Wind
The anemometer measures wind speed and direction.
Temperature
The weather station houses a temperature sensor, the sensor is in a vented and shielded enclosure that minimises the solar radiation induced temperature error.
There are 3 types of temperature:
- Wind chill, takes into account how the speed of the wind affects our perception of the air temperature. Our bodies warm the surrounding air molecules by transferring heat from the skin. If there’s no air movement, this insulating layer of warm air molecules stays next to the body and offers some protection from cooler air molecules. However, wind sweeps that warm air surrounding the body away. The faster the wind blows, the faster heat is carried away and the colder you feel. Wind has a warming effect at higher temperatures.
- Heat index, The Heat Index uses temperature and the relative humidity to determine how hot the air actually “feels.” When humidity is low, the apparent temperature will be lower than the air temperature, since perspiration evaporates rapidly to cool the body. However, when humidity is high (i.e., the air is more saturated with water vapor) the apparent temperature “feels” higher than the actual air temperature, because perspiration evaporates more slowly.
- THSW Index, this is the Temperature/Humidity/Sun/Wind Index. The THSW Index uses humidity and temperature like for the Head Index, but also includes the heating effects of sunshine and the cooling effects of wind (like wind chill) to calculate an apparent temperature of what it “feels” like out in the sun. The THSW Index requires a solar radiation sensor.
Humidity
Humidity itself simply refers to the amount of water vapor in the air. However, the total amount of water vapor that the air can contain varies with air temperature and pressure. Relative humidity takes into account these factors and offers a humidity reading which reflects the amount of water vapor in the air as a percentage of the amount the air is capable of holding. Relative humidity, therefore, is not actually a measure of the amount of water vapor in the air, but a ratio of the air’s water vapor content to its capacity. When we use the term humidity in the manual and on the screen, we mean relative humidity.
It is important to realize that relative humidity changes with temperature, pressure, and water vapor content. A parcel of air with a capacity for 10 g of water vapor which contains 4 g of water vapor, the relative humidity would be 40%. Adding 2 g more water vapor (for a total of 6 g) would change the humidity to 60%. If that same parcel of air is then warmed so that it has a capacity for 20 g of water vapor, the relative humidity drops to 30% even though water vapor content does not change.
Relative humidity is an important factor in determining the amount of evaporation from plants and wet surfaces since warm air with low humidity has a large capacity to absorb extra water vapor.
Dew Point
Dew point is the temperature to which air must be cooled for saturation (100% relative humidity) to occur, providing there is no change in water vapor content. The dew point is an important measurement used to predict the formation of dew, frost, and fog. If dew point and temperature are close together in the late afternoon when the air begins to turn colder, fog is likely during the night.
Dew point is also a good indicator of the air’s actual water vapor content, unlike relative humidity, which takes the air’s temperature into account. High dew point indicates high water vapor content; low dew point indicates low water vapor content. In addition a high dew point indicates a better chance of rain, severe thunderstorms, and tornados. You can also use dew point to predict the minimum overnight temperature. Provided no new fronts are expected overnight and the afternoon relativehumidity is greater than or equal to 50%, the afternoon’s dew point gives you an idea of what minimum temperature to expect overnight, since the air can never get colder than the dew point.
Rain
The weather station incorporates a tipping-bucket rain collector that measures 0.2mm for each tip of the bucket. Here in Australia we reset the rain count at 9am every day. This means that the daily rain is calculated on the 24hrs period from 9am - 9am next day.
Barometric Pressure
The weight of the air that makes up our atmosphere exerts a pressure on the surface of the earth. This pressure is known as atmospheric pressure. Generally, the more air above an area, the higher the atmospheric pressure, this means that atmospheric pressure changes with altitude. For example, atmospheric pressure is greater at sea level than on a mountaintop. To compensate for this difference and facilitate comparison between locations with different altitudes, atmospheric pressure is generally adjusted to the equivalent sea level pressure. This adjusted pressure is known as barometric pressure.
Barometric pressure also changes with local weather conditions, making barometric pressure an extremely important and useful weather forecasting tool. High pressure zones are generally associated with fair weather while low pressure zones are generally associated with poor weather. For forecasting purposes, however, the absolute barometric pressure value is generally less important than the change in barometric pressure. In general, rising pressure indicates improving weather conditions while falling pressure indicates deteriorating weather conditions.
Solar Radiation
What we call “current solar radiation” is technically known as Global Solar Radiation, a measure of the intensity of the sun’s radiation reaching a horizontal surface. This irradiance includes both the direct component from the sun and the reflected component from the rest of the sky. The solar radiation reading gives a measure of the amount of solar radiation hitting the solar radiation sensor at any given time, expressed in Watts/sq. meter (W/m2).
Sunshine used interchangeably with the more precise term bright sunshine, when the sun casts an obvious shadow. The World Meteorological Organization defines sunshine as solar direct irradiance exceeding 120 W/m2.
Sunshine Duration
The length of time for which the sun casts an obvious shadow. The threshold tolerance for bright sunshine (based on World Meteorological Organization) is direct irradiance of 120 W/m plus or minus 20%.
UV (Ultra Violet) Radiation
Energy from the sun reaches the earth as visible, infrared, and ultraviolet (UV) rays. Exposure to UV rays can cause numerous health problems, such as sunburn, skin cancer, skin aging, cataracts, and can suppress the immune system. There are two way of displaying this:
- UV MEDs, MED (Minimum Erythemal Dose) is defined as the amount of sunlight exposure
necessary to induce a barely perceptible redness of the skin within 24
hours after sun exposure. In other words, exposure to 1 MED will result in a
reddening of the skin. Because different skin types burn at different rates, 1
MED for persons with very dark skin is different from 1 MED for persons
with very light skin.
Both the U.S. Environmental Protection Agency (EPA) and Environment Canada have developed skin type categories correlating characteristics of skin with rates of sunburn.
| Skin Phototype | Skin Color | Tanning & Sunburn history | Min UV MED Dose that causes burn |
1 - Never tans,
always burns |
Pale or milky white; alabaster |
Develops red sunburn; painful swelling, skin
peels |
0.5 - 1.5 |
2 - Sometimes tans,
usually burns |
Very light brown; sometimes
freckles |
Usually burns, pinkish or red coloring appears;
can gradually develop light brown tan |
1.5 - 2.5 |
3 - Usually tans,
sometimes burns |
Light tan; brown, or olive;
distinctly pigmented |
Rarely burns; shows moderately rapid tanning
response |
2 - 3.5 |
4 - Always tans;
rarely burns |
Brown, dark brown, or black |
Rarely burns; shows very rapid tanning response |
2.5 - 5.5 |
- UV Index, an intensity measurement first defined by Environment Canada and since been adopted by the World Meteorological Organization. UV Index assigns a number between 0 and 16 to the current UV intensity. The US EPA categorizes the Index values as shown in table belowThe lower the number, the lower the danger of sunburn. The Index value published by the U.S. National Weather Service is a forecast of the next day’s noontime UV intensity. The index values displayed by this weather station are real-time measurements.
| Index Values | Exposure Category |
| 0 - 2 | Low |
| 3 - 4 | Moderate |
| 5 - 6 | High |
| 7 - 9 | Very High |
| 10+ | Extreme |
Evapotranspiration (ET)
Evapotranspiration (ET) is a measurement of the amount of water vapor returned to the air in a given area. It combines the amount of water vapor returned through evaporation (from wet surfaces) with the amount of water vapor returned through transpiration (exhaling of moisture through plant stomata) to arrive at a total. Effectively, ET is the opposite of rainfall, and it is expressed in the same units of measure (inches, millimeters). This is calculated one a hour.
Leaf Wetness
Leaf wetness provides an indication of whether the surface of foliage in the area is wet or dry by indicating how wet the surface of the sensor is. The leaf wetness reading ranges from 0 (dry) to 15.
Soil Moisture
Soil Moisture, as the name suggests, is a measure of the moisture content of the soil. Soil moisture is measured on a scale of 0 to 200 centibars, and can help choose times to water crops. The soil moisture sensor measures the vacuum created in the soil by the lack of moisture. A high soil moisture reading indicates dryer soil; a lower soil moisture reading means wetter soil.
THSW
Temperature/Humidity/Sun/Wind (THSW) index, uses humidity and temperature like the Heat Index, but also includes the heating effects of sunshine and the cooling effects of wind (like Wind chill) to calculate an apparent temperature of what it “feels” like out in the sun.
Anthracnose (Colletotrichum graminicola)
Anthracnose can occur both as a foliar blight and a rot of the crown, stem base, and roots (basal rot). Anthracnose foliar blight typically occurs during mid-summer and attacks the leaves and stems of most cool-season turfgrass species. Particularly severe cases can develop on annual bluegrass fairways on golf courses. Anthracnose basal rot can occur during spring, summer, and fall and develops in the crowns, stem bases, and roots of annual bluegrass and creeping bentgrass, usually on golf course putting greens.
Anthracnose foliar blight appears as irregular yellow or bronze patches of diseased turf. Symptoms on individual plants first appear as yellow or red lesions on the oldest (outermost) leaves, then progress to a blighting of younger leaves and shoots. Occasionally, fungal fruiting structures called acervuli can be observed with a good quality hand lens on diseased leaves and stems. Acervuli resemble small, black pin cushions and are the location of spore production.
Anthracnose basal rot symptoms vary depending on the grass species affected. On annual bluegrass, symptoms appear as a bright yellowing of the turf in irregular patches. Affected bentgrass turf typically appears as irregular red or bronze basal rot, a dark brown or black color is present at the base of the plant. As the disease worsens, the darkening (rotting) progresses up the stem and acervuli can be observed with a hand lens on stem and leaf tissue.
Brown Patch (Rhizoctonia solani)
Brown patch is a major summer disease of lawns and golf courses. The most susceptible grass species include perennial ryegrass, tall fescue, and the bentgrasses. Occasionally, brown patch becomes a problem on Kentucky bluegrasses in mid- to late-summer during extended periods of high temperature and humidity.
On high-cut turf, patches may be up to several feet in diameter and circular. In early morning on dew-covered turf, white mycelium of the causal fungus can often be seen on and between grass leaves and stems in the patch. Sometimes, all the grass within the patch is killed, creating a sunken or "pocket" effect. More often, the turf in these patches is thinned rather than completely killed. Occasionally, no circular pattern can be seen, and disease appears as a diffuse blight.
On tall fescue, symptoms of brown patch can be observed on individual leaves and not necessarily in patches. Symptoms on leaves appear as irregular tan or light brown lesions surrounded by dark brown borders. In severe cases, the entire stand may look discolored and thinned.
Dollar Spot (Sclerotinia homoeocarpa)
With regular watering of home lawns throughout much of the growing season, many turfgrass diseases, once problems only on golf courses and recreational turf areas, now appear commonly. Perhaps the most important of these is dollar spot.On golf course greens cut at or below 3/16 inch, this disease appears as white or tan spots of dead turf about the size of a silver dollar. Hence the name dollar spot. On home lawns cut at 1 to 3 inches, dead areas may reach 2 to 4 inches in diameter. These spots may run together, producing large areas of dead turf. Affected leaves initially show yellow-green blotches, which progress to a light straw color with a reddish-brown margin. Occasionally, white mycelium can be seen covering affected leaves in early morning on dew-covered grass. Dollar spot symptoms occur anytime from early to late summer. The disease usually reaches peak activity when air temperatures are in the 80° F range and under high humidity. Symptoms also may appear in the fall. The most severe cases of dollar spot occur on turf receiving closely-spaced summer irrigation. The disease may also occur on nonirrigated turf when humidity is high from prolonged muggy summer weather. Dollar spot is more severe under nitrogen deficiency or when grass grows slowly.
Mildew (Erysiphe graminis)
his fungus first appears as isolated wefts of fine, gray-white, powdery growth on the upper surface of the grass leaf. This growth rapidly becomes more dense and may cover the entire leaf, giving the leaf a gray-white appearance. In severe outbreaks, entire portions of the turf stand may be dull white, rather than green. Individual leaves look as though they are covered with flour or white powder.
