Richard B. Rood (Room 2525, SRB) AOSS 401 Geophysical Fluid Dynamics: Atmospheric Dynamics Prepared: 20131010 Climate, Weather, Geography, Earth / Thermal Wind Richard B. Rood (Room 2525, SRB) rbrood@umich.edu 734-647-3530 Cell: 301-526-8572

Class News Ctools site (AOSS 401 001 F13) First Examination on October 22, 2013 Second Examination on December 10, 2013 Homework posted: Ctools Assignments tab Due Thursday October 10, 2013 Derivations (using notes)

Weather National Weather Service Weather Underground Model forecasts: Weather Underground NCAR Research Applications Program

Outline Tour of the Earth Thermal wind Revisit the Tour of the Earth Geography Planet Physics Thermal wind Revisit the Tour of the Earth Vertical structure

Building the Radiative Balance Redistribution by atmosphere, ocean, etc. RS Top of Atmosphere / Edge of Space 1) The absorbed solar energy is converted to terrestrial thermal energy. 2) Then it is redistributed by the atmosphere, ocean, land, ice, life. CLOUD ATMOSPHERE SURFACE

Another important consideration Latitudinal dependence of heating and cooling Top of Atmosphere / Edge of Space After the redistribution of energy, the emission of infrared radiation from the Earth is ~ equal from all latitudes. CLOUD ATMOSPHERE Because of tilt of Earth, Solar Radiation is absorbed preferentially at the Equator (low latitudes). SURFACE South Pole (Cooling) Equator (On average heating) North Pole (Cooling)

Transfer of heat north and south is an important element of the climate at the Earth’s surface Redistribution by atmosphere, ocean, etc. Top of Atmosphere / Edge of Space This predisposition for parts of the globe to be warm and parts of the globe to be cold means that measuring global warming is difficult. Some parts of the world could, in fact, get cooler because this warm and cool pattern could be changed. CLOUD ATMOSPHERE heat is moved to poles cool is moved towards equator cool is moved towards equator SURFACE This is a transfer. Both ocean and atmosphere are important!

Scientific Method What follows are a series of pictures, plots, graphs – mostly of observations. As we go through them think first How do I describe the picture? What type of behavior might be represented? Patterns, correlations How might I investigate this behavior? Scientific investigation is based first on observations. What is actually in the figure? What do I know? What do I think I know? What do I want to know? What do I believe versus what do I know? What do I want to believe? What is the relation with other knowledge not represented in this particular figure.

Long as I remember the rain been comin’ down [from the National Atlas (1970)] (1930-1961) Grange, October 2006

Ocean Surface Currents (From Steven Dutch, U Wisconsin, Green Bay) Good Material at National Earth Science Teachers Association

The Thermohaline Circulation (THC) (Global, organized circulation in the ocean) (The “conveyer belt”, “rivers” within the ocean) Blue shading, low salt Green shading, high salt Where there is localized exchange of water between the surface and the deep ocean (convection) Warm, surface currents. Cold, bottom currents.

Transfer of heat north and south is an important element of the climate at the Earth’s surface. Redistribution by atmosphere, ocean, etc. Top of Atmosphere / Edge of Space Large scale weather systems transport large quantities of thermal energy from equator toward the poles CLOUD ATMOSPHERE heat is moved to poles cool air moved towards equator cool air moved towards equator SURFACE This is a transfer. Both ocean and atmosphere are important!

Tropospheric Mean Meridional Circulation This is not exactly physical, but is a common conceptual model.

Dynamic atmosphere: Hurricanes --- Vortices Satellite image Storm that originates over warm ocean water Scale of the motion:1000 km

Hurricanes and heat Sea Surface Temperature (blue cool / warm orange)

Hurricanes and heat

Mid-latitude cyclones - waves

Mid-latitude cyclones & Heat

What goes on vertically?

Some basics of the atmosphere Troposphere ------------------ ~ 2 Mountain Troposphere ------------------ ~ 1.6 x 10-3 Earth radius Troposphere: depth ~ 1.0 x 104 m This scale analysis tells us that the troposphere is thin relative to the size of the Earth and that mountains extend half way through the troposphere.

An estimate of the January mean temperature note where the horizontal temperature gradients are large mesosphere stratopause stratosphere tropopause troposphere south summer north winter

An estimate of the January mean zonal wind note the jet streams south summer north winter

An estimate of the July mean zonal wind note the jet streams south winter north summer

Let’s spend some time with the atmosphere. Start with a typical upper tropospheric chart. What is a good estimate of the pressure at the surface? What is a good estimate of the pressure in the upper troposphere? How could you figure out the geometric height?

Geostrophic wind 300 hPa How does this example relate to global scales?

300 hPa

Geopotential contours at 300 hPA Northern Hemisphere September 17, 2008

Wind and geopotential 200 hPa Note: Variability in east-west of the wind field. Note: Time variability of the wind field. Note: Troughs associated with mountain ranges, continents

Geopotential contours at 850 hPa Northern Hemisphere September 17, 2008

700 hPa

500 hPa

300 hPa

50 hPa

North-south / Winter-summer

DJF 500 hPa Average

JJA 500 hPa Average

Anomaly 100 hPa

23 October 2006, Geopotential Height

23 October 2006, Ozone

The thermal wind Connecting horizontal temperature structure to vertical wind structure in a balanced atmosphere

Equations of motion in pressure coordinates (plus hydrostatic and equation of state)

Geostrophic wind

Hydrostatic Balance

Schematic of thermal wind. Thickness of layers related to temperature. Causing a tilt of the pressure surfaces. from Brad Muller

What is a tactic for exploring vertical behavior?

Geostrophic wind Take derivative wrt p. Links horizontal temperature gradient with vertical wind gradient.

Thermal wind p is an independent variable, a coordinate. Hence, x and y derivatives are taken with p constant.

A excursion to the atmosphere. Zonal mean temperature - Jan approximate tropopause south (summer) north (winter)

A excursion to the atmosphere. Zonal mean temperature - Jan ∂T/∂y ? south (summer) north (winter)

A excursion to the atmosphere. Zonal mean temperature - Jan ∂T/∂y ? <0 <0 <0 <0 >0 <0 south (summer) north (winter)

A excursion to the atmosphere. Zonal mean temperature - Jan ∂T/∂y ? ∂ug/∂p ? <0 >0 <0 <0 >0 <0 <0 <0 > 0 >0 >0 <0 south (summer) north (winter)

A excursion to the atmosphere. Zonal mean wind - Jan south (summer) north (winter)

Relation between zonal mean temperature and wind is strong This is a good diagnostic – an excellent check of consistency of temperature and winds observations. We see the presence of jet streams in the east-west direction, which are persistent on seasonal time scales. Is this true in the tropics?

Thermal wind

Thermal wind

Thermal wind

Thermal wind ?

From Previous Lecture Thickness Note link of thermodynamic variables, and similarity to scale heights calculated in idealized atmospheres Z2-Z1 = ZT ≡ Thickness - is proportional to temperature is often used in weather forecasting to determine, for instance, the rain-snow transition.

Similarity of the equations There is clearly a relationship between thermal wind and thickness.

Schematic of thermal wind. Thickness of layers related to temperature. Causing a tilt of the pressure surfaces. from Brad Muller

Another excursion into the atmosphere. 850 hPa surface 300 hPa surface from Brad Muller

Another excursion into the atmosphere. 850 hPa surface 300 hPa surface from Brad Muller

Another excursion into the atmosphere. 850 hPa surface 300 hPa surface from Brad Muller

Another excursion into the atmosphere. 850 hPa surface 300 hPa surface from Brad Muller

Summary of Key Points The weather and climate of the Earth are responses to basic attributes (geometry) of energy sources. The patterns of weather and climate that we see are not random or accidental. Basic redistribution of energy Determined by characteristics of Earth – especially relation of Earth to Sun and rotation Determined by geography Determined by surface energy characteristics Dynamics of atmosphere and ocean, though complex, organize the air and water into features that we can characterize quantitatively  and predict There is strong consistency between energy, thermodynamic variables, and motion (momentum)