Is the San Joaquin Valley really a desert? (Los Angeles, San Jose: pine, areas)

[BayAreaHillbilly]

Originally Posted by Chimérique

I figured the Redding comparison would come up.

Redding is a special case as it is completely blocked and surrounded by a series of mountains and receives warm northerly downdrafts of heat from those hills in the summer which keeps it very toasty even at night. (But within 15 mins you get high enough in elevation where it is comfortable because Redding is close to those mountains)

Latitude makes a difference: Redding is a lot colder and lot wetter than anywhere in the Great Central Valley which includes the San Joaquin Valley. Being further north makes a difference especially in the fall, winter and spring that's why the Sacramento Valley is so much wetter and in different climate zone than the San Joaquin Valley.

Latitude makes a difference: The further north you go the more of an impact marine cooling has inland. Marine cooling up norther is colder, stronger and lasts longer. Sacramento is a good example of that and any coastal valley up north from the Bay Area on up. The Russian River Valley (just north of the Bay Area) is another good example, the marine cooling and fog that it receives in the middle of the summer can be quite cold. The Napa Valley is another good example, the marine cooling it gets in the summer is pretty strong and cooler than a coastal valley down by San Luis Obispo or Santa Barbara or the LA Basin.

Ever been in Calistoga mid summer?

Heck, even St. Helena or Yountville.

[JGC97]

Originally Posted by BayAreaHillbilly

Ever been in Calistoga mid summer?

Heck, even St. Helena or Yountville.

Oh yes. Spent a lot of time there in the 70's and 80's. It got hot there but it was so beautiful, I just overlooked it and drank a lot of iced tea.

[Chimérique]

Originally Posted by BayAreaHillbilly

Ever been in Calistoga mid summer?

Heck, even St. Helena or Yountville.

Yes, I go to many Napa Valley towns quite often being that they are so close to Sacramento :-)

Again, microclimates, ...ever cross the Napa River on the highway 12 bridge when the cool bay breezes are blowing strong and fog pushes into downtown Napa in the middle of the summer.

There is reason why there are so many grape growing zones in the Napa Valley because the cool bay breezes and fog blow into Napa Valley.

From coolest to hottest: Napa River/Bay to Downtown Napa to Yountville to Rutherford to St. Helena to Calistoga. Calistoga being the hottest as the cool air/wind and fog doesn't make it that deep into the Napa Valley or when it does its diminished and doesn't last as long. Downtown Napa is often 15 degrees cooler and windier than Calistoga many hours of the day and night in the summer.

Latitudes make a difference: The Santa Clara Valley aka Silicon Valley is much cooler than its southern coastal valley sisters in the Southland (south of Monterey, especially south of Santa Barbara).

Nowhere in the San Joaquin Valley do you get this time of cooling for any length of time to make much of a difference in the middle of the summer.

[tstieber]

The reason I had brought up Redding was because of the topographical effect. Although latitude has some effect everywhere in the world, our microclimates in California are such that there can be more difference in areas only 20 miles apart than areas that are 200 miles apart. So I might suggest that topography/microclimate is responsible for 75 percent of California climates, and latitude for about 25 percent. (Roughly).

[Chimérique]

Originally Posted by tstieber

The reason I had brought up Redding was because of the topographical effect. Although latitude has some effect everywhere in the world, our microclimates in California are such that there can be more difference in areas only 20 miles apart than areas that are 200 miles apart. So I might suggest that topography/microclimate is responsible for 75 percent of California climates, and latitude for about 25 percent. (Roughly).

If you compare similar NorCal topographic places with similar SoCal topographic places you find something like this:

Wet Season 2016/2017:

Redding : 46 inches of rain - Sacramento Valley/NorCal

Bakersfield: 7 inches of rain - San Joaquin Valley/SoCal

Latitude makes a difference.

[tstieber]

Originally Posted by Chimérique

If you compare similar NorCal topographic places with similar SoCal topographic places you find something like this:

Wet Season 2016/2017:

Redding : 46 inches of rain - Sacramento Valley/NorCal

Bakersfield: 7 inches of rain - San Joaquin Valley/SoCal

Latitude makes a difference.

Agreed when it comes to winter months during the rainy season. During the dry months, I'd say microclimates dominate more.
But even in winter, rainfall totals can be higher in southern locations than northern ones due to topography, for example:

San José: 18.40
Los Angeles 18.99

Rain shadows make big differences that counteract latitude.
Then there is the issue of accumulated rainfall vs number of rainy days, which is a whole other topic that's interesting. Kind of like max temps vs temps by hour. Redding averages about as much rainfall as Seattle, but Redding is one of the sunniest cities in the country while Seattle is one of the cloudiest and rainiest. So many nuances from so many factors!

[bentobox34]

Originally Posted by Ruth4Truth

I didn't say I thought it wasn't. I agree that it is. I said I've seen a variety of definitions, some narrower than others.

Definitely the first time I've heard the suggestion that Los Banos is not in the valley.

The main source of debate/ambiguity I've generally heard is the distinction between the single "Central Valley" vs. the two valleys, Sacramento Valley from the delta on up, and San Joaquin Valley from the delta downward.

Growing up in Southern California and even when I first moved to the Bay Area, I always thought the terms "Central Valley" and "San Joaquin Valley" were synonyms and referred to the entire flat expanse from Bakersfield to Redding. I knew where Sacramento was, but never once heard the term "Sacramento Valley" until I actually moved there.

[BayAreaHillbilly]

Originally Posted by tstieber

Agreed when it comes to winter months during the rainy season. During the dry months, I'd say microclimates dominate more.
But even in winter, rainfall totals can be higher in southern locations than northern ones due to topography, for example:

San José: 18.40
Los Angeles 18.99

Rain shadows make big differences that counteract latitude.
Then there is the issue of accumulated rainfall vs number of rainy days, which is a whole other topic that's interesting. Kind of like max temps vs temps by hour. Redding averages about as much rainfall as Seattle, but Redding is one of the sunniest cities in the country while Seattle is one of the cloudiest and rainiest. So many nuances from so many factors!

An anecdote. I once lived in an apartment that was ESE of the FiDi, on the lee side of Rincon Hill, near the Bay Shore. Even in The City, the Bayshore effect I noted upthread regarding areas like FC / RWS or more extreme, the S'vale - Milpitas stretch, happens.

Now admittedly, this was at the end of the 1987 - 1991 Drought. In any case, I couldn't believe how little rain I got at that location. It was a real life lesson regarding microclimates. And in summer, very little fog or wind there. Now we know why people like AT&T park so much.

[BayAreaHillbilly]

Originally Posted by tstieber

Agreed when it comes to winter months during the rainy season. During the dry months, I'd say microclimates dominate more.
But even in winter, rainfall totals can be higher in southern locations than northern ones due to topography, for example:

San José: 18.40
Los Angeles 18.99

Rain shadows make big differences that counteract latitude.
Then there is the issue of accumulated rainfall vs number of rainy days, which is a whole other topic that's interesting. Kind of like max temps vs temps by hour. Redding averages about as much rainfall as Seattle, but Redding is one of the sunniest cities in the country while Seattle is one of the cloudiest and rainiest. So many nuances from so many factors!

One thing spiking Redding's precip is orographic impacts. Ever notice how it goes from a semi arid steppe to open oak forest to heavy pine / Doug Fir heading north on I-5, over the relatively short distance from Red Bluff to Dunsmuir?

[ABQConvict]

Is the San Joaquin valley desert?

Geographers often define a desert based on precipitation, evapotranspiration (the rate at which water is lost from the environment to the atmosphere) temporal distribution of rainfall, and other factors, but the general rule is that deserts are defined as an area of landmass receiving 10 inches or fewer of precipitation per year.

According to the map below, the majority of the San Joaquin Valley, especially the southern portion, is indeed desert as the areas in pale green and warmer colors receive little rainfall. Fresno sits just on the semi-arid (steppe) side with about 11 inches of rainfall per year.