  We estimate the power spectra of CMB temperature anisotropy in localized
regions on the sky using the WMAP 7-year data. Here, we report that the north
hat and the south hat regions at the high Galactic latitude (|b| >= 30 deg)
show anomaly in the power spectrum amplitude around the third peak, which is
statistically significant up to 3 sigma. We try to figure out the cause of the
observed anomaly by analyzing the low Galactic latitude (|b|< 30 deg) regions
where the galaxy contamination is expected to be stronger, and regions that are
weakly or strongly dominated by the WMAP instrument noise. We also consider the
possible effect of unresolved radio point sources. We found another but less
statistically significant anomaly in the low Galactic latitude north and south
regions whose behavior is opposite to the one at the high latitude. Our
analysis shows that the observed north-south anomaly at high latitude becomes
weaker on the regions with high number of observations (weak instrument noise),
suggesting that the anomaly is significant at sky regions that are dominated by
the WMAP instrument noise. We have checked that the observed north-south
anomaly has weak dependences on the bin-width used in the power spectrum
estimation and the Galactic latitude cut. We have also discussed the
possibility that the detected anomaly may hinge on the particular choice of the
multipole bin around the third peak. We anticipate that the issue of whether
the anomaly is intrinsic one or due to the WMAP instrument noise will be
resolved by the forthcoming Planck data.
