Hydrometeorology Flashcards
CLSU- Part 2
study of hydrologic cycle focusing on the interrelationship of its atmospheric and terrestrial phases
Hydrometeorology
an earth science that focuses on the distribution and occurrence of water on and under the earth’s surface
Hydrology
the vertical and horizontal movement of water as either vapor, liquid, or solid between the earth’s surface, subsurface, atmosphere, and oceans that occurs continuously in nature.
Hydrologic cycle (water cycle or water transfer cycle)
process whereby liquid water is converted to water vapour (vaporization) and removed from the evaporating surface such as adjacent soil
Evaporation
process of liquid water vaporization/ removal contained in plant tissues to the atmosphere through the stomata.
transpiration
process by which water vapor becomes a liquid (reverse of evaporation)
condensation
the fall of moisture from atmosphere to the earth’s surface in any form
precipitation
water flowing over the land making its way towards rivers, lakes, oceans, etc. as surface or subsurface flow.
runoff
process of filtration of water to the inner layers of soil based on its structure and nature
infiltration
vertical movement of water through the soil profile
percolation
flow of water under gravitational force thru permeable layers; lateral movement (MOVING SIDEWAYS) of water in the soil
seepage
can take different forms such as rain, snow, hail, and sleet
precipitation
some precipitations are also evaporated immediately without reaching the ground
virga
on the AVERAGE, water stays in the ATMOPSHERE to approximately ___ days before it returns to the ground.
9 days
water in RIVERS and STREAMS stays for approximately ___ months.
2-6 months
the residence time of water in LAKES and GLACIERS varies between ____ years.
20-100 years
the longest residence time of water are in OCEANS reaching to approximately ___ years and GROUNDWATER with residence time of up to ____ years.
3200 and 10,000 years
Earth’s water is distributed to __ % freshwater and __% saline water.
3 and 97
surface water is mostly stored in lakes comprising __% of surface water
87
also known as “water budget equation”
hydrologic budget equation
describes the quantities of water that goes thru the different processes in the hydrologic cycle in a given hydrologic system (e.g. watershed, lake, and reservoir) over a period of time
water budget equation
a structure or volume in space enclosed by a boundary that accepts water and other inputs, operates on them internally and produces them as output
hydrologic system
also known as “catchment area”, “drainage basin”, “river basin”, or “basin”
watershed
an area that topographically appears to contribute all the water that passes thru a specified cross section of a stream (the outlet)
watershed
or simply DIVIDE, the BOUNDARY LINE along topographic ridges that separates two adjacent watershed
watershed divide
typically defined by the highest elevation that drains a stream.
watershed divide/ divide
watershed is made up of
tributaries
a stream that flows into a larger stream or the other body of water.
tributary/ affluent
the first order stream called _____ are smallest streams at the outer limits of a watershed
head waters
a _____ or “outlet”, “measuring point” is located in a single point at which all surface drainage from a basin comes together or concentrates as outflow from the basin in the stream channel
concentration point
process or identifying and delineating the boundary or divide of a watershed
watershed delineation (delineation- describing or portraying)
the water storage of a watershed corresponds to its area, larger area has larger water storage and also larger runoff and streamflow
watershed area classification
( one of the watershed area classification) these watersheds have area <250 km^2
small watershed
( one of the watershed area classification) these watersheds have area ranging from 250 km^2- 2500 km^2
medium watershed
( one of the watershed area classification) these watersheds have area >2500 km^2
large watershed
watershed area classifications
small, medium, and large watersheds
water characteristics
drainage area
drainage basin length
basin slope
basin shape
factors that influences the ability of a watershed to store and discharge water. the runoff and hydrologic processes in the watershed are affected by these factors:
watershed characteristics
reflects the volume of water that can be generated from a rainfall.
drainage area
larger catchment are produces ____ runoff volume
larger runoff volume
the distance measured along the main channel from the watershed outlet to the basin divide.
drainage basin length
for small watershed, length (L in km) can be estimated using its area (A in km^2)
L= 1.312A^0.568
rate of change of elevation to the distance along the principal flow path
basin slope
_____ is an important factor in runoff as it determines the magnitude of streamflow. ____ watershed tends to produce faster peak flow compared to ___
slope, steeper, flat watershed
the shape of the basin reflects how runoff will be collected at the watershed outlet.
basin shape
_______ watershed tends to produce peak flows at short period of time unlike _____ watershed.
circular, elongated
portion of the precipitation that makes way towards stream channels, lakes, oceans as surface or subsurface flow.
runoff (excess precipitation)
refers to precipitation that does not reach the soil, intercepted by the leaves
interception
surface water that flows through creeks, streams, and rivers towards and outlet (e.g ocean) over a fixed period of time
streamflow
sources of streamflow
DIRECT PRECIPITATION
OVERLAND FLOWS
SURBSURFACE FLOW
BASEFLOW
on stream surfaces and its tributaries.
direct precipitation
also knows as “surface runoff”, thin sheet of water that flows over the land surface
overland flows
also known as INTERFLOW, infiltrated water that moves laterally in the vadose and then joins the streamflow
subsurface flow
also known as GROUNDWATER FLOW, flow of water in the groundwater that contributes to streamflow.
baseflow
refers to the height of water surface or stream level measured from an arbitrary datum (it can be the mean sea level)
stage or river stage
the equation the relates stage and discharge is called
rating curve
measured using staff gauges, wire gauges and float gauges.
river stage
measure the depth of the water. are graduated staff made of durable materials that are fixed rigidly to structure installed vertically into the cross section of a stream
staff gauges
gauges that measures the water level from above the surface such as bridges or other structure.
wire-weight gauges
a wire is suspended from a bridge and measure the height from the bridges to the water’s surface.
wire-weight gauges
automatic stage recorder. float movement fluctuates with change in stage and this is recorded by a chart.
float-gauge recorder
velocity-area method
streamflow measurement (Q=AV)
ways to measure the water velocity
- manning’s velocity equation
- velocity by float method.
- current meter method
only measures the surface water velocity
velocity by float method
area method that uses a device is called ___. it is more applicable to larger streams or rivers
current meter method
from experiments and experience, the average velocity is approximately equivalent to ____% of the surface velocity
80%
showing the rate of flow (discharge) vs time past a specific point. known as storm or flood hydrograph.
hydrograph
parts of a hydrograph
- rising limb
- crest segment
- falling limb
also called excess rainfall. amount of rainfall that becomes the DIRECT RUNOFF at the watershed outlet.
effective rainfall
graphical representation of the representation of the distribution of rainfall intensity over time.
hyetograph
factors affecting hydrograph are group into
physiographic and climatic factors
this influences the time for the most remote water in the watershed to arrive in the outlet (time of concentration)
watershed shape
larger size watershed will have larger catchment area.
watershed size
_____ determines the velocity of water flow in streams. STEEPER STREAMS will have a faster water depletion.
watershed slope
elastic reduction of water
water depletion
it is the ration of the total stream length to the are of the watershed.
watershed drainage density
_______ will result to faster depletion of water out of the watershed.
larger drainage density
urban, forest, agricultural etc., influences the hydrograph because of the different land covers.
land use
________ such as rainfall intensity, rainfall duration and direction of storm influences the hydrographs.
climatic factors.
time from the beginning of the rising limb to the occurrence of the peak discharge.
time to peak
the time required for water to travel from the most hydraulically remote point in the basin to the basin outlet.
time of concentration
time between the center of mass of the effective rainfall hyetograph and the center of mass of the direct runoff hydrograph
lag time
the duration of the direct runoff hydrograph
time base
a direct runoff hydrograph resulted from 1 unit of excess precipitation or rainfall (1cm or 1 inch) that occurs uniformly over a watershed over a specific time. 1 unit excess rainfall
unit hydrograph
these are water that fills the voids in a geologic stratum. a rechargeable resource widely distributed under the ground which can be used to supplement water supply in irrigation and other usage
groundwater
a water bearing geologic formation or stratum capable of transmitting water thru its spores at a rate SUFFICIENT for economic extraction by wells
aquifer
a geologic formation, which can absorb water but CANNOT TRANSMIT SIGNIFICANT AMOUNTS
aquiclude
____ formations are example of aquiclude
clay
a geologic formation of rather impervious nature, which transmit water at a SLOW RATE compared to an aquifer
aquitard
INSUFFICIENT for pumping from wells. ______ formations are sandy clay (impermeable rock)
aquitard
a geologic formation with no interconnected pores and hence can neither absorb nor transmit water.
aquifuge
these are formations made of massive compact rocks without any fractures. NOT POROUS NOR PERMEABLE
aquifuge
also known as WATER TABLE AQUIFER, an aquifer just beneath the water table; a groundwater that is NOT CONFINED by a strata under pressure higher than atmospheric
unconfined aquifer
wells that are drilled into unconfined aquifer
water table wells
a special case of unconfined aquifer, occurs whenever a groundwater body is separated from the groundwater by a relatively impermeable stratum of small areal extent by the zone of aeration above the main body of groundwater
perched aquifer
“artesian aquifer” or “ pressure aquifer” occurs when groundwater is confined under pressure greater than atmospheric pressure by an overlying impermeable stratum.
confined aquifer
also known as “potentiometric surface” in confined aquifer it is an imaginary line that coincides with the hydrostatic pressure level of the water in the aquifer
piezometric surface
two kinds of wells drilled into an artesian aquifer
- flowing artesian well
- non flowing artesian well
also called as FREE FLOWING WELLS, wells that are drilled in areas where ground surface is lower than the piezometric surface. water rises above the ground
flowing artesian well
wells that are drilled in area where GROUND SURFACE is above the piezometric surface
non flowing artesian well
aquifers that are completely confined or unconfined occur less frequently than do leaky of semi-confined aquifers
leaky aquifers
aquifers that assumes the groundwater storage and flow to be homogeneous and isotropic.
idealized aquifer
assumes that all hydrological processes everywhere are identical
homogeneous aquifer
this aquifer properties are independent of directions.
isotropic aquifer
classifications of an aquifer
- unconfined aquifer
- confined aquifer
- leaky aquifer
- idealized aquifer
also known as “vadose zone”, layers where it is partially occupied by water and partially by air
zone of aeration
moisture in this zone is less than saturation except during rainfall occurrence or irrigation
soil-water zone
water held tightly to the surface of the soil particle by adsorption forces
hygroscopic water
water held by forces of surface tension and continuous film around soil particles
capillary water
this zone connect the zone near the ground surface and zone near the water table
immediate vadose zone
also known as “capillary fringe”, these zones extend from the water table to the capillary rise of water.
capillary zone
commonly known as “groundwater”, also known as PHREATIC ZONE all layers are filled with water under hydrostatic pressure
zone of saturation
measure the void spaces of soil and it is the ration of void spaces volume to the total volume of soil. values ranges from 0 to 1 can be expressed in percentage.
porosity
in groundwater, _____ is a measure of water bearing capacity of the formation
porosity
volume of water expressed as a percentage of the total volume of the SATURATED AQUIFER that will drain by gravity when the water table drops due to pumping or drainage
specific yield
volume of water expressed as percentage of the total volume of saturate aquifer which WILL NOT DRAIN by gravity.
specific retention
the volume of water given out by a unit prism of aquifer when the piezometric surface (confined aquifers) or the water table (unconfined aquifers) drops or rises by unit depth
storage coefficient
states that “the velocity of flow in a porous medium is proportional to the hydraulic gradient”
Darcy’s Law
coefficient of permeability is also known as
hydraulic conductivity
slope of the water level/ piezometric level or simply the change in water level per unit distance along the direction of max head decrease
hydraulic gradient
also known as “transmissivity”, flow capacity of an aquifer per unit width under unit hydraulic gradient and is equal to the product of permeability time the saturated thickness of the aquifer.
transmissibility
Darcy’s law is valid for laminar flow with reynolds number (Rc) of _____ or equal to unity (1). It is also not applicable to laminar flow with Rc _____ unity.
less than, greater than
the flow does not change over time
steady flow
reduction of hydraulic head or the distance at which the water level is lowered
drawdown
also known as DRAWDOWN CONE, shows the variation of drawdown with distance from the well. cone of the depression describes the shape of the_____
drawdown cruve
pertain to the are from the outer limit of the cone of depression (zero drawdown) to the well
area of influence of a well
______ of a well is the discharge per unit drawdown in the well. measure of effectiveness of the well
specific capacity
well that is usually dug up to 7 meters is called
shallow well
a well that is dug more than 7 meters are called
deep wells
the overall instantaneous condition of the atmosphere at a certain place and time;
weather
______ refers to the state of the atmosphere for a given place over time; average of many years of weather observation _______ years
climate, 30 years
it is a short term, limited area, can change rapidly, and difficult to predict
weather
it is a long-term, wide area, seasonal changes, and measures over long spans of time
climate
a relatively thin, gaseous envelope that comprises mostly nitrogen and oxygen with small amounts of other gases, such as water vapor and carbon dioxide
atmosphere
rate of decrease in temperature along the vertical
lapse rate
the lower most (12-18 km) of the atmosphere and it is where all weather occurs; temp decreases with altitude at a rate of about 6.5 deg km
troposphere
about 12-50 km, layer where temperature inversion occurs (temperature increase with height)
stratosphere
the location of the ozone layer which causes the inversion
stratosphere
_____ absorbs ultra violet rays which lead to warming
ozone
the air at this level is extremely thin (50-80km) and the atmospheric pressure is quite low, averaging about 1 milibar (mB)
mesosphere
no well-defined upper limit and the “hot layer” above mesosphere (90-700 km); fraction of atmosphere’s mass is contained in this region; gases moving at high speeds
thermosphere
any form of water particles- liquid or solid that falls from the atmosphere and reaches the ground
precipitatiio
term use for precipitation that are less than 0.1 mm
trace
the average value of rainfall at a particular date month or year over a specified 30-year period. the 30 yr normal are recomputed every decade.
normal rainfall
a light steady rain in fine drops that are < 0.5 mm in size and intensity of < 1 mm/hr
drizzle
the condensed water vapor of the atmosphere falling in drops that are >0.5 mm in size (maximum size 6 mm) from the clouds.
rain
ice crystals resulting from sublimation (i.e. water vapor condenses to ice
snow
freezing of drizzle or rain when they come in contact with cold objects
glaze
frozen ran drops while falling thru air at subfreezing temp
sleet
ice crystals fused together
snowflakes
small lumps of ice (>5mm in diameter) formed by alternate freezing and melting, when they are carried up and down in highly turbulent air currents.
hail
moisture condensed from the atmosphere in small drops upon cool surfaces
dew
a feathery deposit of ice formed on the ground or on the surface of exposed objects by dew or water vapor that has frozen
frost
a thin cloud of varying size formed at the surface of the earth by condensation of atmospheric vapor (interfering with visibility)
fog
a very thin fog
mist
forms of precipitation
drizzle, rain, glaze, sleet, snow, snowflakes, hail, dew, frost, fog, mist
types of precipitation
- convectional precipitation
- frontal precipitation
- orographic precipitation
- cyclonic precipitation
type of precipitation in the form of local thunderstorm. air on the earth’s surface is heated causing them to rise forming thunder storms
convectional precipitation
type of precipitation in the form of fronts.
frontal precipitation
____ are the boundary between two different air masses.
fronts
this occurs when cold air mass advances towards a warm air mass
cold front
this occurs when warm air mass move towards cold air mass
warm front
this occurs when cold front overtake a warm front
occluded front
this occurs when neither cold and warm air masses advances
stationary front
type of precipitation that is caused by orographic lifting
orographic precipitation
caused by a barrier e.g., mountain range
orographic lifting
type of precipitation that is caused by air converging into a low-pressure area e.g., cyclones
cyclonic precipitation
process of producing precipitation by liquid particles (cloud droplets and raindrops) thru colliding and joining (coalescing), occurs in warm clouds
collision-coalescence process
process of rain formation is extremely important in middle and high latitudes, where clouds extend upward into regions where the air temp is well below freezing
ice crystal (bergeron) process
any instrument designed to measure rain amount; it includes recording, non-recording, and rain-intensity gauges.
rain-gauge
instrument that automatically records the amount of precipitation collected as a function of time.
recording rain-gauge
a recording rain gauge in which the water collected continuously drains thru a funnel into one of a pair of chambers or buckets that are balanced stably on a horizontal axis.
tipping-bucket rain gauge
a recording rain gauge in which the weight of water collected is measured as a function of time and converted to rainfall depth
weighing rain gauge
a probe consisting of a stainless-steel rod covered by a teflon sheath set inside a cylindrical rainwater collector
capacitance rain gauge
a gauge that measures the scintillation in an optical beam produced by raindrops falling between light source and an optical receiver.
optical rain gauge
MANUAL GAUGES, any member of the class of rain gauges in which rain amount as a function of time is not automatically recorded.
non-recording rain gauge
a non -recording cylindrical rain gauge with a collector diameter of 20.3 cm (8in)
eight-inch rain gauge
also called RAIN-RATE GAUGE, RATE OF RAINFALL GAUGE, an instrument that measures the rate at which is falling
rain-intensity gauge
also called MICROPLUVIOMETER, a rain gauge capable of measuring very small amounts of precipitation, amounts that are less than could be measured by an ordinary rain gauge
ombrometer
measure of the degree of hotness and coldness of air. measured by a a thermometer. measures of the average speed/ motion of molecules, faster motion corresponds to higher temperature
air temperature
an instrument for measuring temp by utilizing the variation of the physical properties of substances accdng to their thermal states
thermometer
a thermometer that utilizes the thermal properties of gas
gas thermometer
a thermometer in which the thermally sensitive element is a liquid contained in a graduated glass envelope
liquid-in-glass thermometer
a thermometer using transducing elements that deform with temperature
deformation thermometer
a thermometer that uses a transducing element with electrical properties that a re a function of its thermal state.
electrical thermometer
a thermometer in which the thermally sensitive element is a liquid contained in a metal envelope, frequently in the form of a bourdon tube
liquid-in-metal thermometer
a thermometer based on the principle that the velocity of a sound wave is a function of the virtual temperature of the medium through which it passes
sonic thermometer
a self-recording thermometer
thermograph
the temp at which saturation occurs
dewpoint temperature
the air temp measured by the dry bulb thermometer of a psychrometer
dry-bulb temperature
the lowest temperature that can be obtained by evaporating water into the air
wet-bulb temperature
the difference in degrees between the air temperature (dry bulb temp) and the _______
wet-bulb temperature
also called BAROMETRIC PRESSURE. pressure (force exerted per unit area) exerted by the atmosphere as a consequence of gravitational attraction exerted upon the “column” of air lying directly above the point in question
atmospheric pressure
an instrument for measuring atmospheric pressure.
barometer
formerly “torricelli’s tube”, a glass manometer, employing mercury in its vertical column, that is used to measure atmospheric pressure
mercury barometer
sometimes called “holosteric barometer”
aneroid barometer
special type of aneroid barometer that converts pressure to altitude.
pressure altimeter
a recording barometer
barograph
standard atmospheric pressure
101.325 millibar/ 1 atm/ 101.325 kPa
the moisture in the air (air’s water vapor content)
humidity
humidity is express as
- absolute humidity
- specific humidity
- mixing ratio
- relative humidity
tells us the mass of water vapor in a fixed volume of air, or the water vapor density
absolute humidity
the mass of the water vapor in the air parcel over the mass of all the air in the parcel (including vapor)
specific humidity
the mass of the water vapor in the parcel over the mass of the remaining dry air
relative humidity
the ratio of the amount of water vapor actually in the air to the max amount of water vapor required for saturation at that particular temp (and pressure)
relative humidity
any instrument that measures the water vapor content of the atmosphere
hygrometer
uses the thermodynamic method. made of 2 thermometers; the dry bulb and wet bulb
psychrometer
an ordinary glass thermometer of psychrometer
dry bulb
has its bulb covered with a jacket of clean muslin that is saturates with distilled water prior to an observation (psychrometer)
wet bulb
hair hygrometer, torsion hygrometer, goldbeater’s-skin hygrometer; it is an example of:
class of instruments that depends upon a change of physical dimensions due to the absorption of moisture
dewpoint hygrometer, frost point hygrometer are an example of
class of instruments that depend upon condensation of moisture
one of the type of hygrometers that is example is diffusion hydrometer
class of instruments that depend upon the diffusion hygrometer
one of the type of hygrometers that its example is spectral hydrometer
class of instruments that depend upon measurements of the absorption spectra of water vapor
air in motion relative to Earth’s surface. it is the workhorse of weather, moving storms and large fair-weather systems around the globe.
wind
an instrument use to measure wind speed and diirection
anemometer
surface breeze that flows from the land toward water bodies
land breeze
surface breeze that flows from the see toward the land
sea breeze
the heated air, being less dense than the air of the same altitude above the valley, rises as a gentle upslope wind
valley breeze
Northeast monsoon, late october to april
amihan season
the cooler, more dense air glides downslope into the valley
mountain breeze
a seasonal change in wind direction caused by a change in the dominant atmospheric pressure pattern
monsoon
visible aggregate of tiny water water droplets or ice crystals suspended in the air.
clouds
southwest monsoon, May or early June to September
Habagat season
condensation occurs thru the presence of condensation_____
nuclei
max distance at which an observer can see and identify and object lying close to the horizontal plane on which he or she is standing (THE GREATEST DISTANCE)
horizontal visibility
______ occurs when the temperature is way below dew point temperature and the relative humidity is several hundred percent (400%)
condensation
serve as surfaces on which water vapor can condense
condensation nuclei
are WATER SEEKING and water vapor rapidly condenses on their surfaces
hygroscopic nuclei
are WATER REPELLING and resist condensation (oils, gasoline, and paraffin waxes)
hydrophobic nuclei
known as thunder storm clouds (large rainfall droplets). rainfall occurs for 2-3 hrs
cumulonimbus
dark gray, WET-looking cloud layers with more or less continuously falling rain or snow, can last for many hours(less intense, small rain drops)
nimbostratUs clouds
RADIANT ENERGY or radiation, total electromagnetic radiation emitted by the sun (1353 kW/m2)
solar radiation
solar-rad that has not been scattered or absorbed (1000kW/m2)
direct solar radiation
solar rad, direct and diffuse, received from a solid angle of 2pi steradians on a horizontal surface
global radiation
solar rad that is scattered at least once before it reaches the surface
diffuse sky radiation
gen name for any instrument used to measure the intensity of radiant energy, ex. sun
actinometer
measures the intensity of direct solar rad
pyrheliometer
measures global rad (combined intensity of direct solar rad and diffuse sky rad)
pyranometer
measures the effective terrestrial rad
pyrgeometer
type of actinometer, instrument that measure the intensity of radiant energy by employing a thermally sensitive electrical resistor
bolometer
instrument for measuring the ultraviolet in solar and sky rad
dosimeter
instrument for measuring the luminance, luminous intensity, or illuminance of a light source
photomoter
instrument that measures radiated electromagnetic power
radiometer
called CONSUMPTIVE USE, total water lost from a cropped (or irrigated) land dur to evaporation from the soil and transpiration by the plants or used by the plants in building up of plant tissue
evapotranspiration
loss of water from the adjacent soil, water surfaces and leaf surfaces
evaporation
water loss from the water entering the plant roots and out to the atmosphere
transpiration
also called potential ET, represented by the evapotranspiration from a standardized vegetated surface or reference surface
reference crop evapotranspiration
evapotranspiration from disease-free, well-fertilized crops, grown in large fields, under optimum soil water conditions and achieving full production under the given climatic conditions
crop evapotranspiration under standard condition
evapotranspiration from actual field condition. accounts all factors such as environment, weather and crop
crop evapotranspiration under non-standard conditions
station gathers and provides on routine basis simultaneous meteorological and biological formation
agrometeorological station
station where observation of almost all meteorological elements is made at fixed observation times and are transmitted to the central office
surface synoptic station
also known as EVAPORIMETER, EVAPORATION GAUGE, ATMIDOMETER, general name for an instrument that measure the evaporation rate of water into the atmosphere
atometer
station that observes meteorological and hydrological elements
hydrometeorological station
2.5-7.5 mm in hr and in next 2 hrs, FLOODING is STILL POSSIBLE in certain areas
moderate rainfall
less than 2.5 mm observed in 1 hr to next 2 hrs, FLOODING is STILL POSSIBLE in certain areas
light rainfall
7.5-15 mm WITHIN 1 hr. FLOODING is STILL POSSIBLE in low lying areas and near river channels
heavy rainfall (yellow rainfall warning)
15-30mm WITHIN 1 hr, FLOODING is THREATENING in low-lying areas and near river channels
intense rainfall (orange rainfall warning)
> 30mm WITHIN 1 HR or >65mm for the past 3 hrs, SEVERE FLOODING is expected, take necessary precautionary measures
torrential rainfall (red rainfall warning)
measured at 10 METER above the ground average over 10 MINUTE duration
maximum sustain wind
wind speed measured at 10 METERS above the ground over 3-5 SECONDS
gust wind
involves the collection and analysis of annual maxima of parameters that are observed daily (temp, precipitation and wind speed)
extreme value frequency analysis
series of extreme events each yr (e.g., daily max rainfall)
annual maximum series
all values above a given base are chosen regardless of the number within a given period.
partial duration series
RECURRENCE INTERVAL, average number of years necessary for the event to occur once, in any given year
return period
