ESS 474 Exam 1 - utk

the environmental questions you are likely to be addressing usually fall into one of what two categories?

• current status

• likely impacts of alternative management

how does a small paper ball dropping through the air differ from a similar piece of paper dropping as a flat sheet?

the sheer has large-scale turbulent eddies

under what conditions of driving force and chaotic resistance can we accurately predict a natural phenomenon?

large driving force relative to scale of chaotic resistance

besides the paper dropping through the air, give an example of a diffuse driving force and large-scale chaotic turbulence

weather patterns

if i drop a sheet of dense metal rather than paper, will the fall time be more or less predictable? and why?

• more predictable

  • larger driving force relative to the scale of turbulence

how are replicates defined, and what purpose do they serve?

• assumed to be the same

  • show inherent variability

list the elements of the hydrologic cycle

• Evapotranspiration, precipitation, infiltration, runoff, subsurface(unsaturated and saturated), interflow, baseflow, and streamflow

via what path does most of the rainfall onto the land surface take in actually enter the ocean?

subsurface flow, very little as subsurface direct

list the driving forces of the hydrologic cycle

sun, gravity, earth’s rotation, earth’s residual heat, NOT wind/physiochemical

which hydrologic cycle element acts as a valve, essentially controlling how fast the water moves?

infiltration

give an example of why it is important to think of the hydrologic cycle over the 3d landscape, not just at a point?

runoff at one spot can infiltrate at another

about what percentage of the earth’s fresh water is in the atmosphere at any time?

0.04%

what percentage of the earth’s precipitation falls on land?

10%

about what portion of the rain falling on lush vegetated land ends up as evapotranspiration?

½

explain why a small hydraulic radius means that you will have a slower flow in your channel

more water in contact with the rough surface

describe what is meant by the solar constant?

fairly constant solar radiation at the edge of the atmosphere

why do we get more solar radiation in knoxville in june than hits the equator?

fairly constant solar radiation at the edge of the atmosphere

about what portion of the incoming sunlight actually makes it to the earth’s surface?

47%

the area north of the Arctic circle gets far more hours of sunlight(24 hrs) during June than we get in Knoxville. Why does that area actually get less radiation?

angle of the sunlight

what are the two main causes of general wind patterns?

• earth’s rotation

• uneven heating

describe the general diurnal wind pattern for near-shore areas

• sea breeze during day

• land breeze at night

describe the general diurnal wind pattern for inland areas

• lowest at daybreak

• highest in late afternoon

what is albedo?

the portion of light reflected back from a surface

number these from highest(1) to lowest(4) in terms of how much solar energy that reaches the earth’s surface actually goes to each

1. evaporating water (latent heat)

2. radiated back to space as longwave radiation (heat)

3. heating the air (sensible heat)

4. stored in plants through photosynthesis

using either words or equations, define how relative humidity and vapor pressure deficit are related

RH = (ea/es)*100

VPD = es - ea

if i heat a closed container, so that no air or water molecules can get in or out) containing moist air but no free water, what happens to the relative humidity of the air in the container and why?

down. ea is the same, but es goes up

what is a main factor that controls the saturation vapor pressure?

air temperature

wind increases evapotranspiration, how?

removes wet air from near the water surface

how does evaporation from snow compare to that from free water at the same temperature?

much lower

describe how evaporation from a wet soil changes over time

when saturated, very similar to free water

as it dries, it drops off quickly

name two places that water goes as part of the photosynthetic process

• hydrogen sources to make sugar

• losses due to evaporation from wet surfaces

how do plants regulate water losses?

stomate guard cells open or close

once we have a value for the reference ET, what do we do with that to get the actual evapotranspiration for our specific crop on this day?

• multiply times crop coefficient comparing crop to base

• adjust for crop stage

• adjust for soil water

what is the most common equation for estimating ET based on climate information?

penman method or some variation thereof

in words, what are the inputs required to use the most common equation for estimating ET?

• incoming solar

• radiation to ground

• wind

plants over their lifetime pump more water than their biomass weight. how much more?

100 times

what does the pyranometer measure

hemispherical shortwave radiation

how is the ‘avg daily temperature’ historically defined and give an example of a case where this would not be a very good value

• avg of max and min

• hot day with sudden cooling late at night

what are the critical factors in operation of a device to measure solar radiation?

• keep clean

• calibrate frequently

what are 2 devices most commonly used to electronically measure temperatures?

• thermistor

• thermocouple

what are the three general use requirements for a device to measure solar radiation?

• shaded

• ventilated

• >30m from extensive radiation absorber or reflector

what does a psychrometer measure, and how does it work?

• relative humidity

• difference between wet bulb and dry bulb temps

what are the 3 concerns mentioned for cup anemometers

1- high threshold speed

2- run on

3- vertical movement

for general meteorology, how far from a 100ft tall tree should you put your wind speed sensor?

4H = 400ft

why is it usually specified that an evaporation pan should be placed on a wooden stand?

get it away from ground temperatures

how is a weighing lysimeter used to estimate ET?

weighs big chunks of soil and included water

how is wind run defined

total of velocity*time over the day

give an example of how we know that ET and the corresponding precipitation may occur far from each other

Caspian sea, southern atlantic near Namibia, southern pacific near chile, near CA

about how much does air temperature change with every 1000ft increase in elevation?

-5.5 degrees farenheit

we mentioned 4 ways in whcih air lifting occurs. describe three of these

1- cyclonic pressure controlled

2- cyclonic frontal

3-convective

4- orographic

why do raindrops rarely exceed 5mm diameter?

tear themselves apart through wind resistance

how does expected rainfall intensity change with an increase in the area of interest?

goes down

how does expected rainfall intensity change with an increase in the time period of interest?

goes down

define what is meant by 2-yr 10-hr storm?

depth of rainfall over any 10 hour period exceeded only once in 2 years

which will occur the most often?

1 year 1 minute storm

which will have the highest instantaneous rainfall intensity

cannot tell based on given info provided

when will i be most interested in the following: rainfall intensity and rainfall depth

intensity - chokepoint

depth - storage

describe the three parts of a good manual raingage

sharp, clearly defined collector. concentrator tube. storage

pros and cons for weighing raingage

pros: digital, accurate, relatively continuous

cons: poor resolution at, evaporation

what must you do to ensure the accuracy of Doppler radar estimates a rainfall?

ground-truth

what is the biggest concern with location of a raingage and how is it addressed?

wind effects and shielding

explain why rain gages should generally not be placed on a sideslope

wind direction affects reading

explain why rain gages should generally not be placed on rooftops

turbulencee

do we generally want rain gages placed on a pattern or randomly distributed?

patter because we are looking for relatively random effects

if rain gages were placed at the density suggested by the weather bureau for general meteorology, how far apart would the gages be?

15 miles or 25 km

i will need more rain gages to adequately cover a specific area under what three conditions?

• summer storms

• orographic effects

• short-term study

if i have storm rainfall values at several locations nearby, describe the procedure that I use to estimate what the rainfall is here?

point estimate method and inverse distance squared rating

how do i check whether a rain gage gives consistent readings over time?

compare to nearby gauges using PEM

if i have storm rainfall values at several locations nearby, how do i get an average rainfall depth over the entire area of interest?

Thiessen Polygon Method, isohyetal method

what are general problems experienced with measuring snow?

• getting snow into the gage

• hits ground very unevenly, drifting

• can be moved again once it hits the ground, so it can be double counted

describe use of a manual or weighing rain gage for measuring snowfall

remove funnel. put known volume of salt solution in the bottom

describe use of a tipping bucket raingage for measuring snowfall

need heated funnel and body

describe use of snow pillows for measuring snowfall

• flat bladder filled with antifreeze

• measure pressure

• placement critical

describe use of a snow survey for measuring snowfall

• lay out transects beforehand

• stay out of poorly-drained areas

• take snow samples for water content

what is the general range of depths of snow equivalent to 1” of water?

5-12”

what impact does soil texture/structure have on infiltration?

pore sizes control ease of movement of water through soil

what impact does soil subsurface water flow patterns have on infiltration?

keeps water from getting out of the way

by what specific processes do ‘good management’ help increase infiltration?

• controls surface sealing

• more macropores

• slows runoff

draw a graph of ‘normal’ infiltration rate over time

• starting high infiltration rate

• steady-state infiltration rate

Make a graph, labeling the axes with time on the x-axis and infiltration rate on the y-axis.  Now draw two curves on that graph.  The first (solid line) should represent what happens under classical Hortonian conditions, and the second (dashed line) what happens under non-Hortonian conditions with an impermeable layer some distance under the surface.

• hortonian - shows decreases and steady-state

• non-hortonian - shows sudden drop

what measured values are used in developing the Horton infiltration equation?

• initial infiltration rate

• steady state infiltration rate

draw a graph of the actual infiltration rate if the rainfall rate is less than the initial infiltration rate but more than the steady-state infiltration rate

straight line over to curve, follow curve down

why are lab tests for infiltration rates questionable?

small scale, variability, rainfall, spatial flow

what is the concern with any ponded infiltration measurement technique?

unrealistic driving force

why is a double ring infiltrometer better than a single ring?

vertical flow

why is a sprinkling infiltrometer better than a double ring infiltrometer?

-larger area

-water applied like rainfall

-allows for various managementwhat

what are the concerns with using normal contact infiltrometers?

small area, no management

according to Poiseuille’s Law, if i double the radius of a tube and all other parameters remain the same, by how much do i increase the flow rate?

2^4= 16

what are the problems with modeling water flow in soils as a series of tubes flowing based on Poiseuille’s Law?

have all sorts of irregularities(tortuosity, dead ends, irregular shapes, interconnectedness)

on what simple engineering concept is Darcy’s Law based?

V = F/R

write the simple Darcy’s equation, using v=velocity, K = conductivity, L = column length, and F = driving force

v = K * F/L

is the actual flow velocity through the pores(seepage velocity) slower or faster than the Darcy’s velocity, and by what factor?

faster, porosity

how big must the subsurface flow representative elemental volume be?

large enough so that the presence or absence of any single pore (R^4) doesn’t matter

what is meant by preferential flow?

most of the water flows through a very small volume of soil

what is meant by wetting front instability or fingering?

flow does not advance evenly

what 2 factors control the gravity force driving the subsurface flow?

1- depth of ponded water above surface

2- length of continuous water column subsurface

if the soil is saturated just to the soil surface, how is darcys law simplified?

F/L=1

how does the adhesion force of soil water change with thickness of the water layer?

Fs prop 1/T^4

how do the adhesion forces between water and soil tend to cause water to move?

wetter to drier, vapor transfer can be important

friction forces of the soil on water flowing through it have what relationship to the velocity of that flow?

Vs²