Thank you for your questions.
1. Our humidity is relative humidity. You can find more details at
2. Sea level pressure is used to help standard pressure readings between locations to eliminate the effect of station altitude between readings (otherwise it would be difficult to compare sea level pressure between stations). Most of our data feeds have already performed the conversion from station surface pressure to sea level pressure as the conversion requires knowledge of the individual station location, altitude and other factors (see https://journals.ametsoc.org/view/journals/wefo/13/3/1520-0434_1998_013_0833_aeouis_2_0_co_2.xml for more information).
3. Our feels like temperature combines temperature, wind chill and heat index to create a consolidated 'feels like' value. This is described at https://www.visualcrossing.com/resources/documentation/weather-101/what-is-the-difference-between-temperature-heat-index-wind-chill-feels-like-temperature-apparent-temperature-and-realfeel-temperature/
4. Our UV index calculation requires solar radiation as one of the input values. We currently have solar radiation data for 2010 onwards including ground observations from 2018 onwards. To obtain solar radiation (and hence UV index) prior to 2018, you can include the solar radiation from remote, satellite sources using the instructions found at https://www.visualcrossing.com/resources/documentation/weather-api/using-remote-data-sources-in-the-weather-api/
Regards
Visual Crossing Support
Hello. Thank you for the swift reply.
1) Could I have the formula that is used to go from the local barometric pressure to the seapressure. I would like to compare my barometric pressure adjusted to sea level pressure, against the dataset from your website.
Is the formula used the following:
P0=P(1−0.0065hT+0.0065h+273.15)−5.257
Where P0 is sealevel pressure, p is barometric pressure, h is elevation and T is temperature.
2) How can I include extra sources for the solar radiation/uv index from 2010 onwards, if I just want to download a dataset and I am not using the API.
For example I need the dataset from 01/01/2010 to 31/12/2019 from Heathrow Airport, UK, that includes UV index.
Please let me know. Thank you!
Any update please?
Thank you for your questions.
For question 1, "P0=P(1−0.0065hT+0.0065h+273.15)−5.257" represents a good approximate of the calculation, yes.
For question #2, you can currently only use the API to include the 'useremote' parameter described in the document. You can use the Weather Data Services page (https://www.visualcrossing.com/weather/weather-data-services) to create the request. From this page, you can use the 'API' view to create a CSV-formatted download link to which you can add the useremote parameter described in the article. You can then copy this link into the browser address to retrieve the CSV in the browser and then save the result.
Regards
Visual Crossing Support
Hello there,
Thanks for you reply.
I have done the API trick with the useremote parameter, and got the file, however, it includes data for very little entries, I would say from 2010 to 2021 there are less than 50 entries with index (most of it is 0).
However, if I then go to the Weather Service page and download specifically 2018-2022, they will all have proper index values.
Why is this issue? Please check attached! Last line before the break is from the API, the next line is from the separate dataset.
Thank you for your email. This should be the form of the API request:
Does this match your request? If it does but you are still seeing missing data, please reply with your API request (without the API key).
Regards
Visual Crossing Support
Hello,
The API request was correct. It is the following: https://weather.visualcrossing.com/VisualCrossingWebServices/rest/services/timeline/London%20Heathrow/2010-01-01/2021-12-31?unitGroup=metric&include=days&key=MY_KEY_HERE&contentType=xlxs&options=useremote,useobs
The issue is the following: If I download 2018-2021 (4 years fully), I get the UV Index. If I download 2010-2021(12 years fully), the UV index from 2018-2021 which was previously present now is 0 in every cell, and even with the "=useremote,useobs" the rest from 2010 to 2017 barely has any UV indexes.
Please let me know what would be the best course of action. Also, is there any other station where you have proper UV indexes for at least 10 years? The station in this case is irrelevant, I just need the actual data and specifically the UV Index.
In this case, the local observations may be not agreeing with the remote observations. We would recommend just looking at the remote information by removing 'useobs':
We do not have station data that covers 10 years of solar radiation (one of the the data element that we use to calculate the UV index) unfortunately.
Regards
Visual Crossing Support
Hey, I used the link you provided, with "useobs" removed, and now it displayed UV index from 2010 to 2021. So it's all solved technically.
Many thanks for all the extremely fast answers. Kind regards.
