Lecture 4 reading assignm. Ch. 3, Hartmann 2.8, 2.9, 4.2 Briefly review energy balance at TOA – resulting requirement on poleward heat transport Energy balance at the surface Controls on temperature Diurnal temperature cycle Annual temperature cycle Interannual temperature variations

Fig. 2.21

Poleward energy transport Albedo increases with latitude because solar zenith angle, cloud cover and snow cover increase OLR does not decrease with latitude as rapidly as the ASR Atmosphere & ocean transport heat poleward to make up for the difference

P lanetary albedo a)Annual mean b)JJA c)DJF

Outgoing long- Wave radiation (OLR) a)Annual mean b)JJA c)DJF

Net incoming radiation at the TOA a)Annual mean b)JJA c)DJF

Averaged over the annual cycle, the globally averaged incoming energy equals the globally averaged outgoing energy at TOA. The above is not true if we only look at a season, or if we do not average over entire globe. Let’s look at time dependent budgets. On the board….

The energy balance for the climate system involves: –The exchange at the top of the atmosphere (R_TOA), net radiative energy flux as measured from satellites –Time rate of change of energy within the region (dE/dt) –The transport of energy through the lateral boundaries by the atmosphere and ocean The energy balance at the surface involves The net radiative flux at the surface latent heat flux (LE) sensible heat flux (SH) the time rate of change within the region (dE_s/dt) the transport of energy trough lateral boundaries by the ocean

The diurnal temperature cycle same definitions apply to annual temperature cycle

Controls on temperature Latitude – insolation depends on latitude as well as time of year and time of day. Surface type – atmosphere is heated from the surface. Vegetation vs. desert. Surface elevation and aspect Distance to large bodies of water.-- Upwind/downwind Cloud cover

Effect of latitude on average temperature at a location, Miami Fl (26N), NY City NY (41N) Annual temperature cycle:

Same locations (Miami and NY), plotted is average incoming solar radiation at TOA

Surface type effect on temperature: Annual temperature cycle in the Sahara and in Miami

Altitude effect on the annual temperature cycle: Mt. Washt. (1746m) and Burlington (91m)

Effect on temperature cycle of distance to a large body of water: Dallas, TX, Los Angeles

Effects of a warm ocean current on the temperature cycle: Trondheim, Norway and Holy Cross Alaska

Temperature difference: Continental vs. maritime regions The specific heat of water is almost three times greater than land. Evaporation of water reduces temperature extremes over and near large bodies of water. Solar radiation absorbed by the water is distributed throughout a certain depth of the water due to mixing. Over land no such mixing can take place.

Effects of cloud cover on temperature

Effects of two different clouds on the flow of radiation. Resulting temperature change.

Effect of cloud cover on temperature in two nearby midwestern cities

Interannual temperature variations: change in temperature from year to year Normal temperature (NT): average over 30 years Temperature anomaly: T_ave – NT ( where T_ave is the average temperature for a certain year. Reasons for variations? volcanic eruptions El Nino, La Nina events increased concentration of greenhouse gases

Global temperature anomalies (w.r.t )

Effect of volcanic eruptions on temp. The lower the latitude, the greater the effect since it is easier to get “stuff” into the stratosphere from low latitudes Interact with solar radiation in stratosphere

Picture from the space shuttle after Mt Pinatubo eruption. The cloud tops are huge cumulus clouds reaching to and above the tropopause