1. Outline Further Reading: Chapter 05 of the text book - factors affecting temperature - diurnal cycle - seasonal cycle Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 10:Temperature-Regimes-01 Feb-07-07 (1 of 10)

2. Introduction Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 10:Temperature-Regimes-01 Feb-07-07 (2 of 10) Previously, we learned that latitudinal patterns in net radiation are due to insolation, albedo, and outgoing longwave radiation –At low latitudes, incoming energy is greater than outgoing energy -> energy surplus –At high latitudes, outgoing energy is greater than incoming energy -> energy deficit –There is a radiation energy imbalance with respect to latitude –Energy must be transported from low latitudes to high latitudes –Done via meridional transport by the ocean and atmosphere Sensible heat: transport of warm air or water Latent heat: evaporation at the equator with condensation in the mid-latitudes Ignoring dynamics for now, let us look at what radiation balance tells us about –Diurnal patterns of temperature –Seasonal patterns of temperature –Latitudinal patterns of temperature

3. Factors Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 10:Temperature-Regimes-01 Feb-07-07 (3 of 10) Five factors determine how temperature varies with location –Insolation –Latitude –Surface Type –Coastal v. Continental location –Elevation Today, we are going to cover the first two; the next lecture we will cover the last three Typically temperature is measured 1.2 meters above the ground –Tries to quantify temperature of the atmosphere (air) near the surface –Called near-surface air temperature or surface temperature We are interested in temperature changes at different time-scales (e.g., diurnal, seasonal, interannual, …)

4. Diurnal Cycle-1 Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 10:Temperature-Regimes-01 Feb-07-07 (4 of 10) Time Radiation 12:00am6:00am12:00pm12:00am6:00pm Time 12:00am7:00am12:00pm12:00am4:00pm Temperature Shortwave-net Longwave-net

5. Diurnal Cycle-2 Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 10:Temperature-Regimes-01 Feb-07-07 (5 of 10) Diurnal Cycle: Discussion –Look at noon: solar radiation is greater than longwave radiation Positive radiation balance Temperature will continue to increase –Look at 4:00 pm: solar radiation is the same as longwave radiation Radiation balance Temperature will no longer increase –Look at midnight: solar radiation is less than longwave radiation Negative radiation balance Temperature will continue to decrease –Look at 7:00 am: solar radiation is the same as longwave radiation Radiation balance Temperature will no longer decrease

6. Diurnal Cycle-3 Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 10:Temperature-Regimes-01 Feb-07-07 (6 of 10) Diurnal Cycle (from book) –Time of temperature minimum Shows how time of minimum temperature changes with the season Time gets later as days get shorter –Time of temperature maximum In this figures, the maximum temperature always occurs at the same time this is not correct

7. Seasonal Cycle-1 Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 10:Temperature-Regimes-01 Feb-07-07 (7 of 10) Time Radiation JanuaryJuneJanuary Time JanuaryMarch (Feb.) JuneJanuaryAugust Temperature Shortwave-net Longwave-net

8. Seasonal Cycle-2 Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 10:Temperature-Regimes-01 Feb-07-07 (8 of 10) Seasonal Cycle: Discussion –Solar energy Change in seasons produces change in solar zenith angle and insolation Maximum occurs in June (in Northern hemisphere) and minimum occurs in December –Longwave radiation Again, we can guess this is going to follow the temperature plot –Temperature In June, there is a positive energy balance, hence the temperature will continue to increase Not until the two are in balance will the temperature stop increasing - this occurs in August The same applies to temperature in December; because there is a negative balance, the temperature will continue to decrease until there is a balance - this occurs in February or so

9. Seasonal Cycle-3 Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 10:Temperature-Regimes-01 Feb-07-07 (9 of 10) Seasonal Cycle (from the book): –Low latitude (Manaus) There is a positive radiation balance all year long Temperature doesn’t continue to increase - hence other factors must be affecting the total energy balance –High latitudes (Yakutsk) Note that the temperature minimum doesn’t occur at the point of zero radiation balance Again, other factors must be affecting the total energy

10. Epilogue Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 10:Temperature-Regimes-01 Feb-07-07 (10 of 10) Seasonal radiation balance, and hence temperature, can also depend upon –Latitude –Proximity to oceans –Influential weather patterns Temperature ultimately depends upon total energy balance –Sensible and latent heat –These can be affected by changes in the radiation balance as well –Leads to changes in dynamics and hydrodynamics We will continue this discussion in the next lecture.