Table 1. Summary of quantities.

Quantities	Definition	Formulations
$V_G$	Group velocity	$V_G=\langle \frac{dx}{dt}\rangle$
$z$	Moving coordinate	$z=x-V_{G}t$
$V_I\left(z\right)$	Instantaneous velocity	$V_I\left(z\right)=\langle \frac{dx\left(z\right)}{dt}\rangle$
$V_D\left(z\right)$	Expected drift velocity	${\displaystyle V_D\left(z\right)=\frac{⟨L_R\left(z\right)\cdot \cos {\theta }_R\left(z\right)⟩}{⟨{\tau }_R\left(z\right)+{\tau }_T\left(z\right)⟩}}$
$\rho \left(z\right)$	Cell density	$\rho \left(z\right)=\frac{\sum i\left(z\right)}{a\cdot \Delta z}$
$S\left(z\right)$	Chemoattractant concentration	$-V_G\frac{dS}{dz}=D_s\frac{{\partial }^{2}S}{\partial z^2}-k\rho$
$g\left(z\right)$	Perceived gradient	${\displaystyle g\left(z\right)=\frac{dln\left(\frac{1+S\left(z\right)/K_{off}}{1+S\left(z\right)/K_{on}}\right)}{dz}}$