Circulation in the atmosphere Lecture 06 Circulation in the Atmosphere

Learning objects Review the general model of atmospheric circulation Explore the basic nature of atmospheric motion on our rotating Earth

What regulates the motion of fluid particles in the ocean and atmosphere? Newton’s Law

What drives the circulation of the atmosphere? Heating by the sun  AIR PRESSURE Equator/Tropics Higher Latitudes surface troposphere

Vertical view of air pressure (global convection) High Pressure Low Pressure High Pressure

x (longitude) y (latitude) + _ Surfaces of constant pressure Horizontal view of air pressure at ocean surface Equator/Tropics Higher Latitudes High Pressure Low Pressure

Newton’s Law Motion across Latitudes Motion along Latitude x (longitude) y (latitude) u v

Non rotating view of Atmospheric Circulation

Hurricane IVAN L H H H H

North Hemisphere A B t1t1 t2t2 t3t3 t4t4 t5t5 F pressure F Coriolis Rate of Rotation High Pressure Low Pressure

Newton’s Law Motion across Latitudes Motion along Latitude x (longitude) y (latitude) u v

North Hemisphere A B t1t1 t2t2 t3t3 t4t4 t5t5 F pressure F Coriolis Rate of Rotation High PressureLow Pressure

Newton’s Law Motion across Latitudes Motion along Latitude x (longitude) y (latitude) u v

Fig.6-3

F pressure F Coriolis F pressure F Coriolis F pressure F Coriolis F pressure F Coriolis When this balance is reached the movement of the particles (and therefore of the flow) is called geostrophic motion

Newton’s Law Motion across Latitudes Motion along Latitude x (longitude) y (latitude) u v

F pressure F Coriolis 1)Particle will have the Coriolis force 90 degrees to the right 2)Particles will tend to move along line of constant pressure 3)Particles will have the high pressure on their right (same as Coriolis) Some practical rules to remember: High Pressure Low Pressure

Hurricane IVAN L H H H H F pressure F Coriolis

Vortices in N.H. L F pressure F Coriolis H F pressure High Pressure System Low Pressure System

Vertical view of the atmosphere Equator Pole

L L L L L L L H HH H H H Eq. Low Subtropical High Subpolar Low Polar High

Vertical view of the atmosphere and Poleward Transport of Heat Equator Pole

Midlatitude Cyclones (N.H.)

Poleward Heat Transport

The seasonal cycle

Differential Heating From Equators to Poles

How the ocean responds to the atmospheric wind and how it contributes to the heat transport

Important Concepts to remember: Redistribution of Heat Effects of Rotation The role of friction Conservation of angular momentum

Schematic depiction of the development of the atmospheric circulation, starting from a state of rest Westerlies Easterlies (Trades) Redistribution of Heat – Large scale convective Cells

Rotation effects, the Coriolis Force

F pressure F Coriolis 1)Particle will have the Coriolis force 90 degrees to the right 2)Particles will tend to move along line of constant pressure 3)Particles will have the high pressure on their right (same as Coriolis) Some practical rules to remember: High Pressure Low Pressure

Schematic depiction of the development of the atmospheric circulation, starting from a state of rest Westerlies Easterlies (Trades)

Circulation in the atmosphere Problem?

Role of Friction

Schematic depiction of the development of the atmospheric circulation, starting from a state of rest Westerlies Easterlies (Trades)

Circulation in the atmosphere Diagram of Atmospheric Circulation

Vertical view of the atmosphere and Poleward Transport of Heat Equator Pole Hadley Cell Ferrel Cell Polar Cell

Role of Friction on synoptic scales

Vortices L F pressure F Coriolis H F pressure High Pressure System Low Pressure System

Hurricane IVAN L H H H H F pressure F Coriolis

Rotation effects are not always important

Land-Sea Breeze

Moonsoons, a continental scale land-sea breeze

Review of Conservation of angular momentum (a second look) The Atmopsheric Circulation (a view from space and from NWS models) A closer look at Huricanes, their formation and the oceanic response Zonal average circulation Radiative Budget

Schematic depiction of the development of the atmospheric circulation, starting from a state of rest Westerlies Easterlies (Trades)

A look at the atmospheric circulation from space ens/loops/wxloop.cgi?wv_moll+/14d/ Advection of water vapour associated with Eastrerlies and Westerlies Strong convection over tropical region Generation of Tropical Cyclones

equator

ITCZ: Inter-Tropical Convergenze Zone

Midlatitude Instabilities /~ovens/loops/wxloop.cgi?ir_centr al+/48h/3h

Warm Front Cold Front Tropical Air Polar Air Tropical Air

Tropical Cyclones Webster P.J, G. J. Holland, J. A. Curry, H.-R. Chang (2005) Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment, SCIENCE Emmanuel, K. (2004) Increasing destructiveness of tropical cyclones over the past 30 years, NATURE Articles RITA ington.edu/~ovens/loop s/wxloop.cgi?fronts_ir_e ast+/48h/ ington.edu/~ovens/loop s/wxloop.cgi?fronts_ir_e ast+/48h/

L F pressure F Coriolis

Why do tropical storms intensify?

Vortices L F pressure F Coriolis H F pressure High Pressure System Low Pressure System

Tropical cyclone have an eye of anticyclonic circulation!

Storm Surge: sea level rises because of the low atmospheric pressure system

Vertical view of the atmosphere and Poleward Transport of Heat Equator Pole Hadley Cell Ferrel Cell Polar Cell They are the views of zonal average circulations

Radiative Budget

Rotation effects are not always important

Land-Sea Breeze

Moonsoons, a continental scale land-sea breeze