GEOL 437: Global Climate Change 2/13/18: Water in the Climate System

Transcription

1 GEOL 437: Global Climate Change 2/13/18: Water in the Climate System The peculiar properties of water The role of water in the climate system Where does water fit into our picture of the climate system?

2 Water in the Climate System Key concepts Density Heat capacity Saturation vapor pressure Latent heat Where does water fit into our picture of the climate system?

3 Where's the water in this picture? Source: Skelgaard home page (

4 Water is everywhere in this picture! Solid Liquid Vapor Skelgaard home page (

5 Density of seawater Density (high) increases as temperature decreases But ice density is 91.7% of liquid density: ice floats! sea water density variations drive deep ocean circulation (Thurs) Source: Millero and Poisson (DSR 28: , 1981) equation of state for seawater at surface; coded in matlab by E.T. Peltzer, MBARI

6 Properties of water: Heat capacity and density Water Specific heat capacity: 4187 J/Kg*K Density (seawater): 1026 Kg/m 3

7 Properties of water: Heat capacity and density Water Specific heat capacity: 4187 J/Kg*K Density (seawater): 1026 Kg/m3 Air Specific heat capacity: 1007 J/Kg*K Density: Kg/m 3 What depth of the ocean contains the same amount of heat as the entire overlying atmosphere? (Gill, 1982)

8 Heat capacity and the ocean-atmosphere system Apr 1997-Mar 1998 SST anomalies from Reynolds and Smith (1994), acc. 2/22/10 El Nino (La Nina) represents a huge sensible heat surplus (deficit) for the atmosphere

9 Saturation vapor pressure saturation vapor pressure as a function of temperature (I. Mosquera, following Goff and Gratch (1946)) Saturation vapor pressure increases exponentially with temperature Warm oceans transfer a lot of latent heat to the atmosphere

10 Hurricane/typhoon formation Source: Naval Research Laboratory HYCOM consortium for data assimilative ocean modeling, SST nowcasts, accessed 2/20/14

11 Super Typhoon Haiyan (Yolanda) Surigao City Wikipedia, Super Typhoon Haiyan, and original sources cited therein, acc 2/13/18 Philippines: 5-6m waves; maximum 1 min winds: 195mph (record, until 2015) Nov 3-11, 2013: maximum 10min sustained winds: 145mph 11.1 rain, much within 12h (Surigao city)

12 Phase changes Schematic from acc. 2/20/14 Specific heat of water = 4 J/g*degC Latent heat of melting/fusion = 3.34 x 10 5 J/Kg: very high Latent heat of vaporization/condensation = 2.25 x 10 6 J/Kg: v. high!

13 Phase changes and heat transport P > E; latent heat of condensation released to air from atm. vapor condensation, fueling circulation P < E; latent heat of vaporization added to atmosphere from ocean; heat stored as water vapor Precip. Evap. Source: Wallace and Hobbs, Atmospheric Science (1977) Much heat transport in the atmosphere arises from transport/phase change of moisture

14 Radiation (albedo) Source: National Sea and Ice Data Center, acc 2/13/18 Albedo varies with phase: ice = 0.9; liquid water = 0.2

15 Percent outgoing longwave radiation absorbed Radiation (absorption) Source: Skinner et al., the Earth System Water vapor is an important greenhouse gas

16 Radiation (clouds) and climate Cirrus (wispy, thin, high altitude clouds) photo from the Univ. of Illinois WW2010 project ( home.rxml). These generally keep the surface warm by radiating to space at a very cold temperature. Low-lying nimbostratus (rain-bearing layered clouds) photo from the Univ. of Illinois WW2010 project ( cldtyp/home.rxml). These generally keep the surface cooler by reflecting a lot of incoming radiation out to space, and by themselves radiating out to space at a relatively high temperature. Cloud radiative effects (absorption, reflection) vary with type, altitude, thickness, water phase, time,...

17 Summary Water is everywhere in the climate system! It affects radiative balance and heat transport via atmosphere and ocean circulation, clouds, storms, among other processes. Processes involving water are among involved in some of the leading uncertainties in climate change projections Thursday: deep ocean circulation; discussion of Cunningham et al. (2007) Answers to reading focus questions on Cunningham et al (2007) are due at beginning of class Thurs, as hard copy