Earth Hydrological Cycle

METR112 Global Climate Change – Lecture 3: Earth Hydrological Cycle

Prof. Menglin Jin, San Jose State University

Relations between heat and water cycles

• Temperature Increase and Pan Evaporation decrease Video

http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/hydrological%20cycle/

DTS-3.mp4

What is hydrological cycle

The 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 cycle Precipitation Evaporation & evapotranspiration Atmospheric transport Runoff and ground water flow Water reservoir (ocean, lake,

glacier, soil water, etc.)

Precipitation: Rain gauge

Standard rain gauge used in observing precipitation

Precipitation: Radar & satellite

Radar detecting the cloud by collecting reflected microwaves

Satellite observe earth in microwave or infrared channels from space and estimate precipitation using retrieval techniques

Precipitation: Observations show great spatial variation

Bosilovich et al. DOI: 10.1175/2008JAMC1921.1

Precipitation: Observations show decadal variation of precipitation change

Precipitation: Observations show decadal variation of precipitation change

alternative

Different data sets all show similar decadal variations

Precipitation:

IPCC AR4

Changes are not spatially uniform

General increase of precipitation in most areas in mid- and high latitude,

Decreased precipitation in the Western, Southern Africa and Sahel

With mixed signs in Eurasia

Precipitation increases in Northwest India

Source: IPCC AR4 - Chapter 3, Adopted from: Richard CJ Somerville, APRU World Institute Workshop, 2007

Precipitation variation is complex over the land

Increases

Decreases

Video

• http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/hydrological%20cycle/

DTS-3.mp4

Precipitation: Changes in seasonal variations vary spatially

(Chen et al. 2002)

Precipitation: Intensified extreme precipitation in mid-latitudes

More wet days (upper 5%) and heavy precipitation (upper 5% percentile) in US and most Europe

Increased possibility of intense precipitation in most extratropical regions

Decrease of heavy precipitation in central Africa, south east Asia, west Europe and west Australia

IPCC AR4

Figure 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 shift

Figure 3.35

East Asian summer monsoon index: Sum of mean sea level pressure differences between 110o and 160oE for 20o to 50oN with 5o difference.

Rainfalldecrease

Figure 3.36

Figure 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 oceans

Figure 3.37

Figure 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 ENSO

Both tropical Pacific and Atlantic SSTs have effects on African Monsoon Many studies show deforestation would amplify draught signals

Evaporation (evapotranspiration) observations are limited

Pan evaporation observes the potential evaporation

Bowen ratio system observes evapotranspiration using energy balance

(Trenberth and Stepaniak 2003)

Would distribution of annual averaged Latent heat flux from 1979 to 2001 from reanalysis

Trend of pan evaporation in US from 1950 to 2001

annual

Warm season

Blue (red) is decrease (increase), circle is sig at 90%

Hobbins and Ramirez 2004

ERA15 (solid curve), COADS (dashed), CE91-95 (dotted curve)

Zonally-averaged annual evaporation shows an M-shaped distribution

15-year ECMWF reanalysis

Garnier et al. 2000

One 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 ground

Robot et al. 1999

soils.usda.gov/use/worldsoils/mapindex/smr.html

Major soil moisture climate regimes

Seasonal cycles of soil moisture for various areas

Robot et al. 1999

Relations between heat and water cycles

• Temperature change and hydrology cycle

Video

http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/hydrological%20cycle/

DTS-9.mp4

Jim Hansen:

The most recent monthly averaged soil moisture for US

Decreased spring snow covered area in Northern America

Statistically significant decline in annual SCA for 2.7x10^4 km^2 SCA maximum shift from February to January and earlier snow melt Melting season shift two weeks earlier from 1972 to 2002

Snow:

Snow cover anomalies in from 1966 to 2006 for northern America

http://www.arctic.noaa.gov/detect/ice-snow.shtml

Snow cover anomalies in from 1966 to 2006 for Eurasia

http://www.arctic.noaa.gov/detect/ice-snow.shtml

Arctic sea ice extent decreases in the last 20 years

annual: -2.7%/dec

Sea ice:

The annual sea ice extent decrease steadily from 1980

summer: -7.4%/dec

Most 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 years

Glacier 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: Himalayas

Muir glacier ， Alaska

1941 2004

Decreased ice extent in Kilimanjaro

Aggressive retreat of Antarctica peninsula ice shelf

Greenland melt extent seeing from satellite

2005 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. 2005

Greenland melt area during summer time increases from 1979 to 2005

Intensified precipitation intensity in 21st century

Shrinking of Greenland ice-sheet in a warmer climate

Evolution of Greenland surface elevation and ice sheet volume versus time in the experiment of Ridley et al. (2005) with the UKMO-HadCM3 AOGCM coupled to the Greenland Ice Sheet model of Huybrechts and De Wolde (1999) under a climate of constant quadrupled pre-industrial atmospheric CO2.

Class Participation 2/10/2010

• Work with your groupmates to

Find out the changes in hydrology cycle (in terms of rainfall, soil moisture, EP, and snow coverage etc) in your grandmother’s hometown/home country