern for the longitudes of North America are strikingly similar to that over the Eastern Pacific it does not seem reasonable to consider the system over North America as monsoonal that is my personal view. Now this is another non monsoonal thing which is Atlantic and there again we are seeing very similar pattern only in one season we are getting a TCZ kind of circulation in January there is none. Since the monsoonal regions are characterized by the seasonal migration of TCZ on to their region in the summer we will consider next the variation of the TCZ over each of the regions on the sub seasonal scale. Now why do we do that because we found that for the Indian monsoon even to understand the monthly scale we had to go to the sub seasonal scale variation it is only when we looked at daily satellite imagery and saw that there were two tropical conversion zone one over the warm equatorial Indian ocean and another over the heated subcontinent to the north and there were fluctuations of these TCZs with northward propagation of the equatorial band on to the heated continent it is only when we realize all this could we understand what the monthly pattern look like. So it is of interest to see are these features actually common to all the monsoonal regions that we have seen or are they special to the Indian region. So to do that we have to again look on the daily scale and I have done it by two ways. Now we had developed because we saw that most of the secret of the tropics was in the tropical conversion zone we had developed a bi-spectral algorithm to identify deep convective clouds. You may remember when I mentioned Garcia's HRC data set highly reflective cloud data set that also was bi-spectral what he had done was first select clouds which were reflecting a lot Albedo was high and then from them filter out clouds which were low or middle height using infrared. Now infrared we have a measure which is OLR which is the standard one most people use and it is not bad because most of the time it is associated with deep convection but we had also developed an algorithm in which we had used two thresholds OLR of 185 watts per meter square and Albedo greater than 0.5 and then use spatial filtering and this was to objectively identify organized convection comprising deep convective clouds. So the both these were available and using this algorithm there is a paper by Godgid and Srinivasan in which we had looked at seasonal sub-seasonal variation of clouds over the entire global tropics. So I am going to just show you what these two things say. So first of all we start from Africa you may remember that 10 degrees east is Africa and June, July, August perhaps I should quickly remind you what that is there we are all right. So this is 10 degrees east here this is the African rain belt that we are looking at and so first of all we are going to see what is the variation in June, July, August of this rain belt and that is what we will see now. This is what we have so that is over 10 degrees east and what we have marked here is actually sorry you are not able to see it but what we have here is again this is less than 200 is the lightest 200 to 180 watts 182 to 160 and below 160, darkest shade is below 160 watts and what you see here is that you know it is a highly intermittent phenomena these deep clouds occur on a regular basis in a certain latitudinal band no doubt and this we have done for 4 years now this is 2009, 2010, 2011 and 2012 this is last year and what you see is that you know it does not last for more than may be 1 or 2 or 3 or 4 days very very short active special and it keeps generating and there are sometimes long spells in which it is absent and these frequency of these long spells is more in some years like you see here then in others 2012 it was an active year and very much more in 2009. In 2009 you see hardly any action going on here and this is for June, July and August 3 months only. So, what you see is there are no propagations the ITCG hangs around in this region and fluctuates in intensity it dies it revives it dies it revives this is the general pattern which is very different from what we saw over the monsoonal region. The first one was OLR and this is from the bi-spectral algorithm that I showed you and this is of course for earlier years 75, 76, 82 and 83 and what you see is something very similar here it appears and disappears not much propagation sometimes it is around for several days most of the time the active spells are very very short. So, this is the nature of the African monsoon you see in contrast now using the very same criteria same shares that we had done for the African one this is 90 degrees east which passes through Kolkata more or less through the head bay of Bengal this is the center of the Asian-Australian monsoon this is for June, July, August and you can see here all the things that we saw that there are two places where it can form either in the south or in the north and there are these very clean northward propagation northward movement that you see this is latitude and this is time and very prominent northward propagation that you see I must mention here this is 2012 normally we have a northward propagation towards last week of July and that you have seen in all these three years very clearly, but this year we had as part of a national climate program we had two ships in the bay trying to study how northward propagation occur one in the head bay near here and one around here and unfortunately you know the ships were here exactly in this period and not a single northward propagation occurred they came back around here and then another propagation occurred see this is the kind of variability we get from year to year. So, even studying it in real life poses its own problem see in other years there are so many frequent northward propagation that we see anyway. So, this is an old story we have seen that 90 degrees is the Indian monsoon there are two modes and there are northward propagation and you see that also with the bi-spectral algorithm again very nice northward propagation that you see here and then hanging around another northward and so many northward propagation here. So, and the fact that there are two places where they get generated here and sometimes here as well. So, the two modes are also very clearly seen now this is 130 is this is just towards the west specific and there also you can see some nice northward propagation somewhat similar to the Indian region and this is 100 west now 100 west is a east specific and what you see here again this is JJA you see that it is always around 10 north. This is the non-monsoonally specific region and it occurs and disappears it appears and disappears it is simply fluctuating in situ there are some propagation, but no clear cut you know dominance of northward propagation or anything like that and you can see there are cases when which it is highly intense and cases in which it is not there at all. So, you get these intense blobs here and here and here when it is very very active, but no propagations and a single location in which it oscillates a band in which it oscillates that is the non-monsoonal one. Now we go to DJF 30 degrees is this is over Africa and over Africa sometimes you do you see some poleward propagation ok. Sometimes you see like in our case a bimodal distribution with a lot of things arising around the equatorial region, but you know they do not occur year after year unlike our region and this is DJF 90 degrees where you are seeing some southward propagations very cleanly, but again only in some years and this is DJF 130. So, now we are getting to the Australian monsoon kind of thing there again there are some cases in which you see very clean poleward propagation, but you do not see them every year it is very different from the Indian region this is again 130 east from our bispectral algorithm there again you see there are seem to be two modes you know here one in the equator and something coming in the north and you see that here as well, but you know both are fluctuating there is no clear cut propagation except you see one here nice propagation which is poleward and this is 70 west. So, this is South America now South America again you see sometimes very nice poleward propagation, but there are also equatorward propagation. So, it is just fluctuating in space as well as in time you know unlike the African one it fluctuates over a much larger latitudinal belt the South American monsoon thing, but there are no clear cut biases towards propagation in one direction you know see for example, here it seems to be propagating towards equator and here also it is propagating towards equator and here it is propagating towards the pole. So, there are differences here and the same story when you look at the bispectral. So, over each of the monsoonal regions the TCG fluctuates from day to day varying in intensity and location with active spells in which it is present continuously for a few days interspersed with spells in which it disappears the most intense TCG is observed over the Asian region and perhaps the weakest is over Africa in June, July, August where it appears to be just an extension if you wish of the TCG over the East Atlantic region. Now poleward propagations are seen over the Indian monsoon region every year during the summer monsoon they are seen in some years over the Asian region and 70 west during the winter djf. In later lectures we shall see that the variation of the monsoon rainfall on sub seasonal scales is a manifestation of this sub seasonal variation of the TCG it also has impacts on inter annual variation. So, now we have a picture of how we get rain over monsoonal regions of the world it is primarily associated with the tropical conversion zone. What is the typical pattern of variation of this tropical conversion zones over different regions from day to day on the sub seasonal scale and of course we can also get variation on the inter annual scale. Now the important thing about identifying the system as a tropical conversion zone is that to understand the fluctuations of this TCG is there are two kinds of hypothesis that we have to test. One is factors that will be important for the oceanic TCG as well these are things like cloud radiation feedback and so on and so forth which can lead to fluctuations of an oceanic TCG. In addition because the monsoonal regions are continental they will be feedbacks that are special to continental TCG which in fact involve things like land surface processes and so on and so forth. So, it is the sum of all these factors that lead to the fluctuations of the monsoonal regions in addition to that of course there is a general factor that TCG is tend to compete with one another. We have seen that for the Indian monsoon region the TCG CTCG competes with the oceanic TCG as well as TCG over the west Pacific and so on. So, there is this tele connections between the different TCG which will also play a role in determining the variability of the TCG and therefore the variability of rainfall. So, there has been some sense in some sense unification of the theories understanding that the monsoon is from one place should not be that different from another the basic system is similar of course differences in topography differences in land surface in the shape and size of continents and so on will have an impact not only on the mean monsoon pattern, but variability and it is only when we understand all this will we be able to predict variability of the monsoon using dynamical models. Thank you.