EME 810
Solar Resource Assessment and Economics

3.10. Climate Regimes


Reading Assignment

When we think about the atmosphere in different regions of the world, we want to look at how different regions seem to have different weather and climate patterns. So, I've created this page to show how three different locales also have three very different meteorological conditions, which we will call climate regimes. And so I pose the question: Why is Maui different from Missouri and each is different from Mumbai?

Time to explore the concept of climate regimes and the influence of meteorological fingerprints in solar resource assessment.

Climate Regimes and Seasonal Fingerprints for Locale

One locale for your client will be divided up into seasons. For us, each season (a block of time) is like an independent region, different from the next season--regions that we will call climate regimes. In the mid-latitudes, we observe four climate regimes, while regions affected by monsoonal swings may have two or three climate regimes.

Recall: there is not one St. Louis, there are four! One for each season, or one statistically different solar resource fingerprint for each synoptic climate regime of St. Louis, Missouri.

Climate regime changes are often noticed by us in terms of the air temperature and humidity, but the sky regimes will change as well, with respect to wind speed, the size of weather cells, and emergent cloud behaviors.

fingerprints. Click on caption for text description
Figure 3.14 These are fingerprints to remind you that the different climate regimes occur for a single given locale in winter, spring, summer, and fall. The grouping of dates for each fingerprint will be different in Maui and Mumbai, and each fingerprint itself will be unique to that region, that climate regime.
Click Here for Text Alternative for Figure 3.14

Four different fingerprints symbolizing the different climate regimes for a given locale in winter, spring, summer, and fall. The first fingerprint here is labeled Dec 1 - Feb 28, the second and fourth fingerprints are not labeled. The third fingerprint is labeled June 1st - Aug 31.

Credit: J. Brownson © Penn State University is licensed under CC BY-NC-SA 4.0

I want you to think about the way that seasonal (or synoptic) variations in a locale will generate multiple fingerprints. While each fingerprint is different from another in a given locale (translated: winter solar is not like summer solar), additionally, each set of fingerprints is different from another regional set (translated Mumbai monsoons are not like humid summers in Missouri). Every one of our locales for solar design is going to have "cloudy conditions" at some time, and everyone will have "sunny days" at other times. How can we better understand the variety of intermittencies and trends for our locale and synoptic climate regime (our fingerprint)?


This is just a play on words to emphasize something that you probably can guess: these three locations are not like each other!

  • St. Louis, MO is representative of the midlatitude climate regime of the intracontinent. Notably, there are four meteorological fingerprints (seasons).
  • Maui (Honolulu, HI) is representative of a Pacific island climate regime, affected by monsoons but without a large landmass.
  • Mumbai (Mumbai, Marharashtra, India) is strongly affected by monsoonal swings but is located in the low latitudes of the tropics (two fingerprints).

Self-Check Questions

Please identify the contributions or physical parameters that relate to the solar resource (other than the sun). First look at the questions and write down your answers in your notes. Then scroll over the answers to see how your thoughts match up. 

1. What is the role of the sky dome in the solar resource?

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ANSWER: The skydome on a clear day (no clouds) is still anisotropic, and light intensity (as measured irradiance) varies with the direction of data collection from an oriented pyranometer (e.g., the Plane of Array measurement, POA).

2. What is the role of clouds in the solar resource?

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ANSWER: Clouds are the major factor contributing to solar conditions and solar intermittency. Clouds can diminish the solar resource by scattering light, but clouds can also have a "lensing" effect by refracting light near the perimeter, causing an intense brightening on a local collector for several minutes. The pulse of intense light can be just as challenging to deal with from a power systems perspective as a drop in intensity.

3. What is the role of aerosols in the solar resource?

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ANSWER: Aerosols are particles suspended within the sky for a period of time. Aerosols are present in the chemistry of the sky even on a "clear day." The concentration and spatial distribution of aerosols is complex and spectrally dependent. Aerosols will affect DNI, or direct normal irradiance measurements, and will be a significant factor to consider for concentrating solar technologies such as CSP and CPV.