  (Abridged) Apertif is a phased-array feed system for WSRT, providing forty
instantaneous beams over 300 MHz of bandwidth. A dedicated survey program
started on 1 July 2019, with the last observations taken on 28 February 2022.
We describe the release of data products from the first year of survey
operations, through 30 June 2020. We focus on defining quality control metrics
for the processed data products. The Apertif imaging pipeline, Apercal,
automatically produces non-primary beam corrected continuum images,
polarization images and cubes, and uncleaned spectral line and dirty beam cubes
for each beam of an Apertif imaging observation. For this release, processed
data products are considered on a beam-by-beam basis within an observation. We
validate the continuum images by using metrics that identify deviations from
Gaussian noise in the residual images. If the continuum image passes
validation, we release all processed data products for a given beam. We apply
further validation to the polarization and line data products. We release all
raw observational data from the first year of survey observations, for a total
of 221 observations of 160 independent target fields, covering approximately
one thousand square degrees of sky. Images and cubes are released on a per beam
basis, and 3374 beams are released. The median noise in the continuum images is
41.4 uJy/bm, with a slightly lower median noise of 36.9 uJy/bm in the Stokes V
polarization image. The median angular resolution is 11.6"/sin(Dec). The median
noise for all line cubes, with a spectral resolution of 36.6 kHz, is 1.6
mJy/bm, corresponding to a 3-sigma HI column density sensitivity of 1.8 x 10^20
atoms cm^-2 over 20 km/s (for a median angular resolution of 24" x 15"). We
also provide primary beam images for each individual Apertif compound beam. The
data are made accessible using a Virtual Observatory interface.
