Earth Hydrological CycleMETR112 Global Climate Change – Lecture 3: Earth Hydrological CycleProf. Menglin Jin, San José State UniversityRelations between heat and water cycles• Temperature change and hydrology cycleVideohttp://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/hydrological%20cycle/DTS-9.mp4Jim Hansen:Notes: While watching this video, think what sub-components of hydrological cycle is mentioned.What is hydrological cycleThe hydrological cycle. Estimates of the main water reservoirs, given in plain font in 103 km3, and the flow of moisture through the system, given in slant font in103 km3/yr, equivalent to Exagrams (1018 g) per year. (Trenberth et al. 2006a).Major components of hydrological cyclePrecipitation Evaporation & evapotranspiration Atmospheric transportRunoff and ground water flowWater reservoir (ocean, lake, glacier, soil water, etc.)Precipitation:Rain gaugeStandard rain gauge used in observing precipitationPrecipitation:Radar & satelliteRadar detecting the cloud by collecting reflected microwavesSatellite observe earth in microwave or infrared channels from space and estimate precipitation using retrieval techniquesTRMM: Unprecedented Views of HurricanesPrecipitation:Observations show great spatial variationU.S. WSR-88D Frequency of Rainfall Occurrence for 1998 - 2000Precipitation:Observations show decadal variation of precipitation changePrecipitation:Observations show decadal variation of precipitation change alternativeDifferent data sets all show similar decadal variationsPrecipitation:IPCC AR4 Changes are not spatially uniformGeneral increase of precipitation in most areas in mid- and high latitude, Decreased precipitation in the Western, Southern Africa and SahelWith mixed signs in EurasiaPrecipitation increases in Northwest IndiaSource: IPCC AR4 - Chapter 3, Adopted from: Richard CJ Somerville, APRU World Institute Workshop, 2007Precipitation variation is complex over the landIncreasesDecreasesVideo• http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/hydrological%20cycle/DTS-3.mp4Figure 3.35. Annual values of the East Asia summer monsoon index derived from MSLP gradients between land and ocean in the East Asia region. The definition of the index is based on Guo et al. (2003) but was recalculated based on the HadSLP2 (Allan and Ansell, 2006) data set. The smooth black curve shows decadal variations.Significant decrease in East Asian Monsoon index since 1976/77 climate shiftFigure 3.35East Asian summer monsoon index: Sum of mean sea level pressure differences between 110oand 160oE for 20oto 50oN with 5odifference.RainfalldecreaseFigure 3.36Figure 3.36. Time series of northern Australian (north of 26°S) wet season (October–April) rainfall (mm) from 1900/1901 to 2004/2005. The individual bar corresponds to the January of the summer season (e.g., 1990 is the summer of 1989/1990). The smooth black curve shows decadal variations. Data from the Australian Bureau of Meteorology.Current global climate a boon for Australian Monsoon?Statistically significant rainfall show up in predominantly northern parts of Australia Primarily due to additional southern Australian land heat up while no/cold Anomalous changes in oceansFigure 3.37Figure 3.37. Time series of Sahel (10ºN –20ºN, 18ºW–20ºE) regional rainfall (April–October) from 1920 to 2003 derived from gridding normalised station anomalies and then averaging using area weighting (adapted from Dai et al., 2004a). The smooth black curve shows decadal variations.African Monsoon shows clear signal due to changes in ENSOBoth tropical Pacific and Atlantic SSTs have effects on African Monsoon Many studies show deforestation would amplify draught signalsEvaporation (evapotranspiration) observations are limitedPan evaporation observes the potential evaporationBowen ratio system observes evapotranspiration using energy balance(Trenberth and Stepaniak 2003)Would distribution of annual averaged Latent heat flux from 1979 to 2001 from reanalysisTrend of pan evaporation in US from 1950 to 2001annualWarm seasonBlue (red) is decrease (increase), circle is sig at 90%Hobbins and Ramirez 2004ERA15 (solid curve), COADS (dashed), CE91-95 (dotted curve)Zonally-averaged annual evaporation shows an M-shaped distribution15-year ECMWF reanalysisGarnier et al. 2000One way of measuring soil moisture: gravimetric method Two types of augers used for gravimetric soil moistureobservations, sitting on a neutron probe. The one on the left is pounded into the ground and used when the ground is frozen. The one on the right is twisted into the groundRobot et al. 1999soils.usda.gov/use/worldsoils/mapindex/smr.htmlMajor soil moisture climate regimesSeasonal cycles of soil moisture for various areasRobot et al. 1999The most recent monthly averaged soil moisture for USDecreased spring snow covered area in Northern AmericaStatistically significant decline in annual SCA for 2.7x10^4 km^2SCA maximum shift from February to January and earlier snow meltMelting season shift two weeks earlier from 1972 to 2002Snow:Snow cover anomalies in from 1966 to 2006 for northern Americahttp://www.arctic.noaa.gov/detect/ice-snow.shtmlSnow cover anomalies in from 1966 to 2006 for Eurasiahttp://www.arctic.noaa.gov/detect/ice-snow.shtmlArctic sea ice extent decreases in the last 20 years annual: -2.7%/decSea ice:The annual sea ice extent decrease steadily from 1980summer: -7.4%/decMost remarkable change is the summer sea ice diminish, in which the interannual to decadal variability is associated with the variability of atmospheric circulation Summer sea ice decrease in tremendous in the last 20 yearsGlacier and ice cap mass loss in response to 1970 warming(Science basis, Chap.4, Fig.4.15)Strong negative specific mess balances in Patagonia, Alaska after mid 90s, cumulative balance equivalent to 10m of water (11m of ice)Total mass loss are contributed mainly from Alaska (0.24 mm/yr of SLE), Arctic (0.19 mm/yr of SLE) and Asia high mountains (0.1 mm/yr of SLE)Glacier:Video: HimalayasMuir glacier ， Alaska1941 2004Decreased ice extent in KilimanjaroAggressive retreat of Antarctica peninsula ice shelfGreenland melt extent seeing from satellite2005 summer ice extent set a record during 27-year period. 2005 also shows a especially long melting season (until late Sep) compared to previous years according to Steffen et al. 2004, Hanna et al. 2005Greenland melt area during summer time increases from 1979 to