Precipitation

Question 1

What is precipitation

Answer 1

The water reaching a catchment as rainfall, snow, hail, dew or occult forms

Question 2

What is average annual rainfall for the world and for Lancaster

Answer 2

1000 mm

Question 3

Where was the highest recorded annual rainfall

Answer 3

At cherrapunji, India

Question 4

How much rainfall did Cherrapunji receive

Answer 4

26,461 mm/yr in 1861

Question 5

What was the highest rainfall in the Uk

Answer 5

Sprinkling Tarn (Scarfell Pike, Cumbria)

Question 6

How much annual rainfall was at scarfell pike

Answer 6

6,528 mm/yr in 1954

Question 7

What is rainfall measurement about

Answer 7

The areal integration (average across an area) over a network of point measurements (individual raingauges catches)

Question 8

How many gauges are the UK Meteorological Office network

Answer 8

6,800 raingauges

Question 9

What are most of the gauges at the UK meteorological office

Answer 9

Daily storage gauges though they also have a number of monthly storage gauges and rainfall recorders

Question 10

What is a monthly storage gauge

Answer 10

Volumetric measurements taken after a month of collection

Question 11

What do rainfall recorders do

Answer 11

Rainfall intensities recorded automatically on charts or electronic data loggers

Question 12

How far above ground does the MET office mark II storage gauge stick

Answer 12

30cm

Question 13

Why is the top of the Met price mark II storage gauge sharp

Answer 13

So when raindrops hit it they are chopped. Knife edge

Question 14

What does the drop above funnel in the Met office mark II storage gauge prevent

Answer 14

Out splash - water jumping out

Question 15

Why is the above funnel of the Met office mark II storage gauge narrow

Answer 15

To minimise evaporation that’s coming out of the bottle between daily measurements

Question 16

Why does the Met office mark II storage gauge use a glass bottle inside

Answer 16

To prevent water from being attracted to side of bottle when you upend it so all water comes out

Question 17

Why is the Met office mark II storage gauge 1ft above ground

Answer 17

Reduces insplash

Question 18

Why is the base of the Met office mark II storage gauge splayed

Answer 18

So when it’s in the ground it’s less likely to move and water is less likely to evaporate

Question 19

Why is there an outercan in the Met office mark II storage gauge

Answer 19

To catch overflow

Question 20

Example of monthly storage gauge

Answer 20

Clougha Pike in Lancaster

Question 21

Why are rainfall recorders useful

Answer 21

We might want to know rainfall every 5 mins or 15 mins so we need some form of automated rain gauge

Question 22

What are the different rain gauges

Answer 22

Siphoning tank rain gauge.

Tipping bucket rain gauge.

Question 23

What does the siphoning tank rain gauge do

Answer 23

Tells rainfall every 15 mins.
Gubbins - rainfall in big funnel getting directly into tank which fills with water. Inside is float connected to arm of gubbin. Arm goes up which is connected to pen that records volume.when at top it pivots and gets emptied and counter weight pulls it back up.

Question 24

What is the chart created in a siphoning rain gauge

Answer 24

Hyetogram - need someone in lab digesting data. Not great

Question 25

How does a tipping bucket rain gauge work

Answer 25

Inside is a double bucket and rain comes in funnel and first of all fills the inside bucket which tips and fills other bucket. Magnet behind bucket is reed switch so it you bring magnet towards it you can record time on data logger.

Question 26

Why do you need a check gauge in tipping bucket

Answer 26

Due to greater error and freezing problems - if it’s frozen and locked nothing happens.

Question 27

What is the effect of sheltering in raingauge sitting

Answer 27

Where you put the raingauge affects the total. Should always have an angle of 30* from rain gauge to highest nearest objected. Should be twice the height away if not degree measurement.

Question 28

What is the effect of turbulence on rain gauges

Answer 28

If rain isn’t coming down vertically turbulence blows rainfall away from rain gauge on windy days so to counteract you build a Huddleston turf wall. 1.5 m away. Or institute of hydrology ground level gauge, need to generate rough surface so water can’t run straight in.

Question 29

How do you produce rough ground

Answer 29

Anti splash grid around gauge in pit

Question 30

What are the problems of snowfall measurement

Answer 30

Burial - not much bother in UK bc not for a lot of snow.

Question 31

How do you counter act burial

Answer 31

Lift rain gauge above ground so it doesn’t get covered by drift. Need to get rid of turbulence on rain gauge.

Question 32

After elevating the rain gauge to deter drift, how do you combat turbulence

Answer 32

Nipher shield | Alter shield - flap around in wind to remove turbulence

Question 33

What are he problems of rainfall measurements in tropical rainforests like Damon valley field centre, Borneo

Answer 33

Has to be 40-60m high bc of high trees. | Have to build out of Borneo iron that doesn’t rust but shiny at night so insects dive into it.

Question 34

Why do they have to put walls around rain gauges in Borneo

Answer 34

So elephants don’t trample it but only covers one rain gauge

Question 35

What are the 2 things needed for areal estimation of rainfall

Answer 35

Catchment average and spatial patterns

Question 36

What are the 6 methods of areal estimation of rainfall

Answer 36

``` Arithmetic mean Thiessen polygon Hypsometric curve Isohyetal Radar Mathematic surface ```

Question 37

How to work out arithmetic mean of distribution

Answer 37

All rainfall and divide by number of gauges.

Question 38

What does arithmetic mean require

Answer 38

Even spacing of rain gauges across catchment - uniform distribution. Can’t have relief

Question 39

What is good for the arithmetic mean

Answer 39

Simple Uniform distribution Flat terrain

Question 40

How does thiessen polygons work

Answer 40

Weight total rainfall according to local area that each gauge represents. Draw line between rain gauge pairs, middle point of that line, draw another line at tangent to first line and join all them up to generate hexagons across catchment. Copes with uneven totals

Question 41

What does the thiessen polygon deal with that arithmetic meal doesn’t

Answer 41

Uneven spacing

Question 42

What is bad about the thiessen polygon method

Answer 42

Flat terrain required

Question 43

How much more rainfall do you get if you go up a meter

Answer 43

1mm more due to orogrqphic enhancement of rainfall

Question 44

What is a better version of the thiessen polygon

Answer 44

Altitude corrected thiessen polygon. Bisection point is median altitude

Question 45

How does the hypsometric curve work

Answer 45

Curve of precipitation on the top right hand graph and area under the curve gives total rainfall weighted according to altitude

Question 46

What is the isohyetal method

Answer 46

At a particular time you have a total amount of rainfall so you can draw lines between equal rainfall. Tot up rainfall for each area and divide by total area. Gives catchment average rainfall but also patterns of rainfall in catchment.

Question 47

What can isohyetal method be subjectively adjusted for

Answer 47

Underlying topography

Question 48

What is radar

Answer 48

Radar reflectively calibrates against point gauges means. Firing signals into atmosphere and receiving a return of things in the atmosphere

Question 49

What is the mathematical surface method

Answer 49

If you got a rain gauge and their totals you can fit mathematical surfaces into it. Kriging is a method for fitting a mathematical surface through data.