The monsoon is the great life-giver and the great destroyer of the subcontinent. Without rain from these annual storms, crops wither, animals die and more than half the world's population suffers from potential famine. With too much rain, crops are inundated, animals drown and people suffer from floods and the diseases that follow in their wake. Observations of this critical climate system stretch back decades, and the overall level of rainfall has changed little over the years. But now researchers have discovered a trend within the annual measurements toward fewer, more extreme downpours--a trend that bodes ill for flooding and other natural disasters.

B. N. Goswami of the Indian Institute of Tropical Meteorology and his colleagues studied rain gauge data from 1,803 stations scattered throughout central India from 1951 to 2000. As expected there was a wide range of rainfall: from a maximum downpour of 58.2 centimeters in one day (nearly 23 inches) to none, with an average of just 5.7 millimeters (just under one quarter of an inch) a day during the season.

The researchers divided storms into several categories ranging from light (between five and 100 millimeters a day) to very heavy (more than 150 millimeters a day). Over the last few decades of the 20th century, such light events have declined significantly while their heavier counterparts have increased. In fact, the largest storms of the 1950s are smaller than their counterparts of the 1990s. "Heavy and very heavy rain events over central India have increased significantly since the 1950s," Goswami notes. "Also, the magnitude of the very heavy events in a given year has shown a clear increasing trend."

This increase in large storms has been masked in the overall rainfall data by the decline in more moderate downpours. "As the weak and moderate events decrease, their contribution to the mean decreased while the increasing number of heavy and very heavy events make an increasing contribution to the mean," Goswami explains. "These two opposing contributions roughly balance each other and keep the mean unchanged."

But even though the average has not changed, the potential for extreme downpours--and hence flooding and other ills--has, jumping 10 percent and still rising. This is an important and increasing risk going forward, according to the researchers. The number of strong tropical cyclones continues to increase as well, linked perhaps to the gradual increase in Indian Ocean sea surface temperatures. "The results are consistent with what may be expected under global warming," Goswami adds. "We are working on various other aspects of the impact of climate change on the Indian monsoon using this data set." In the meantime, his forecast calls for floods.

1 Comments

1. 1. chondral7 11:28 AM 7/5/09

   Why extreme climate model predictions above 5 Celcius increase may be unrealistic Hotlist
   by chondrally [Unsubscribe] [Edit Diary]
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   Thu May 28, 2009 at 08:51:35 AM PDT
   
   Water vapour and liquid water are highly underrated in analyzing climate. All the talk is about CO2, methane and CFCs etc..., why they always say that water is a greenhouse gas, and that it is the most important one, they never tell you why or what about it makes it a very unique GHG, and how water vapour and water vapour alone, might curtail the extremely long fat tail of the Nature Journal climate sensitivity probability distributions for the likely or probable temperature increase for a doubling of CO2 and the entrained methane increase in the atmosphere.
   
   I describe that the heat capacity of water and its ability to act as a substantial heat sink and capacitance for heat, and the atmospheres ability to hold extra evaporated water vapour exponentially as it heats up and subsequent precipitation really cools things down and clears the air.
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   Water vapour and liquid water are highly underrated in analyzing climate. All the talk is about CO2, methane and CFCs etc..., why they always say that water is a greenhouse gas, and that it is the most important one, they never tell you why or what about it makes it a very unique GHG, and how water vapour and water vapour alone, might curtail the extremely long fat tail of the Nature Journal climate sensitivity probability distributions for the likely or probable temperature increase for a doubling of CO2 and the entrained methane increase in the atmosphere. I describe that the heat capacity of water and its ability to act as a substantial heat sink and capacitance for heat, and the atmospheres ability to hold extra evaporated water vapour exponentially as it heats up and subsequent precipitation really cools things down and clears the air.
   
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   * chondrally's diary :: ::
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   I want to talk about specific and relative humidity in the atmosphere, and how it might prevent the worst extremes of climate heating from happening.
   
   First of all, methane when combusted produces CO2 and water in the following equation:
   
   CH4 + 2 O2 --> CO2 + 2 H2O
   
   it uses up Oxygen from the atmosphere and produces twice as much water per mol of methane as it does CO2
   
   similarly octane in vehicles produces:
   
   C8H18 + 12.5 O2 --> 8 CO2 + 9 H2O
   
   this uses 12.5 mols of O2 for every mol of octane, and produces 8 mols of CO2 and 9 mols of H2O
   
   Coal can be examined too, and is the subject of a previous blog and depends very much on the quality of the coal and its impurities and hence source. but for every mol of actual carbon
   
   C + O2 --> CO2
   
   it only produces carbon dioxide and not water, so it is the most dangerous of all fossil fuels.
   
   Heres why:
   
   Its a very good thing the other fossil fuels produce water vapour.
   
   We should try at some time to estimate how much extra water has been released from fossil fuel combustion since pre-industrial times..... it would really be an interesting statistic and a crucial and possibly planet saving one at that.
   
   There are data about the amount of water vapour and clouds and precipitation in the atmosphere going back to 2003 on a minute by minute basis, the AIRS and AMSU satellite programs use microwave bands to probe the water vapour and humidity content of the atmosphere and revisit the same spot twice in one day, and cover the globe every half day. Similarly, the infra red satellites accomplish monitoring of the water cycle and energy cycle of the earth 24/7.
   
   'http://www.mad.zmaw.de/wdc-for-climate/
   
   'http://wdc.dlr.de/sensors/amsu/
   
   see also the info for AIRS
   
   'http://lwf.ncdc.noaa.gov/oa/ncdc.html
   
   'http://www.nsof.class.noaa.gov/saa/products/catSearch?keyword=AMSUhttp://www.nsof.class.noaa.gov/sa a/products/search?datatype_family=IASI
   
   With this information, temperature and humidity and precipitation information can be gathered as well as cloud formation information going back to 2003.
   
   Beware this is a LOT of data. you will also need access to the documentation and tools for processing the database information.
   
   Half a days data is about 12 GB, and covers the planet Earth once in about 12 hours.
   
   I notice todays weather locally is a bit foggy and very humid in southern ontario. It is also very cool.
   
   The heat capacity of water at constant pressure as a gas (at 100 degrees Celcius, 212 degrees Fahrenheit, 373.15 Kelvin) is about 33.6 Joules/mol/degree Kelvin(Celcius) so it takes 33.6 Joules of energy to heat up one mol of water as a gas by one degree Kelvin(Celcius also). Water as a liquid has a heat capacity at constant pressure is about 70 J/mol/K
   
   So liquid water has a higher heat capacity than the gas does. There are many tiny aerosol,pollen and dust (just look at the difference between the southern and northern maldives) particles in the air. when the temperature dips a little, water can condense from the humidity gaseous state to tiny clumps of water aroud these 'seed droplets'. They may contain 21 to 50 molecules of water more or less.
   
   Quantum mechanics has been able to model clusters of water molecules and their heat capacities up to clusters of 20 molecules of H2O, beyond that we are in ignorance, below that , we can do some modeling with QM results.
   
   Ref: Attention, these links don't work as hot links, you need to type them or copy and paste to get them to work.
   'http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JCPSA600012800000909430400 0001&idtype=cvips&gifs=yes
   
   'http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JCPSA600007900000500237500 0001&idtype=cvips&gifs=yes
   
   'http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JCPSA600010800002401016200 0001&idtype=cvips&gifs=yes
   
   'http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JCPSA600011700001400657300 0001&idtype=cvips&gifs=yes
   
   'http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JCPSA600011300001600665200 0001&idtype=cvips&gifs=yes
   '
   'http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JCPSA600009700000400262600 0001&idtype=cvips&gifs=yes
   
   So there is also chaos theory applied to water , and also Avogadros number
   
   6.023E23 approximately molecules per mol of water. This makes QM results alone impossible and bulk thermodynamic properties of clouds and supersaturated air need to be taken into account, probably from satellite data.
   
   But the real story is the huge heat capacity of water and water vapour.
   
   It means it takes a huge amount of energy to raise the temperature of water in clouds which have a constant pressure heat capacity between 33.6 and 70 J/mol/K, as they are not a complete liquid and not a complete gas, with aerosol like clusters of liquid water suspended in humid air.
   
   Relative humidity is relative to saturated air 100%, and air can become supersaturated under some conditions. We will talk now about specific saturation in g of H2O per kg of air, independent of pressure and volume.
   
   The following reference is useful.
   
   'http://74.125.95.132/search?q=cache:7gceueOIbJIJ:www.questgarden.com/53/80/0/070804084322/files/Hum idity_and_Temperature_in_the_Atmosphere.doc+modeling+humidity+and+temperature+in+the+atmosphere& cd=1&hl=en&ct=clnk&gl=ca&client=firefox-a
   
   The following chart shows the saturation specific humidity (100% relative humidity) at different temperatures in the atmosphere.
   Saturation Specific Humidity versus Temperature in the Atmosphere Temp. (� C) Spec. Hum. (g/kg)
   -40 0.1
   -30 0.3
   -20 0.75
   -10 2
   0 3.5
   5 5
   10 7
   15 10
   20 14
   25 20
   30 26.5
   35 35
   40 47
   
   The relationship is postualated to be exponential.
   
   This chart is crucial, in that it shows that the air can hold more water as the temperature increases, and does so exponentially (postulated). It means that there might be a natural feedback system , if there is sufficient water vapour present, to control and act as a capacitance or heat sink to moderate temperature increases, remember, as the temperature increases, more evaporation occurs, and the more the air will hold of moisture.
   
   Remember also that the 71% of the Earths surface is covered by water, salty or fresh. So that evaporation from these sources would occur if the temperature got high enough or there were also concommittent winds.
   
   This process could well lead to more storms and precipitation.
   
   Because of Quantum mechanics, Relativity and chaos theory and Avogadros number, and the inability to solve for turbulent fluid flow with computers in any reasonable time frame, it is impossible to predict specific weather far enough out into the future, however bulk statistics of median and extreme behaviour including extreme value distributions can be useful in predicting the frequency of extreme events under bulk conditions. It is also , due to the high heat capacity of water
   
   Possible to say that the very fat tail of the climate sensitivity plots in the recent Nature journal are unlikely because this heat sink and the feedback effect elucidated here, are more likely to offset extreme temperature increases. Simulations taking this into account need to be completed before definitive findings can be announced however.
   
   just add Nox and methane hydrates as a friend said, and temperature becomes pretty unstable.
   Numerical methods themselves, required to solve partial differential equations in 5D, space-time and matter-energy are required and stephane mallat can make a contribution to this to the required scale of accuracy.
   also Wesson, also Mitra.
   Relativity comes into it in terms of the dark holes out there that exist in human consciousness, equivalent to dark holes that attract wealth and matter and people into them. but this is a bit hand wavy too.
   Nothing like a bit of vagueness and handwaving to get a controversy going.
   
   but then you have to nail it down with facts later on.
   I submit that Chaos theory and Numerical Methods and Mallat's signal processing will play a crucial role in predicting, if at all possible, but it needs a dictionary and an order N FFT equivalent to work, and on only the scales of importance, if those small scales have lyapunov exponents that propagate up in space and time or energy and matter to any significant momentum, they need to be identified and perhaps mitigated. Ocean acidification and the uncertainty of temperature are huge effects that for any rational human being, should determine a change of course, rather than MAD.
   
   Maybe Mallat and music and cuisine and the perimeter institute have something to do with it in the dark hole bistro.... hope Hawking recovers...
   i'm going to put on some nice guitar music by Andrei Krylov and get mellow, for the time being. Biology and dogs and cats and horses and sheep and cows and pgis probably have something to do with it too...
   
   They can take a film (a 2D representation) of a turbulently flowing waterfall, or they can set up an elaborate MRI device for a small section of it to get 3D and time (never been done yet) and record it, but they can't model it and predict it in real time.
   
   Best regards,
   
   Chondrally
   
   Without constraints it is unlikely that anything of any value will ensue Richard Belshaw Wellington-Halton Hills EDA
   

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