<p>I am trying to create a program that calculates the ideal climate based on a set of inputs and weights. Something similar to <a href="http://www.400cities.com/" rel="nofollow noreferrer">400 cities</a> but based on more climate based options that the user can configure. Some example questions;</p>

<ul>
<li>What is your ideal daily mean temperature, answer must be between 0-40(celsius) ? how important is this, answer 1-5 with 5 being the most important ?</li>
<li>How important is it for you to be near the mountains, answer 1-5 with 5 being the most important ?</li>
</ul>

<p>One of the problems I am having is with the sunshine duration metric as calculated by the Campbell–Stokes recorder.</p>

<p>DISCLAIMER 1: All stats below are approximations / anecdotal
DISCLAIMER 2: I may need some statistical calculations explained.</p>

<p>Taking some rough figures from <a href="https://en.wikipedia.org/wiki/Sunshine_duration" rel="nofollow noreferrer">wiki</a>, Los Angeles has 3254 hours of sunshine and London has 1633 hours per year. Maximum sunshine duration in a day is approximately 4380 hours giving LA a sunshine 74% of the days on average and London sunshine 37% of the day on average so we could roughly say that LA has 2x the sunshine hours of London</p>

<p>This does not make sense to me. I want to initially create a metric that more accurately represents the quality of weather. I would then like to refine it to give a metric (configurable) like 'good days' that may need to pass params like > 25C, sunny > 70% of day, cloud coverage &lt; 20%, UV strength > 4. </p>

<p>For example (my brother lives in LA) in August this year there were 25 days in LA that were 'sunny days', lets say sunny for > 70% of the day. In London there were 4, giving values of 83% and 13% approx so we could roughly say that LA has 6X more sunny days per month than London. </p>

<p>My questions are;</p>

<ol>
<li>Why do the number of sun hours in London seem so high when anecdotally the difference is much much larger. </li>
<li>Where can I find data that is more suitable for my project or alter the data on sunshine hour to suit it.</li>
</ol>

<p>Many thanks.</p>

CC BY-SA 3.0
2017-11-24T15:32:50.023Z
Something to think about. Are the hours of sunshine in the data being confused with hours of daylight? On a cloudy day there's daylight, but no sunshine on the ground.
Fred
CC BY-SA 3.0
2017-11-24T17:32:10.033Z
Well the definition of the metric found on wikipedia for the internationally used device is; The Interim Reference Sunshine Recorder (IRSR).[1] In 2003, the sunshine duration was finally defined as the period during which direct solar irradiance exceeds a threshold value of 120 W/m². This does not make sense to me. It seems that the threshold for a sunlight hour is too low somehow.
Iain Watt
CC BY-SA 3.0
2017-11-27T10:28:50.923Z
Ok but is there a place to get sunshine hours over a specific value ? so that i can match it with could cover data to get the metric thats useful
Iain Watt
<sun>
Understanding the sunshine duration metric
Iain Watt
# Understanding the sunshine duration metric

(Asked by: username_0 on 2017-11-24)

I am trying to create a program that calculates the ideal climate based on a set of inputs and weights. Something similar to [400 cities](http://www.400cities.com/) but based on more climate based options that the user can configure. Some example questions;

* What is your ideal daily mean temperature, answer must be between 0-40(celsius) ? how important is this, answer 1-5 with 5 being the most important ?
* How important is it for you to be near the mountains, answer 1-5 with 5 being the most important ?

One of the problems I am having is with the sunshine duration metric as calculated by the Campbell–Stokes recorder.

DISCLAIMER 1: All stats below are approximations / anecdotal
DISCLAIMER 2: I may need some statistical calculations explained.

Taking some rough figures from [wiki](https://en.wikipedia.org/wiki/Sunshine_duration), Los Angeles has 3254 hours of sunshine and London has 1633 hours per year. Maximum sunshine duration in a day is approximately 4380 hours giving LA a sunshine 74% of the days on average and London sunshine 37% of the day on average so we could roughly say that LA has 2x the sunshine hours of London

This does not make sense to me. I want to initially create a metric that more accurately represents the quality of weather. I would then like to refine it to give a metric (configurable) like 'good days' that may need to pass params like > 25C, sunny > 70% of day, cloud coverage < 20%, UV strength > 4.

For example (my brother lives in LA) in August this year there were 25 days in LA that were 'sunny days', lets say sunny for > 70% of the day. In London there were 4, giving values of 83% and 13% approx so we could roughly say that LA has 6X more sunny days per month than London.

My questions are;

1. Why do the number of sun hours in London seem so high when anecdotally the difference is much much larger.
2. Where can I find data that is more suitable for my project or alter the data on sunshine hour to suit it.

Many thanks.

**Tags:** sun

> **Comments:**
> **username_1**: Something to think about. Are the hours of sunshine in the data being confused with hours of daylight? On a cloudy day there's daylight, but no sunshine on the ground.  
> **username_0**: Well the definition of the metric found on wikipedia for the internationally used device is; The Interim Reference Sunshine Recorder (IRSR).[1] In 2003, the sunshine duration was finally defined as the period during which direct solar irradiance exceeds a threshold value of 120 W/m². This does not make sense to me. It seems that the threshold for a sunlight hour is too low somehow.  
> **username_0**: Ok but is there a place to get sunshine hours over a specific value ? so that i can match it with could cover data to get the metric thats useful  

---

## 0 answers

