| \(A\) | 
surface or cross-sectional area (\(m^2\)) | 
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| \(a\) | 
altitude angle of the sun (degrees) (subscripts: s, for normal to a slope; c ,for the axis of a cylinder); solar absorptivity (proportion) (subscripts: \(l\), lizard thermal absorptivity; \(s\), lizard solar absorptivity) | 
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| \(Acondfact\) | 
proportion of the animal surface area that is in contact with the ground | 
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| \(Agradfact\) | 
proportion of the animal projected area exposed to radiation from the ground | 
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| \(air_{pressure}\) | 
air pressure (kPa) | 
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| \(aran\) | 
scale performance value for performance curve? if aran = 0, no scaling; if aran = 1, includes a thermodynamic effect on mean performance | 
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| \(breadth\) | 
breadth of the thermal performance curve | 
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| \(c\) | 
specific heat capacity (subscripts: \(a\), air; \(p\), air at constant pressure; \(so\), soil) (\(J kg^{-1}K^{-1}\) or \(J kg^{-1}{°C}^{-1}\)) | 
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| \(CT\) | 
critical thermal limit (\(°C\)) (subscripts: min, minima; max, maxima), the lower and upper temperature limit for performance | 
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| \(D\) | 
characteristic dimension (\(m\)); thoracic diameter (\(cm\)) | 
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| \(d\) | 
thickness of material (\(m\)); diameter of a cylinder (\(m\)) | 
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| \(day\) or \(doy\) | 
day of year | 
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| \(deg\) | 
angle (degrees) | 
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| \(depth\) | 
depth (\(cm\)) | 
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| \(e\) | 
water vapor pressure (\(N m^{-2}, mbar\)) (subscripts: \(a\), of the air; \(s\), at saturation) | 
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| \(ef\) | 
enhancement factor, used to adjust convective heat transfer coefficient to field conditions | 
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| \(elev\) | 
elevation above mean sea level (\(m\)). | 
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| \(F\) | 
view factor between the animal and radiation stream (dimensionless) (subscripts: \(a\), atmospheric radiation; \(d\), diffuse solar radiation; \(g\), ground thermal radiation; \(r\), reflected solar radiation) | 
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| \(g_{a}\) | 
a shape factor for soil particles | 
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| \(H_L\) or \(H\) | 
convective heat transfer coefficient (\(W m^{-2}{°C}^{-1}\) or \(W m^{-2}K^{-1}\)) | | 
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| \(h\) | 
height (\(m\)); length of a cylinder (\(m\)); relative humidity (decimal fraction); Planck’s constant (\(J s\)); hour angle (rad) | 
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| \(hp\) | 
mean month relative humidity (percentage) | 
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| \(hour\) | 
hour (0-24) | 
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| \(K\) | 
thermal conductance (\(W m^{-2}{°C}^{-1}\)) (subscripts f, fur; g, substrate; s, skin; sf, skin and fur; o, overall heat conductance for an animal; c, surface boundary layer for convection; so, soil). | 
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| \(k\) | 
von Karman’s constant (dimensionless), k~0.41 | 
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| \(k_{so}\) | 
soil thermal conductivity (\(W m^{-1}K^{-1}\) or \(W m^{-1}C^{-1}\)) | 
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| \(K_t\) or \(kt\) | 
clearness index, the ratio of the global solar radiation measured at the surface to the total solar radiation at the top of the atmosphere (dimensionless) | 
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| \(L\) | 
Monin-Obukhov length (\(m\)), a measure of the instability of heat flow | 
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| \(l\) or \(L\) | 
length (\(m\)) | 
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| \(lon\) | 
longitude (degrees) | 
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| \(lat\) | 
latitude (degrees) | 
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| \(LDT\) | 
lower developmental threshold (\(°C\)) | 
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| \(lw\) | 
downward flux of near-infrared radiation (\(Wm^{-2}\)) | 
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| \(m\) | 
mass (\(kg\) or \(g\)); air mass (dimensionless) | 
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| \(P\) | 
monthly precipitation (\(mm\)) | 
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| \(psa\) | 
proportion surface exposed (dimensionless) (subscripts: \(air\), for exposure to air; \(ref\), for exposure to ground; \(dir\), for exposure to sky or enclosure; \(g\), for exposure to substrate) | 
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| \(Q_{abs}\) | 
solar and thermal radiation absorbed (\(W\)) | 
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| \(Q_{emit}\) | 
thermal radiation emitted (\(W\)) | 
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| \(Q_{conv}\) | 
energy exchange between an animal and the surrounding substance due to convection (\(W\)) | 
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| \(Q_{cond}\) | 
energy exchange between an animal and the surface due to conduction (\(W\)) | 
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| \(Q_{met}\) | 
energy emitted due to metabolism (\(W\)) | 
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| \(Q_{evap}\) | 
energy emitted due to evaporative water loss (\(W\)) | 
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| \(r\) | 
reflectance (decimal fraction) (subscripts: \(g\), of ground; \(S\), to direct sunlight; \(s\), to skylight); diffusion resistance to water vapor (\(s m^{-1}\)) (subscripts: \(b\), boundary layer; \(i\), internal or intercellular); resistance to heat flow (\(s m^{-1}\)) (subscripts: \(h\), \(ha\), boundary layer; \(j\), diffusion resistance to molecular species j; radius (\(m\)) (subscripts: \(b\), of inside body wall of animal; \(r\), of outer surface of animal) | 
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| \(rad\) | 
angle (radians) | 
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| \(raz\) | 
solar azimuth angle (degrees) | 
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| \(S\) | 
amount of sunlight incident upon the earth’s surface (\(W m^{-2}\)) (subscripts: \(dir\), direct solar radiation; \(dif\), diffuse solar radiation; \(h\), on a horizontal surface; \(ref\), reflected solar radiation) | 
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| \(shade\) | 
whether soil temperature is calculated in the shade or not | 
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| \(shift\) | 
mode of the thermal performance curve | 
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| \(skew\) | 
skewness of the thermal performance curve | 
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| \(sol.elev\) | 
solar elevation angles (degrees) | 
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| \(SSA\) | 
solar absorptivity of soil surface (proportion) | 
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| \(svl\) | 
lizard snout vent length (\(mm\)) | 
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| \(t\) | 
time (\(hr\) or \(s\)) (subscripts: \(as\), after sunset; \(n\), time of minimum temperature; \(r\), sunrise; \(s\), sunset; \(p\), rise the following day; \(x\), time of maximum temperature) | 
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| \(T\) | 
temperature (\(°C\) or \(K\) or \(°F\)) (subscripts: \(a\), air; \(g\), ground; \(s\), surface; \(sh\), shade; \(sky\), effective radiant temperature of the sky) | 
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| \(T_{dewpoint}\) | 
dewpoint temperature (\(°C\)) | 
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| \(T_{e}\) | 
Operative environmental temperature (\(°C\)) | 
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| \(T_{max}\) | 
maximum temperature of the day (\(°C\)) | 
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| \(T_{min}\) | 
minimum temperature of the day (\(°C\)) | 
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| \(Tg_{max}\) | 
maximum soil surface temperature of the day (\(°C\)) | 
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| \(Tg_{min}\) | 
minimum soil surface temperature of the day (\(°C\)) | 
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| \(T_{opt}\) | 
thermal optima, the temperature at which peak performance occurs (\(°C\)) | 
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| \(T_{soil0}\) | 
initial soil temperature (\(°C\)) | 
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| \(tolerance\) | 
maximal breath (\(°C\)) of the thermal performance curve | 
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| \(u\) | 
wind speed (\(m s^{-1}\)) (subscripts: \(r\), reference height or heights) | 
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| \(UDT\) | 
upper developmental threshold (\(°C\)) | 
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| \(V\) | 
volume (\(m^{3}\)) | | 
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| \(water_{content}\) | 
water content (percent) | 
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| \(x\) | 
vector of volume fractions of soil constituents (e.g., clay, quartz, minerals other than quartz, organic matter, water, air) | 
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| \(z\) | 
distance, or height above a surface (\(m\)) | | 
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| \(zr\) | 
reference height (\(m\)) | 
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| \(z0\) | 
roughness height (\(m\)) | 
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