Understanding Earth's Water Cycle and Climates | Anthony R. Lupo

1. AtmsSci 3600: Climates of the World Anthony R. Lupo

2. Day 1 • Hydrologic Cycle • Describes the movement of water and processes through the earth-climate system • General outline of atmospheric water cycle

3. Day 1

4. Day 1 • Water evaporates, forms clouds, clouds precipitate over land and water, over land we get runoff back to water sources…and begins all over again. • Can’t ignore transpiration (plants, etc.), hydrological processes underground, etc. • Residence time for water vapor ~ 8 days.

5. Day 1 • Water Resources • 97% in Oceans • Cryosphere is about 1.5% of entire water mass (frozen water) • Fresh Water: 0.09%

6. Day 1 • In Atmos: 1/1000th of a percent • A lot of importance though • Where do we find this small percentage in the atmosphere?

7. Day 1 • Water Vapor • Water vapor in the vertical • Since temp decreases with height (lapse rate 6.5 deg C per km, 3.8 F per 1kft)

8. Day 1 • Therefore water vapor content decreases with height • mixing ratio drops off more dramatically with height than temperature • Above 850 mb, water content drops off rapidly • Most is contained between 1000-850 mb

9. Day 1 • Water Content (cont) • Where is the water mass on the earth? • See handouts given in class…NCAR Tech Memo- Distribution of Topographical Quantities 1995 • Winter cloud cover- in mid-latitudes over the oceans (both northern and southern hemisphere) • India and Sahara less cloudy regions in winter, some subtropical regions as well

10. Day 1 • Winter cloud cover- in mid-latitudes over the oceans (both northern and southern hemisphere) • India and Sahara less cloudy regions in winter, some subtropical regions as well

11. Day 1 • Cloudiness (cont.) • In summer, in mid-latitudes over ocean is still cloudy • In summer the cloudiness in N.H. moves slightly northward

12. Day 1 • July-August low cloudiness, major deserts, Saudi Arabia, Australia, Sahara • Cloud cover over land ~50%

13. Day 1 • Page 1.40 • Relative humidity with height ,averaged in latitudinal bands • Features are fairly similar in both winter and summer • Values greater than 70% represent the boundary layer, which makes sense • In the S.H. boundary layer is fairly moist from equator to pole, N.H dries out around 30 N….trade wind deserts

14. Day 1 • Function of the land • N.H. 39 % land, and 61 % ocean • S.H. 19% land, and 81 % ocean • Big land ocean dist asymmetry

15. Day 1 • RH x-y plots • Oceanic areas more humid, land masses are dry, except for the tropical rain forests • Siberia in the summer is relatively humid • SE US with humidity in the summer can be some of the most uncomfortable places in the world

16. Day 1 • Figure 1.43- PW • Precipitable Water (PW)= The sum of the values of mixing ratio in a column of atmosphere • Lots of PW near the equator where it is warmest • In summer in N.H. high PW values reach the Southern US

17. Day 1/2 • Figure 1.45 • Average precipitation over all longitudes for each latitude belt • High amounts are found in the equatorial regions, where it is warmest (among other processes---ITCZ) • Secondary maximums around 30 N and 30 S…mid-latitude jet streams are found here • X-Y plot is the final diagram…more handouts coming in the near future when we discuss gen circ further

18. Day 2 • Cloud Formation • 3-legged stool example • 3 things to get cloud • Moisture • Vertical motion (lift) • Cloud Condensation Nuclei (CCN)

19. Day 2 • Natural CCN • Sea Salt, Sand/dirt, Bugs, Pollen, etc. • Anthropogenic CCN • Pollution Sources, etc.

20. Day 2 • Cloud types • Cloudiness impacts temperature- cloudy nights warmer than clear, for example • High Clouds • Cirrus-type clouds, ice crystals

21. Day 2 • Middle Clouds • Alto, ice crystals and supercooled droplets • Low Clouds • Main Precip producers…Nimbostratus (uniform sheet) vs. Cumulonimbus (convective heap)

22. Day 2 • Precip Clouds (cont.) • In N.H. nimbostratus dominate in winter, cumulonimbus dominate in warmer seasons • Nimbostratus, are uniform with a large area of weak forcing, warm frontal (stratiform) precipitation • Cumulonimbus can grow up to 60000+ feet, severe thunderstorms, heavy convective precipitation, high albedo only snow is higher…climate impacts

23. Day 2 • Drought • Places that are typically moist, but can become dry over a long duration, 2003, 2005-2007 was a recent drought locally • 1988 was a widespread drought in the US • Drought “begets” drought – speech to the National Press Club

24. Day 2 • Different types of drought • Meteorological  precipitation versus normal • Agricultural  stress on plants • Hydrological  level of the rivers and lakes

25. Day 2 • Drought • Basic drought equation: precipitation minus evaporation • If evaporation exceeds precip for quite a time, the result is a drought • Meteorological drought compares P-E to climatology

26. Day 2 • Palmer Index • Rates a severity for drought • Long term index (5-6 month composite) …cannot tell you if you have had relief due to a month being rainy

27. Day 2 • For more information • www.drought.noaa.gov/palmer.html • Also see the Drought Mitigation Center…University of Nebraska-Lincoln • www.drought.unl.edu/whatis/indicies.htm • For a summer season forecast see: • Global Climate Change Group (MU) • http://weather.missouri.edu/gcc

28. Day 2

29. Day 2 • Last Time • Latent heat of fusion: going to solid to liquid or liquid to solid • Snow melting takes energy from atmosphere (cooling), snow on ground takes heat from atmos and surface • Freezing opposite

30. Day 2 • General Circ and Climate • Two ideas that are closely related • General Circulation: features of the general circulation are statistical entities, long-term statistical analysis of the atmosphere (no specific time scale)

31. Day 2 • Gen Circ has a specific time and space scale unlike climate which is just a time • Gen Circ- large time and large space (global) scale

32. Day 2 • Time Scales • For the most part you cannot see general circulation patterns on a weather map • Long-term for gen circ refers to: • Monthly • Seasonally • Annually • These mean features can show through in as little as 15 days

33. Day 2 • General Circulation Pattern • 3 Belts • 3 cell model (or 3 belts) of the earth’s atmosphere, Coriolis gives rise to this (earth’s rotation) • See figure (Draw on Board)

34. Day 2 • Sir George Hadley • If warm air rises and cold air sinks, there has to be this rising air at the equator and sinking at the pole • Had right idea but did not to take in account earth’s rotation

35. Day 2 • Earned him the naming rights of the tropical cells (Hadley cells on diagram). • Mid-latitude cells are called the Ferrel cell, and we have the nameless Polar Cells

36. Day 2 • 3 Questions to Answer • Q: What gives rise to the Gen. circ? • Q: Why westerlies in midlatitudes, why easterlies in tropics? • Answer: Temp and Momentum Transport

37. Day 2 • Third Question • Why are these temperature and momentum transports necessary? • Good Exam Question! • We will get at this answer in the next two lectures • Good detailed answer coming up in the future

38. Day 2 • Other Planets • Can almost see the banded structure on Earth • Not as evident as Jupiter, but banded nonetheless • If we double the rotation of earth, we would have nine bands • Jupiter is about double our rotation…hence has about nine belts (cells)

39. Day 2 • Jupiter Saturn

40. Day 2 • Venus Pluto

41. Day 3 • Features of the Gen Circ • Existing characteristics • Gen Circ Features migrate with the seasons • System sloshes northward during summer • We’ll start at the equator and move to higher latitudes

42. Day 3 • ITCZ • Inter-tropical convergence zone • Belt of low pressure • Rising motions

43. Day 3

44. Day 3 • Is a place where the horizontal winds are weak (Doldrums) • Rising motions give way to strong convection (thunderstorms) • Can see this in satellite images as bands of convective areas near the equator

45. Day 3 • ITCZ • Starting point for the energy (temp and momentum) transport toward the North begins • ITCZ will be located as far north as the mid-latitudes in the summer (India and Florida) • Does not progress too far south of the equator due to the large amount of ocean (weak temp gradients) • Meeting ground of the two belts of the trade winds • Height of tropopause (16-17km) greatest here…warmest temps

46. Day 3 • Subtropical Highs • Located right around 30°N/S • Highs tend to be stronger over the ocean • Associated with anticyclonic and downward motion

47. Day 3

48. Day 3 • Correspond with the majority of the world’s deserts (Great Basin, Sahara, Middle East, Kalahari, Great Sandy Desert) • Circulations give rise to the trade winds (NE wind in N.H., SE wind in S.H.) • Names: Bermuda and Azores High (Atlantic), SE Pacific High

49. Day 3 • Mid-latitudes • 30°N/S-60°N/S • Battle zone of air masses • Winds are generally westerly aloft and at the surface • Balance between (PGF-Coriolis) • We find jet streams in this region

50. Day 3 • Jet Streams and Polar Front • Were predicted in 1910’s before upper air measurements, all based on math, jet stream was discovered during WWII over the Pacific during bombing runs • Is a gen circ feature (large time and spatial scales)