![]() ![]() This is often due to dense fog, air pollution, or a combination of the two. So the exact number given for visibility should be considered more of a guideline than an absolute.Īs for visibility range, there are many situations where the visibility range can be near zero. At night, you should be able to do the same for a “moderately intense light source.” However, the exact definition of these terms remain somewhat ambiguous and vary across different station implementations. In general, during the daytime you should be able to “see and identify” a “prominent dark object” on the horizon at the given visibility distance. ![]() Visibility is more ambiguously defined than most other weather measures. That means that in the standard system, the unit is miles and in the metric system, the unit is kilometers. Visibility is reported in the long-distance unit of the units system chosen for your query. What are the units and range for historical cloud and visibility data? So, if appropriate, you should consider other visibility characteristics of your location in combination with raw cloud cover data. Note that the cloud cover measure does not take into account pollution or other conditions that may limit vertical visibility. The more clouds, the less able we are to see stars, planets and other objects in the sky including the sun for solar power. It tells us how much of the sky is blocked by clouds at a given time from a given location. That is, if you are looking out at other points on the Earth, the visibility measure tells you how far away objects can be and still be identifiable.Ĭloud cover tells a similar story in the vertical dimension. ![]() The visibility measure describes the horizontal opacity of the atmosphere. The two key measures, Visibility and Cloud Cover, are related in their ability to measure the visibility of the sky and the surrounding views on Earth. What cloud and visibility measures are available? Whether you are looking for cloud data to analyze solar panel performance, manage air travel, or determine the best places and nights for stargazing, a weather data service such as Visual Crossing Weather can provide cloud cover and visibility data easily using global historical reports going back to 1970. For this, you would need to find a weather station, but it would have to be at the exact spot, not several kilometres away, which is rarely possible.Historical cloud cover and visibility data are useful weather measures that are needed in various transportation, business, and recreational activities. Simulation data cannot capture the exact timing and intensities of isolated extreme weather events. If you want to know if on the 22nd of February 1992, there was a local thunderstorm with 100 mm of rain and winds over 80 km/h, unfortunately this will not be possible. However, even for those locations and time periods, you can easily analyse trends over the years, seasons, months, weeks, or even day-to-day changes, always taking into account that there may be biases in the absolute values. in narrow valleys or on mountain tops, cannot be captured accurately, and between 19, data accuracy might be lower due to the absence of satellite observations in this period. The data have a spatial resolution of 4 to 30 km, depending on location and period. ![]()
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