Final Flashcards
What does ENSO stand for
El Nino Southern Oscillation
El Nino
(“The Little Boy”)
Refers to the weakening or potentially even the reversal of the easterly trade winds along the equator, allowing warm water from the western Pacific Ocean to move east to produce warmer than normal sea surface temperatures in the central to eastern Pacific Ocean
La Nina
(“The Little Girl”)
Refers to the normal or “stronger than normal” conditions where easterly trade winds push the warm water of the Pacific to the west, allowing upwelling of cold deep water to occur in the eastern tropical Pacific Ocean, causing colder than normal sea surface temperatures in this region
Teleconnection
An event or process that influences weather/climate pattern 1000s of miles away or even globally
Southern Oscillation Index
Negative Phase
- Below normal air pressure at Tahiti and above at Darwin
- Means warmer than normal water in the eastern Pacific (warm water means warmer, rising air and lower atmospheric pressure) and colder than normal in the western Pacific -> El Nino
Southern Oscillation Index
Positive Phase
- Above normal air pressure at Tahiti and below at Darwin
- Means colder than normal water in the eastern Pacific (cold water means colder, sinking air and higher atmospheric pressure) and warmer than normal in the western Pacific -> La Nina
Equatorical Southern Oscillation Index
Uses pressure anomalies over Indonesia and the far eastern Pacific over the equator
Weather
The day to day variation in sky conditions, temperature, precipitation, wind, etc.
Climate
The distribution of a particular weather variable over a period of time
(normally 30 years)
Climate Normal
A 30 year average of a weather/climate variable (eg. temperature)
- Also includes degree days, probabilities, standard deviations, etc.
Plate Tectonics Theory
A theory that states that the outer portion of Earth is made up several individual plates, which move in relation to one another upon a partically molten zone below
- As the plates moves, so do the continents
Whats climate change, specifically?
Its a change in the distribution of a variable
Milankovitch Cycle
Systematic changes in 3 elements of Earth’s Orbit
- Eccentricity
- Obliquity
- Precession
Eccentricity
Refers to the shape of Earth’s orbit around the sun
(ie how much the orbit is squashed)
Obliquity
Refers to axial tilt of Earth with respect to its orbital place
- Shift from 22.1-24.5 and back again
Precession
Wobbling of Earth’s axis like spinning top that winding down
How does La Nina Influence Weather
Blocking high pressure pushes the colder air towards northern part of the United States
How does El NinoInfluence Weather
Low pressure pushes the warm air towards the southern part of the United States
Below Normal Air Pressure at Tahiti and Above Normal at Darwin
Negative Phase
(El Nino)
(Lower Atmospheric Pressure)
Above Normal Air Pressure at Tahiti and Below Normal at Darwin
Positive Phase
(La Nina)
(Higher Atmospheric Pressure)
Volcanoes
Large eruptions eject sulfur dioxide into the stratosphere where it turns into sulfate aerosols that block a fraction of incoming solar radiation from reaching Earth’s surface
Fossil Fuels
Use of coal, oil and natural gas releases carbon dioxide and potentially methane into the atmosphere
Land Use/Land Cover (LULC) Change
Changes in land cover/land use also influence climate by changing the absorptive properties of the surface
Model Parameterization
Parameterization in a weather or climate model within numerical weather prediction is a method of replacing processes that are too small-scale or complex to be physically represented in the model by a simplified process
Climate Change Feedback
Physical process that can amplify (positive) or decreases (negative) the influences of climate change (CO2 increases)
Positive Feedbacks
(Climate Change Feedback)
- Sea Ice Melting
- Permafrost Melting
- Forest Fires
- Water Vapor Feedback
“Tipping Point”
The level at which an effect of climate change causes an irreversible (or at least a very large) effect on a earth system
Model Resolution
How much spatial and temporal detail the model simulates
Model Guidance
NWP models do not produce the exact forecast you receive. There’s always a human component to the forecast
- Models only produce what is called “guidance”
What’s ET
ET refers to the water that is evaporated from the surface into the atmosphere
(evaporation + transpiration)
Types of ET
Actual or Crop ET
- Crop “water usage”
Types of ET
Reference ET
- Potential ET
What does ET form
Forms the basis for the hydrologic cycle
How is the amount of ET determined?
- The amount of water available to evaporate/transpire
- The amount of energy available to evaporate/transpire that water
Actual ET
(Crop ET)
The amount of water that’s actually evaporated and/or transpired
Potential ET
The amount of water that would evaporate or transpire given no limitis on the availability of water
How is actual ET limited?
Limited by both
- the amount of water available to evaporate/transpire
- the amount of energy available to evaporate/transpire that water
How is potential ET limited?
Limited only by the aount of energy available
Difference between Hydrologic Cycle vs Water Balance
Scale on which they occur
Definition
Vertical Wind Shear
Change in wind speed and/or wind direction
Describe the process that causes water temperature in the eastern Pacific to change during El Nino
Weakening and reversal of easterly trade winds pushing warm water from the west to move to the easterly Pacific warming the cold water
Describe the process that cuases water temperature in the eastern Pacific to change during La Nina
Strengthening of the easterly trade winds pushing cold water from the east to the west cooling the western Pacific
Definition
Parameterization
In a weather or climate model within numerical weather prediction is a method of replacing processes that are too small-sclae or complex to be physically represented in the model by a simplified process
Whats a forecast ensemble
An ensemble forecast is a forecast made up of distinct forecasts each generated using slightly different initial conditions or slightly different physics
Agricultural water balance is largely a ____ water balance
Soil
An SPI (standardized precipitation index) value of -2 means
Precipitation is 2 standard deviations below normal for the periodn
Definition
Field Capacity
A measure of how hard the soil holds on to the water against gravity
Meterological Drought
A lack of precipitation over a period of time
Agricultural Drought
A decline in and lack of soil moisture, leading to crop losses and/or failures
Hydrological Drought
A period of inadequate surface and subsurface water resources for established water uses for a given water resources management system
Soci-Economic Drought
The failure of water resource systems to meet water demands because of a weather related shortfall in water supply
3 Major Aspects of Drought
- Duration
- Severity
- Geographic Extent
Drought Indices attempts to:
Characterize drought levels by assimilating data from one or more variables (ie precipitation, temperature, soil moisture, etc.) into a single valve
Porosity
Proportion of pore space in a volume of soil
Matric Potential
Describes how hard soil “holds” on to water
Volumetric Water Content
Ratio of water volume to soil volume
Permanent Wilting Point
Volumetric water content of the soil beyond which a plant cannot extract water
Plant Available Water (PAW)
Volume of water thats available for the plant to uptake
PAW
Field Capacity - Permanent Wilting Point
Hydraulic Conductivity
A measure of “how easy” it is for water to move in the soil
Definition
Micrometeorology
Weather/climate processes that occur at scales of 1km or less
(all the way down to mm scale)
Influences of Small Scale Atmospheric Processes
- Synoptic Scale Weather
- Land Use/Land Cover
- Topography
Crop Canopy Closure
When the aboveground portion of the crop completely shades the soil and other vegetation, etc beneath it
Radiation Use Efficiency
Ratio of crop dry matter produced per unit of intercepted photosynthetically active radiation
Plant Population Density
How many plants/acre is necessary to achieve the highest yield and radiation use efficiency while balancing costs of fertilizer, seeds, etc
Vertical Wind Profile
how the wind changes speed with height and how this relationship varies by the roughness of the surface its flowing over
Roughness Length
An empirically determined (from observations) coefficient that describes the friction a particular surface type places on wind
How do snow fences work?
Wind is forces to go through and around fence losing speed and energy. Snow particles drop out as wind decreases forming drifts in front of and behind fences
Cold Air Pooling (CAP)
Cold air draining to the lowest point in a field
What causes Cold Air Pooling
Local cause of inversion a layer of warmer air above a layer of colder air
Precipitation
Convective
Can be intense and very heavey but is often much local
Outlooks
Outlooks are simple, just displaying the probability that the period in question will be below, above or at normal for temperature and precipitation
Definition
Sources
Precipitation, rivers/streams/groundwater moving into a system, irrigation
Definition
Sinks
ET, rivers/streams/groundwater moving into a system
“Sources”
Inputs of water
“Sinks”
Processes or means by which water is removed
Greenhouse Gases
- About 25% of the sun’s energy (“shortwave” radiation) is reflected off the top of the atmosphere
- Remaining energy from is sun is “transparent” so that most of it reaches the earth’s surface
- About 20% of the sun’s energy is reflected off the Earth’s surface - rest is absorbed and causes the temperature of the surface to rise
Greenhouse Gases
- Water Vapor
- Nitrous Oxide
- Methane
- Carbon Dioxide
If it rains heavily during the night, and the next day is a sunny, hot, windy day with low RH, what will the actual ET be?
Low, because of evaporation rain increases relative humidity.
If it rains heavily during the night, and the next day is a sunny, hot, windy day with low RH, what will the PET be?
High
