2.4 - Weather Flashcards
Weather
The short-term day to day changes in the atmosphere for a place.
Meteorologists
Measure the weather and predict the forecast.
Why do we need to know the weather? (name 3)
- Been able to gather information about the weather is extremely important to society
- The weather can have huge impacts on what people do
- It can even have a national or even global impact (e.g. flights, floods etc.)
- It is very important to gather accurate data for the weather, small mistake can create hazards
- It is very useful to predict weather conditions for the future (e.g. trade, commercial usage, industry, for individual people)
What is describing weather conditions based on?
- temperature
- percipitation
- moisture
- air pressure
- wind speed
- wind direction
- amount of sunshine
- cloud type/cover
- visibility
Percipitation
Moisture that falls from the sky
(rain, snow, hail, sleet)
Easiest measuring instrument for temperature
A digital thermometer
* measured in Celcius
Measuring instrument for maximum and minimum temperature
Six’s thermometer/maximum minimum thermometer measures current temperature and the temperature range in a period of time
* measures in celcius
How is Six’s thermometer used?
- Shade temperature is measured, as air temperature is variable due to direct insolation and cloud cover
- If the temperature rises, the alcohol in the right tube evaporates and fills the air space.
* This allows the mercury to move upwards
* The index is pushed upwards and its bottom marker marks the maximum temperature. - If the temperature falls, the mercury retreats but the index stays in place.
* The antagonistic movement can be noticed in the left tube. - Can have a diurnal temperature range
Insolation
Incoming Solar Radiation: the incoming shortwave radiative energy received from the sun
Diurnal temperature range
Differences between the hottest and coldest temperature in a 24 hour range (min - max)
Formula to calculate daily average temperature
(max + min) / 2
Measuring instrument to measure percipitation
Rain gauge
* measured usually in mm
How is percipitation measured?
- The rain gauge is usually anchored in the ground with the top of the gauge
- around 30cm above the ground surface to ensure that rain splash does not affect the results.
- The depth of the rain in millimetres can be read from the side of the container (or the rain gathered can be poured into a measuring cylinder)
Measuring instrument to measure wind direction
Wind vane
* using compass directions
How is wind direction measured?
It is reported by the direction it is blowing from not to (e.g. blowing from the west to the east, it is a westerly wind)
Measuring instrument to measure wind speed
Anenometer
* measured in knots, km/h or m/s
How is wind speed measured?
- The anemometer consists of 3 or 4 cups fixed on metal arms that rotate freely on a 10m vertical shaft
* The stronger the wind, the faster the cups rotate, and more rotations are recorded on the counter - The digital handheld anemometers need to be held into the oncoming wind with outstreched arms and as the fan rotates, the number is shown on the screen
- Wind vanes and anemometers are placed well away from any buildings or trees that can interfere with air movement
Measuring instrument to measure humidity
Hygrometer
* as a percentage
Measuring instrument to measure air pressure
Barometer
* in millibars
General properties of air humidity
- Warm air can hold more water vapour than cold air
- When the air is holding as much moisture as it can, it’s said to be saturated
- Relative humidity: how much water vapour the air is holding in relation to the maximum amount of water vapour it could hold at a specific temperature
How is a mercury barometer used?
- The open end is placed in a bath of mercury
- Mercury is forced up the tube by atmospheric pressure on the mercury in the bath
- When the two pressures equalise, mercury will stop rising in the tube
- The height of the column of mercury will change with air pressure:
* Rising as air pressure rises
* Dropping as air pressure falls
How is an aneroid barometer used?
- There is a strong metal spring within the chamber that prevents it from collapsing
* The spring will expand and contract with changes in atmospheric pressure - Levers magnify these changes
* a pointer moves across a calibrated scale to show atmospheric pressure at that time
What is an aneroid barometer?
It has a partly vacuumed, corrugated metal chamber inside
What is a mercury barometer?
A hollow tube with all the air extracted
What is normal air pressure?
Normal pressure is 1000mb with a reading above this being regarded as high pressure and a reading below regarded as low pressure
* low air pressure means a higher chance for rain
Measuring instrument to measure visibility (and how)
Sensors send off light signals and see how far they can be seen for
* in metres
Measuring instrument to observe cloud cover (and how)
A table split into eight squares is held up into an area of the sky
* in oktas which represent one eight of the sky covered by clouds
Measuring instrument to measure sunshine
Campbell-Stokes sunshine recorder
* in hours and minutes
How is sunshine measured?
- Sunshine recorder is placed in an open space, south-facing in northern hemisphere or north-facing in southern hemisphere
* making sure that the sunshine is not covered by anything - The recorder is a glass sphere partly surrounded by a metal frame
- Sunlight is concentrated through the sphere onto a recording card placed beneath the focal point
* The rays burn a trace on the card - The length of the trace shows the sunshine duration at that location
* At day’s end, the card is replaced
Clouds and how rain forms and falls
- Clouds consist of tiny water droplets or ice particles that are too light to fall to Earth
- Clouds will form when air rises, cools and condenses into water droplets or ice crystals if cold enough
- The tallest clouds form in the tropical regions, as the tropopause is at its highest and clouds do not form beyond it
- Clouds produce precipitation if they have enough water or ice particles that can collide and join together
* The particles will then grow too big and heavy to be supported in the air and will fall through the rising air currents
Tropopause
The atmospheric dividing line between the troposphere and the stratosphere
Cirrus
- Level: High above 6km
- Description: Thin, white and made of ice crystals. Forms narrow wisps, threads or feathers (cirrus means hair-like)
- Weather: fine
Cirrostratus
- Level: high above 6km
- Description: Thin, white layers made of ice crystals with a wide horizontal spread, often covers whole sky
- Weather: fine
Altostratus
- Level: medium 2-6 km
- Description: Can be thin and white or grey and thick with layer of water droplets
- Weather: fine
Cirrocumulus
- Level: high above 6km
- Description: Thin, white, heaped cloud with ice crystals
- Weather: fine
Stratus
- Level: low 0-2 km
- Description: Thin, uniform, grey sheet of small water droplets with a fairly flat base
- Weather: fine drizzle
Cumulus
- Level: low 0-2 km
- Description: White with a darker, flat base and a billowy/globular upper surface. Made of water droplets and can be compact or have height
- Weather: sunny by day fine weather
Stratocumulus
- Level: low 0-2 km
- Description: White and grey partly heaped cloud made of water droplets
- Weather: fine
Nimbostratus
- Level: Base can be low or above 2 km
- Description: Thick, dark grey layers of water droplets
- Weather: steady rain or drizzle
Cumulonimbus
- Level: Low base, but cloud usually extends to high levels
- Description: Dense, dark grey with vertical height, commonly referred to as storm clouds.
* They grow from cumulous clouds and have a billowy head.
* The head flattens if it reaches the tropopause and will then spread out in an anvil shape.
* Composed of ice crystals at the higher levels and water droplets at the lower levels - Weather: Very heavy rain, snow showers or hail with thunder and lightening
Stevenson screen
A white box into which a lot of the weather equipment is placed to record a collective of data in one place
Stevenson screen location and reasons
- Away from buildings: to avoid any heat or shadows from them
-
In the open: placed away from hills, trees etc. to ensure that air is allowed to circulate and the screen is away from shade.
* The screen should be twice the distance from any object as the object height - Height above ground: should be at least 1.2 metres above the ground so that it does not recieve heat from the ground
- Grass surface (albedo): avoid reflection from white surfaces or absorption from black surfaces
Stevenson screen design and reasons
- Painted white to reflect incoming solar radiation
- should not absorb heat because if it does it will not give an accurate reading of the air
- Has a roof to protect the instruments from percipitation
- rain could affect temperature or humidity readings
- The door should face away from the sun
- meaning the northern hemisphere should face the north
- It has slats to allow air to circulate freely around the instruments
What instruments are in a stevenson screen?
- Six’s thermometer
- Rain gauge
- Hygrometer
- Wind vane
- Barometer
- Anenometer
Tropical storm
the collective name for deep, low-pressure systems with spirals of strong air
Types of tropical storms (3)
- Typhoons in the South China Sea and west Pacific Ocean
- Hurricanes in the Gulf of Mexico, Caribbean Sea and west coast of Mexico
- Cyclones in the Bay of Bengal, Indian Ocean and northern Australia
How do tropical storms form and move?
- They develop as intense low-pressure systems over the warm tropical oceans
- Winds spiral rapidly around a calm central area known as the eye
- strongest and most destructive winds being found within the eyewall
- The path of a hurricane can be erratic, so landfall is not easy to predict, and this makes evacuation times short
- Ocean temperature above 27 celcius
Storm surge
A storm surge is a rise in sea level that occurs during tropical cyclones, intense storms also known as typhoons or hurricanes.
* The storms produce strong winds that push the water into shore, which can lead to flooding.
Category 1 on Sarrif-Simpson scale
- Wind speed: 119-153 km/h
- Damage: some
Sarrif-Simpson scale
A scale of 1-5 categories based solely on a hurricane’s maximum sustained wind speed
Category 2 on Sarrif-Simpson scale
- Wind speed: 154-177 km/h
- Damage: extensive
Category 3 on Sarrif-Simpson scale
- Wind speed: 178-208 km/h
- Damage: devastating
Category 4 on Sarrif-Simpson scale
- Wind speed: 209-251 km/h
- Damage: catastrophic
Category 5 on Sarrif-Simpson scale
- Wind speed: 252 km/h
- Damage: catastrophic
Presenting temperature data
Temperature data is collected across weather stations and the mean temperature is calculated.
It is usually presented on an isotherm map
Presenting rainfall data
Average rainfall collected and the average is calculated
Usually presented on an isohyet map
Presenting pressure data
Pressure is recorded on a barometer and an average is calculated.
Usually presented on an isobar
Presenting wind data
The direction of the wind can be measured and recorded daily.
Usually portrayed on a wind rose map
Presenting humidity data
Relative Humidity (RH) is measured by using a table that looks at the temperature of the dry bulb and the difference between the wet bulb and the dry bulb.
How to calculate relative humidity?
First you view the dry-bulb temperature. You then calculate the difference between this and the wet-bulb temperature.
Vertical Bar Graphs
A bar graph uses rectangular bars to show how values vary between variables and how they change over time or space. Vertical bar graphs show each variable separately. These are placed on the x-axis
Horizontal Bar Graphs
A bar graph uses rectangular bars to show how values vary between variables. Horizontal bar graphs show each variable separately. These are placed on the y-axis
Divided Bar Graphs
A bar graph uses rectangular bars to show how values vary between variables, divided bar graphs show all the variables together in one bar.
Line Graphs
A line graph is plotted as a series of points and then connected with straight lines.
Line graphs compare two variables, with one variable quite often being time. They are used when wanting to investigate the relationship between two variables. Each variable is plotted along an axis
These are usually used to present average or minimum and maximum temperatures
Scatter Graphs
Scatter diagrams are used to represent and compare two sets of data. By looking at the distribution of the points you can try to determine whether there is any correlation between the data.
Many times, lines of best fit are drawn on these
Radial Graphs
A radial graph shows points for multiple variables on the same graph. They must all have the same scale so that each ‘spoke’ can be proportional to any other. Lines are drawn connecting the points.
Dispersion Graphs
Dispersion graphs are like scatter graphs but the points are plotted against an individual line on a vertical scale. Multiple lines can be drawn on the same dispersion graph
Wind barbs
When looking at a weather map, wind direction and strength are shown using wind barbs
Barbs point to the direction the wind is travelling from
The arrow tip points to the direction of the wind
Wind rose
The direction of wind for a specific place is shown on a wind rose
It is made of circles that radiate rectangles representing points of a compass
Lengths of the rectangles show number of days or time that the wind blew from that direction
Synoptic charts
Meteorological station readings are plotted on synoptic charts which show a collection of data at a current time
Advantages of line graphs
- Shows changes in data
- Can be simple (one line) or compound (multiple lines) depending on data collected
- Key and colour coding possible
- Can show 2 sets of data with scales on both axis’.
Disadvantages of line graphs
- Too many lines makes interpretation difficult
- Awkward scales can distort the effectiveness
- Data manipulation is needed for compound line graphs
Improvements/alternatives to line graphs
- Could add values to data points to make it easier to read.
- Grid lines behind the graph make data retrieval easier
Advantages of bar graphs
- Shows relationship between two variables
- Shows proportion
- Visually attractive
- Bars can be quantitative or qualitative variables.
- Can show positive and negative values
- Simple to construct and understand
Disadvantages of bar graphs
- Too many bars can make the graph cluttered and difficult to interpret
- If data range is wide, it can be difficult to read accurately
- Can become complicated if class intervals are uneven
- Class intervals can hide patterns
Improvements/alternatives to bar graphs
Could convert data to a % to make data comparison easier
Advantages of scatter graphs
- Used when data is available for many locations.
- Easily shows anomalies
- Trends can be indicated by a best fit line the 2 data sets
- Can identify patterns and trends easily
Disadvantages of scatter graphs
- Correlation can emerge when relationship is coincidental
- Can only show two variables
- Too much data can be difficult to read
Improvements/alternatives to scatter graphs
- Add values on to the points when plotting
- Add grid lines to make data retrieval easier
- Can overlay over a bar chart to look at multiple variables
Advantages of dispersion graphs
- Visually effective way to show the spread of a set of data
- The data range id identifiable
- Clustering can be seen clearly
- Box and Whisker plots can be used for further data analysis increasing geographical understanding.
Disadvantages of dispersion graphs
- Comparison of multiple sets of data is only possible when they have the same scale
- Doesn’t show causative relationship as only one variable plotted
- No key – do not time / space
- Box and Whisker removes anomalies as IQR is used
Improvements/alternatives to dispersion graphs
- Box and whisker over the dispersion to show IQR
- Multiple data sets in a variety of colors to show relationship (same scale)
Advantages of radial graphs
- Visual analysis, finding patterns and relationship is easy
- Spatial relationship between factors
- Shows comparison of multiple sets of data or changes over time
Disadvantages of radial graphs
- They are difficult to plot
- Anomalies are concealed often
- Limited applications – can only be used with discrete data sets
Improvements/alternatives to radial graphs
- Include a variety of variables to show greater causation
- Use colours to show multiple data sets
