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Extreme Radiational Cooling Differences Due To Soil Type
Overview: "Under ideal radiational cooling conditions, i.e. clear skies and calm winds, isolated locations along the coastal plain of eastern North Carolina often have much colder minimum temperatures than the surrounding area. Under ideal conditions it is not uncommon for some of these areas to have minimum temperatures that are 10 to 15 degrees colder than weather stations located nearby."
Motive: "The interest in documenting this microclimate came from a spike in calls that we received from blueberry farmers each spring telling us that our forecast minimum temperatures were off by as much as 10 degrees on some nights"
Research: "The first cold spot was located roughly where the calls from the blueberry farmers came. The other two cold spots were more puzzling and unexpected because they were closer to the coast and therefore expected to be warmer. These other two cold spots however would prove to be the key in understanding why these cold spots may exist"
Soil Type: "Synoptically speaking, it was apparent that typical criteria for good radiational cooling nights would determine when extreme differences would be possible in our CWA, but it still did not explain what made these areas unique. Past research in the Northeastern US showed that large minimum temperature extremes occurred in New Jersey in an area known as the Pine Barrens. These temperature extremes were related to soil type, where the Pine Barrens area had a soil that was a good radiator of heat. This research led me to study the soil types of the area as a possible explanation of the cold spot phenomena. The state of North Carolina soil type map (image 6), constructed in 1974, shows that the three cold spots in our CWA have similar soil types (soil type 43). Some isolated areas of the Green Swamp and especially the Holy Shelter game land, where Back Island is located, have soil type 41. Soil type 41 tends to not have as many clay particles in it as soil type 43. Both soil types 41 and 43 appear to be good radiators of heat and this allows for extreme minimum temperature departures from the surrounding area. Soil type 41, which is located in the Green Swamp and Holly Shelter game lands, is a slightly better radiator than soil type 43, due to content consisting more of sand. Image 1 which showed that these cold spots were not unique to our CWA, but existed up the coast, matches up well with image 7 which shows soil type 41 occurs up the coast of North Carolina in isolated pockets."
"Due to the type of sandy and loam soil the region has, clear skies and light winds are very conducive to an increased radiational cooling effect when compared to surrounding sites. The lack of urbanization coupled with a sparse population within the Pine Barrens further accentuates any nocturnal radiational cooling effects. There are also very few observation stations within the Pine Barrens to truly try to determine an average temperature difference compared to surrounding areas. This makes temperature forecasting within the Pine Barrens a little tougher"
My favorite day was the morning of February 21, 2015.
On that morning LGA in western Long Island had a morning low of 13F (-10C) thanks to UHI caused by all of the concrete.
Meanwhile, FOK in eastern Long Island had a low of -12F (-25C) thanks to super-radiative cooling which is caused by the soil as well as the lack of development there.
That effect is pretty common in summer too. In the early morning FOK can be as low as 50F while LGA and JFK might be at 70F: KFOK , KLGA
My favorite day was the morning of February 21, 2015.
On that morning LGA in western Long Island had a morning low of 13F (-10C) thanks to UHI caused by all of the concrete.
Meanwhile, FOK in eastern Long Island had a low of -12F (-25C) thanks to super-radiative cooling which is caused by the soil as well as the lack of development there.
That effect is pretty common in summer too. In the early morning FOK can be as low as 50F while LGA and JFK might be at 70F: KFOK , KLGA
Yup, I was doing double takes when I was seeing a big difference there, thinking it was an error... Then I found out why and its pretty interesting. They have Sandy soil (well drained) along with other helping factors
The Long Island we know today was formed by Pleistocene glaciers that molded irregular lines of hills in an east-west orientation. These are glacial moraines, formed at the edge of the glacial ice sheet. Most of the material in the moraines is glacial till, an unsorted mixture of boulders, pebbles, sand, soil and clay. Other glacial formations on Long Island are outwash plains; flat areas along the south shore and between moraines. These are formed by coalescing deltas deposited by glacial meltwaters
Conclusions
1. Analyzed soil samples from the Long Island Dwarf Pine Plains may be classified as slightly gravelly (pebbly) sands, with up to nearly 10% silt-sized and fmer particles.
The sandy soil on the Lake Wales Ridge is some of the poorest in the state for holding moisture. Summer lows are cooler here than anywhere else in Florida. However, because the soil can heat up quickly with little moisture, max temps are higher than you would expect for its location.
Like the above user alluded to, sandy soils are better for lower mins and higher maxes because they retain little moisture compared to other soils like clay. Other than that, I doubt it makes much difference.
The sandy soil on the Lake Wales Ridge is some of the poorest in the state for holding moisture. Summer lows are cooler here than anywhere else in Florida. However, because the soil can heat up quickly with little moisture, max temps are higher than you would expect for its location.
I can't believe it's been 36 F (2 C) there in May.
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