Trewartha climate scheme - where does Eureka, CA fit? (warm, temperatures, rainfall)

[redtitan23]

Hello,
I know there's a lot of fans of the Trewartha climate classification system here. I think I found a flaw in the system, and wanted to ask you if maybe I'm understanding this incorrectly and for some clarification.

My goal is to make a Trewartha climate map for Wikipedia, but some areas in California seem to not fit in any category.

I'm using Table 1 from this paper as my guide: http://www.int-res.com/articles/cr_oa/c059p001.pdf


I'm having trouble with the 'C' category, particulary with the 'Cs' sub-category. It's criteria are:

-Precipitation during the winter half-year must be at least 3x that of the summer half-year
-Annual precipitation must be <89 cm
-Driest summer month must be <3 cm

However, cities like Eureka, CA are left out (going off this data here: https://en.wikipedia.org/wiki/Eureka,_California). Eureka doesn't have annual precipitation <89 cm, but meets the other criteria. You couldn't classify it as 'Cf' though, since 'Cf' has a no-dry period requirement, where no month can have <3 cm precipitation. It certainly doesn't qualify as Cw, which requires a summer precipitation maximum.

For those familiar with Trewartha, how would you handle this? For my map, I'm thinking of abandoning the 89 cm annual precip. requirement, so I can fill in this white space in Northern California.

*EDIT: If I were to fill in the white areas that don't fit into any of the sub-categories, as "Cf", and ignore its no dry-period requirement, then California gets filled up with more land classified as "Cf", Trewartha's equivalent of humid subtropical, than "Cs", the Mediterranean climate equivalent.

Thanks,
Adam

[FirebirdCamaro1220]

Originally Posted by redtitan23

Hello,
I know there's a lot of fans of the Trewartha climate classification system here. I think I found a flaw in the system, and wanted to ask you if maybe I'm understanding this incorrectly and for some clarification.

My goal is to make a Trewartha climate map for Wikipedia, but some areas in California seem to not fit in any category.

I'm using Table 1 from this paper as my guide: http://www.int-res.com/articles/cr_oa/c059p001.pdf


I'm having trouble with the 'C' category, particulary with the 'Cs' sub-category. It's criteria are:

-Precipitation during the winter half-year must be at least 3x that of the summer half-year
-Annual precipitation must be <89 cm
-Driest summer month must be <3 cm

However, cities like Eureka, CA are left out (going off this data here: https://en.wikipedia.org/wiki/Eureka,_California). Eureka doesn't have annual precipitation <89 cm, but meets the other criteria. You couldn't classify it as 'Cf' though, since 'Cf' has a no-dry period requirement, where no month can have <3 cm precipitation. It certainly doesn't qualify as Cw, which requires a summer precipitation maximum.

For those familiar with Trewartha, how would you handle this? For my map, I'm thinking of abandoning the 89 cm annual precip. requirement, so I can fill in this white space in Northern California.


Thanks,
Adam

Eureka is 'Do' in Trewartha, Oceanic, because to be Cs, if the annual rainfall is over 890mm, it doesn't matter if the driest month is under 30mm or not. This has to do with the water table and evaporation rates

[redtitan23]

Originally Posted by FirebirdCamaro1220

Eureka is 'Do' in Trewartha, Oceanic, because to be Cs, if the annual rainfall is over 890mm, it doesn't matter if the driest month is under 30mm or not. This has to do with the water table and evaporation rates

From what I understood, C and D were separated by the number of months with mean temperatures above 10C, with C climates have 8-12 months above 10C and D climates having 4-7 months above 10C. Eureka still has 8 months above 10C.

Are you saying that if a location has more than the annual rainfall for the "Cs" sub-type, then that trumps the major classification requirements, and it skips to Do?

From what I understand, Cf and Cw climates could theoretically have annual precipitation >890 mm, so I'm a bit confused as to why things would jump from Cs to Do in that case.

EDIT: I found another, perhaps stronger example of the climate gap. Ukiah, CA (https://en.wikipedia.org/wiki/Ukiah,_California) which definitely matches perceptions of a Mediterranean climate more than Eureka, would also fall through this gap.

[FirebirdCamaro1220]

Originally Posted by redtitan23

From what I understood, C and D were separated by the number of months with mean temperatures above 10C, with C climates have 8-12 months above 10C and D climates having 4-7 months above 10C. Eureka still has 8 months above 10C.

Are you saying that if a location has more than the annual rainfall for the "Cs" sub-type, then that trumps the major classification requirements, and it skips to Do?

From what I understand, Cf and Cw climates could theoretically have annual precipitation >890 mm, so I'm a bit confused as to why things would jump from Cs to Do in that case.

Napoli, Italy (anglicised as Naples ughh) is Humid Subtropical rather than Mediterranean under Trewartha due to their annaul rainfall being over 890mm, despite a driest month under 30mm in the summer

That was what I was getting at, and since Eureka never really warms up in the summer, I'd say Do would be a safer bet than Cf

[redtitan23]

Yikes! California is ending up with rather few areas of Mediterranean climate in my Trewartha map.

Based on where all the blank area is, it makes more sense to shift it towards humid subtropical, like the Naples example, since I have to shift it one way or another to be consistent in my mapping program and a lot of it is further inland (e.g. along the Sierras).

Looks like Trewartha ends up giving California twice as much humid subtropical climate as Mediterranean.

Interestingly, steppe climate (BS) took up a lot of land that's otherwise Mediterranean under Koeppen, so the area got reduced from that end as well.

[forgotten username]

So we are a D climate here because we have only 7 months that are above 10c (in a normal year. March is at 9c here). That's interesting.

[Joe90]

Originally Posted by redtitan23

Based on where all the blank area is, it makes more sense to shift it towards humid subtropical, like the Naples example, since I have to shift it one way or another to be consistent in my mapping program and a lot of it is further inland (e.g. along the Sierras).

Looks like Trewartha ends up giving California twice as much humid subtropical climate as Mediterranean.

.

A bad idea. Eureka fits the definition of a Mediterranean climate. as cool season mid latitude frontal systems turn to a warm season semi permanent high pressure zone. Mediterranean climates are first and foremost about rainfall distribution -ignoring that for some sort of golden rule (rainfall > 890mm) lacks logic.

No system can provide consistent classification.

[redtitan23]

Originally Posted by Joe90

A bad idea. Eureka fits the definition of a Mediterranean climate. as cool season mid latitude frontal systems turn to a warm season semi permanent high pressure zone. Mediterranean climates are first and foremost about rainfall distribution -ignoring that for some sort of golden rule (rainfall > 890mm) lacks logic.

No system can provide consistent classification.

So I found another source that backed up the Naples example, so I felt it was more in line with the outlines of Trewartha to shift areas > 890 mm to humid subtropical. Frankly, I'm more interested in objectively representing how the climate systems handle Mediterranean climates than accurately portraying my own thoughts, so people can judge the climate classification systems for themselves.

I'm with you about Eureka - I'd say it's Mediterranean and would go with Koeppen in that case. However, where I live (in the temperate rainforest of WA state), I'm classified as living in a Mediterranean climate (Csb). Feels a bit more oceanic here. I'd say the often used example of Victoria, CA as being misclassified as Mediterranean actually feels more Mediterranean than where I live.

I was thinking Trewartha might do a bit better, but it nearly eliminated the Mediterranean climate zone altogether. I'm not impressed with it.

Here's a link to the map I generated if anyone's interested in checking it out: http://commons.wikimedia.org/wiki/File:US_trewartha.svg

I made it in GIS, using climate normals data from PRISM, so I just put the constraints in for Trewartha types and it calculated the geographic extent for each type (so no subjective judgements on my part). I did leave out the Highland type, because it would have been extremely complicated to calculate and I felt the category didn't contain much meaningful climate data.

EDIT: For comparison, here's my Koeppen map of the US West Coast. Mediterranean climate is everywhere: https://commons.wikimedia.org/wiki/F...ast_koppen.svg

[Joe90]

Originally Posted by redtitan23

So I found another source that backed up the Naples example, so I felt it was more in line with the outlines of Trewartha to shift areas > 890 mm to humid subtropical. Frankly, I'm more interested in objectively representing how the climate systems handle Mediterranean climates than accurately portraying my own thoughts, so people can judge the climate classification systems for themselves.

I'm with you about Eureka - I'd say it's Mediterranean and would go with Koeppen in that case. However, where I live (in the temperate rainforest of WA state), I'm classified as living in a Mediterranean climate (Csb). Feels a bit more oceanic here. I'd say the often used example of Victoria, CA as being misclassified as Mediterranean actually feels more Mediterranean than where I live.

I was thinking Trewartha might do a bit better, but it nearly eliminated the Mediterranean climate zone altogether. I'm not impressed with it.

Here's a link to the map I generated if anyone's interested in checking it out: http://commons.wikimedia.org/wiki/File:US_trewartha.svg

I made it in GIS, using climate normals data from PRISM, so I just put the constraints in for Trewartha types and it calculated the geographic extent for each type (so no subjective judgements on my part). I did leave out the Highland type, because it would have been extremely complicated to calculate and I felt the category didn't contain much meaningful climate data.

I guess if the goal is portraying Trewartha's classification on a map, then Trewartha's rules apply. It will be misleading though, as Eureka will be portrayed as a climate with no dry season, when that is most obvious climatic feature Eureka has.

I wonder what Trewartha's logic is on that one? Eureka has a bigger ratio of summer/winter rain than many Mediterranean climates, but that counts for nothing.

I will have to look at the maps later computer is on a go-slow.

[redtitan23]

Originally Posted by Joe90

I guess if the goal is portraying Trewartha's classification on a map, then Trewartha's rules apply. It will be misleading though, as Eureka will be portrayed as a climate with no dry season, when that is most obvious climatic feature Eureka has.

I wonder what Trewartha's logic is on that one? Eureka has a bigger ratio of summer/winter rain than many Mediterranean climates, but that counts for nothing.

I know Trewartha specifically set out to ensure the Pacific Northwest was squarely within the oceanic climate zone. Since we have a distinct seasonal summer drought here in the PNW, he had to change a few criteria to ensure Washington and Oregon were left out.

First, he required locations to have 8-12 months with a mean temperature above 10C to be Mediterranean (Cs). That left out all of Washington and everything in Oregon but the far southern coastline.

Then, the 890 mm annual precipitation threshold takes out most of the rest of the rainier parts of northern California.

Trewartha does have a dry-summer requirement for Mediterranean climates, but if the precipitation is too high, or there's 5 or more months where the mean monthly temp is <10C, then it counts for nothing under his system.

I feel like he overcorrected.