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Since 1961 the statistics have referred to the number of days with grass minimum temperature below 0°C. Occasionally, the term ground frost can still be seen, but it means simply a minimum temperature below 0 °C. [2]
On the empirical temperature scales that are not referenced to absolute zero, a negative temperature is one below the zero point of the scale used. For example, dry ice has a sublimation temperature of −78.5 °C which is equivalent to −109.3 °F. [97] On the absolute Kelvin scale this temperature is 194.6 K.
The Fermi temperature is defined as this maximum energy divided by the Boltzmann constant, and is on the order of 80,000 K for typical electron densities found in metals. For temperatures significantly below the Fermi temperature, the electrons behave in almost the same way as at absolute zero.
Dca is used where the warmest month has a mean temperature of 22.2 °C (72.0 °F) or higher, and Dcb is used for cool-summer temperate climates, where the warmest month has a mean temperature below 22.2 °C.
Low-temperature helium is the only known exception to the general rule. [7] Helium-3 has a negative enthalpy of fusion at temperatures below 0.3 K. Helium-4 also has a very slightly negative enthalpy of fusion below 0.8 K. This means that, at appropriate constant pressures, heat must be added to these substances in order to freeze them. [8]
This convention means that temperature and energy quantities have the same dimensions. [51] [52] In particular, the SI unit kelvin becomes superfluous, being defined in terms of joules as 1 K = 1.380 649 × 10 −23 J. [53] With this convention, temperature is always given in units of energy, and the kelvin unit is not explicitly needed in ...
A few hours later during the early morning hours of Feb. 4, as the temperature dipped further to 10 degrees below zero, this broke that date's record low of 2 degrees below zero from 1886.
The zero-curtain effect occurs in cold (particularly periglacial) environments where the phase transition of water to ice is slowed due to latent heat release. The effect is notably found in arctic and alpine permafrost sediments, and occurs where the air temperature falls below 0 ° C (the freezing point of water) followed by a rapid drop in ...