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We present the ensemble variability analysis results of quasars using theDark Energy Camera Legacy Survey (DECaLS) and the Sloan Digital Sky Survey(SDSS) quasar catalogs. Our dataset includes 119,305 quasars with redshifts upto 4.89. Combining the two datasets provides a 15-year baseline and permitsanalysis of the long timescale variability. Adopting a power-law form for thevariability structure function, $V=A(t/1yr)^{\gamma}$, we use themulti-dimensional parametric fitting to explore the relationships between thequasar variability amplitude and a wide variety of quasar properties, includingredshift (positive), bolometric luminosity (negative), rest-frame wavelength(negative), and black hole mass (uncertain). We also find that $\gamma$ can bealso expressed as a function of redshift (negative), bolometric luminosity(positive), rest-frame wavelength (positive), and black hole mass (positive).Tests of the fitting significance with the bootstrap method show that, evenwith such a large quasar sample, some correlations are marginally significant.The typical value of $\gamma$ for the entire dataset is $\gtrsim 0.25$,consistent with the results in previous studies on both the quasar ensemblevariability and the structure function. A significantly negative correlationbetween the variability amplitude and the Eddington ratio is found, which maybe explained as an effect of accretion disk instability.

The ensemble photometric variability of over $10^5$ quasars in the Dark Energy Camera Legacy Survey and the Sloan Digital Sky Survey