The phrase "are lower when the" is correct and usable in written English.
It can be used in contexts where you are comparing levels or values that decrease under certain conditions.
Example: "The temperatures are lower when the sun sets in the evening."
Alternatives: "decrease when the" or "drop when the".
Birth weights are lower when the calf is carried through the last trimester in hot conditions.
Angular variations on emissivity are lower when the emissivity of the soil and the emissivity of the vegetation are closer.
Returns are mean-reverting: expected returns are lower when the market has recently done well, and higher when it has done badly.
In both Ti3SiC2 and 6H-SiC these initial peak values for both properties are lower when the basal planes are oriented perpendicular or edge on to the surface.
It is shown that sub-critical crack growth rates are lower when the material experiences sustained far field loading than during cyclic far field loading.
Compared with the response during linear viscoelastic deformation, the values of the reduced birefringence and the reduced stress are higher when the elongation is performed with ϵ = const., and are lower when the elongation is carried out with λ = const., The stress-optical coefficient turns out to be a function of duration and rate of deformation.
Chances of yellow fever affecting Americans are lowered when the disease is addressed when and where it crops up abroad.
Likewise, λmax was lower when the movement was constrained.
The pressure, the vapor pressure, of the water is going to be lower when the sugar is there.
Note that in most ears, thresholds were lower when the ipsilateral hand was used to trigger the sound.
Ad libitum energy intake was lower when the meal was eaten slowly, and satiety was higher at meal completion.
