http://www.ncdc.noaa.gov/oa/climate/research/2005/ann/ann05.html

Local Weather and Climate: The North American Monsoon

• Tucson gets half of its rainfall during the summer• Sonora, Mexico gets most of its rainfall during the summer• During summer, high pressure sets up to the

east/northeast of Arizona which brings moisture in from the south

• The monsoon is still going: Thunderstorms yesterday• For a monsoon overview and daily forecast, see:

http://www.wrh.noaa.gov/twc/monsoon/monsoon.php

http://www.atmo.arizona.edu/products/models/forecasts/forecast.html

Local: Recent Monsoon Rainfall

• Record water flow through the Sabino and Rillito Creeks on July 31

• Rillito flow higher than Colorado river!

See http://fpnew.ccit.arizona.edu/kkh/rillito.flood.jul.06.htm

Course Building Blocks

• Intro 1st week or so

• Energy ~2 weeks

• Moisture ~2 weeks

• Dynamics ~3 weeks

Above are interdependent

• Specific Topics ~6 weeks

Atmospheric CompositionPermanent Gases

• N2 and O2 are most abundant gases

• Percentages hold constant up to 80 km

• Ar, Ne, He, and Xe are chemically inert

• N2 and O2 are chemically active, removed & returned

Ahrens, Table 1.1, 4th Ed.

N2

Boiling point: 77 °K or -196°C or –320 °F

O2

Boiling point: 90 °K or -183 °C or -297 °F

N2 and O2

Balance between input (production) and output (destruction):

Input:plant/animal decaying

Output: soil bacteria;

oceanic plankton-->nutrients

Input:plant photosynthesis

Output: organic matter decay

chemical combination (oxidation)

breathing

Atmospheric CompositionImportant Trace Gases

Ahrens, Table 1.1, 3rd ed.

Which of these is now wrong even in the 4th edition of Ahrens?

Sourcesvegetative decayvolcanic eruptionsanimal exhalationcombustion of fossil fuels(CH4 + 2 O2 > 2 H2O + CO2)

Sinksphotosynthesis (oxygen production)dissolves in waterphytoplankton absorption (limestone formation)

Carbon Dioxide COCarbon Dioxide CO22

CO2 Trend

“Keeling Curve”

Some gases vary by season and over many years.

The CO2 trend is the cause for concern about global warming.

CO2 increases in northern spring,

decreases in northern fall

See http://earthguide.ucsd.edu/globalchange/keeling_curve/01.html

H2O Vapor VariabilityPrecipitable Water (mm)

Some gases can vary spatially and daily

Aerosols

1 cm3 of air can contain as many as 200,000non-gaseous particles.

– dust– dirt (soil)– ocean spray– volcanic ash– water– pollen– pollutants

Aerosols - Volcanic Ash

Fig. 1-4, p.6

Aerosols - Dust Particles

Dust Storm on Interstate 10, between Phoenix and Tucson, AZ.

Aerosols

• Provide condensation nuclei for water vapor.• Provide a surface area or catalyst needed for

much atmospheric chemistry.• Aerosols can deplete stratospheric ozone.

They can also cool the planet by reflecting sunlight back to space.

Reading Assignment

• AhrensPages 1-22; 425-426-427 (Appendix A: Units etc.), 431-432 (Appendix C: Weather chart symbols)Problems 1.2, 1.3, 1.10, 1.14, 1.17, 1.18, 1.20

(1.17 Chapter 1, Question 17)Don’t Forget the 4”x6” Index Cards