jinftl wrote:Reminds me some of the differences that can be found between the climate on Miami Beach (barrier island....Biscayne Bay to the west, Atlantic to the east) and areas inland even just 10 miles away...
Total Annual Rainfall is 46.85" on Miami Beach, while annual rainfall at Miami International Airport (less than 10 miles to the west) averages 60.00" - over 13" difference. The seabreezes tend to stabilize the air over the beach....with the sea breeze convergences that lead to heavy summer storms taking place inland a bit. There are many days, where it is sunny on the beach, clear as you look east over the atlantic, and huge thunderstorm build-up off to the west.
The ocean effect leads to warmer average nights on Miami Beach than at the airport for all 12 months. For example, the average low temp in December is 64.8 deg on Miami Beach and 61.8 deg at the airport. During wintertime, there can be the 10-15 degree differences you mention in St. Pete.
At the same time, the high temps are the opposite...it is warmer in terms of average high temp at the airport than on Miami Beach by a couple of degrees for all 12 months. Interesting stat - Miami Beach averages only 16.8 days above 90 deg each year....while less than 10 miles inland, the airport averages 62.5 days over 90. But Miami Beach also has many nights where the low doesn't drop below 80 in the summer...reflective of the temp spread you might see in the Caribbean.
In regards to the bolded portion, the proximity of the barrier islands (and adjacent coastal locales) to the Atlantic Ocean greatly influences daily maximum highs as well. The local moderating effects of the sea breeze mitigate daily highs along the immediate coastline and mainland areas near Biscayne Bay; therefore, inland high temperatures are greater than coastal highs. This factor also maintains warmer overnight lows in these coastal areas, as opposed to locales several blocks/miles inland from Biscayne Bay and the Atlantic Ocean. The contrast between coastal highs and inland highs is determined by the location where wind vectors shift from east to south and southwest. Inland, southerly/southwesterly low level wind vectors result in considerably higher maximum temperatures. You can detect a very sharp difference as you traverse locations that are situated a few blocks inland from Biscayne Bay and the coast. The daily highs several blocks westward from Coral Gables may be several degrees warmer than the waterfront locales on the Biscayne Bay shorelines.
The best opportunities for exceptionally high coastal temperatures (during the day) occur when the predominant low level wind vectors are south-southwest/southwest across all regions of southern Florida. This allows warmer maximum temperatures on the barrier islands and coastal mainland locales, since the moderating sea breeze is negated by the strong southwesterly wind vectors. If the southwesterly wind vectors are occurring inland, the sea breeze prevents higher maximum temperatures along coastal southeastern Florida.
It's also interesting to note that microclimates play distinct roles as well. For example, the soil content, degree/type of vegetation, and geology of some coastal locations can maintain warmer temperatures than surrounding areas. All barrier islands are not equal; Key Biscayne is a notable example. This barrier island often experiences warmer maximum temperatures than the majority of the barrier islands from Miami Beach northward along the coast. I believe the geology and vegetation patterns of the island (i.e. more exposed rock/sediments and sparser vegetation) results in greater transevaporation and warmer maximum highs than other barrier islands. Key Biscayne's infiltration patterns and hydrology may differ from adjacent barrier islands farther north. Past human activity on Key Biscayne (i.e. farming/agriculture) may influence the geology and vegetation as well. All of these factors affect temperatures and climate. If you traverse daily highs on a warm day, Key Biscayne is often solidly warmer than all of the barrier islands from Miami Beach to Jupiter.
Another interesting example of microclimates is the shell mounds. These pre-Columbian middens (Indian "trash heaps") contain multifarious mollusks, including bivalves, conchs, whelks, clams, oysters, et al. They are indicators of past human activity, including fishing. The heat retention of the shells results in distinct microclimates. The shell mounds often feature warmer and cooler temperature extremes than surrounding areas. The warmer temperature extremes result in environments for subtropical/tropical plant species well north of their typical distribution. For example, Turtle Mound (a pre-Columbian Timucuan mound) is located north of 28 N in the northern portion of the Canaveral National Seashore. The absolute location is 28°55′51″N 80°49′37″W. The mound contains several species of tropical plants, despite the fact that the mound is situated near New Smyrna Beach.
Turtle Mound article:
http://en.wikipedia.org/wiki/Turtle_Mound
