One of the major accomplishments of the IGY was the establishment of a number of weather stations around the Antarctic continent, allowing the collection of much more weather data from that continent, and the synoptic (simultaneous over space) determination of intracontinental Antarctic meteorological conditions, as well as changes over time. From the snapshots of meteorological conditions that comprise weather, we can also infer climate, a summary of weather conditions indicated by averages and variability.
One common climate classification scheme is the Köppen or Köppen-Geiger system, which is summarized nicely in Wikipedia. It depends on seasonal patterns of temperature and precipitation. I always found this system a great framework for teaching about climate.
Wikipedia summarizes the major climate regimes as follows:
Group A: Tropical climates. This type of climate has every month of the year with an average temperature of 18 °C (64.4 °F) or higher, with significant precipitation.
Group B: Dry climates. This type of climate is defined by little precipitation.
Group C: Temperate climates. This type of climate has the coldest month averaging between 0 °C (32 °F) (or −3 °C (27 °F)) and 18 °C (64.4 °F) and at least one month averaging above 10 °C (50 °F).
Group D: Continental climates. This type of climate has at least one month averaging below 0 °C (32 °F) (or −3 °C (27 °F)) and at least one month averaging above 10 °C (50 °F).
Group E: Polar and alpine climates, This type of climate has every month of the year with an average temperature below 10 °C (50 °F)
Antarctica is a Group E climate, as shown in the temperature graphs below, none of the which show any monthly average temperatures above 10°C.
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| Temperature curves for various sub- and Antarctic meteorological stations |
Even though Antarctica is heavily glaciated, it is technically a desert. Antarctic locations get 4-8" of precipitation a year. A desert is said to have less than 10" of precipitation a year, so Antarctica qualifies as the largest desert on Earth. Over long enough periods of time, as the scant annual precipitation still exceeds water loss by runoff and evaporation, the water will freeze and accumulate as glacial ice. Global warming may change all that, but I'll leave that topic for another time.
As shown in the Köppen-Geiger map below, climate regimes are related to latitude, proximity to coasts, hemispherical asymmetries in ocean configurations, and other large-scale meteorological patterns.
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| Global map of Köppen-Geige climate types |
The more detailed climate designation in Lancaster is Cfa. The C is the temperate described above, the second letter indicates the seasonal precipitation type, while the third letter indicates the level of heat. So Cfa is a humid subtropical climate, with: the coldest month averaging above 0 °C (32 °F); at least one month's average temperature above 22 °C (71.6 °F); at least four months averaging above 10 °C (50 °F); no significant precipitation difference between seasons. This is shown in the Lancaster climatograph below.
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| Lancaster climatograph, with average daily temperature lows and highs (left y-axis scale), and monthly (rain) precipitations (right y-axis scale) |
I am thinking about weather and climate because today we're in the midst of a sizable snowstorm here in southeastern Pennsylvania. According to NOAA, we have had about 1/2" of water (rain)-equivalent precipitation (as snow) in the last day. At 10" of snow per inch equivalent of water, that's about 6" of snow (just verified that is about right with a ruler in the back yard). Another 6-12" of snow is predicted for today and tomorrow, so a winter storm warning is out.
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| View out my front door, mid-afternoon |
This suggests that for Groundhog's Day tomorrow, our local groundhog, Octoraro Orphie, would not see its own shadow under cloudy skies, and not be scared back into his den. So folklore suggests we'll have an early Spring. I wouldn't complain if that turns out to be true, even though the science behind groundhog-based weather predicting is obscure to me. Local ceremonies with Orphie are canceled this year due to covid, as is the local food-beer fest and parade at Valentino's Cafe that I attended for the first time last year.
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| Groundhog's Day celebration, 2020, Valentino's Cafe, Lancaster, PA |
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