Effects of Land Cover Change on local and regional climateOutlineLitvak Lab ThemeLitvak Lab Theme:My own research: SavannasJuniper encroachment in Texas savannasSlide 7Land Cover ChangesSlide 9Deforestation and forest degradationSlide 11Slide 12Slide 13Slide 14Deforestation of tropical forestBoreal deforestationSlide 17Slide 18Deforestation of boreal forestsUrban growthSlide 21Urban Heat IslandsSlide 23Slide 24ConclusionsEffects of Land Cover Change on local and regional climateAnn ThijsPhysical ClimatologyDecember 1, 2005Tropical deforestation, BorneoOutlineThe Litvak Lab just a bit of my own researchLand Cover ChangeDeforestation tropical forestDeforestation boreal forestUrban developmentLitvak Lab ThemeHow does vegetation change alter biogeochemical cycles?Vegetation Changes studied:Succession after fire in boreal forestEffect of burn season in savanna grasslandsEffect of invasive grass KR Bluestem Woody encroachment in Texas savannasWoody encroachment in New Mexico Pinon-Juniper woodlandsLitvak Lab Theme:Biogeochemical cycles:Biosphere-Atmosphere exchange of energy, water and CO2(importance for carbon cycle and local / regional climate)Soil processes: nitrogen cycle, carbon sequestrationMy own research: SavannasOne eighth of global land surfaceContinuous herbaceous layer and a discontinuous stratum of shrubs and treesWoody encroachment: “the addition of woody canopies without major losses of herbaceous cover”Causes: chronic overgrazing, disturbance of the natural fire cycle, rising CO2 levels, altered precipitation regimes, nitrogen pollution1965 1975 1990 1995Juniper encroachment in Texas savannasAltered ecosystem function:Energy balance:decreased albedo ???higher latent and sensible heat exchange ???lower surface temperatures ???Water balance:increased evapotranspiration ???lower groundwater recharge ???Carbon balance: Considered a carbon sink, but remains one of the largest unknowns in the North American carbon balance.Eddy covariance towerLand Cover ChangesEnvironmental Issue of global significance – 35 % land surface already alteredLinked to other global issues:BiodiversityClimate System and Carbon CycleSustainability of agriculture Provision of safe drinking waterInfectious diseasesLand Cover ChangesDeforestation tropical forestDeforestation boreal forestUrban development: UHIDeforestation and forest degradationMain areas of forest-cover change over 20 years (1980-2000) (Lepers et al, 2005)Hotspots:Tropical:Amazon basinSoutheast AsiaBoreal:SiberiaTropical deforestationSnyder et al, 2004Tropical deforestationSnyder et al, 2004Tropical deforestationSnyder et al, 2004Tropical deforestationSnyder et al, 2004- 30 %+0.6 -- +3.8 °C-1.0 – 1.6 mm/dayDeforestation of tropical forestMostly changes in water balanceModel Results:Decreased surface roughnessoReduced ET, latent heat fluxoIncreased surface temperaturesoPrecipitation decreasesIncreased albedo, lower net radiation (smaller effect)Boreal deforestationSnyder et al, 2004Boreal deforestationSnyder et al, 2004Boreal deforestationSnyder et al, 2004156 % increase-2.8°C+9%Deforestation of boreal forestsMostly changes in surface energy balanceEspecially in winter/spring: removal of vegetation exposes snow surfaces and increase albedo, leading to lower net radiation and lower surface temperaturesClimate response can be amplified by a SST / sea ice / albedo positive feedbackUrban growthPopulation density in 1995 and most populated and changing cities over 750000 inhabitants between 1980 and 2000 (Lepers et al, 2005)Highest densities:India China JavaMajor cities:Western Europe East coast US India East AsiaGrowth:Tropical beltvisibleearth.nasa.govUrban Heat IslandsUrban Heat IslandsIncreased minimum temperature at nightSmall increase or decrease maximum temperature during dayDecrease in diurnal range of temperaturesUrban Heat IslandsTraditional methodInnovative method:Time series from weather stationsTime series from NCEP/NCAR-DOE re-analysis (R-1 or R-2) (estimate of surface T solely dependent on atmospheric measurements - independent of surface coverContribution of warming due to land cover change or increased greenhouse effectZhou et al, 2004Traditional estimate warming effect:0.06-0.15°C per century in the US Estimate using innovative method0.37°C per century in eastern US (Kalnay and Cai, 2003)0.5°C per century in China (Zhou et al, 2004)Urban Heat IslandsConclusionsLand Cover Change extensive and has demonstrated impact on climateStudy methods:Very localized empirical measurements - e.g. eddy covariance, FLUXNETModeling approaches – mostly coupled atmosphere-biosphere models; need to use coupled atmosphere-biosphere-ocean modelsTime series analysis – e.g.
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