We present five spectra of the quasar HS1603+3820 (zem=2.542) taken over intervals of 0.2–1.6 years (0.7–5.4 months in the quasar rest frame) with the High Dispersion Spectrograph on the Subaru telescope, for the purpose of studying its intrinsic narrow absorption lines (NALs). This quasar shows a rich complex of C IV NALs near the emission redshift (dN/dz ∼ 12). We perform time variability analysis as well as covering factor analysis to separate intrinsic NALs, which are physically related to the quasar, from intervening NALs in 8 C IV systems. Only one of them, at zabs ∼ 2.43, shows both partial coverage and large variation in line strength, width, and position. Assuming that a change in the ionization state of the absorber causes the variability, a lower limit can be placed on the electron density (ne > 3.2 × 104 cm-3) and an upper limit on the distance from the continuum source (r < 6 kpc). On the other hand, if motion of clumpy gas causes the variability, the crossing velocity and the distance from the continuum source are estimated to be νcross > 8,000 km s-1 and r < 3 pc, assuming that the observed shift velocity does not exceed the escape velocity at that radius. If we adopt the dynamical model of Murray et al. (1995), we can obtain a much more strict constraint on the radius of the gas parcel, r < 0.2 pc. We are planning to monitor this quasar for several years so as to use intrinsic absorber’s behavior as a direct check of wind models. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]