- What is OMI?
The Ozone Monitoring Instrument (OMI) on board NASA's EOS-AURA satellite is a Dutch-Finnish instrument which measures several atmospheric constituents, like ozone and NO2. These measurements are used in stratospheric and tropospheric chemistry research and in climate research.
- What means VFD?
It means "Very Fast Delivery". VFD-products are processed and published immediately after the Aura satellite overpasses the Satellite Data Center at Sodankyla, Northern Finland. The data is received as Direct Broadcast (DB) which means that the instrument measures the data and sends it to the receiver as it is measured.
- How is "total ozone" defined?
Total ozone gives the total amount of ozone in the atmosphere. The units are in Dobson Units (DU). One DU is 2.7x10^16 ozone molecules per square centimeter. One Dobson unit refers to a layer of ozone that would be 0.01 millimeter thick under standard temperature and pressure. For example, 300 Dobson units of ozone brought down to the surface of the Earth at 0 degrees Celsius would be a layer of 3 mm thick.
- What is "UV Index"?
UV Index is a measure of the human skin relevant intensity of UV radiation on the Earth's surface. UV Index is a unit less quantity that is linearly related to th erythemally weighted dose rate (1 UV Index equals 25 mW per square meter). UV Index varies throughout the day due to the solar elevation and cloud attenuation. The clear-sky UV Index of the UV Record service is an estimate of the local solar noon UV Index assuming cloud free conditions. Thus, the clear-sky UV Index usually overestimates the actual intensity of the UV radiation reaching the Earth's surface. However, it is a useful measure for informing of the potential harmful effects of UV radiation. People with fair skin should protect onself if the UV index is three or more and if exposed to UV radiation. UVI values six or more means strong UV radiation whereas values 8 or more means very strong UV radiation.
- How about "daily dose"?
Daily dose is the diurnally integrated amount of harmful UV radiation on the Earth's surface. The daily dose of the UV Record service, that is given in kJ per squre meter units, is an estimate of the erythemally weighted daily dose taking into account the attenuating effect of clouds. Additionally, the estimate is corrected for strongly absorbing aerosols in the clear-sky case.
- What is a composite product?
In composite image all of the individual ozone (or UV) images are merged together. The new images overlap the older ones, although some part of the older images can also be seen. The newest image is brighter than the older ones.
- Where are the data processed?
Data is received and processed at FMI Satellite Data Centre at Sodankylä.
- Why are there gaps in the maps?
Gaps in the maps exist because of two reasons. First is that the satellite-receiving station geometry determines which areas can be seen. For example, when OMI is measuring over North Africa, the satellite is not visible from Sodankyla and therefore VFD products can not reach that area. The second reason is the data dumping from satellite's memory to receiving station. This data dump and DB can not happen at the same time. One receiving station is located at Svalbard and moments of data dumb is seen as data gab especially along the orbits east of Finland.
Yes, but only for uncommercial purposes. If you use the images, for example, in a presentation, we kindly ask that you include an acknowledgement as follows: "OMI VFD images are provided by FMI. OMI is a joint effort of KNMI, NASA, and FMI, and is managed by NIVR/Netherlands."