What is the Climate of the Earth’s Land Surface? (basics)

1. What is the Climate of the Earth’s Land Surface?(basics) CLIM 101

2. Organizing Schema Weather Climate Ecosystems Humans

3. Land Surface - Climate Weather Climate Terrestrial Ecosystems

4. Questions What processes on the land surface play a role in climate? What determines the distribution of vegetation around the globe? Why does the landscape change over time?

5. Topics • Differences between Ocean and Land w.r.t. Climate • Role of Land Surface & Vegetation (Photosynthesis) • Paleoclimate (Continental Drift) • Climate Determines Biomes • Mean Characteristics • Soil moisture • Snow • Vegetation • Albedo • Vegetation Influences Climate

6. S, , a, g, Ω O3 H2O CO2 Ω CLIMATE DYNAMICS OF THE PLANET EARTH g  (albedo) Gases: H2O, CO2, O3 S r T4 h*: mountains, oceans (SST) w*: forest, desert (soil wetness) CLIMATE . stationary waves (Q, h*), monsoons WEATHER hydrodynamic instabilities of shear flows; stratification & rotation; moist thermodynamics day-to-day weather fluctuations; wavelike motions: wavelength, period, amplitude

7. What is the “Climate System”? Orbital parameters/Extraterrestrial Impacts Geology/Volcanology Internal versus external Human Impacts (LUCC/Industry) Biochemistry/Biology Aerosols/Chemistry Ocean Land Atmosphere

8. What is the “Climate System”? Internal versus external Land Atmosphere

9. Ocean versus Land • Water • Water flows • High heat capacity (4.2x106 J m-3 K-1) • Moderate heat conductivity (0.6 J m-1K-1s-1) • Dark (α=0.05) • Evaporation at potential rate • Dry Soil • Stationary (essentially) • Low heat capacity (0.6-1.3x106 J m-3 K-1) • Low heat conductivity (0.08-0.2 J m-1K-1s-1) • Light (α=0.13-0.50) • No evaporation • Vegetation • Varies with time (species, density, color, coverage) • Canopy creates microenvironment for radiation, heat exchange, interception of rain and snow • Generally dark (α=0.08-0.25) • Transpiration controlled by photosynthesis, moisture stress • Wet Soil • Water flows • Moderate heat capacity (2.2-2.9x106 J m-3K-1) • High heat conductivity (0.8-1.7 J m-1K-1s-1) • Not as light (α=0.1-0.4) • Evaporation is a function of soil moisture

10. Topics • Differences between Ocean and Land w.r.t. Climate • Role of Land Surface & Vegetation (Photosynthesis) • Paleoclimate (Continental Drift) • Climate Determines Biomes • Mean Characteristics • Soil moisture • Snow • Vegetation • Albedo • Vegetation Influences Climate

11. Photosynthesis: Plants use this chemical reaction to combine H2O, CO2 and energy from the sun to form sugars that provide the basic fuel for the cells inside the plants. Plants employ various mechanisms to maximize photosynthesis while minimizing loss of water. Plants respire oxygen as a waste product of the photosynthesis reaction, which is why Earth has an oxygen-rich atmosphere. Plants participate in the energy cycle, the hydrological cycle, the carbon cycle, and the nitrogen cycle. On the land surface, by fixing carbon and nitrogen mass in their stems and leaves, plants provide a physical barrier to erosion by water flowing over the landscape as well as a surface feature that alters the flow over the wind surface.

12. Biochemistry/Biology Aerosols/Chemistry What is the “Climate System”? Internal versus external Land Atmosphere

13. Global Carbon Cycle

14. Topics • Differences between Ocean and Land w.r.t. Climate • Role of Land Surface & Vegetation (Photosynthesis) • Paleoclimate (Continental Drift) • Climate Determines Biomes • Mean Characteristics • Soil moisture • Snow • Vegetation • Albedo • Vegetation Influences Climate

15. ~ 10 Ma Like today’s continents Most land in mid- and high-latitude Northern Hemisphere Large continent at South Pole (ice platform)

16. ~ 180 Ma Like today’s continents Single continent from pole to pole Even distribution of land at most latitudes Very little land at poles

17. ~ 360 Ma Single land mass plus large islands Most land in mid- and high-latitude Southern Hemisphere Very large continent at South Pole (ice platform)

18. The map shows the present “potential” vegetation (i.e., without human impacts) for North America. In this series of slides, we will go back in time through the last ice age, and see how the changing climate affected vegetation, and speculate on how the vegetation may have fed back on climate. Today’s vegetation

19. End of the last ice age - little ice left. The deserts of the west are much more extensive, and cool forests extend much further south than today. 8 ka

20. 11 ka Note how far west the eastern forests extend. Northern Mexico supports vast woodlands. The rainforests are strongly confined to equatorial regions.

21. Evident are the Beringia land bridge and the supposed gap through the ice sheet to the east of the Rockies (through which the first Americans may have passed from Asia. Taiga extends to 35 degrees north. 13 ka

22. Taiga to the Gulf of Mexico. Florida is a desert Arizona is open woodland The Appalachian mountains peak above the treeline in North Carolina. 18 ka

23. Topics • Differences between Ocean and Land w.r.t. Climate • Role of Land Surface & Vegetation (Photosynthesis) • Paleoclimate (Continental Drift) • Climate Determines Biomes • Mean Characteristics • Soil moisture • Snow • Vegetation • Albedo • Vegetation Influences Climate

24. Main Climate Drivers for Natural Land Cover Climate Constraints • Temperature • annual and seasonal means, extremes, timing of first frost, ice free days, growing degree days • Moisture • annual and seasonal means, extreme events (floods and droughts), precipitation, actual and potential evapotranspiration

25. Regional Patterns • Climate Zones • Köppen (1928) - map coauthored by student Geiger (P & T) • USDA “Hardiness” Zones (minimum T) • Potential Natural Vegetation • climax vegetation • A.W. Kuchler (1964) • EPA and other groups have updated

26. A Tropical humid Af Tropical wet No dry season Short dry season; heavy Am Tropical monsoonal monsoonal rains in other Aw Tropical savanna Winter dry season B Dry BWh Subtropical desert Low-latitude desert BSh Subtropical steppe Low-latitude dry BWk Mid-latitude desert Mid-latitude desert BSk Mid-latitude steppe Mid-latitude dry C Mild Mid-Latitude Csa Mediterranean Mild with dry, hot summer Mild with dry, warm summer Csb Mediterranean Mild with no dry season, hot summer Cfa Humid subtropical Mild with dry winter, hot summer Cwa Humid subtropical Mild with no dry season, Cfb Marine west coast warm summer Mild with no dry season, cool summer Cfc Marine west coast Humid with severe winter, no dry season, Severe Mid- D Latitude Dfa Humid continental hot summer Humid with severe winter, no dry season, warm summer Dfb Humid continental Humid with severe, dry Dwa Humid continental winter, hot summer Humid with severe, dry Dwb Humid continental winter, warm summer Severe winter, no dry season, cool summer Dfc Subarctic Severe, very cold winter, no dry season, cool summer Dfd Subarctic Severe, dry winter, cool Dwc summer Subarctic Severe, very cold and dry winter, cool summer Dwd Subarctic Polar tundra, no true summer E Polar ET Tundra EF Ice Cap Perennial ice H Highland Köppen-Geiger Climate Classification System

27. Koppen Climate Classification A - Tropical humid B - Dry C - Mild Mid-latitude D - Severe Mid-latitude E - Polar H - Highland

28. World Biomes

29. USDA Plant Hardiness Gardeners in the U.S. are familiar with the USDA classification scheme, which is based solely on minimum temperature extremes (assuming precipitation is irrelevant because gardeners can water their plants during dry weather).

31. Issue: The components of the water cycle operate at different timescales... Residence time ~ 4,000 yr 2 weeks - 10,000 yr 2 weeks - 1 yr 10 - 400,000 yr ~ 10 yr 1 - 10 yr 2 weeks 1 week 10 days

32. The global water balance and the land surface is inextricably tied to the global energy balance.

33. Energy Balance Over Land Absorbed energy raises the surface temperature; heat radiated from the surface increases The sun is the ultimate source of all energy Shortwave Longwave Evapotranspiration Sensible Heat If there is moisture available, most of the remaining energy will go towards evaporating it. Water has a high heat, capacity, so retards warming. Dry soil will warm quickly, increasing sensible heat flux. Ta Energy which reaches the ground and is not reflected is absorbed Ta4 Ts4 Ts

34. Only about 45% of the Sun’s energy is visible Plants mostly make use of visible light for photo-synthesis

35. The rest is in infrared (43%) and UV (12%) The ozone layer blocks most of the UV from reaching the surface

36. Topics • Differences between Ocean and Land w.r.t. Climate • Role of Land Surface & Vegetation (Photosynthesis) • Paleoclimate (Continental Drift) • Climate Determines Biomes • Mean Characteristics • Soil moisture • Snow • Vegetation • Albedo • Vegetation Influences Climate

37. Mean Annual Cycles – Soil Wetness Magnitude of annual cycle (top) and standard deviation of April soil wetness (bottom).

38. Mean Annual Cycles - Snow JAN APR

39. Variance of Boreal Summer LAI over 8 years (1987-1994)

40. April

41. Albedo movie

42. PAR movie

43. LAI movie

44. Mean annual NPP (1981-2000) NPP (gC m-2 yr-1) estimated with a DVM (8 km res.)

45. Topics • Differences between Ocean and Land w.r.t. Climate • Role of Land Surface & Vegetation (Photosynthesis) • Paleoclimate (Continental Drift) • Climate Determines Biomes • Mean Characteristics • Soil moisture • Snow • Vegetation • Albedo • Vegetation Influences Climate

46. Many of the interactions between the climate and the land surface are summarized here: Bowling, PILPS 2-e

47. Land-Climate Interaction Fluxes at the land surface Evap Sensible Heat Radiation 20-30% 70-80% Albedo Roughness Soil Wetness Local circulation Large-scale dynamics Humidity Temperature Winds Soil water Vegetation Snow Land surface Air near the surface Solar rad. Precip. Temperature Winds Vertically through the atmosphere

48. 4 4 2 2 3 3 1 1 1 3 3 2 3 2 2 4 4 Land determines the location of precipitation • Tropical convection clusters at 60W (Amazon), 30E (Africa), and 120E (Indonesia) • Mid-latitude storm tracks form on the eastern margins of continents. • Deserts form in the subtropics on the western sides of continents. • Mid-latitude rain forests form where oceanic westerlies hit the coast.

49. Monsoons • Over land, monsoons characterized by rainy/dry seasons • Summer wet / winter dry monsoons exist primarily in the subtropical regions, but can extend into mid-latitudes. • Winter monsoons (a.k.a. Mediterranean climates) exist in the Northern Hemisphere (California, North Africa, Middle East)

50. Precipitation and Soil Moisture • Lack of precipitation leads to dry soil (drought). • Does dry soil lead to lack of precipitation? • This is an example of positive feedback between land and atmosphere.