Presentation on theme: "Microclimate Climatic measurement has revealed that there are many dependencies in atmospheric conditions: where measurements are made significantly affects."— Presentation transcript:
Microclimate Climatic measurement has revealed that there are many dependencies in atmospheric conditions: where measurements are made significantly affects the values observed local microclimates can be distinctive over short distances and differ significantly from the surrounding broader (macroclimate) area One response to this knowledge is the standardization of monitoring methods: to avoid experimental error, measurements follow internationally sanctioned observation procedures established by the World Meteorological Organization http://www.wmo.int/pages/publications/bulletin_en/59_1_nash_en.html http://www.wmo.int/pages/publications/bulletin_en/59_1_nash_en.html 1
Microclimatic differences may be due to: height above the ground (or depth below), time of day, time of year, soil type and condition (porosity, moisture presence), slope steepness and aspect, surface type vegetation type, age, height etc., land use, permeability, albedo, heat emissivity snow cover and type), influences of regional processes (air masses and fronts) Variation in any of these could be seen to produce a distinctive very local microclimate 2
InfluencesComparisons height / depthcooler, windier conditions with increasing height with depth: cooler in summer; warmer in winter timediurnal and annual thermal cycles are well documented surface: soil / slopes sandier soils are more porous and permeable drier and warmer than organic or clay soils hillcrests and steep soils dry out they are warmer south-facing slopes drier they are warmer urban heat sources raise winter and summer temperatures impermeable (urban) surfaces drier they are warmer rural and suburban areas are windier than cities snowforests are warmer than clearings in winter, cooler in summer snow-covered ground is warmer, less variable temperatures in winter; in spring snow-covered ground is damper and cooler regional processesinversions and land/lake breeze only develop if there is no disturbance by air mass fronts or cyclonic activity Some of the patterns these exhibit include: 3
many microclimatic differences relate to the effects of local human activity on the landscape climatic variations exist naturally at many scales, from as fine as one would want to imagine to global One of the most widely discussed is the climatic regimes of cities. the energy budget of cities contrasts with natural landscapes because of the fabricated surface materials (concrete, asphalt, metal etc.), also, because of the concentration of unnatural heat sources – vehicles buildings (heat leakage in winter, air conditioning in summer; longwave radiation at night) industrial processes What is known as a heat island develops in areas of cities as where: foliage is lacking Water is absent elevated temperatures clearly differentiate urban areas from the surrounding rural ones, both diurnally and annually 4
Toronto Urban Heat Island from: http://ess.nrcan.gc.ca/ercc-rrcc/proj2/theme1/act5_e.phphttp://ess.nrcan.gc.ca/ercc-rrcc/proj2/theme1/act5_e.php 7 See also: http://www.urbanheatislands.com/torontohttp://www.urbanheatislands.com/toronto
8 In 1991 the City of Toronto undertook an initiative to combat global warming and improve air quality in Toronto by establishing the Toronto Atmospheric Fund (http://www.city.toronto.on.ca/taf/).http://www.city.toronto.on.ca/taf/ activities have been directed at: reducing the urban heat island because of its contribution to global warming, but also because of the health risk posed by higher ambient temperatures, the resulting chemical reactions that produce smog the heightened emissions from power plants generating electricity for air conditioners. While some successes have been realized, there is still a lot to be done to achieve sustainable goals (http://www.city.toronto.on.ca/taf/pdf/execsum021202.pdf ).http://www.city.toronto.on.ca/taf/pdf/execsum021202.pdf
9 http://www.cleanairpartnership.org/urban_heat_islandhttp://www.cleanairpartnership.org/urban_heat_island Conference (May, 2010): Strategies to mitigate against urban heat included: Cool Roofs - lower air temperatures and improve quality of life in urban areas Green Roofs - improve air quality and liveability; City of Toronto Green Roof bylaw and Green Roof Development Standard Paving options - to mitigate against urban heat Urban Forestry and Landscaping - trees and landscaping options to lower urban heat and conserve energy; strategic planting Policy and Planning Strategies - strategies in place to reduce urban heat, both in Toronto and Canada as a whole; changes to building standards, use of voluntary action incentives, community/secondary/official/master plans, tree protection bylaws and other actions; health impacts of extreme heat; populations vulnerable to extreme heat events Mapping Tools - web based tools for identifying hotspots and vulnerable populations, and enhancing communication around the urban heat island effect; Torontos hot weather response plan as well as Torontos spatially explicit heat vulnerability assessment
10 Contrasts between the citys microclimate and its surrounding areas are more complex: due to the rapid sprawl in the immediate suburbs during the 30-year normals period of calculation because of the presence of Lake Ontario (restrains temperature extremes along its shores) because of the presence of the Oak Ridges Moraine (adds the effect of increased elevation in creating contrasts with the urban area)
11 Within the city centre, there are several microclimatic zones as well (City of Toronto, 1976). Planning concerns were raised in this study, including the disruption of air circulation as taller buildings were proposed for the waterfront Island west shore Island parks Island south shore Outer headland Toronto Bay Eastern industrial zone Urban-harbour transition Urban residential Urban core Don Valley
12 Climatic Change / Scales The concept that climates are changing is now pervasive, but the scientific community is not convinced that the changes have started nor that CO 2 emissions are capable of the dramatic and potentially disastrous shifts being forecast (http://www.greeningearthsociety.org/climate/overview/overview.htm, http://climatechange.unep.net/). Scientific confidence comes only after evidence-based logic which is very difficult to achieve in climatic research, due to the extreme variability of atmospheric conditions. At the same time, there is a logical explanation for, and what seems to be mounting evidence of a general warming at a world-wide scale.http://www.greeningearthsociety.org/climate/overview/overview.htm http://climatechange.unep.net/ It should be noted that prior to 1960, there was no discussion of human impacts on global climates, (http://atlantic.evsc.virginia.edu/~bph/CED5_2/constant.html)http://atlantic.evsc.virginia.edu/~bph/CED5_2/constant.html and that the early advocates were more concerned with cooling. Scientific literature is unambiguous in its determination that all life systems depend on climatic conditions (e.g. http://nigec.ucdavis.edu/publications/annual97/midwestern/project57.html) There is therefore a need to ensure that climates are not significantly altered; quantum changes in climate cannot be taken lightly. http://nigec.ucdavis.edu/publications/annual97/midwestern/project57.html
13 To confirm warming or cooling: science must first document temperature at an early time t 1 Then again at a later time t 2 then subtract As with microclimates, observations are not that simple many circumstances change over time: elements of the energy budget (latent heat, ground heat absorption), as land surfaces change, both naturally and due to human activities some of these may be progressive change (like aging = one-way), others may be cyclical: diurnal annual longer cycles El Niňo La Niňa episodes of sunspot activity These are well known but because of the complexity of energy budgets, their effects cannot be isolated with a scientific level of certainty
14 Climatic variations/changes have occurred in the past and can be categorized by the scale (time span) they cover (secular, historical, geological: Secular climate based on direct measurements (observations) therefore confined to the period during which actual measurements have been recorded (1840 or so) suggest that the average annual temperature for Toronto is 7.8 ° C but like many older weather stations, the site where the measurements were recorded has not remained static: downtown, the Pearson Airport a much shorter period of continuous observation, presumably free from the dramatic surface changes and urban heat island development that have occurred deeper in the city with the effects of local pollution, airport-maintenance procedures and nearby construction, this would be difficult to confirm conclusively. uncertainty may also be introduced by methodological inconsistencies – available instruments have been improved, as has the standardization of where, how frequently and how consistently observations are made.
15 Instruments continue to evolve, so attention to back-calibration will continue to be an issue. For some purposes (e.g. energy conservation) the origin of any apparent rise in temperatures is irrelevant. However for global generalization or prediction of future conditions, causality is important. Eventually measurement records will be long enough to test current hypotheses regarding the modern climatic episode more convincingly, but the currently available observed records permit uncertainty due to their extreme variability and the subtlety of expected changes.
16 Historical climate changes episodes have been inferred from secondary evidence dated by conventional methods used by historians and palaeo- environmental scientists anecdotes (observations of unusual conditions/events – freezing of the Thames River, advance of a glacier over an alpine village, retreat of glacial ice) records of taxation levels for harvested crops topics of paintings sedimentary records (pollen, ice-age and more recent sediments, with corroborating/calibrating of carbon isotope dating) dendrochronology (counting tree rings and measuring oxygen isotopes present in them) anomalies and regularity are typically documented without the tight time control available as evidence for secular changes uncertainty is therefore heightened when only historical inferences are available.
17 Geological-time changes in climates also derived from inferences, but without the corroboration of concurrent written records. largely from sedimentary evidence (pollen, rock strata, with isotope dating) Devils Hole is a tectonically formed caveDevils Hole is a tectonically formed cave developed in the discharge zone of a regional aquifer in south-central Nevada. (See Riggs, et al., 1994.) The walls of this subaqueous cavern are coated with dense vein calcite which provides an ideal material for precise uranium-series dating via thermal ionization mass spectrometry (TIMS). Devils Hole Core DH-11 is a 36-cm-long core of vein calcite from which we obtained an approximately 500,000-year-long continuous record of paleotemperature and other climatic proxies. Data from this core were recently used by Winograd and others (1997) to discuss the length and stability of the last four interglaciations. http://pubs.usgs.gov/of/1997/ofr97-792/http://pubs.usgs.gov/of/1997/ofr97-792/ There is inconsistency between the Devils Hole record and the Milankovitch hypothesis: (that the timing and duration of the Pleistocene ice ages are a direct consequence of variations in solar insolation, in response to changes in the precession, obliquity and eccentricity of the Earth's orbit. The 500,000-year Devils Hole d 18 O record presents four challenges to this theory with respect to: the timing of the penultimate glacial-interglacial transition; the duration of the interglacial climates; the apparent non-stationarity of paleoclimatic time series; and the occurrence of a well-developed glacial-interglacial cycle at a time (450,000-350,000 years ago) when orbital theory indicates that none should occur. ( http://water.usgs.gov/nrp/devils.html) http://water.usgs.gov/nrp/devils.html
18 natural inconsistencies in the stratigraphic record including the compression of time in older deposits significantly reduces the certainty, but it is undeniable that significant changes in climate have occurred in the past. The geological records are seldom so time-specific as to confirm the global- scale synchroneity of climatic episodes, but the presence of fossils, in particular, confirms that climate has not been static. Explanation of the causes of climatic changes over geological and recent time have focussed attention on: terrestrial – properties of the planet and its atmosphere extra-terrestrial hypotheses (are they progressive or cyclical?) To be in a position to predict future climates, or to regulate human activities in order to avert unnatural climatic consequences, requires that explanations be rigorously evaluated.
19 Kelly (2000, http://www.cru.uea.ac.uk/cru/info/causecc/) summarizes the arguments:http://www.cru.uea.ac.uk/cru/info/causecc/ variations in emitted solar energy due to cyclical sunspot activity (about 11 years at present); absence of sunspots in the 1600's coincided with the Little Ice Age or Maunder Minimum, the coldest episode in post-glacial time in Europe, but otherwise not coinciding with climatic amelioration or deterioration Milankovitch Hypothesis: suggested that cyclicity in climates coincide with changes in the earths relationship with the sun: glacial cycles depended on summer radiation due to changes in the earths orbit (http://www.ngdc.noaa.gov/paleo/milankovitch.html):http://www.ngdc.noaa.gov/paleo/milankovitch.html the tilt angle (obliquity) of the earth's axis is not always exactly 23.5° relative to its orbital plane and varies over a 41 000 year cycle (more tilt causes more seasonality) the earths orbit (revolution) varies in two ways: during the year (aphelion [sun is further], and perihelion [sun is closer]), but over a 22 000 year period (seasonal precession) the dates of aphelion [now July] and perihelion [now January]) alternate imperfect roundness, or eccentricity, of the earth's orbit varies on cycles of 100,000 and 400,000 years, affecting how important the timing of perihelion is to the strength of the seasons theoretical but radiometric dating has not been supportive
20 Terrestrial explanations (from Kelly (2000)) include atmospheric changes and well documented are particulates effects: atmospheric dust (from dry periods) but especially volcanic activity - gases or ash reaching the tropopause then encircling the globe interfering with transmission of both short-wave and long-wave radiation e.g. 1991 Mt Pinatubo eruption in the Philippines: Global-mean monthly temperature for the period 1980-1999, showing the effects of the eruption of Pinatubo in 1991. The upper graph shows the complete global-mean temperature record as context.
21 According to CSIRO Australia (http://www.dar.csiro.au/publications/greenhouse_2000e.htm ):http://www.dar.csiro.au/publications/greenhouse_2000e.htm The injection into the stratosphere of 14-26 million tonnes of sulfur dioxide led to a global surface cooling of 0.5°C a year after the eruption. The climatic impact of the Pinatubo aerosol was stronger than the warming effects of either El Niño or human-induced greenhouse gas changes during 1991-93. Superimposed on the sporadic short-lived episodes of volcanic temperature forcing is the impact of industrial society due to its release of CO 2 and other gases (nitrous oxide, and methane) that contribute to enhancing the greenhouse effect. C.D. Keeling and his research team from the Scripps Institute of Oceanography have been recording ambient CO 2 in the atmosphere at Mauna Loa, Hawaii since 1958. Trends display both an annual periodicity (carbon taken up by northern-hemisphere plants in summer, released in winter decomposition) and a year-to-year progressive trend. A similar rise in methane concentration has also been found for some time (Etheridge, D.M., G.I. Pearman, and P.J. Fraser (1994). There is therefore evidence for progressive human interference in the atmospheric properties known to affect global climates.
23 whether the changes or fluctuations that have been observed correspond to the changes in these gases has been controversial in the scientific and political communities for many years (http://www.cato.org/dailys/6-30- 97.html, http://www.climatechangedispatch.com/, http://wonkroom.thinkprogress.org/2010/03/01/science-v-snake-oil/, http://www.financialchat.com/blogs/2010-warmest-year-ever-igniting-climate- change-debate )http://www.cato.org/dailys/6-30- 97.htmlhttp://www.climatechangedispatch.com/ http://wonkroom.thinkprogress.org/2010/03/01/science-v-snake-oil/ http://www.financialchat.com/blogs/2010-warmest-year-ever-igniting-climate- change-debate the public has become aware of what was previously an esoteric climatic issue, especially once climatic phenomena such as the North Atlantic Oscillation, El Niňo and La Niňa, and political activism (Montreal, Rio, Kyoto and Johannesburg accords) were presented widely and intensely in the media North Atlantic Oscillation: the difference in atmospheric pressure that seems to enable prediction of climatic trends in western Europe just as ENSO is the acronym for the El Niňo Southern Oscillation: El Niňo and La Niňa affect conditions around parts of the Pacific Ocean, especially in Australasia, southeast Asia, and South and North America
24 La Niña the little girl, Walker Circulation, or Southern Oscillation cooler than normal waters in the eastern and central Pacific Ocean from patterns to the rainfall in South America noted associations among: Asian monsoons drought in Australia, Indonesia, India and parts of Africa driven by strengthened SE trade winds (in the south Pacific) heavier rainfall in Indonesia and cool upwelling along South America In northern mid-latitudes, the jet stream departs from its normal location and strength, redistributing frontal storm paths; the Weather Network suggests winters have large month-to-month variations in temperature, precipitation and storminess across Canada; wetter and snowier than normal conditions in British Columbia ( http://www.theweathernetwork.com/news/storm_watch_stories3&stormfile=learning_about_l a_nina_060910 ) http://www.theweathernetwork.com/news/storm_watch_stories3&stormfile=learning_about_l a_nina_060910 Canada is affected by mild winters, particularly in the west La Niña animations : http://www.bom.gov.au/climate/enso/surface_anim.gif (observations)http://www.bom.gov.au/climate/enso/surface_anim.gif http://www.bom.gov.au/lam/Students_Teachers/elnanim/elani.shtml (pattern model)http://www.bom.gov.au/lam/Students_Teachers/elnanim/elani.shtml
25 El Niño the little boy, North Atlantic Oscillation (NAO), (also ENSO for full cycle) warmer than normal waters in the eastern and central Pacific Ocean near the equator, initially off the coast of Peru NAO: a difference in atmospheric pressure that seems to enable prediction of climatic trends in western Europe: index of the NAO based on the difference of normalized sea level pressure between Lisbon and Reykjavik, especially in the winter ( http://www.cgd.ucar.edu/cas/jhurrell/nao.stat.winter.html) http://www.cgd.ucar.edu/cas/jhurrell/nao.stat.winter.html In northern mid-latitudes, the jet stream departs from its normal location and strength, redistributing frontal storm paths temperature and precipitation anomalies over Europe: wetter in the north and a drier along the Mediterranean in a high NAO winter; the reverse if a low NAO Environment Canada (Auld and MacIver, 2007) reports the likelihood that intensified droughts and floods will be experienced in many regions more cold-air outbreaks to occur from Western Canada through the Great Lakes. recurrence every few years (4-7year cycle), but certainly not perfectly cyclical
26 The El Niño Southern Oscillation graph (negative values are La Niña events, in blue) ENSO index is multivariate, based on attributes of the tropical Pacific atmosphere : Sea level pressure, zonal and meridonal winds, sea surface temperatures total cloudiness fraction of the sky. research continues, addressing multivariate fluctuations in the intensities of events. Note the two strongest El Niño events in the winters of 1982-83 and 1997-98. http://www.ec.gc.ca/adsc-cmda/default.asp?lang=En&n=DF225829-1 time series from National Oceanic Atmospheric Administration in the United StatesNational Oceanic Atmospheric Administration in the United States El Niño La Niña
27 Note: sea-level pressure anomalies at Lisbon and Reykjavik were normalized by division of each seasonal mean pressure by the long-term mean (1864-1983) standard deviation. normalization is used to avoid the series being dominated by the greater variability of the northern station. positive values of the index indicate stronger-than-average westerlies over the middle latitudes. station data from the World Monthly Surface Station Climatology.World Monthly Surface Station Climatology Additionally, the jet stream pattern tends to allow La Niña conditions in the Pacific Ocean can impact the hurricane season in the Atlantic Ocean. Generally, La Niña conditions are associated with an increased number of hurricanes in the Atlantic, particularly those that originate from waves of low pressure that move westward from Africa and cross the tropical Atlantic Ocean. Hurricanes require very uniform winds from the ground to the jet stream level, and La Niña conditions tend to support this requirement. The opposite occurs during El Niño when increased wind shear across the tropical Atlantic Ocean tends to disrupt hurricane development.
28 Kelly concludes that: For many of the world's population, El Niño and La Niña present a far more tangible threat than the possibility of long-term global warming (http://www.cru.uea.ac.uk/cru/info/causecc/) and others have presented similar interpretations, that fluctuation rather than progressive change dominates global climatehttp://www.cru.uea.ac.uk/cru/info/causecc/ The debate about climatic change versus variability is less of an issue than the one over human implications of the changes. How society copes with climate is an issue given the present state of climatic phenomena. That so many are referred to as natural disasters is an indication of how ill-prepared we are for the extremes that currently exist, regardless of whether or not they intensify in the future. Mere statistical probability suggests that we have not yet recorded the all-time extremes. Action: CO 2 emissions are correlated with emissions of other contaminants with strong acute (immediate) and chronic (long-term) effects once definitive irrevocable causational evidence has become demonstrable, it will be too late to reverse the damage research needs to continue to model scenarios of the geographic extent and quantitative magnitude of predicted and observable changes:
30 options for adaptation need to be addressed: Cities and Communities: The Changing Climate and Increasing Vulnerability of Infrastructure Climate Change: Building the Adaptive Capacity The Americas: Building the Adaptive Capacity to Global Environmental Change Biometeorology and Adaptation: An Overview Influences on the Sugar Maple Industry in North America Changing Weather Patterns, Uncertainty and Infrastructure Risks Adaptation Options for Infrastructure under Changing Climate Conditions Weathering of Building Infrastructure and the Changing Climate Planning for Atmospheric Hazards and Disaster Management Impacts of Climate Extremes on Biodiversity in the Americas A Review of Lightning-related Damage and Disruption Literature Coastal Zone Management under a Changing Climate in the Great Lakes (Environment Canada: http://www.ec.gc.ca/sc-cs/default.asp?lang=En&n=9AF9494E-1)http://www.ec.gc.ca/sc-cs/default.asp?lang=En&n=9AF9494E-1
31 Applications of Climate Understanding Climates set limits on perceived opportunities. What we regard as sustainable activities from agriculture, to transport, and even recreation are based on experiences, whether systematic (scientific) or casual. as more climatic data accumulate, climate change and/or variability should become better known and the sustainability of practices should become clearer if we are attentive Buildings are usually designed to withstand the extremes that are likely, in some societies the reaction to threats such as hurricanes is to expect to rebuild in Canada the National Building Code was developed with the Engineering Climatology Section of Environment Canada, based on specific design elements: winter cold, summer heat and humidity, cooling degree days, snow load, wind, ground frost, and rainfall data geographic records of Wind Energy Resources, Solar Radiation Data and resource assessments for specific locations are also avaialable
32 Climatology applications, continued: climatology also offers opportunities to regulate the extreme temperatures of parking lots (http://wcufre.ucdavis.edu/products/coolparking.pdf)http://wcufre.ucdavis.edu/products/coolparking.pdf cities (http://www.city.toronto.on.ca/taf/pdf/factsheet2.pdf,http://www.city.toronto.on.ca/taf/pdf/factsheet2.pdf optimize sunlight, daylight, wind speed and noise conditions around buildings, (http://www-building.arct.cam.ac.uk/sidgwick/engineering/microclimate.html),http://www-building.arct.cam.ac.uk/sidgwick/engineering/microclimate.html minimize the winter harshness and summer heat of Canadian cities (http://www.city.toronto.on.ca/taf/ct_fact1.ht ) placement of snow fences to collect snow drifts thereby reducing snow risks on highways and railwayshttp://www.city.toronto.on.ca/taf/ct_fact1.ht design of wind-breaks to protect cropland from wind erosion of soils (http://www.forestry.iastate.edu/res/Shelterbelt.html )http://www.forestry.iastate.edu/res/Shelterbelt.html select sites for aerogenerators (consistent winds)
33 Climatology applications, continued: Managing microclimate as an objective in many agricultural practices including crop selection (http://www.heritage.nf.ca/environment/climate_applications.html)http://www.heritage.nf.ca/environment/climate_applications.html choosing of row orientation (north-south, rather than east-west) pruning of trees and vines to maximize sun exposure deciding to grade, spray and/or burn to reduce frost damage excavating and draining to dry the ground to raise spring soil temperature The World Meterological Organization has hosted conferences on the relationship between climate and food production, including one dealing with the uncertainties introduced by climatic variability and change (http://www.wmo.ch/web- en/fooden.html).http://www.wmo.ch/web- en/fooden.html Knowledge of climate has even been applied to espionage (Anonymous (1974). CIA Report: A Study of Climatological Research as it Pertains to Intelligence Problems. pp. 161-196 in The Weather Conspiracy: The coming of the New Ice Age Ballentine Books (1977), in particular to prediction of crop yields.
34 References AFP, 2011, Thawing permafrost may speed global warming: study http://www.france24.com/en/20110217-thawing-permafrost-may-speed-global-warming- study-0 Ahrens, C.D., 1999, Meteorology Today, West Publishing, St. Paul, Minnesota. Auld, H., and MacIver D., 2007, Changing Weather Patterns, Uncertainty and Infrastructure Risks: Emerging Adaptation Requirements, Environment Canada Adaptation and Impacts Research Division (AIRD), Occasional paper # 9Occasional paper # 9 Bryson RA, 1966: Air masses, streamlines, and the boreal forest. Geographic Bulletin, 8: 228– 267. Bryson, R.A., Irving, W.N., and Larsen, J.A. (1965). Radiocarbon and soil evidence of former forest in the southern Canadian Tundra. Science, 147(3653):46-48. Etheridge, D.M., G.I. Pearman, and P.J. Fraser, 1994, http://www.epa.gov/methane/links.htmlhttp://www.epa.gov/methane/links.html Houghton, J., 1997: Global Warming, Cambridge Univ. Press, Cambridge, U.K. City of Toronto, 1976, Climate, Central Waterfront Planning Committee, Planning Board. Kelly, M., 2000, The causes of climatic change, Climatic Research Unit, School of Environmental Sciences, University of East Anglia Norwich, UK. (http://www.cru.uea.ac.uk/cru/info/causecc/)http://www.cru.uea.ac.uk/cru/info/causecc/
35 Munn, R., Hirt, M., and Findlay, B., 1969, A climatological study of the Urban temperature anomaly in the lakeshore environment at Toronto, J. of Applied Meteorology v. 8, No. 3, pp 411-422. Miess, M., 1979, The climate of cities, Ch 4, in Laurie., I., (Ed), Nature in Cities, Wiley, New York, pp91-114. Oke, T.R., 1987: Boundary Layer Climates, Routledge, London, U.K. Walker, G.T., 1924: Correlations in seasonal variations of weather. I. A further study of world weather. Mem. Indian Meteorol. Dep. 24, 275-332.