  Cosmic rays (CRs) have been studied extensively in the last century to
understand the processes in the universe as well as in the solar system. In
today's satellite era, although many observations are made from space, CR
observations from the ground are still viewed as an important tool. These
observations, however, mostly detect the secondary cosmic rays (SCRs) such as
neutron, muon, and gamma. It is well known that the atmospheric pressure plays
an important role in the SCR flux observed on the ground. Barometric pressure
correction is standard practice for neutron monitor (NM) data. However, no such
correction is applied to gamma-ray, being massless. But the pressure affects
the particles such as $e^{\pm}$, $\mu^{\pm}$, which produce gamma rays in the
cascade. Subsequently, the indirect pressure dependence of the gamma-ray flux
can be anticipated.
  We examine this aspect in detail by studying the gamma-ray counts detected by
the NaI (Tl) detector. The present study confirms that there is no correlation
between the atmospheric pressure and the total gamma-ray counts collected from
all energies. However, the scenario differs when the gamma-ray fluxes of
different energies are investigated separately. The gamma rays of energy below
$\sim$3 MeV are primarily due to the radioactivity originating from the ground,
whereas gamma rays above 3 MeV are mainly produced in the CR cascade. It is
observed that the counts of energy above 3 MeV are well anti-correlated with
the atmospheric pressure and hence need to be corrected. It is demonstrated
that applying the barometric correction formula successfully removes the
pressure dependence in the gamma-ray flux above 3 MeV. Therefore, we suggest
that the gamma-ray data above 3 MeV needs to be corrected for the local
atmospheric pressure variations.
