// lecture 27

Question 1

increased temperatures affect air quality in various ways:

Answer 1

1. pollen season is longer in middle and high latitudes.
2. photochemical smog likes hot weather. this combined with the increased production of the precursors of smog (fossil fuel related) will cause greatly reduced air quality, all else being equal.
3. mold does better.
4. wildfires cause smoke and ash hazards.

Question 2

smog

Answer 2

fog or haze combined with smoke or other air pollutants.

Question 3

photochemical smog is

Answer 3

produced when pollutants interact with sunlight at warm temps. to produce ozone and other harmful stuff.

Question 4

precursors of photochemical smog include:

Answer 4

volatile organic compounds (VOC), sulfur dioxide (SO2), and nitrous oxide (NOx). NOx is formed when fossil fuels are burned in air.

Question 5

photochemical smog likes

Answer 5

NOx (traffic), high temps., sunlight, and calm winds.

Question 6

at least 2.4 million people worldwide

Answer 6

die prematurely each year from the effects of air pollution. most of these deaths occur in Asia, with China having 656,000 deaths a year.

Question 7

In U.S., deaths range from

Answer 7

150,000 to 350,000 people.

Question 8

EPA says that

Answer 8

each year, more than 125,000 Americans get cancer from breathing soot-laden diesel fumes emitted by buses and trucks.

Question 9

ozone can cause

Answer 9

the muscles in the airways to constrict, trapping air in the alveoli. leads to wheezing and shortness of breath. also can cause COPD.

Question 10

ozone enters the stomata

Answer 10

of leaves and damages them. strong oxidant.

Question 11

in polluted areas,

Answer 11

it is likely that ozone concentrations will increase simply owing to the temp. increase. depends on what we do in other areas though.

Question 12

hadley cell =

Answer 12

more rising near equator, more sinking in subtropics.

Question 13

topography

Answer 13

rains on mountains, and upstream side of mountain ranges.

Question 14

general circulation of atmosphere:

Answer 14

• rains a lot near the equator (10N - 10S), which is the rising branch of the Hadley Cell.
• rains much less in subtropics (15N - 40N, 15S - 40S), which is the sinking branch of the Hadley Cell.
• rains a lot in the middle and high latitudes (40-70 N & S), which is associated with midlatitude storms.
• polar latitudes: gets too cold to precipitate much.

Question 15

as the atmosphere warms,

Answer 15

water vapor concentrations increase. winds bring even more moisture into the rainy regions.

Question 16

climate model projections of precipitation change

Answer 16

wet gets wetter, dry regions expand.

Question 17

wet gets wetter

Answer 17

• more water vapor is brought into the regions that are already rainy.
• specifically, tropical regions, monsoons, storm tracks, and high latitudes are expected to moisten.

Question 18

dry regions expand

Answer 18

• more evaporation from dry land surfaces at higher temps.
• tendency for midlatitude weather to shift poleward. many subtropical regions (in between tropics and midlatitudes) are expected to dry.

Question 19

uncertainty about specific regional precipitation responses though

Answer 19

• regional responses could change significantly due to shifts in rising motion. small shifts can make a big difference for rain.
• precipitation is much harder to predict than temp.

Question 20

southwestern north america predicted to

Answer 20

dry dramatically. as bad as the dust bowl by 2060 in some models.

Question 21

drought

Answer 21

prolonged period of abnormally low rainfall; a shortage of water resulting from this.

Question 22

drought moves around from

Answer 22

place to place from year to year. might be related to variations in the temp. of the ocean from place to place. El Nino and similar phenomena.

• probably mostly natural variability, things that would have taken place even i n the absence of GHG increase.
• however, it might be that the dry events are getting worse, as models predict.
• also true that water resources in semi-arid areas are stressed to the limit for human uses, e.g. California.

Question 23

Los Angeles

Answer 23

settles fued with residents of Owens Lake Region from which the city “stole” the water in 1913 and drained the lake within 10 years. dry lakebed resulted in dust and other air quality issues.

Question 24

In Texas

Answer 24

the summer of 2011 has been both the hottest and driest on record. the drought has cost billions in economic losses, mainly due to agricultural impacts and from wildfires.

Question 25

from 1930~36

Answer 25

the prairies of the US and Canada experienced severe dust storms brought about by a drought exacerbated by poor soil use practice.

Question 26

many all-time temp. records in the US Great Plains were set during

Answer 26

the 1930s. severe drying of the american prairie.

Question 27

drying out of land led to

Answer 27

more extremes in temp.

Question 28

the dust bowl

Answer 28

centered near where the states of Colorado, Kansas, Oklahoma, and Texas meet.

Question 29

the dust bowl drought seems to have been associated with

Answer 29

anomalies SST patterns, most likely colder than normal in the tropical pacific, coupled with warmer than normal in the Atlantic (model results).

Question 30

collapse of mayan civilization

Answer 30

• were among the most vibrant civilizations in central America 250-900 AD.
• they abandoned their southern cities in 8th and 9th centuries maybe due to drought?
• was the southward shift of the rainband the cause?

Question 31

sahel region

Answer 31

is between the desert and the region drenched by the african monsoon.

Question 32

sahel drought

Answer 32

This shift around 1970 (from a wet period to an extended drought now) is believed to be due to the changing sea surface temperature patterns in the tropical Atlantic (possible driven by aerosol forcing)

Question 33

why the shift?

Answer 33

• Model work shows that tropical precip shifts towards the warmer hemisphere (even if the warming happens at high latitudes)
• Models also indicate that aerosol cooling causes the southward shift of rain in the models (aerosols are mostly in the NH and rain shifts away from the sahel, which is in the northern edge of the african monsoon)

Question 34

shifts are hard to predict

Answer 34

Shifts in rising motion or mid latitude storms could happen due to:

• Differences in forcings (aerosols cooling the oceans in places)
• Differences in feedbacks (cloud responses)
• Changes in ocean currents (a natural ex that messes with rain patterns is El Nino)

Question 35

how about the most intense storms?

Answer 35

• The strongest downpours require a lot of water vapor in the atmosphere
• Warmer temps. leads to more water vapor
• Thus heavy rainfall events should become more extreme
• Also heavy snowfall events!
• It is important to note that the observational evidence for greater floods and droughts is so far not much above natural variability level