Lab 8: Climate & Water Availability


At the end of this lab, you should be able to answer the following questions:

  • How does climate change when moving from the equator to the North Pole?
  • How does the movement of the ITCZ affect water availability?
  • How does the interaction between temperature and precipitation impact water availability?
Introduction of lab by instructor

1. Click Climate_Types to open the file in Google™ Earth.

  • Note where the climate types below are typically located.  The legend for the climate types is below Africa.

Af (tropical wet)

Aw (tropical savanna)

BWh (subtropical desert)

BSk (mid-latitude steppe)

Cfa (humid subtropical)

Csa (Mediterranean)

Cfb (marine west coast)

Dfb (humid continental)

Dfc (subarctic)

ET (tundra)

Q1: What is the typical latitudinal zone where the Af climate exists?

Q2: What is the typical latitudinal zone where the Aw climate exists?

Q3: What is the typical latitudinal zone where the BWh climate exists?

Q4: Are you more likely to find the BSk climate on the coast or towards the interior of a continent?  What is the typical latitudinal zone where this climate exists?

Q5: On what portion of a continent are you most likely to find the Cfa climate?  What is the typical latitudinal zone where this climate exists?

Q6: On what side of a continent are you most likely to find the Csa climate?  What is the typical latitudinal zone where this climate exists?

Q7: On what side of a continent are you most likely to find the Cfb climate?  What is the typical latitudinal zone where this climate exists?

Q8: What is the typical latitudinal zone where the Dfb climate exists?  Where is this climate type located with respect to the Cfb climate?

Q9: What is the typical latitudinal zone where the Dfc climate exists? Where is this climate type located with respect to the Dfb climate?

Q10: What is the typical latitudinal zone where the ET climate exists? Where is this climate type located with respect to the Dfc climate?

Your instructor is going to post the answers to the above questions.

Background Information

Climate is the typical atmospheric conditions of a location over a long period of time.  Climates can be classified according to the average and typical ranges of different atmospheric variables, such as temperature and precipitation.  The Köppen climate classification is based on the concept that native vegetation is the best expression of climate; thus, climate-type boundaries have been selected with vegetation distribution in mind.  It combines mean annual and monthly temperatures and precipitation along with the seasonality of precipitation.  A climate type is denoted by a combination of two or three letters.  Click Köppen_Tables for a description of the letters used in the Köppen climate classification and a brief description of 23 climate types.  The Hadley Cell is an important control of many climate types.  Click Hadley_Cell_Movement and then click “Show Hadley Cells Profile,” “Show ITCZ,” “Show Pressure,” and the button to see the intra-annual migration of the Hadley Cell and associated features.

Click Climate&WaterAvailability to view an Adobe® Acrobat® file that contains the above information along with information on the water balance.

Q11. When is the ITCZ farthest north?

Q12. When is the ITCZ farthest south?

Q13. When is the polar front (i.e. boundary between warm and cold air masses) farthest north?

Q14. When is the polar front (i.e. boundary between warm and cold air masses) farthest south?

Q15. When are high-pressure cells over Canada and Russia?  What air mass would you expect to be associated with those high-pressure cells? Click Temperature&SpecificHumidity to view global variations in temperature and specific humidity during January.

The most prevalent general climate type is the “B” climate type: it covers at least 20% of Earth’s land area.  These climates have soil-moisture deficits; therefore, the demand for water exceeds that which is actually available from the soil.  For example, Yuma, Arizona receives about 75 mm of rain per year but over 2,000 mm of water could evaporate over the course of a year.  “B” climates in the subtropics are caused by sub-tropical high pressure cells, while “B” climates in the middle latitudes are caused by the rainshadow effect, continentality, or both.

2. Click Climate_Types and Cities_Climographs to open the files in Google™ Earth.  The ten yellow-orange circles denote ten cities for which you will be exploring climate.  The ten cities and corresponding climate types are as follows:

Iquitos, Peru – Af

Cuidad Bolivar, Venezuela – Aw

Yuma, AZ USA – BWh

Boise, ID USA – BSk

Atlanta, GA USA – Cfa

Los Angeles, CA USA – Csa

Vancouver, Canada – Cfb

Minneapolis, MN USA – Dfb

Fairbanks, AK USA – Dfc

Barrow, AK USA – ET

  • Examine the climographs for all nine cities by clicking the placemark for the city.  A climograph is a chart showing both the average monthly temperature and precipitation of a place.  The climographs represent well the expected climographs for the particular climate types.  Click Climographs to view all climographs on a single page.   You also can access the climographs by clicking on the following links: Iquitos, Ciudad_Bolivar, Yuma, Boise, Atlanta, Los_Angeles, Vancouver, Minneapolis, Fairbanks, and Barrow.

Q16: Which city receives the most precipitation?  Why?

Q17: How does summer and winter precipitation differ at Ciudad Bolivar?  What is the major cause of seasonal differences in precipitation at Ciudad Bolivar?

Q18: How do the factors that cause the aridity at Yuma and Boise differ between the two cities?

Q19: How does temperature and precipitation change when moving up the coast from Los Angeles to Vancouver?

Q20: Why are temperatures at Fairbanks and Barrow below freezing for at least six months of the year? Refer to Lab 1.

Q21: With respect to the jet stream and air masses, why do Fairbanks and Barrow receive more precipitation in summer than in winter?

Q22: Why do Barrow and other high-latitude places receive so little precipitation?

3. Click Cities_WaterBalance to open the file in Google™ Earth.  The water balance layer has water-balance images for each of the ten cities.  The four variables are DEF (deficit), -DST (the decrease in soil water from the end of the previous month to the end of the current month), +DST (the increase in soil water from the end of the previous month to the end of the current month), and SURP (surplus).  A deficit (DEF) occurs when the demand for soil water by vegetation is greater than the supply; this occurs when there is no soil water.  A decrease in soil water (-DST) occurs when vegetation uses more soil water than the amount that was added to the soil through precipitation.  An increase in soil water (+DST) occurs when vegetation uses less soil water than the amount that was added to the soil through precipitation; the extra water goes into storage.  A surplus (SURP) occurs when the soil cannot hold any more water (i.e. the soil is at field capacity) and the amount of precipitation exceeds the demand of soil water by vegetation; the excess water is runoff.  Click WaterBalance_Interpretation to view of an interpretation of the water balance for Atlanta.  The water balance for a city can be seen by clicking on the city’s icon.  Click Water_Balances to view all water balances on a single page.   You also can access the water balances by clicking on the following links: Iquitos, Ciudad_Bolivar, Yuma, Boise, Atlanta, Los_Angeles, Vancouver, Minneapolis, Fairbanks, and Barrow.

Q23: Why is there always a surplus of water at Iquitos?

Q24: During what month is there a surplus of water at Cuidad Bolivar?  What caused the increased rainfall that eventually led to the surplus?

Q25: During what months is there a water deficit at Ciudad Bolivar?

Q26: Why is there always a deficit of water at Yuma?  When is the deficit the largest?

Q27: If Yuma never has a water surplus, then how can this place exist? Check out this Web site for more information.

Q28: How does the water balance for Boise, which has a cold steppe climate, differ from the water balance for Yuma, which has a hot desert climate?

Q29: During what months is there a water deficit at Los Angeles?

Q30: If Los Angeles never has a water surplus, then how can this place exist? Check out this Web site to get some information.

Q31: Compared to Los Angeles, why does Vancouver have less severe of a water deficit during the summer?

Q32: Why does Vancouver, rather than Los Angeles, have a water surplus during the winter months?

Q33: During what months is there a water surplus at Atlanta?

Q34: During what months is there a water deficit at Atlanta?  What is the major cause of the deficit?


  • Click Atlanta_Precipitation to see a comparison of the monthly precipitation totals in 2004 with the mean monthly totals during the 1961-1990 period.

Q35: What month in 2004 had the largest difference in precipitation from the mean total for 1961-1990?

Q36: What type of storms turned the above month into a surplus month when it was historically a deficit month? Please refer back to Lab 8.


4. Click LandCover and Cities_WaterBalance to open the files in Google™ Earth.  The land-cover layer, which is comprised of satellite imagery from 31 December 2003 through 30 November 2004, shows seasonal changes to the land surface (e.g., vegetation and snow changes).  Clouds are not visible in the imagery.

  • Zoom in on Iquitos, Peru and click the   button to run the animation showing change in land cover during 2004.  Run the animation several times.

Q37: During how many months of the year is Iquitos “green”?  How does this relate to the monthly water availability at Iquitos?


  • Zoom in on Ciudad Bolivar, Venezuela and click the   button to run the animation showing change in land cover during 2004.  Run the animation several times.

Q38: During what months is Cuidad Bolivar “green” and during what months is it “brown”?  How does this relate to monthly changes in water availability at Cuidad Bolivar?


  • Zoom in on Yuma, AZ USA and click the   button to run the animation showing change in land cover during 2004.

Q39: During what months, if any, is Yuma green?  How does this relate to the monthly water availability at Yuma?


  • Zoom in on Minneapolis, MN USA and click the   button to run the animation showing change in land cover during 2004.

Q40: During what many months of the year was Minneapolis covered with snow?

  • Zoom in on Fairbanks, AK USA and click the   button to run the animation showing change in land cover during 2004.

Q41: During what many months of the year was Fairbanks covered with snow?

  • Zoom in on Barrow, AK USA and click the   button to run the animation showing change in land cover during 2004.

Q42: During what many months of the year was Barrow covered with snow?

Q43: What is the major cause of the increase in soil moisture or surplus or both at Minneapolis, Fairbanks, and Barrow during the spring?

5. Revisit the initial questions and answer each question using the information gathered in this exercise.

Q44: How does climate change when moving from the equator to the North Pole?
(a) mean annual temperatures and annual precipitation totals typically decrease
(b) mean annual temperatures increase and annual precipitation totals typically decrease
(c) mean annual temperatures decrease and annual precipitation totals typically increase
(d) mean annual temperatures and annual precipitation totals typically increase


Q45: How does the movement of the ITCZ affect water availability?
(a) when the ITCZ is over a region there is usually a water deficit
(b) when the ITCZ is over a region there is no precipitation
(c) when the ITCZ is over a region there is usually a water surplus
(d) both a and b


Q46: How does the interaction between temperature and precipitation impact water availability?
(a) if a city had identical precipitation totals during summer (i.e. the warm season) and winter (i.e. the cold season), then water availability would be higher during the winter
(b) if a city had identical precipitation totals during summer (i.e. the warm season) and winter (i.e. the cold season), then water availability would be higher during the summer
(c) a decrease in temperature and precipitation always results in a decrease in water availability
(d) none of the above
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